tellurium and tellurous-acid

Mitochondrial diseases are a group of genetic disorders characterized by dysfunctional mitochondria. Within eukaryotic cells, mitochondria contain their own ribosomes, which synthesize small amounts of proteins, all of which are essential for the biogenesis of the oxidative phosphorylation system. The ribosome is an evolutionarily conserved macromolecular machine in nature both from a structural and functional point of view, universally responsible for the synthesis of proteins. Among the diseases afflicting humans, those of ribosomal origin - either cytoplasmic ribosomes (80S) or mitochondrial ribosomes (70S) - are relevant. These are inherited or acquired diseases most commonly caused by either ribosomal protein haploinsufficiency or defects in ribosome biogenesis. Here we review the scientific literature about the recent advances on changes in mitochondrial ribosomal structural and assembly proteins that are implicated in primary mitochondrial diseases and neurodegenerative disorders, and their possible connection with metalloid pollution and toxicity, with a focus on MRPL44, NAM9 (MNA6) and GEP3 (MTG3), whose lack or defect was associated with resistance to tellurite. Finally, we illustrate the suitability of yeast Saccharomyces cerevisiae (S. cerevisiae) and the nematode Caenorhabditis elegans (C. elegans) as model organisms for studying mitochondrial ribosome dysfunctions including those involved in human diseases.

Topics: Alzheimer Disease; Animals; Caenorhabditis elegans; Humans; Mitochondrial Diseases; Ribosomal Proteins; RNA, Ribosomal; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Tellurium

Topics: Bacteria; Selenious Acid; Selenium; Tellurium

The perceived importance of tellurium (Te) in biological systems has lagged behind selenium (Se), its lighter sister in the Group 16 chalcogens, because of tellurium's lower crustal abundance, lower oxyanion solubility and biospheric mobility and the fact that, unlike Se, Te has yet to be found to be an essential trace element. Te applications in electronics, optics, batteries and mining industries have expanded during the last few years, leading to an increase in environmental Te contamination, thus renewing biological interest in Te toxicity. This chalcogen is rarely found in the nontoxic, elemental state (Te(0)), but its soluble oxyanions, tellurite (TeO(3)(2-)) and tellurate (TeO(4)(2-)), are toxic for most forms of life even at very low concentrations. Although a number of Te resistance determinants (Tel) have been identified in plasmids or in the bacterial chromosome of different species of bacteria, the genetic and/or biochemical basis underlying bacterial TeO(3)(2-) toxicity is still poorly understood. This review traces the history of Te in its biological interactions, its enigmatic toxicity, importance in cellular oxidative stress, and interaction in cysteine metabolism.

Topics: Bacteria; Bacterial Proteins; Drug Resistance, Bacterial; Oxidative Stress; Tellurium

Tellurium compounds are used in several industrial processes, although they are relatively rare in the environment. Genes associated with tellurite resistance (TeR) are found in many pathogenic bacteria. Tellurite can be detoxified through interactions with cellular thiols, such as glutathione, or a methyltransferase-catalyzed reaction, although neither process appears involved in plasmid-mediated TeR.

Topics: Anti-Bacterial Agents; Bacteria; Drug Resistance, Microbial; Humans; Tellurium

Pollution by metalloids, e.g., tellurite and selenite, is of serious environmental concern and, therefore, there is an increasing interest in searching for ecologically friendly solutions for their elimination. Some microorganisms are able to reduce toxic tellurite/selenite into less toxic elemental tellurium (Te) and selenium (Se). Here, we describe the use of the environmentally relevant β-proteobacterium Aromatoleum sp. CIB as a platform for tellurite elimination. Aromatoleum sp. CIB was shown to tolerate 0.2 and 0.5 mM tellurite at aerobic and anaerobic conditions, respectively. Furthermore, the CIB strain was able to reduce tellurite into elemental Te producing rod-shaped Te nanoparticles (TeNPs) of around 200 nm length. A search in the genome of Aromatoleum sp. CIB revealed the presence of a gene, AzCIB_0135, which encodes a new methyltransferase that methylates tellurite and also selenite. AzCIB_0135 orthologs are widely distributed in bacterial genomes. The overexpression of the AzCIB_0135 gene both in Escherichia coli and Aromatoleum sp. CIB speeds up tellurite and selenite removal, and it enhances the production of rod-shaped TeNPs and spherical Se nanoparticles (SeNPs), respectively. Thus, the overexpression of a methylase becomes a new genetic strategy to optimize bacterial catalysts for tellurite/selenite bioremediation and for the programmed biosynthesis of metallic nanoparticles of biotechnological interest.

Topics: Metal Nanoparticles; Methyltransferases; Rhodocyclaceae; Selenious Acid; Selenium; Tellurium

Aromatic compounds and metalloid oxyanions are abundant in the environment due to natural resources and industrial wastes. The high toxicity of phenol and tellurite poses a significant threat to all forms of life. A halotolerant bacterium was isolated and identified as Lysinibacillus sp. EBL303. The remediation analysis shows that 500 mg/L phenol and 0.5 mM tellurite can be remediated entirely in separate cultures within 74 and 56 h, respectively. In addition, co-remediation of pollutants resulted in the same phenol degradation and 27% less tellurite reduction within 98 h. Since phenol and tellurite exhibited inhibitory behavior, their removal kinetics fitted well with the first-order model. In the characterization of biosynthesized tellurium nanoparticles (TeNPs), transmission electron microscopy, dynamic light scattering, FE-SEM, and dispersive X-ray (EDX) showed that the separated intracellular TeNPs were spherical and consisted of only tellurium with 22-148 nm in size. Additionally, investigations using X-ray diffraction and Fourier-transform infrared spectroscopy revealed proteins and lipids covering the surface of these amorphous TeNPs. Remarkably, this study is the first report to demonstrate the simultaneous bioremediation of phenol and tellurite and the biosynthesis of TeNPs, indicating the potential of Lysinibacillus sp. EBL303 in this matter, which can be applied to environmental remediation and the nanotechnology industry.

Topics: Bacillaceae; Biodegradation, Environmental; Nanoparticles; Phenol; Phenols; Tellurium

A series of tellurite-based glasses are prepared by using a melt-quenching method. The effect of cerium on the physical, thermal, structural, optical, spectroscopic, and shielding properties of barium tellurite glass samples is studied. It has been observed that the thermal stability factor increases with increasing cerium ion (Ce

Topics: Barium; Cerium; Spectrum Analysis; Tellurium

Natural and anthropogenic activities, such as weathering of rocks and industrial processes, result in the release of toxic oxyanions such as selenium (Se) and tellurium (Te) into the environment. Due to the high toxicity of these compounds, their removal from the environment is vital.. In this study, two yeast strains, Yarrowia lipolytica and Trichosporon cutaneum, were selected as the superior strains for the bioremediation of tellurium and selenium. The reduction analyses showed that exposure to selenite induced more detrimental effects on the strains compared to tellurite. In addition, co-reduction of pollutants displayed almost the same results in selenite reduction and more than ~ 20% higher tellurite reduction in 50 h, which shows that selenite triggered higher tellurite reduction in both strains. The selenite and tellurite kinetics of removal were consistent with the first-order model because of their inhibitory behavior. The result of several characterization experiments, such as FE-SEM (Field emission scanning electron microscopy), dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD), and dispersive X-ray (EDX) on Te-Se nanoparticles (NPs) revealed that the separated Te-Se NPs were needle-like, spherical, and amorphous, consisted of Te-Se NPs ranging from 25 to 171 nm in size, and their surface was covered with different biomolecules.. Remarkably, this work shows, for the first time, the simultaneous bioreduction of tellurite and selenite and the production of Te-Se NPs using yeast strains, indicating their potential in this area, which may be applied to the nanotechnology industry and environmental remediation.

Topics: Coculture Techniques; Nanoparticles; Selenium; Tellurium; Yarrowia

Escherichia albertii is an emerging diarrheagenic pathogen causing food- and water-borne infection in humans. However, no selective enrichment broths for E. albertii have ever been reported. In this study, we tested several basal media, selective supplements and culture conditions which enabled selective enrichment of E. albertii.. We developed a selective enrichment broth, novobiocin-cefixime-tellurite supplemented modified tryptic soy broth (NCT-mTSB). NCT-mTSB supported the growth of 22 E. albertii strains, while inhibited growth of other Enterobacteriaceae at 37°C, except for Escherichia coli and Shigella spp. Enrichment of E. albertii was improved further by growth at 44°C, a temperature that suppresses growth of several strains of E. coli/Shigella. Combined use of NCT-mTSB with XR-DH-agar, xylose-rhamnose supplemented deoxycholate hydrogen sulphide agar, enabled isolation of E. albertii when at least 1 CFU of the bacterium was present per gram of chicken meat. This level of enrichment was superior to those obtained using buffered peptone water, modified-EC broth, or mTSB (with novobiocin).. Novobiocin-cefixime-tellurite supplemented modified tryptic soy broth enabled effective enrichment of E. albertii from poultry samples and was helpful for isolation of this bacterium.. To our knowledge, this is the first report of selective enrichment of E. albertii from poultry samples.

Topics: Animals; Caseins; Cefixime; Culture Media; Escherichia; Food Microbiology; Novobiocin; Poultry; Protein Hydrolysates; Tellurium

Shielding glass materials doped with heavy metal oxides show an improvement in the effectiveness of the materials used in radiation shielding. In this work, the photon shielding parameters of six tellurite glass systems doped with several metal oxides namely, 70TeO2-10P2O5- 10ZnO- 5.0PbF2- 0.0024Er2O3- 5.0X (where X represents different doped metail oxides namely, Nb2O5, TiO2, WO3, PbO, Bi2O3, and CdO) in a broad energy spectrum, ranging from 0.015 MeV to 15 MeV, were evaluated. The shielding parameters were calculated using the online software Phy-X/PSD. The highest linear and mass attenuation coefficients recorded were obtaibed from the samples containing bismuth oxide (Bi2O3), and the lowest half-value layer and mean free path were recorded among the other samples. Furthermore, the shielding effectiveness of tellurite glass systems was compared with commercial shielding materials (RS-369, RS-253 G18, chromite, ferrite, magnetite, and barite). The optical parameters viz, dispersion energy, single-oscillator energy, molar refraction, electronic polarizability, non-linear refractive indices, n2, and third-order susceptibility were measured and reported at a different wavelength. Bi2O3 has a strong effect on enhancing the optical and shielding properties. The outcome of this study suggests the potential of using the proposed glass samples as radiation-shielding materials for a broad range of imaging and therapeutic applications.

Topics: Glass; Oxides; Photons; Radiation Protection; Tellurium

Tellurium is a rare metalloid that exerts high toxicity on cells, especially on bacteria, partly due to reactive oxygen species (ROS) generation. Moreover, it has also been observed that tellurite can target free cell thiols groups (RSH) (i.e. reduced glutathione (GSH)), enhancing the cellular redox imbalance. Additionally, in vitro experiments have suggested that several enzymes can reduce tellurite (IV) to its elemental form (0); where RSH present on their active sites may be responsible for the process. Nevertheless, the mechanisms implemented by bacteria for tellurite reduction and its role in resistance have not been evaluated in vivo.. This work shows that tellurite reduction to elemental tellurium is increased under anaerobic conditions in E. coli cells. The in vivo tellurite reduction is related to the intracellular concentration of total RSH, in the presence and absence of oxygen. This metabolization of tellurite directly contributes to the resistance of the bacteria to the oxyanion.. We demonstrated that in vivo tellurite reduction is related to the intracellular thiol concentration, i.e. large availability of cellular RSH groups, results in a more significant reduction of tellurite. Furthermore, we observed that, when the bacterium exhibits less resistance to the oxyanion, a decreased tellurite reduction was seen, affecting the growth fitness. Together, these results let us propose that tellurite reduction and the intracellular RSH content are related to the oxyanion bacterial resistance, this tripartite mechanism in an oxygen-independent anaerobic process.

Topics: Anaerobiosis; Escherichia coli; Oxidation-Reduction; Tellurium

The performance of Aspergillus niger pellets to remove selenite and tellurite from wastewater using batch and continuous fungal pelleted bioreactors was investigated. The acid hydrolysate of brewer's spent grain (BSG) was utilized by A. niger as the electron donor for selenite and tellurite reduction. The dilution of BSG hydrolysate using mineral medium had a positive effect on the selenite and tellurite removal efficiency with a 1:3 ratio giving the best efficiency. However, selenite and tellurite inhibited fungal growth with a 40.9% and 27.3% decrease in the A. niger biomass yield in the presence of 50 mg/L selenite and tellurite, respectively. The maximum selenite and tellurite removal efficiency using 25% BSG hydrolysate in batch incubations amounted to 72.8% and 99.5% Two fungal pelleted bioreactors were operated in continuous mode using BSG hydrolysate as the substrate. Both the selenite and tellurite removal efficiencies during steady state operation were > 80% with tellurite showing a maximum removal efficiency of 98.5% at 10 mg/L influent concentration. Elemental Se nanospheres for selenite and both Te nanospheres and nanorods for tellurite were formed within the fungal pellets. This study demonstrates the suitability BSG hydrolysate as a low cost carbon source for removal of selenite and tellurite using fungal pellet bioreactors.

Topics: Aspergillus niger; Lignin; Selenious Acid; Tellurium

Herein we report the use of an environmental multimetal(loid)-resistant strain, MF05, to biosynthesize single- or multi-element nanostructures under anaerobic conditions. Inorganic nanostructure synthesis typically requires methodologies and conditions that are harsh and environmentally hazardous. Thus, green/eco-friendly procedures are desirable, where the use of microorganisms and their extracts as bionanofactories is a reliable strategy. First, MF05 was entirely sequenced and identified as an Escherichia coli-related strain with some genetic differences from the traditional BW25113. Secondly, we compared the CdS nanostructure biosynthesis by whole-cell in a design defined minimal culture medium containing sulfite as the only sulfur source to obtain sulfide reduction from a low-cost chalcogen reactant. Under anaerobic conditions, this process was greatly favored, and irregular CdS (ex. 370 nm; em. 520-530 nm) was obtained. When other chalcogenites were tested (selenite and tellurite), only spherical Se0 and elongated Te0 nanostructures were observed by TEM and analyzed by SEM-EDX. In addition, enzymatic-mediated chalcogenite (sulfite, selenite, and tellurite) reduction was assessed by using MF05 crude extracts in anaerobiosis; similar results for nanostructures were obtained; however Se0 and Te0 formation were more regular in shape and cleaner (with less background). Finally, the in vitro nanostructure biosynthesis was assessed with salts of Ag, Au, Cd, and Li alone or in combination with chalcogenites. Several single or binary nanostructures were detected. Our results showed that MF05 is a versatile anaerobic bionanofactory for different types of inorganic NS. synthesis.

Topics: Anaerobiosis; Cadmium; Complex Mixtures; Nanostructures; Salts; Selenious Acid; Sulfides; Sulfites; Sulfur; Tellurium

Antibacterial tellurium nanoparticles have the advantages of high activity and biocompatibility. Microbial synthesis of Te nanoparticles is not only a green technology but builds new ecological relationships in diverse environments. However, the antibacterial mechanism of Te nanoparticles is largely unclear. In this study, we report the bacterial synthesis of rod-shaped Te nanoparticles (BioTe) with high antibacterial activity against

Topics: Anti-Bacterial Agents; Escherichia coli; Nanoparticles; Reactive Oxygen Species; Sulfur; Tellurium

The intense use of tellurium (Te) in industrial applications, along with the improper disposal of Te-derivatives, is causing their accumulation in the environment, where oxyanion tellurite (TeO

Topics: Extracellular Polymeric Substance Matrix; Micromonospora; Protein Aggregates; Superoxide Dismutase; Tellurium

Tellurium (Te) is an industrially useful element but causes environmental contamination. The formation of biogenic Te nanorods (Te-BgNRs) in plants is one of the Te detoxification pathways associated with the phytoremediation of Te because Te-BgNRs contain low-toxicity Te at high densities. In this study, we investigated the mechanism of Te-BgNR formation in a common unicellular green alga, Chlamydomonas reinhardtii, on the basis of elemental analysis by inductively coupled plasma mass spectrometry (ICP-MS). After exposure to 1000 μM sodium tellurate (Na2TeO4) for 2 weeks, the alga accumulated 65.2 fg of Te per cell, and 55.8% of which was present in an insoluble form. Electron microscopic observations revealed that the insoluble Te was rod-shaped elemental Te, i.e. Te-BgNRs, and had a highly crystalline nanostructure. We determined the Te contents in Te-BgNRs by single-particle ICP-MS analysis and found that these nanorods were formed at tellurate exposure concentrations of 100 to 1000 μM. In contrast, soluble Te compounds were found in algal cells even at exposure concentrations lower than 100 μM. These findings suggest that the algal cells initially metabolized tellurate to form soluble Te compounds, and excess tellurate that could not be metabolized was then transformed to Te-BgNRs, which are less toxic than tellurate. Our findings provide a novel approach to Te remediation through the formation of BgNRs in C. reinhardtii.

Topics: Biodegradation, Environmental; Chlamydomonas reinhardtii; Nanotubes; Tellurium

Tellurates have attracted the attention of researchers over the past decade due to their properties and as less toxic forms of tellurium derivatives. However, the speciation of Te(VI) in aqueous solutions has not been comprehensively studied. We present a study of the equilibrium speciation of tellurates in aqueous solutions at a wide pH range, 2.5-15 by

Topics: Anions; Magnetic Resonance Spectroscopy; Tellurium; Water

A previously unreported tellurate reducing capacity was found in a marine bacteria Sporosarcina sp. Te-1, which was isolated from Bohai Sea, China. In this work, the complete genome of strain Te-1 was obtained using hybrid Nanopore/Illumina assemble method. A circular chromosome of 4,297,762 bp with a G + C content of 44.44 mol% was assembled. The genome harbors 4530 predicted protein-encoding genes, 71 tRNA genes, and 9 rRNA genes. Genes involved in tellurate metabolism, urea metabolism and salinity adaption were identified. These metabolic features reveal the genetic basis for the tellurate metabolism in the marine environment, which help us to further understand the marine tellurium biogeochemical cycle.

Topics: Bacteria; Base Composition; Sporosarcina; Tellurium

Topics: Diacetyl; Oxidation-Reduction; Tellurium

The tellurium oxyanion tellurate is toxic to living organisms even at low concentrations; however, its mechanism of toxicity is poorly understood. Here, we show that exposure of Escherichia coli K-12 to tellurate results in reduction to elemental tellurium (Te[0]) and the formation of intracellular reactive oxygen species (ROS). Toxicity assays performed with E. coli indicated that pre-oxidation of the intracellular thiol pools increases cellular resistance to tellurate-suggesting that intracellular thiols are important in tellurate toxicity. X-ray absorption spectroscopy experiments demonstrated that cysteine reduces tellurate to elemental tellurium. This redox reaction was found to generate superoxide anions. These results indicate that tellurate reduction to Te(0) by cysteine is a source of ROS in the cytoplasm of tellurate-exposed cells.

Topics: Cysteine; Escherichia coli K12; Oxidation-Reduction; Oxidative Stress; Tellurium

Tellurium (Te) is an emerging contaminant and its chemical transformation in the environment is strongly influenced by microbial processes. In this study, we investigated the adsorption of tellurite [Te(IV), TeO

Topics: Adsorption; Bacteria; Sulfhydryl Compounds; Tellurium

Cells of the facultative photosynthetic bacterium Rhodobacter capsulatus exploit the simultaneous presence in the cultural medium of the toxic oxyanion tellurite (TeO

Topics: Crystallization; Nanoparticles; Naphthoquinones; Oxidation-Reduction; Rhodobacter capsulatus; Tellurium

The bacterial genus Exiguobacterium includes several species that inhabit environments with a wide range of temperature, salinity, and pH. This is why the microorganisms from this genus are known generically as polyextremophiles. Several environmental isolates have been explored and characterized for enzyme production as well as for bioremediation purposes. In this line, toxic metal(loid) reduction by these microorganisms represents an approach to decontaminate soluble metal ions via their transformation into less toxic, insoluble derivatives. Microbial-mediated metal(loid) reduction frequently results in the synthesis of nanoscale structures-nanostructures (NS) -. Thus, microorganisms could be used as an ecofriendly way to get NS.. We analyzed the tolerance of Exiguobacterium acetylicum MF03, E. aurantiacum MF06, and E. profundum MF08 to Silver (I), gold (III), and tellurium (IV) compounds. Specifically, we explored the ability of cell-free extracts from these bacteria to reduce these toxicants and synthesize NS in vitro, both in the presence or absence of oxygen. All isolates exhibited higher tolerance to these toxicants in anaerobiosis. While in the absence of oxygen they showed high tellurite- and silver-reducing activity at pH 9.0, whereas AuCl. This nanostructure-synthesizing ability makes these isolates interesting candidates to get NS with biotechnological potential.

Topics: Aerobiosis; Anaerobiosis; Anti-Bacterial Agents; Biodegradation, Environmental; Cell Extracts; Exiguobacterium; Gold; Metal Nanoparticles; Microbial Sensitivity Tests; Silver; Tellurium; Temperature

Microbial reduction of selenite [Se(IV)] and tellurite [Te(IV)] to Se(0) and Te(0) can function as a detoxification mechanism and serve in energy conservation. In this study, Bacillus sp. Y3 was isolated and demonstrated to have an ability of simultaneous reduction of Se(IV) and Te(IV) during aerobic cultivation, with reduction efficiencies of 100% and 90%, respectively. Proteomics analysis revealed that the putative thioredoxin disulfide reductase (TrxR) and sulfate and energy metabolic pathway proteins were significantly upregulated after the addition of Se(IV) and Te(IV). qRT-PCR also showed an increased trxR transcription level in the presence of Se(IV) and Te(IV). Compared with a wild-type Escherichia coli strain, the TrxR-overexpressed E. coli strain showed higher Se(IV) and Te(IV) resistance levels and reduction efficiencies. Additionally, the TrxR showed in vitro Se(IV) and Te(IV) reduction activities when NADPH or NADH were present. When NADPH was used as the electron donor, the optimum conditions for enzyme activities were pH 8.0 and 37°C. The Km values of Te(IV) and Se(IV) were 16.31 and 2.91 mM, and the Vmax values of Te(IV) and Se(IV) were 12.23 and 11.20 µM min-1 mg-1, respectively. The discovery of the new reductive enzyme TrxR enriches the repertoire of the bacterial Se(IV) and Te(IV) resistance and reduction mechanisms. Bacillus sp. Y3 can efficiently reduce Se(IV) and Te(IV) simultaneously. Strain Y3 provides potential applications for selenite and tellurite bioremediation. The TrxR enzyme shows high catalytic activity for reducing Se(IV) and Te(IV). The discovery of TrxR enriches the bacterial Se(IV) and Te(IV) reduction mechanisms.

Topics: Bacillus; Escherichia coli; NAD; Oxidation-Reduction; Selenious Acid; Tellurium; Thioredoxin-Disulfide Reductase

Formation and recovery of elemental tellurium (Te

Topics: Bacterial Physiological Phenomena; Biofilms; Bioreactors; Membranes, Artificial; Methane; Nanostructures; Phylogeny; RNA, Bacterial; RNA, Ribosomal, 16S; Tellurium; Waste Disposal, Fluid; Wastewater

Tellurium (Te) has been increasingly used as a semiconductor material in copious amounts, with a concomitant increase in its discharge from industrial effluents and mining wastewater into the environment. However, soluble Te, such as tellurate (VI) and tellurite (IV), is toxic to organisms. Thus, highly efficient technologies need to be developed for a double-benefit detoxification and recovery of soluble Te from industrial and mining wastewater. Since industrial wastewater contains high concentrations of salt, salt-tolerant microorganisms that metabolize rare metals such as Te have been the subject of focus for the effective detoxification and recovery of Te. In the present study, a total of 52 salt-tolerant tellurate-reducing microorganisms were isolated from marine environmental samples. Of these, 18 strains achieved greater than, or equal to, 50% removal of water-soluble Te from a medium containing 0.4 mM tellurate after 72 h incubation. The 18 isolated strains belonged to 13 species of the following 9 genera: Sulfitobacter, Ruegeria, Hoeflea, Alteromonas, Marinobacter, Pseudoalteromonas, Shewanella, Idiomarina, and Vibrio. No microorganism has been reported to reduce tellurate and tellurite from six of the aforementioned genera, namely, Sulfitobacter, Ruegeria, Alteromonas, Marinobacter, Idiomarina, and Vibrio. Especially, one of the isolates Sulfitobacter sp. strain TK39B, removed 82% (w/w) of soluble Te with a 4% NaCl tolerance. These results showed that salt-tolerant tellurate-reducing bacteria that can be used in the detoxification and recovery of Te are widely present in the marine environment.

Topics: Bacteria; Biodegradation, Environmental; Biodiversity; DNA, Bacterial; Geologic Sediments; Phylogeny; RNA, Ribosomal, 16S; Salt Tolerance; Seawater; Sequence Analysis, DNA; Sodium Chloride; Tellurium; Waste Disposal, Fluid; Water Pollutants, Chemical

Semiconducting polymer (SP) nanoparticles (NPs) have recently emerged as one of the most promising agents for photoacoustic imaging (PAI)-guided photothermal/photodynamic therapy (PTT/PDT). Herein, a triplet tellurophene-based SP (PNDI-2T) was synthesized with efficient tin-free direct heteroarylation polycondensation. The PNDI-2T NPs display remarkable near-infrared absorption and low cytotoxicity. In addition, PNDI-2T NPs can generate abundant reactive oxygen species (ROS) since tellurophene facilitates the intersystem crossing to generate triplet excited states. Remarkably, PNDI-2T NPs present a high photothermal conversion efficiency (η = 45%) and a high ROS yield (ΦΔ = 38.7%) under 808 nm laser irradiation. Furthermore, we showed that PNDI-2T NPs could be excellent PAI-guided PTT/PDT agents for cancer theranostics. This study provides a new route to developing highly efficient and low cytotoxic agents for PAI-guided PTT/PDT.

Topics: Cell Proliferation; HeLa Cells; Humans; Nanoparticles; Photoacoustic Techniques; Photochemotherapy; Polymers; Reactive Oxygen Species; Semiconductors; Tellurium; Theranostic Nanomedicine

The fungi Aureobasidium pullulans, Mortierella humilis, Trichoderma harzianum and Phoma glomerata were used to investigate the formation of selenium- and tellurium-containing nanoparticles during growth on selenium- and tellurium-containing media. Most organisms were able to grow on both selenium- and tellurium-containing media at concentrations of 1 mM resulting in extensive precipitation of elemental selenium and tellurium on fungal surfaces as observed by the red and black colour changes. Red or black deposits were confirmed as elemental selenium and tellurium, respectively. Selenium oxide and tellurium oxide were also found after growth of Trichoderma harzianum with 1 mM selenite and tellurite as well as the formation of elemental selenium and tellurium. The hyphal matrix provided nucleation sites for metalloid deposition with extracellular protein and extracellular polymeric substances localizing the resultant Se or Te nanoparticles. These findings are relevant to remedial treatments for selenium and tellurium and to novel approaches for selenium and tellurium biorecovery.

Topics: Biodegradation, Environmental; Fungi; Nanoparticles; Oxidation-Reduction; Selenium; Selenium Compounds; Tellurium

The increasing industrial utilization of tellurium has resulted in an important environmental pollution with the soluble, extremely toxic oxyanion tellurite. In this context, the use of microorganisms for detoxifying tellurite or tellurium biorecovery has gained great interest. The ability of different Shewanella strains to reduce tellurite to elemental tellurium was assessed; the results showed that the reduction process is dependent on electron transport and the ∆pH gradient. While S. baltica OS155 showed the highest tellurite resistance, S. putrefaciens was the most efficient in reducing tellurite. Moreover, pH-dependent tellurite transformation was associated with tellurium precipitation as tellurium dioxide. In summary, this work highlights the high tellurite reduction/detoxification ability exhibited by a number of Shewanella species, which could represent the starting point to develop friendly methods for the recovery of elemental tellurium (or tellurium dioxide).

Topics: Biodegradation, Environmental; Electron Transport; Inactivation, Metabolic; Oxidation-Reduction; Shewanella; Tellurium

Moderately halotolerant selenate- and tellurite-reducing bacteria were characterized for wastewater treatment applications. A selenate-reducing strain 9a was isolated from the biofilm of a leachate treatment plant at a sea-based waste disposal site. A tellurite-reducing strain Taa was isolated from an enrichment culture derived from brackish sediment. Both bacterial strains were Shewanella species. Strain 9a could anaerobically remove 45-70% of 1.0 mM selenate and selenite from water containing up to 3% NaCl within 4 days, while strain Taa could anaerobically and aerobically remove 70-90% of 0.4 mM tellurite from water containing up to 6% NaCl within 3 days. Globular particles of insoluble selenium were observed both outside and inside the cells of strain 9a. The insoluble tellurium formed by strain Taa was globular under microaerobic conditions but nanorod under aerobic conditions. These bacteria will yield a range of useful selenium and tellurium nanomaterials as well as wastewater treatment applications.

Topics: Bacteria; Bacteria, Aerobic; Bacteria, Anaerobic; Japan; Oxidation-Reduction; Saline Waters; Salt Tolerance; Selenic Acid; Tellurium

Shiga toxin-producing Escherichia coli (STEC) are globally important food-borne pathogens. The isolation of non-O157 STEC is a significant public health challenge due to the dramatic diversity of their phenotypes and genotypes. In the present study, 476 non-O157 STEC strains representing 95 different O-serogroups were used to evaluate tellurite resistance and the performance of 12 different chromogenic agars. Of 476 strains, only 108 (22.7%) strains showed the minimal inhibitory concentration (MIC) values for potassium tellurite being higher than 4μg/ml, and 96 (20.2%) strains harbored intact ter genes cluster. The presence of ter genes was significantly correlated with tellurite resistance. Six commercial chromogenic agars (TBX, MAC, SMAC, Rainbow® Agar O157, CHROMagar™ ECC, and Fluorocult O157) supported the growth of all strains. However, CT-SMAC, CHROMagar™ O157, and CHROMagar™ STEC agars exhibited 12.2%, 31.1%, and 38.0% of growth inhibition, respectively. Furthermore, 4.6%, 33.2%, and 45.0% of strains were inhibited on RBA-USDA, RBA-NT, and BCM O157 agar media. Variations in tellurite resistance and colony appearance might result in discrepant performance of non-O157 STEC recovery from different chromogenic agars. Using inclusive agars or less selective agar in combination with highly selective agar should be suggested to recover most non-O157 STEC strains, which would increase the probability of recovering STECs from complex background microflora.

Topics: Agar; Antineoplastic Agents; Culture Media; Drug Resistance, Bacterial; Escherichia coli O157; Microbial Sensitivity Tests; Serogroup; Shiga-Toxigenic Escherichia coli; Tellurium

Simultaneous removal of selenite and tellurite from synthetic wastewater was achieved through microbial reduction in a lab-scale upflow anaerobic sludge blanket reactor operated with 12 h hydraulic retention time at 30 °C and pH 7 for 120 days. Lactate was supplied as electron donor at an organic loading rate of 528 or 880 mg COD L

Topics: Anaerobiosis; Bioreactors; Hydrogen-Ion Concentration; Lactates; Microscopy, Electron, Scanning; Nanostructures; Oxidation-Reduction; Selenious Acid; Spectrum Analysis, Raman; Tellurium; Temperature; Time Factors; Trace Elements; Wastewater; Water Pollutants, Chemical; Water Purification; X-Ray Diffraction

The

Topics: Bacterial Proteins; Ferric Compounds; Fumarates; Geobacter; Oxidation-Reduction; Porins; Selenious Acid; Tellurium

Although tellurite is highly toxic to organisms, elemental tellurium nanomaterials (TeNMs) have many uses. The microbe-mediated reduction of tellurite to Te(0) has been shown to be a green and cost-effective approach for turning waste into wealth. However, it is difficult to tune the morphology of biogenic nanomaterials. In this study, a series of experiments was conducted to investigate the factors influencing tellurite reduction by the tellurite-reducing bacterium Lysinibacillus sp. ZYM-1, including pH, tellurite concentration, temperature, and heavy metal ions. The optimal removal efficiency of tellurite was respectively achieved at pH 8, 0.5 mM tellurite, and 40 °C. All of the tested metal ions retarded the reduction of tellurite, especially Cd

Topics: Bacillaceae; Biodegradation, Environmental; Hydrogen-Ion Concentration; Nanostructures; Oxidation-Reduction; Tellurium; Temperature

Environmental contamination by Te and Se oxyanions has become a serious concern, with the search for green, ecologically friendly methods for removal gaining ground. Bacteria capable of reducing these highly toxic compounds to a virtually non-toxic elemental form could provide a solution. In this study, four strains of bacteria with potential for bioremediation of Te and Se oxyanions were investigated. Under aerobic conditions over 48 h, Erythromicrobium ramosum, strain E5 removed 244 µg/ml tellurite and 98 µg/ml selenite, Erythromonas ursincola, KR99 203 µg/ml tellurite and 100 µg/ml selenite, AV-Te-18 98 µg/ml tellurite and 103 µg/ml selenite and ER-V-8 93 µg/ml tellurite and 103 µg/ml selenite. In the absence of oxygen, AV-Te-18 and ER-V-8 removed 10 µg/ml tellurite after 24 and 48 h, respectively and 46 and 25 µg/ml selenite, respectively, over 48 h. ER-V-8 removed 14 µg/ml selenate after 5 days. This highlights the great potential of these microbes for use in bioremediation.

Topics: Anions; Bacteria; Biodegradation, Environmental; Environmental Pollutants; Selenium; Tellurium

The metalloid tellurite is highly toxic to microorganisms. Several mechanisms of action have been proposed, including thiol depletion and generation of hydrogen peroxide and superoxide, but none of them can fully explain its toxicity. Here we use a combination of directed evolution and chemical and biochemical approaches to demonstrate that tellurite inhibits heme biosynthesis, leading to the accumulation of intermediates of this pathway and hydroxyl radical. Unexpectedly, the development of tellurite resistance is accompanied by increased susceptibility to hydrogen peroxide. Furthermore, we show that the heme precursor 5-aminolevulinic acid, which is used as an antimicrobial agent in photodynamic therapy, potentiates tellurite toxicity. Our results define a mechanism of tellurite toxicity and warrant further research on the potential use of the combination of tellurite and 5-aminolevulinic acid in antimicrobial therapy.

Topics: Aminolevulinic Acid; Anti-Bacterial Agents; Biosynthetic Pathways; Drug Resistance, Bacterial; Escherichia coli; Genome, Bacterial; Heme; Iron Deficiencies; Metalloids; Microbial Sensitivity Tests; Models, Biological; Mutation; Protoporphyrins; Superoxides; Tellurium

Being one of the most abundant trace elements in the human body, the therapeutic potential of tellurium-based compounds has been a target of interest. Recent reports denoted their redox-modulating and anti-inflammatory activities in experimental endotoxemia. However, their potential nephroprotective effect against endotoxemic kidney injury is yet to be elucidated. This study investigated the possible renoprotective effect of telluric acid (TEL) against lipopolysaccharide (LPS)-induced acute kidney injury (AKI) in mice, targeting toll-like receptor 4 (TLR4), phosphoinositide 3-kinase (PI3K)/Akt, and nuclear factor-erythroid 2-related factor-2 (Nrf2) pathways as possible mechanistic contributors to TEL's effect. AKI was induced by LPS (2 mg/kg). TEL (60 μg/kg; i.p.) was administered once daily for seven consecutive days before LPS injection. Pretreatment with TEL alleviated LPS-induced AKI as evidenced by the hampered serum levels of creatinine and cystatin C. TEL also opposed LPS-induced elevation in renal kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, nuclear factor-kappa B p65, interleukin-1β, and thiobarbituric acid-reactive substance contents. This was accompanied by a replenishment of renal glutathione, transcriptional upregulation of Nrf2, enhancement of heme oxygenase-1 activity, and a marked upregulation of phospho-PI3K and phospho-Akt protein expressions. Histopathological findings corroborated with the amendment of biochemical parameters. In view of these findings, we may conclude that TEL pretreatment purveyed novel nephroprotective effects against endotoxemic kidney injury, which might be partly attributed to the modulation of TLR4, PI3K/Akt, and Nrf2 signaling pathways and may hence provide a valuable asset for the management of endotoxemic renal complications.

Topics: Acute Kidney Injury; Animals; Endotoxemia; Lipopolysaccharides; Mice; NF-E2-Related Factor 2; Phosphatidylinositol 3-Kinases; Premedication; Proto-Oncogene Proteins c-akt; Signal Transduction; Tellurium; Toll-Like Receptor 4

Soluble forms of tellurium are environmental contaminants that are toxic to microorganisms. While tellurite [Te(IV)] is a well-characterized antimicrobial agent, little is known about the interactions of tellurate [Te(VI)] with bacterial cells. In this study, we investigated the role of sulfate transporters in the uptake of tellurate in Escherichia coli K-12. Mutant strains carrying a deletion of the cysW gene in the CysPUWA sulfate transporter system accumulated less cellular tellurium and exhibited higher resistance to tellurate compared with the wild-type strain. Complementation of the mutation restored tellurate sensitivity and uptake. These results indicate that tellurate enters E. coli cells to cause toxic effects via the CysPUWA sulfate transporter.

Topics: Anti-Bacterial Agents; Biological Transport; Drug Resistance, Bacterial; Escherichia coli K12; Escherichia coli Proteins; Genetic Complementation Test; Mutation; Protein Subunits; Tellurium

Bacteria have developed different mechanisms for the transformation of metalloid oxyanions to non-toxic chemical forms. A number of bacterial isolates so far obtained in axenic culture has shown the ability to bioreduce selenite and tellurite to the elemental state in different conditions along with the formation of nanoparticles-both inside and outside the cells-characterized by a variety of morphological features. This reductive process can be considered of major importance for two reasons: firstly, toxic and soluble (i.e. bioavailable) compounds such as selenite and tellurite are converted to a less toxic chemical forms (i.e. zero valent state); secondly, chalcogen nanoparticles have attracted great interest due to their photoelectric and semiconducting properties. In addition, their exploitation as antimicrobial agents is currently becoming an area of intensive research in medical sciences.. In the present study, the bacterial strain Ochrobactrum sp. MPV1, isolated from a dump of roasted arsenopyrites as residues of a formerly sulfuric acid production near Scarlino (Tuscany, Italy) was analyzed for its capability of efficaciously bioreducing the chalcogen oxyanions selenite (SeO. In conclusion, Ochrobactrum sp. MPV1 has demonstrated to be an ideal candidate for the bioconversion of toxic oxyanions such as selenite and tellurite to their respective elemental forms, producing intracellular Se- and TeNPs possibly exploitable in biomedical and industrial applications.

Topics: Aerobiosis; Arsenicals; Axenic Culture; Catalysis; Iron Compounds; Italy; Metal Nanoparticles; Microscopy, Electron; Minerals; Ochrobactrum; Selenious Acid; Selenium; Sulfides; Tellurium

Three qnrS2-containing isolates of Pseudoalteromonas and Shewanella were collected from the seawater samples of Qingdao in China during 2014. They displayed resistance to ampicillin, ciprofloxacin, kanamycin, nalidixic acid and sulfamethoxazole. The qnrS2 genes were identified in the chromosomes of Pseudoalteromonas strains E8 and S16, and in a 140-kb plasmid in Shewanella strain S14, respectively. In addition, two copies of qnrS2 were identified in the strain E8. Sequence analyses revealed that there was an identical DNA segment located in the downstream of qnrS2 in strain S14 and E8, coding for a TetR transcriptional regulator, two putative integrases and a hypothetical protein. However, different genetic structures were identified in the upstream sequences: the terB gene associated with tellurite resistance in the strain S14, and a putative integron with dfrA6 and aadA13 gene cassettes or the Tn7-related gene complex tnsABC in the strain E8. In Pseudoalteromonas strain S16, qnrS2 was bracketed by the endonuclease I and III genes, and the electron transport complex rsxCDGE was located in the upstream sequences. This is the first report of two copies of the qnrS2 gene existing in one bacterial chromosome, and also the first identification of qnrS2 in Shewanella.

Topics: Anti-Bacterial Agents; China; Drug Resistance, Multiple, Bacterial; Integrons; Microbial Sensitivity Tests; Plasmids; Pseudoalteromonas; Quinolones; Seawater; Sequence Analysis, DNA; Shewanella; Tellurium

Continuous removal of tellurite (TeO

Topics: Anaerobiosis; Biological Oxygen Demand Analysis; Biomass; Bioreactors; Lactic Acid; Polymers; Sewage; Tellurium; Waste Disposal, Fluid; Wastewater

A sampling trip to Central Gold Mine, Nopiming Provincial Park, Canada, was taken in September 2011. Abundance, distribution, and physiology of aerobic anoxygenic phototrophs (AAP) from 4 locations were studied. Enumeration revealed 14.6% of culturable microbes were AAP. Five strains (NM4.16, NM4.18, C4, C9, C11) were chosen for analysis. All grow best on complex media without vitamin requirements and with an optimal pH 7.0-8.0, with strain C4 preferring pH 6.0. Strain NM4.18 tolerates the highest pH 11.0. Optimal temperature for all is 28 °C (range of 2-37 °C except NM4.16, which survives 45 °C). Strains C9, C11, and NM4.18 grew in 1.0%, 2.0%, and 5.0% NaCl, respectively, while NM4.16 and C4 grew only without NaCl. Isolates were all highly resistant to toxic metal(oid) oxides: tellurite (1500 μg/mL, all), tellurate (1500 μg/mL, C11), selenite (5000 μg/mL, C9, C11, and NM4.18), selenate (1000 μg/mL, C9 and C11), and orthometavanadate and metavanadate (5000 μg/mL, C11 and NM4.18). They could reduce tellurite to the less toxic elemental tellurium. Full 16S rRNA gene sequencing revealed all strains are Alphaproteobacteria, with C4 and NM4.16 closely related to Porphyrobacter colymbi (99.4% and 99.7% sequence similarity, respectively), C9 to Brevundimonas variabilis (99.1%), C11 to Brevundimonas bacteroides (98.6%), and NM4.18 to Erythromonas ursincola (98.5%).

Topics: Alphaproteobacteria; Canada; DNA, Bacterial; Gold; Manitoba; Mining; Phylogeny; RNA, Ribosomal, 16S; Sodium Chloride; Tellurium; Temperature

Mercury salts and tellurite are among the most toxic compounds for microorganisms on Earth. Bacterial mercury resistance is established mainly via mercury reduction by the mer operon system. However, specific mechanisms underlying tellurite resistance are unknown to date. To identify new mechanisms for tellurite detoxification we demonstrate that mercury resistance mechanisms can trigger cross-protection against tellurite to a group of Pseudomonads isolated from the Chilean Antarctic territory. Sequencing of 16S rRNA of four isolated strains resulted in the identification of three Pseudomonads (ATH-5, ATH-41 and ATH-43) and a Psychrobacter (ATH-62) bacteria species. Phylogenetic analysis showed that ATH strains were related to other species previously isolated from cold aquatic and soil environments. Furthermore, the identified merA genes were related to merA sequences belonging to transposons commonly found in isolated bacteria from mercury contaminated sites. Pseudomonas ATH isolates exhibited increased tellurite resistance only in the presence of mercury, especially ATH-43. Determination of the growth curves, minimal inhibitory concentrations and growth inhibition zones showed different tellurite cross-resistance of the ATH strains and suggested a correlation with the presence of a mer operon. On the other hand, reactive oxygen species levels decreased while the thiol content increased when the isolates were grown in the presence of both toxicants. Finally, qPCR determinations of merA, merC and rpoS transcripts from ATH-43 showed a synergic expression pattern upon combined tellurite and mercury treatments. Altogether, the results suggest that mercury could trigger a cell response that confers mercury and tellurite resistance, and that the underlying mechanism participates in protection against oxidative damage.

Topics: Antarctic Regions; Chile; Gene Expression Regulation, Bacterial; Geography; Mercury; Microbial Sensitivity Tests; Phenotype; Phylogeny; Pseudomonas; Reactive Oxygen Species; Real-Time Polymerase Chain Reaction; Sulfhydryl Compounds; Tellurium

The tellurite resistance gene operon (ter) is widely spread among bacterial species, particularly pathogenic species. The ter operon has been implicated in tellurite resistance, phage inhibition, colicine resistance, and pathogenicity. The TerC protein represents one of the key proteins in tellurite resistance and shows no significant homology to any protein of known function. So far, there is no experimental evidence for TerC interaction partners. In this study, proteomic-based methods, including blue native electrophoresis and co-immunoprecipitation combined with LC-MS/MS, have been used to identify TerC interaction partners and thus providing indirect evidence for tentative functions of TerC in Escherichia coli. An interactome has been constructed and robust physical interaction of integral membrane protein TerC with TerB, DctA, PspA, HslU, and RplK has been shown. The TerC-TerB complex appears to act as a central unit that may link different functional modules with biochemical activities of C4-dicarboxylate transport, inner membrane stress response (phage shock protein regulatory complex), ATPase/chaperone activity, and proteosynthesis. In previous reports, it was hypothesized that a transmembrane unit formed by TerC protein may interact with the TerD family, but herein neither TerD nor TerE proteins were identified as TerC complex components. We propose that TerD/TerE participates in tellurite resistance through TerC-independent action.

Topics: Drug Resistance, Bacterial; Escherichia coli; Escherichia coli Proteins; Proteomics; Tellurium

This article reports on the optical characterization of Pr(3) (+) -, Er(3) (+) - and Nd(3) (+) -doped cadmium lead boro tellurite (CLBT) glasses prepared using the melt quenching method. The visible-near infrared (Vis-NIR) absorption spectra of these glasses were analyzed systematically. On measuring the NIR emission spectra of Er(3) (+) :CLBT glasses, a broad emission band centered at 1536 nm ((4) I13 /2  → (4) I15 /2 ) was observed, as were three NIR emission bands at 900 nm ((4) F3 /2  → (4) I9 /2 ), 1069 nm ((4) F3 /2  → (4) I11 /2 ) and 1338 nm ((4) F3 /2  → (4) I13 /2 ) from Nd(3) (+) :CLBT glasses and an NIR emission band at 1334 nm ((1) G4  → (3) H5 ) from Pr(3) (+) :CLBT glasses at an excitation wavelength (λex ) of 514.5 nm (Ar(+) laser). Copyright © 2016 John Wiley & Sons, Ltd.

Topics: Boron; Cadmium; Erbium; Glass; Luminescence; Optics and Photonics; Praseodymium; Tellurium

This Letter presents a novel type of single-crystalline tellurite optical fiber (SC-TOF) for potential hydrophonic applications. Both single-mode and multimode SC-TOF were fabricated. Compared with conventional devices, our preliminary results indicate that the novel device has considerably wider sensing ranges of acoustic frequency (10 Hz to 5.6 MHz or more), acoustic intensity (70 to -236  dB), and directional sensitivity (0.094 to 0.04  nm/deg) to the incident direction of an acoustic wave in a SC-TOF.

Topics: Acoustics; Optical Fibers; Optical Phenomena; Tellurium

A novel cellulose (Cell) derivative, sodium-tellurato (Cell-TeO(OH)4(ONa)/Cell-Cl), has been synthesized from the reaction of 6-chloro-6-deoxycellulose (Cell-Cl) with telluric acid in the presence of sodium hydroxide. The subsequent reaction of this polymeric material with chromium(III) in aqueous solution yields the [Cr(Cell-TeO3(OH)3/Cell-Cl)(Cell-TeO2(OH)4/Cell-Cl)(H2O)3] complex. The molecular structures and morphology of the new polymer and the Cr(III) complex have been examined using elemental analysis, solid-state (13)C NMR, UV-vis, XRD and FTIR spectroscopy, and SEM-EDX, TGA and magnetic measurements. The results are considered to be consistent with the formulations proposed. The deprotonation constants of the modified cellulose and the stability constant of the Cr(III) complex have been determined by pH-metric measurements.

Topics: Cellulose; Chromium; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Polymers; Protons; Tellurium

Detection of Shiga toxin-producing Escherichia coli (STEC) has evolved significantly since the introduction of sorbitol-MacConkey agar. This study compares four chromogenic media (CHROMagar™ STEC, Rainbow® O157 agar, CHROMagar™ O157, and Colorex® O157) in their identification of non-O157 STEC. When 161 non-O157 STEC were directly inoculated onto each medium, detection rates on CHROMagar™ STEC, Rainbow® O157 agar, CHROMagar™ O157 and Colorex® O157 were 90%, 70%, 3.7% and 6.8%, respectively. Tellurite minimal inhibitory concentrations (MICs) correlated with growth on CHROMagar™ STEC as 20 of 22 isolates with poor or no growth had MICs ≤1μg/mL. Stool spiking experiments revealed that CHROMagar™ STEC had the highest recovery of the six most common non-O157 STEC, ranging from 30% (in mucoid stool) to 98% (in watery stool). When using clinical stool samples, CHROMagar™ STEC had a sensitivity, specificity, positive predictive value, and negative predictive value of 84.6%, 87%, 13.9%, and 99.6%, respectively.

Topics: Anti-Bacterial Agents; Bacteriological Techniques; Chromogenic Compounds; Culture Media; Escherichia coli Infections; Humans; Microbial Sensitivity Tests; Predictive Value of Tests; Sensitivity and Specificity; Shiga-Toxigenic Escherichia coli; Tellurium

The comparative tests of growth mediums for isolation and accumulation of diphtheria bacteria were implemented. The testing consisted of six series of growth medium "Corynebacagar" produced by the state research center of applied microbiology and biotechnology and three series of blood tellurite agar. The concluding results of identification of biological indicators of all series of growth nutrient mediums are presented The "Corynebacagar" is recommended for application in health care practice for primary inoculation of pathological material during implementation of cultural analysis on diphtheria.

Topics: Agar; Corynebacterium diphtheriae; Culture Media; Diphtheria; Humans; Tellurium

The oxyanion tellurite (TeO

Topics: Bacterial Proteins; Biological Transport, Active; Escherichia coli; Monocarboxylic Acid Transporters; Protein Multimerization; Protein Structure, Secondary; Rhodobacter capsulatus; Tellurium

Hypermethylated cancer populations are hard to treat due to their enhanced chemo-resistance, characterized by aberrant methylated DNA subunits. Herein, we report on invoking response from such a cancer lineage to chemotherapy utilizing multifunctional copper telluride (Cu

Topics: Antineoplastic Agents; Breast Neoplasms; Cell Line, Tumor; Contrast Media; Copper; Drug Carriers; Drug Resistance, Multiple; Drug Therapy, Combination; Female; Humans; Hyperthermia, Induced; Models, Biological; Nanostructures; Photoacoustic Techniques; Photochemotherapy; Photosensitizing Agents; Tellurium; Theranostic Nanomedicine; X-Rays

Ho(3+)/Yb(3+) codoped TeO₂-WO₃-ZnO-ZnX₂(X=F, Cl) glasses were prepared by melt-quenching method. The absorption spectra, transmittance spectra, X-ray diffraction (XRD) curves, Raman spectra and mid-infrared fluorescence spectra were measured, along with the Judd-Ofelt intensity parameters, stimulated emission and absorption cross-sections were calculated to evaluate the effects of halide amount of the spectroscopic properties. It is shown that the introduction of an appropriate amount of halide can further improve the mid-infrared fluorescence intensity through an enhanced phonon-assisted energy transfer between Ho(3+)/Yb(3+) ions and the energy transfer mechanisms are investigated quantitatively in detail by calculating energy transfer microparameters and phonon contribution ratios. The results indicate that this kind of glasses is a promising material for mid-infrared optical fiber.

Topics: Energy Transfer; Fluorescence; Glass; Halogenation; Holmium; Tellurium; X-Ray Diffraction; Ytterbium

Oxidative stress resistant Deinococcus radiodurans surprisingly exhibited moderate sensitivity to tellurite induced oxidative stress (LD50 = 40 μM tellurite, 40 min exposure). The organism reduced 70% of 40 μM potassium tellurite within 5 h. Tellurite exposure significantly modulated cellular redox status. The level of ROS and protein carbonyl contents increased while the cellular reduction potential substantially decreased following tellurite exposure. Cellular thiols levels initially increased (within 30 min) of tellurite exposure but decreased at later time points. At proteome level, tellurite resistance proteins (TerB and TerD), tellurite reducing enzymes (pyruvate dehydrogense subunits E1 and E3), ROS detoxification enzymes (superoxide dismutase and thioredoxin reductase), and protein folding chaperones (DnaK, EF-Ts, and PPIase) displayed increased abundance in tellurite-stressed cells. However, remarkably decreased levels of key metabolic enzymes (aconitase, transketolase, 3-hydroxy acyl-CoA dehydrogenase, acyl-CoA dehydrogenase, electron transfer flavoprotein alpha, and beta) involved in carbon and energy metabolism were observed upon tellurite stress. The results demonstrate that depletion of reduction potential in intensive tellurite reduction with impaired energy metabolism lead to tellurite toxicity in D. radiodurans.

Topics: Bacterial Proteins; Deinococcus; Energy Metabolism; Oxidation-Reduction; Oxidative Stress; Reactive Oxygen Species; Sulfhydryl Compounds; Tellurium

Escherichia coli exposed to tellurite shows augmented membrane lipid peroxidation and ROS content. Also, reduced thiols, protein carbonylation, [Fe-S] center dismantling, and accumulation of key metabolites occur in these bacteria. In spite of this, not much is known about tellurite effects on the E. coli electron transport chain (ETC). In this work, tellurite-mediated damage to the E. coli ETC's NADH dehydrogenases and terminal oxidases was assessed. Mutant lacking ETC components showed delayed growth, decreased oxygen consumption and increased ROS in the presence of the toxicant. Membranes from tellurite-exposed E. coli exhibited decreased oxygen consumption and dNADH/NADH dehydrogenase activity, showing an impairment of NDH-I but not of NDH-II activity. Regarding terminal oxidases, only the bo oxidase complex was affected by tellurite. When assaying NDH-I and NDH-II activity in the presence of superoxide, the NDH-I complex was preferentially damaged. The activity was partly restored in the presence of reducing agents, sulfide and Fe(2+) under anaerobic conditions, suggesting that damage affects NDH-I [4Fe-4S] centers. Finally, augmented membrane protein oxidation along with reduced oxidase activity was observed in the presence of the toxicant. Also, the increased expression of genes encoding alternative terminal oxidases probably reflects a cell's change towards anaerobic respiration when facing tellurite.

Topics: Aerobiosis; Anaerobiosis; Cell Membrane; Escherichia coli; Escherichia coli Proteins; Gene Expression Regulation, Bacterial; Isoenzymes; NADH Dehydrogenase; Oxidation-Reduction; Oxidoreductases; Oxygen Consumption; Protein Carbonylation; Superoxides; Tellurium

Tellurite-based selective growth media are used for several bacterial pathogens. We found that, in Klebsiella pneumoniae, tellurite resistance is strongly associated with hypervirulent clonal group 23 (CG23), CG65, and CG86, providing a novel approach for screening environmental or carriage samples. The terW gene was also associated with these groups.

Topics: Anti-Bacterial Agents; Culture Media; Drug Resistance, Bacterial; Klebsiella pneumoniae; Tellurium; Virulence

Stress response plays an important role on microbial adaptation under hostile environmental conditions. It is generally unclear how the signaling transduction pathway mediates a stress response in planktonic and biofilm modes of microbial communities simultaneously. Here, we showed that metalloid tellurite (TeO3(2-)) exposure induced the intracellular content of the secondary messenger cyclic di-GMP (c-di-GMP) of Pseudomonas aeruginosa. Two diguanylate cyclases (DGCs), SadC and SiaD, were responsible for the increased intracellular content of c-di-GMP. Enhanced c-di-GMP levels by TeO3(2-) further increased P. aeruginosa biofilm formation and resistance to TeO3(2-). P. aeruginosa ΔsadCΔsiaD and PAO1/p(lac)-yhjH mutants with low intracellular c-di-GMP content were more sensitive to TeO3(2-) exposure and had low relative fitness compared to the wild-type PAO1 planktonic and biofilm cultures exposed to TeO3(2-). Our study provided evidence that c-di-GMP level can play an important role in mediating stress response in microbial communities during both planktonic and biofilm modes of growth.

Topics: Bacterial Proteins; Biofilms; Cyclic GMP; Drug Resistance, Bacterial; Escherichia coli Proteins; Microscopy, Electron, Scanning; Phosphorus-Oxygen Lyases; Proteome; Pseudomonas aeruginosa; Reactive Oxygen Species; Signal Transduction; Spectrometry, X-Ray Emission; Tellurium

Corynebacterium diphtheriae, the aetiologic agent of diphtheria, also represents a global medical challenge because of the existence of invasive strains as causative agents of systemic infections. Although tellurite (TeO32-) is toxic to most microorganisms, TeO32--resistant bacteria, including C. diphtheriae, exist in nature. The presence of TeO32--resistance (TeR) determinants in pathogenic bacteria might provide selective advantages in the natural environment. In the present study, we investigated the role of the putative TeR determinant (CDCE8392_813gene) in the virulence attributes of diphtheria bacilli. The disruption of CDCE8392_0813 gene expression in the LDCIC-L1 mutant increased susceptibility to TeO32- and reactive oxygen species (hydrogen peroxide), but not to other antimicrobial agents. The LDCIC-L1 mutant also showed a decrease in both the lethality of Caenorhabditis elegans and the survival inside of human epithelial cells compared to wild-type strain. Conversely, the haemagglutinating activity and adherence to and formation of biofilms on different abiotic surfaces were not regulated through the CDCE8392_0813 gene. In conclusion, the CDCE8392_813 gene contributes to the TeR and pathogenic potential of C. diphtheriae.

Topics: Animals; Anti-Bacterial Agents; Bacterial Adhesion; Bacterial Proteins; Caenorhabditis elegans; Corynebacterium diphtheriae; Epithelial Cells; Humans; Microbial Sensitivity Tests; Tellurium; Virulence; Virulence Factors

Ho(3+)-doped and Ho(3+)/Yb(3+)-codoped multicomponent germanium tellurite (MGT) glasses with multifarious emission channels in the near-infrared wavelength region have been fabricated and characterized. Judd-Ofelt intensity parameters of Ho(3+)-doped MGT glasses are solved to be Ω2=5.32×10(-20)  cm(2), Ω(4)=2.73×10(-20)  cm(2), and Ω(6)=1.12×10(-20)  cm(2), indicating a higher asymmetric and stronger covalent environment around Ho(3+) ions in MGT glasses. Efficient infrared fluorescences have been observed in MGT glasses, and spontaneous emission probabilities are derived to be 230.4, 79.9, and 138.3  s(-1) for the (5)I(6)→(5)I(8), ((5)F(4),(5)S(2))→(5)I(5), and (5)I(7)→(5)I(8) radiative transitions, respectively. In Ho(3+)/Yb(3+)-codoped MGT glasses, the maximum stimulated emission cross-section of 2.0 μm emission is calculated to be 4.93×10(-21)  cm(2), and the corresponding gain cross-section is derived to be 3.62×10(-21)  cm(2) when the excited state population fraction P reaches 0.8. Multifarious infrared emissions show that Ho(3+) in MGT glasses is a good candidate for optical amplifiers and optoelectronic devices.

Topics: Equipment Design; Fluorescence; Germanium; Glass; Holmium; Hot Temperature; Infrared Rays; Luminescence; Optical Devices; Optics and Photonics; Probability; Spectrophotometry; Spectroscopy, Fourier Transform Infrared; Tellurium; Temperature; Ytterbium

The tellurium oxyanion tellurite is harmful for most microorganisms. Since its toxicity occurs chiefly once the toxicant reaches the intracellular compartment, unveiling the toxicant uptake process is crucial for understanding the whole phenomenon of tellurium toxicity. While the PitA phosphate transporter is thought to be one of the main paths responsible for toxicant entry into Escherichia coli, genetic and physiological evidence have identified the ActP acetate carrier as the main tellurite importer in Rhodobacter capsulatus. In this work, new background on the role of these transporters in tellurite uptake by E. coli is presented. It was found that, similar to what occurs in R. capsulatus, ActP is able to mediate toxicant entry to this bacterium. Lower reactive oxygen species levels were observed in E. coli lacking the actP gene. Antioxidant enzyme catalase and fumarase C activity was almost unchanged after short exposure of E. coli ΔactP to sublethal tellurite concentrations, suggesting a low antioxidant response. In this strain, tellurite uptake decreased significantly during the first 5 min of exposure and inductively coupled plasma optical emission spectroscopy assays using an actP-overexpressing strain confirmed that this carrier mediates toxicant uptake. Relative gene expression experiments by qPCR showed that actP expression is enhanced at short times of tellurite exposure, while pitA and pitB genes are induced later. Summarizing, the results show that ActP is involved in tellurite entry to E. coli and that its participation occurs mainly at early stages of toxicant exposure.

Topics: Biological Transport; Escherichia coli; Escherichia coli Proteins; Gene Deletion; Gene Expression Profiling; Monocarboxylic Acid Transporters; Phosphate Transport Proteins; Real-Time Polymerase Chain Reaction; Tellurium; Transcriptional Activation

Exposure to the tellurium oxyanion tellurite (TeO3(2-)) results in the establishment of an oxidative stress status in most microorganisms. Usually, bacteria growing in the presence of the toxicant turn black because of the reduction of tellurite (Te(4+)) to the less-toxic elemental tellurium (Te(0)). In vitro, at least part of tellurite reduction occurs enzymatically in a nicotinamide dinucleotide-dependent reaction. In this work, we show that TeO3(2-) reduction by crude extracts of Escherichia coli overexpressing the zwf gene (encoding glucose-6-phosphate dehydrogenase) takes place preferentially in the presence of NADPH instead of NADH. The enzyme responsible for toxicant reduction was identified as 6-phosphogluconate dehydrogenase (Gnd). The gnd gene showed a subtle induction at short times after toxicant exposure while strains lacking gnd were more susceptible to the toxicant. These results suggest that both NADPH-generating enzymes from the pentose phosphate shunt may be involved in tellurite detoxification and resistance in E. coli.

Topics: Drug Resistance, Bacterial; Escherichia coli; Inactivation, Metabolic; NADP; Oxidation-Reduction; Phosphogluconate Dehydrogenase; Tellurium

The newly discovered strain CM-3, a Gram-negative, rod-shaped bacterium from gold mine tailings of the Central Mine in Nopiming Provincial Park, Canada, is capable of dissimilatory anaerobic reduction of tellurite, tellurate, and selenite. CM-3 possesses very high level resistance to these oxides, both aerobically and anaerobically. During aerobic growth, tellurite and tellurate resistance was up to 1500 and 1000 µg/ml, respectively. In the presence of selenite, growth occurred at the highest concentration tested, 7000 µg/ml. Under anaerobic conditions, resistance was decreased to 800 µg/ml for the Te oxides; however, much like under aerobic conditions, growth with selenite still took place at 7000 µg/ml. In the absence of oxygen, CM-3 couples oxide reduction to an increase in biomass. Following an initial drop in viable cells, due to switching from aerobic to anaerobic conditions, there was an increase in CFU/ml greater than one order of magnitude in the presence of tellurite (6.6 × 10(3)-8.6 × 10(4) CFU/ml), tellurate (4.6 × 10(3)-1.4 × 10(5) CFU/ml), and selenite (2.7 × 10(5)-5.6 × 10(6) CFU/ml). A control culture without metalloid oxides showed a steady decrease in CFU/ml with no recovery. ATP production was also increased in the presence of each oxide, further indicating anaerobic respiration. Partial 16S rRNA gene sequencing revealed a 99.0 % similarity of CM-3 to Pseudomonas reactans.

Topics: Adenosine Triphosphate; Bacteria, Anaerobic; Base Sequence; Cell Respiration; Geologic Sediments; Gold; Mining; Molecular Sequence Data; Phylogeny; Pseudomonas; RNA, Ribosomal, 16S; Selenious Acid; Tellurium

A turnkey fiber laser source generating high-quality pulses with a spectral sech shape and Fourier transform-limited duration of order 100 fs widely tunable in the 1.6-2.65 μm range is presented. It is based on Raman soliton self-frequency shifting in the suspended-core microstructured TeO2-WO3-La2O3 glass fiber pumped by a hybrid Er/Tm fiber system. Detailed experimental and theoretical studies, which are in a very good agreement, of nonlinear pulse dynamics in the tellurite fiber with carefully measured and calculated parameters are reported. A quantitatively verified numerical model is used to show Raman soliton shift in the range well beyond 3 μm for increased pump energy.

Topics: Infrared Rays; Lasers; Nonlinear Dynamics; Optical Fibers; Spectrum Analysis, Raman; Tellurium

The recently annotated genome of the bacterium Cronobacter sakazakii BAA-894 suggests that the organism has the ability to bind heavy metals. This study demonstrates heavy metal tolerance in C. sakazakii, in which proteins with the heavy metal interaction were recognized by computational and experimental study. As the result, approximately one-fourth of proteins encoded on the plasmid pESA3 are proposed to have potential interaction with heavy metals. Interaction between heavy metals and predicted proteins was further corroborated using protein crystal structures from protein data bank database and comparison of metal-binding ligands. In addition, a phylogenetic study was undertaken for the toxic heavy metals, arsenic, cadmium, lead and mercury, which generated relatedness clustering for lead, cadmium and arsenic. Laboratory studies confirmed the organism's tolerance to tellurite, copper and silver. These experimental and computational study data extend our understanding of the genes encoding for proteins of this important neonatal pathogen and provide further insights into the genotypes associated with features that can contribute to its persistence in the environment. The information will be of value for future environmental protection from heavy toxic metals.

Topics: Amino Acid Sequence; Arsenic; Biodegradation, Environmental; Cadmium; Cluster Analysis; Copper; Cronobacter sakazakii; Drug Resistance, Bacterial; Lead; Mercury; Metals, Heavy; Phylogeny; Plasmids; Silver; Tellurium

Corynebacterium diphtheriae strains continue to circulate worldwide causing diphtheria and invasive diseases, such as endocarditis, osteomyelitis, pneumonia and catheter-related infections. Presumptive C. diphtheriae infections diagnosis in a clinical microbiology laboratory requires a primary isolation consisting of a bacterial culture on blood agar and agar containing tellurite (TeO3(2-)). In this study, nine genome sequenced and four unsequenced strains of C. diphtheriae from different sources, including three samples from a recent outbreak in Brazil, were characterized with respect to their growth properties on tellurite-containing agar. Levels of tellurite-resistance (Te(R)) were evaluated by determining the minimum inhibitory concentrations of potassium tellurite (K2TeO3) and by a viability reduction test in solid culture medium with K2TeO3. Significant differences in Te(R) levels of C. diphtheriae strains were observed independent of origin, biovar or presence of the tox gene. Data indicated that the standard initial screening with TeO3(2-)-selective medium for diphtheria bacilli identification may lead to false-negative results in C. diphtheriae diagnosis laboratories.

Topics: Anti-Bacterial Agents; Bacterial Proteins; Corynebacterium diphtheriae; Diphtheria; Drug Resistance, Bacterial; Humans; Microbial Sensitivity Tests; Phylogeny; Tellurium; Virulence Factors

Holmium (Ho3+)-doped fluorotellurite microstructured fibers based on TeO2-BaF2-Y2O3 glasses are fabricated by using a rod-in-tube method. By using a 1.992 μm fiber laser as the pump source, lasing at 2.077 μm is obtained from a 27 cm long Ho3+-doped fluorotellurite microstructured fiber. The maximum unsaturated power is about 161 mW and the corresponding slope efficiency is up to 67.4%. The influence of fiber length on lasing at 2.1 μm is also investigated. Our results show that Ho3+-doped fluorotellurite microstructured fibers are promising gain media for 2.1 μm laser applications.

Topics: Holmium; Lasers; Optical Fibers; Tellurium

Bacillus anthracis, the causative agent of anthrax, relies on multiple virulence factors to subvert the host immune defense. Using Caenorhabditis elegans as an infection model, we screened approximately 5,000 transposon mutants of B. anthracis Sterne for decreased virulence. One of the attenuated mutants resulted in loss of expression of yceG and yceH, the last two genes in a six-gene cluster of tellurite resistance genes. We generated an analogous insertional mutant to confirm the phenotype and characterize the role of yceGH in resistance to host defenses. Loss of yceGH rendered the mutants more sensitive to tellurite toxicity as well as to host defenses such as reactive oxygen species and the cathelicidin family of antimicrobial peptides. Additionally, we see decreased survival in mammalian models of infection, including human whole blood and in mice. We identify a novel role for the yceGH genes in B. anthracis Sterne virulence and suggest that C. elegans is a useful infection model to study anthrax pathogenesis.

Topics: Animals; Anthrax; Bacillus anthracis; Bacterial Proteins; Caenorhabditis elegans; Immunity, Innate; Mutation; Tellurium; Virulence; Virulence Factors

Tellurite, the most soluble tellurium oxyanion, is extremely harmful for most microorganisms. Part of this toxicity is due to the generation of reactive oxygen species that in turn cause oxidative stress. However, the way in which tellurite interferes with cellular processes is not well understood to date. Looking for new cellular tellurite targets, we decided to evaluate the functioning of the electron transport chain in tellurite-exposed cells. In this communication we show that the E. coli ndh gene, encoding NDH-II dehydrogenase, is significantly induced in toxicant-exposed cells and that the enzyme displays tellurite-reducing activity that results in increased superoxide levels in vitro.

Topics: Cell Membrane; Escherichia coli; Oxidation-Reduction; Oxidoreductases; Superoxides; Tellurium

2.0 μm emission property of a new germanate-tellurite (GT) glass with Ho³⁺/Yb³⁺ codoping is synthesized and analyzed. Efficient 2.0 μm emission of Ho³⁺ ions sensitized by Yb³⁺ ions from the host glass was observed under 980 nm pumping. Based on the measured absorption spectra, the Judd-Ofelt parameters were calculated and discussed. The maximum emission cross section of Ho³⁺ ions transition is 4.36×10(-21) cm2 around 2.0 μm. The energy transfer efficiency is calculated and fitted the decay signals. The good spectroscopic properties suggest that Ho³⁺/Yb³⁺-codoped GT glass may become an attractive host for developing solid state lasers operating in the mid-infrared.

Topics: Energy Transfer; Equipment Design; Equipment Failure Analysis; Germanium; Glass; Holmium; Lasers, Solid-State; Luminescence; Tellurium; Ytterbium

The dihydrolipoamide dehydrogenase (LpdA) from the tellurite-resistant bacterium Aeromonas caviae ST reduces tellurite to elemental tellurium. To characterize this NADH-dependent activity, the A. caviae lpdA gene was subjected to site-directed mutagenesis and genes containing C45A, H322Y and E354K substitutions were individually transformed into Escherichia coli Δlpd. Cells expressing the modified genes exhibited decreased pyruvate dehydrogenase, dihydrolipoamide dehydrogenase and TR activity regarding that observed with the wild type A. caviae lpdA gene. In addition, cells expressing the altered lpdA genes showed increased oxidative stress levels and tellurite sensitivity than those carrying the wild type counterpart. The involvement of Cys residues in LpdA's TR activity was analyzed using specific inhibitors that interact with catalytic cysteines and/or disulfide bridges such as aurothiomalate, zinc or nickel. TR activity of purified LpdA was drastically affected by these compounds. Since LpdA belongs to the flavoprotein family, the involvement of the FAD/NAD(P)(+)-binding domain in TR activity was determined. FAD removal from purified LpdA results in loss of TR activity, which was restored with exogenously added FAD. Substitutions in E354, involved in FAD/NADH binding, resulted in low TR activity because of flavin loss. Finally, changing H322 (involved in NAD(+)/NADH binding) by tyrosine also resulted in altered TR activity.

Topics: Aeromonas caviae; Dihydrolipoamide Dehydrogenase; Escherichia coli; Gene Expression Regulation, Bacterial; Mutagenesis, Site-Directed; Oxidation-Reduction; Tellurium

Ba-La-tellurite glasses doped with Yb(3+) ions have been prepared through melt quenching technique by modifying their composition with the inclusion of varied concentration of Al2O3 to elucidate its effects on glass structural, elastic, thermal properties and Yb(3+) ion NIR luminescence performance. The FTIR spectral analysis indicates Al2O3 addition is promoting the conversion of BOs from NBOs which have been generated during the process of depolymerisation of main glass forming TeO4 units. The elastic properties of the glass revealed an improved rigidity of the glass network on addition of Al2O3. In concurrence to this, differential thermal analysis showed an increase in glass transition temperature with improved thermal stability factor. Also, Yb(3+) fluorescence dynamics demonstrated that, Al2O3 inclusion helps in restraining the detrimental radiation trapping of ∼1μm emission.

Topics: Aluminum Oxide; Barium; Elasticity; Glass; Lanthanum; Luminescence; Radiation; Tellurium; Thermodynamics; Transition Temperature; Ytterbium

Oxyanions of tellurium, like tellurate (TeO4 (2-)) and tellurite (TeO3 (2-)), are highly toxic for most microorganisms. There are a few reports on the bacterial tellurite resistance mechanism(s). Salinicoccus iranensis, a Gram-positive halophilic bacterium, shows high tellurite resistance and NADH-dependent tellurite reduction activity in vitro. Since little is known regarding TeO3 (2-) resistance mechanisms in halophilic microorganisms, here one of the enzymatic reduction activities presented in this microorganism is investigated. To enhance the enzymatic activity during purification, the effect of different parameters including time, inoculation, different pHs, different tellurite concentrations and different salts were optimized. We also examined the tellurite removal rates by diethyldithiocarbamate (DDTC) during optimization. In the culture medium the optimum conditions obtained showed that at 30 h, 2 % inoculum, pH 7.5, without tellurite and with 5 % NaCl (w/v) the highest enzyme activity and tellurite removal were observed. Results of the purification procedure done by hydroxyapatite batch-mode, ammonium sulfate precipitation, followed by phenyl-Sepharose and Sephadex G-100 column chromatography, showed that the enzyme consisted of three subunits with molecular masses of 135, 63 and 57 kDa. In addition to tellurite reduction activity, the enzyme was able to reduce nitrate too. Our study extends the knowledge regarding this process in halophilic microorganisms. Besides, this approach may suggest an application for the organism or the enzyme itself to be used for bioremediation of polluted areas with different contaminants due to its nitrate reductase activity.

Topics: Bacterial Proteins; Biotransformation; Salt Tolerance; Staphylococcaceae; Tellurium

Tellurite (TeO3(2-)) is harmful for most microorganisms, especially Gram-negative bacteria. Even though tellurite toxicity involves a number of individual aspects, including oxidative stress, malfunctioning of metabolic enzymes and a drop in the reduced thiol pool, among others, the general mechanism of toxicity is rather complex and not completely understood to date. This work focused on DNA microarray analysis to evaluate the Escherichia coli global transcriptomic response when exposed to the toxicant. Confirming previous results, the induction of the oxidative stress response regulator soxS was observed. Upregulation of a number of genes involved in the global stress response, protein folding, redox processes and cell wall organization was also detected. In addition, downregulation of aerobic respiration-related genes suggested a metabolic switch to anaerobic respiration. The expression results were validated through oxygen consumption experiments, which corroborated that tellurite-exposed cells effectively consume oxygen at lower rates than untreated controls.

Topics: Anaerobiosis; Escherichia coli; Gene Expression Profiling; Microarray Analysis; Oxygen; Tellurium

Tellurium-based devices, such as photovoltaic (PV) modules and thermoelectric generators, are expected to play an increasing role in renewable energy technologies. Tellurium, however, is one of the scarcest elements in the earth's crust, and current production and recycling methods are inefficient and use toxic chemicals. This study demonstrates an alternative, bacterially mediated tellurium recovery process.. We show that the hydrothermal vent microbe Pseudoalteromonas sp. strain EPR3 can convert tellurium from a wide variety of compounds, industrial sources and devices into metallic tellurium and a gaseous tellurium species. These compounds include metallic tellurium (Te(0)), tellurite (TeO3(2-)), copper autoclave slime, tellurium dioxide (TeO2), tellurium-based PV material (cadmium telluride, CdTe) and tellurium-based thermoelectric material (bismuth telluride, Bi2Te3). Experimentally, this was achieved by incubating these tellurium sources with the EPR3 in both solid and liquid media.. Despite the fact that many of these tellurium compounds are considered insoluble in aqueous solution, they can nonetheless be transformed by EPR3, suggesting the existence of a steady state soluble tellurium concentration during tellurium transformation.. These experiments provide insights into the processes of tellurium precipitation and volatilization by bacteria, and their implications on tellurium production and recycling.

Topics: Bismuth; Cadmium Compounds; Pseudoalteromonas; Tellurium

Tellurium, a metalloid belonging to group 16 of the periodic table, displays very interesting physical and chemical properties and lately has attracted significant attention for its use in nanotechnology. In this context, the use of microorganisms for synthesizing nanostructures emerges as an eco-friendly and exciting approach compared to their chemical synthesis. To generate Te-containing nanostructures, bacteria enzymatically reduce tellurite to elemental tellurium. In this work, using a classic biochemical approach, we looked for a novel tellurite reductase from the Antarctic bacterium Pseudomonas sp. strain BNF22 and used it to generate tellurium-containing nanostructures. A new tellurite reductase was identified as glutathione reductase, which was subsequently overproduced in Escherichia coli. The characterization of this enzyme showed that it is an NADPH-dependent tellurite reductase, with optimum reducing activity at 30°C and pH 9.0. Finally, the enzyme was able to generate Te-containing nanostructures, about 68 nm in size, which exhibit interesting antibacterial properties against E. coli, with no apparent cytotoxicity against eukaryotic cells.

Topics: Anti-Bacterial Agents; Bacterial Proteins; Biotransformation; Enzyme Stability; Glutathione Reductase; Nanostructures; Oxidation-Reduction; Pseudomonas; Tellurium

Although the novel cadmium-zinc-telluride (CZT) camera system provides excellent image quality, its diagnostic value using thallium-201 as assessed on coronary angiography (CAG) and fractional flow reserve (FFR) has not been validated. METHODS AND RESULTS: To evaluate the diagnostic accuracy of the CZT ultrafast camera system (Discovery NM 530c), 95 patients underwent stress thallium-201 single-photon emission computed tomography (SPECT) and then CAG within 3 months. Image acquisition was performed in the supine and prone positions after stress for 5 and 3 min, respectively, and in the supine position at rest for 10 min. Significant stenosis was defined as ≥90% diameter narrowing on visual estimation, or a lesion with <90% and ≥50% stenosis and FFR ≤0.75. To detect individual coronary stenosis, the respective sensitivity, specificity, and accuracy were 90%, 64%, and 78% for left anterior descending coronary artery stenosis, 78%, 84%, and 81% for left circumflex stenosis, and 83%, 47%, and 60% for right coronary artery (RCA) stenosis. The combination of prone and supine imaging had a higher specificity for RCA disease than supine imaging alone (65% vs. 47%), with an improvement in accuracy from 60% to 72%.. Using thallium-201 with short acquisition time, combined with prone imaging, CZT SPECT had a high diagnostic yield in detecting significant coronary stenosis as assessed using FFR.

Topics: Blood Flow Velocity; Cadmium; Coronary Angiography; Coronary Stenosis; Female; Humans; Male; Middle Aged; Sensitivity and Specificity; Tellurium; Tomography, Emission-Computed, Single-Photon; Zinc

Silver tellurides find applications in the development of infrared detection, imaging, magnetics, sensors, memory devices, and optic materials. However, only a limited number of silver tellurides have been described to date. Laser ablation synthesis (LAS) was selected to generate new Ag-Te clusters.. Isothermal adsorption was used to study the formation of silver nano-particles-tellurium aggregates. Laser desorption ionization quadrupole ion trap time-of-flight mass spectrometry (LDI-QIT-TOFMS) was used for the generation and analysis of Agm Ten clusters. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to visualize the structure of materials. The stoichiometry of the generated clusters was determined by computer modeling of isotopic patterns.. A simple, one-pot method for the preparation of Ag-Te nano-composite was developed and found suitable for LAS of silver tellurides. The LDI of Ag-Te nano-composite leads to the formation of 11 unary and 52 binary clusters. The stoichiometry of the 34 novel Agm Ten clusters is reported here for the first time.. LAS with TOFMS detection was proven to be a powerful technique for the generation of silver telluride clusters. Knowledge of the stoichiometry of the generated clusters might facilitate the further development of novel high-tech silver tellurium nano-materials.

Topics: Ions; Mass Spectrometry; Microscopy, Electron, Scanning; Nanocomposites; Silver; Tellurium

The genetic identity and cofactor composition of the bacterial tellurate reductase are currently unknown. In this study, we examined the requirement of molybdopterin biosynthesis and molybdate transporter genes for tellurate reduction in Escherichia coli K-12. The results show that mutants deleted of the moaA, moaB, moaE, or mog gene in the molybdopterin biosynthesis pathway lost the ability to reduce tellurate. Deletion of the modB or modC gene in the molybdate transport pathway also resulted in complete loss of tellurate reduction activity. Genetic complementation by the wild-type sequences restored tellurate reduction activity in the mutant strains. These findings provide genetic evidence that tellurate reduction in E. coli involves a molybdoenzyme.

Topics: Coenzymes; Enzyme Activation; Escherichia coli K12; Escherichia coli Proteins; Gene Deletion; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Genes, Bacterial; Genetic Complementation Test; Metalloproteins; Molybdenum Cofactors; Protein Transport; Pteridines; Sulfurtransferases; Tellurium

A simple all-solid tellurite microstructured optical fiber which has only one layer of high-index rods in the cladding is proposed and fabricated in the paper. The core and the cladding with the low index are made from the TeO(2)-ZnO-Na(2)O-La(2)O(3) glass, and the high-index rods are made from the TeO(2)-Li(2)O-WO(3)-MoO(3)-Nb(2)O(5) glass. The guiding regime in this fiber can be explained by ARROW model. The fiber can support the near- and mid-infrared light transmitting in the core within the transmission bands while the all-solid silica microstructured optical fiber cannot. When the pump light is outside the transmission bands, the light will transmit in six TLWMN rods.

Topics: Computer Simulation; Equipment Design; Equipment Failure Analysis; Light; Miniaturization; Models, Theoretical; Optical Fibers; Scattering, Radiation; Tellurium

The octave-spanning spectrum was generated in a tellurite glass based microstructured fiber pumped by a 528 MHz repetition rate Yb:fiber ring laser without amplification. The laser achieved 40% output optical-to-optical efficiency with the output power of 410 mW. By adjusting the grating pair in the cavity, this oscillator can work at different cavity dispersion regimes with the shortest dechirped pulse width of 46 fs. The output pulses were then launched into a high-nonlinearity tellurite fiber, which has the zero-dispersion wavelength at ~1 μm. The high nonlinearity coefficient (1348 km⁻¹W⁻¹) and the matched zero-dispersion wavelength with pump laser enable the octave-spanning supercontinuum generated from 750 nm to 1700 nm with the coupled pulse energy above 10 pJ.

Topics: Equipment Design; Equipment Failure Analysis; Fiber Optic Technology; Lasers; Miniaturization; Signal Processing, Computer-Assisted; Telecommunications; Tellurium

We investigated the ballistic imaging technique using femtosecond optical Kerr gate of a tellurite glass. High contrast images of an object hidden behind turbid media were obtained. Compared to the conventional femtosecond optical Kerr gate using fused quartz, the optical Kerr gate using tellurite glass has more capacity to acquire high quality images of the object hidden behind a high optical density turbid medium. The experimental results indicated that the tellurite glass is a good candidate as the optical Kerr material for the ballistic imaging technique due to its large optical nonlinearity.

Topics: Equipment Design; Equipment Failure Analysis; Glass; Image Enhancement; Nephelometry and Turbidimetry; Refractometry; Tellurium; Tomography

In this work we present, for the first time to our knowledge, laser emission under wavelength selective laser-pulsed pumping in Nd(3+)-doped TeO(2)-ZnO-ZnF(2) bulk glass for two different Nd(3+) concentrations. The fluorescence properties of Nd(3+) ions in this matrix which include, Judd-Ofelt calculation, stimulated emission cross-section of the laser transition and lifetimes are also presented. The site-selective emission and excitation spectra along the (4)I(9/2)→(4)F(3/2) absorption band show the inhomogeneous behaviour of the crystal field felt by Nd(3+) ions in this fluorotellurite glass which allows for spectral tuning of the laser output pulse as a function of the pumping wavelength. The emission cross-section obtained from the Judd-Ofelt analysis and spectral data (4.9x10(-20) cm(2)) is in fairly good agreement with the value obtained from the analysis of the laser threshold data (4x10(-20) cm(2)).

Topics: Equipment Design; Equipment Failure Analysis; Fluorine; Glass; Lasers; Materials Testing; Neodymium; Tellurium

Germanium- and tellurium-based glasses have been largely studied due to their recognized potential for photonics. In this paper, we review our recent studies that include the investigation of the Stokes and anti-Stokes photoluminescence (PL) in different glass systems containing metallic and semiconductor nanoparticles (NPs). In the case of the samples with metallic NPs, the enhanced PL was attributed to the increased local field on the rare-earth ions located in the proximity of the NPs and/or the energy transfer from the metallic NPs to the rare-earth ions. For the glasses containing silicon NPs, the PL enhancement was mainly due to the energy transfer from the NPs to the Er(3+) ions. The nonlinear (NL) optical properties of PbO-GeO2 films containing gold NPs were also investigated. The experiments in the pico- and subpicosecond regimes revealed enhanced values of the NL refractive indices and large NL absorption coefficients in comparison with the films without gold NPs. The reported experiments demonstrate that germanate and tellurite glasses, having appropriate rare-earth ions doping and NPs concentration, are strong candidates for PL-based devices, all-optical switches, and optical limiting.

Topics: Germanium; Materials Testing; Metal Nanoparticles; Refractometry; Semiconductors; Tellurium

The reduction of tellurite (Te(IV)) by dissimilatory metal reducing bacterium, Shewanella oneidensis MR-1, was promoted in the presence of Fe(III) in comparison with Te(IV) bioreduction in the absence of Fe(III). Electron microscopic analyses revealed that iron promoted Te(IV) reduction led to form exclusively extracellular crystalline Te(0) nanorods, as compared to the mostly intracellular formation of Te(0) nanorods in the absence of Fe(III). The Te K-edge X-ray absorption spectrometric analyses demonstrated that S. oneidensis MR-1 in the presence of Fe(III) reduced Te(IV) to less harmful metallic Te(0) nanorods through the precipitation of tellurite (Te(IV)Ox) complex by the bacterial respiration of Fe(III) to Fe(II) under anaerobic conditions. However, Fe(II) ion itself was only able to precipitate the solid tellurite (Te(IV)Ox) complex from the Te(IV) solution, which was not further reduced to Te(0). The results clearly indicated that bacterial S. oneidensis MR-1 plays important roles in the reduction and crystallization of Te(0) nanorods by as yet undetermined biochemical mechanisms. As compared to the slow bacterial Te(IV) reduction in the absence of Fe(III), the rapid reduction of Te(IV) to Te(0) by the concerted biogeochemical reaction between Fe(II) and S. oneidensis MR-1 could be applied for the sequestration and detoxification of Te(IV) in the environments as well as for the preparation of extracellular Te(0) nanorod structures.

Topics: Iron; Microscopy, Electron, Transmission; Nanotubes; Oxidation-Reduction; Shewanella; Tellurium; X-Ray Absorption Spectroscopy

Acinetobacter baumannii is an important nosocomial pathogen that has become increasingly resistant to multiple antibiotics. Genetic manipulation of MDR A. baumannii is useful especially for defining the contribution of each active efflux mechanism in multidrug resistance. Existing methods rely on the use of an antibiotic selection marker and are not suited for multiple gene deletions.. A tellurite-resistant (sacB⁺, xylE⁺) suicide vector, pMo130-TelR, was created for deleting the adeFGH and adeIJK operons in two clinical MDR A. baumannii, DB and R2 from Singapore. Using a two-step selection, plasmid insertion recombinants (first-crossover) were selected for tellurite resistance and the deletion mutants (second-crossover) were then selected for loss of sacB. The DNA deletions were verified by PCR while loss of gene expression in the ΔadeFGH, ΔadeIJK and ΔadeFGHΔadeIJK deletion mutants was confirmed using qRT-PCR. The contribution of AdeFGH and AdeIJK pumps to MDR was defined by comparing antimicrobial susceptibilities of the isogenic mutants and the parental strains. The deletion of adeIJK produced no more than eight-fold increase in susceptibility to nalidixic acid, tetracycline, minocycline, tigecycline, clindamycin, trimethoprim and chloramphenicol, while the deletion of adeL-adeFGH operon alone had no impact on antimicrobial susceptibility. Dye accumulation assays using H33342 revealed increased dye retention in all deletion mutants, except for the R2ΔadeFGH mutant, where a decrease was observed. Increased accumulation of ethidium bromide was observed in the parental strains and all pump deletion mutants in the presence of efflux inhibitors. The efflux pump deletion mutants in this study revealed that only the AdeIJK, but not the AdeFGH RND pump, contributes to antimicrobial resistance and dye accumulation in MDR A. baumannii DB and R2.. The marker-less gene deletion method using pMo130-TelR is applicable for creating single and multiple gene deletions in MDR A. baumannii. The adeFGH and adeIJK operons were successfully deleted separately and together using this method and the impact of each efflux pump on antimicrobial resistance could be defined clearly.

Topics: Acinetobacter baumannii; Anti-Bacterial Agents; Drug Resistance, Multiple, Bacterial; Gene Deletion; Genetic Vectors; Genetics, Microbial; Humans; Molecular Biology; Selection, Genetic; Tellurium

Gene cluster "ter" conferring high tellurite resistance has been identified in various pathogenic bacteria including Escherichia coli O157:H7. However, the precise mechanism as well as the molecular function of the respective gene products is unclear. Here we describe protein-protein association and localization analyses of four essential Ter proteins encoded by minimal resistance-conferring fragment (terBCDE) by means of recombinant expression. By using a two-plasmid complementation system we show that the overproduced single Ter proteins are not able to mediate tellurite resistance, but all Ter members play an irreplaceable role within the cluster. We identified several types of homotypic and heterotypic protein-protein associations among the Ter proteins by in vitro and in vivo pull-down assays and determined their cellular localization by cytosol/membrane fractionation. Our results strongly suggest that Ter proteins function involves their mutual association, which probably happens at the interface of the inner plasma membrane and the cytosol.

Topics: Centrifugation; Drug Resistance, Bacterial; Escherichia coli O157; Escherichia coli Proteins; Genes, Essential; Genetic Complementation Test; Multigene Family; Protein Binding; Protein Interaction Mapping; Tellurium

Reactive oxygen species (ROS) damage macromolecules and cellular components in nearly all kinds of cells and often generate toxic intracellular byproducts. In this work, aldehyde generation derived from the Escherichia coli membrane oxidation as well as membrane fatty acid profiles, protein oxidation, and bacterial resistance to oxidative stress elicitors was evaluated. Studies included wild-type cells as well as cells exhibiting a modulated monounsaturated fatty acid (MUFA) ratio. The hydroxyaldehyde 4-hydroxy 2-nonenal was found to be most likely produced by E. coli, whose levels are dependent upon exposure to oxidative stress elicitors. Aldehyde amounts and markers of oxidative damage decreased upon exposure to E. coli containing low MUFA ratios, which was paralleled by a concomitant increase in resistance to ROS-generating compounds. MUFAs ratio, lipid peroxidation, and aldehyde generation were found to be directly related; that is, the lower the MUFAs ratio, the lower the peroxide and aldehyde generation levels. These results provide additional evidence about MUFAs being targets for membrane lipid oxidation and their relevance in aldehyde generation.

Topics: Aldehydes; Escherichia coli; Fatty Acids, Monounsaturated; Membrane Lipids; Oxidation-Reduction; Oxidative Stress; Reactive Oxygen Species; Tellurium

We investigated the Acinetobacter baylyi gene ACIAD1960, known from previous work to be expressed during long-term stationary phase. The protein encoded by this gene had been annotated as a Conserved Hypothetical Protein, surrounded by putative tellurite resistance ("Ter") proteins. Sequence analysis suggested that the protein belongs to the DUF1796 putative papain-like protease family. Here, we show that the purified protein, subsequently named StiP, has cysteine protease activity. Deletion of stiP causes hypersensitivity to tellurite, altered population dynamics during long-term batch culture, and most strikingly, dramatic alteration of normal cell morphology. StiP and associated Ter proteins (the StiP-Ter cluster) are therefore important for regulating cell morphology, likely in response to oxidative damage or depletion of intracellular thiol pools, triggered artificially by tellurite exposure. Our finding has broad significance because while tellurite is an extremely rare compound in nature, oxidative damage, the need to maintain a particular balance of intracellular thiols, and the need to regulate cell morphology are ubiquitous.

Topics: Acinetobacter; Amino Acid Sequence; Bacterial Proteins; Cloning, Molecular; Computational Biology; Cysteine Proteases; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Genes, Bacterial; INDEL Mutation; Multigene Family; Oxidation-Reduction; Protein Structure, Tertiary; Soil Microbiology; Tellurium

Tellurite containing compounds are in use for industrial processes and increasing delivery into the environment generates specific pollution that may well result in contamination and subsequent potential adverse effects on public health. It was the aim of the current study to reveal mechanism of toxicity in tellurite-sensitive and tellurite-resistant E. coli at the protein level. In this work an approach using gel-based mass spectrometrical analysis to identify a differential protein profile related to tellurite toxicity was used and the mechanism of ter operon-mediated tellurite resistance was addressed. E. coli BL21 was genetically manipulated for tellurite-resistance by the introduction of the resistance-conferring ter genes on the pLK18 plasmid. Potassium tellurite was added to cultures in order to obtain a final 3.9 micromolar concentration. Proteins from tellurite-sensitive and tellurite-resistant E. coli were run on 2-D gel electrophoresis, spots of interest were picked, in-gel digested and subsequently analysed by nano-LC-MS/MS (ion trap). In addition, Western blotting and measurement of enzymatic activity were performed to verify the expression of certain candidate proteins. Following exposure to tellurite, in contrast to tellurite-resistant bacteria, sensitive cells exhibited increased levels of antioxidant enzymes superoxide dismutases, catalase and oxidoreductase YqhD. Cysteine desulfurase, known to be related to tellurite toxicity as well as proteins involved in protein folding: GroEL, DnaK and EF-Tu were upregulated in sensitive cells. In resistant bacteria, several isoforms of four essential Ter proteins were observed and following tellurite treatment the abovementioned protein levels did not show any significant proteome changes as compared to the sensitive control. The absence of general defense mechanisms against tellurite toxicity in resistant bacteria thus provides further evidence that the four proteins of the ter operon function by a specific mode of action in the mechanism of tellurite resistance probably involving protein cascades from antioxidant and protein folding pathways.

Topics: Antioxidants; Drug Resistance, Bacterial; Escherichia coli; Escherichia coli Proteins; Protein Folding; Proteome; Tellurium

The constant emergence of antibiotic multi-resistant pathogens is a concern worldwide. An alternative for bacterial treatment using nM concentrations of tellurite was recently proposed to boost antibiotic-toxicity and a synergistic effect of tellurite/cefotaxime (CTX) was described. In this work, the molecular mechanism underlying this phenomenon is proposed. Global changes of the transcriptional profile of Escherichia coli exposed to tellurite/CTX were determined by DNA microarrays. Induction of a number of stress regulators (as SoxS), genes related to oxidative damage and membrane transporters was observed. Accordingly, increased tellurite adsorption/uptake and oxidative injuries to proteins and DNA were determined in cells exposed to the mixture of toxicants, suggesting that the tellurite-mediated CTX-potentiating effect is dependent, at least in part, on oxidative stress. Thus, the synergistic tellurite-mediated CTX-potentiating effect depends on increased tellurite uptake/adsorption which results in damage to proteins, DNA and probably other macromolecules. Our findings represent a contribution to the current knowledge of bacterial physiology under antibiotic stress and can be of great interest in the development of new antibiotic-potentiating strategies.

Topics: Anti-Bacterial Agents; Cefotaxime; Cell Wall; Escherichia coli; Tellurium

Tellurite is toxic to most microorganisms because of its ability to generate oxidative stress. However, the way in which tellurite interferes with cellular processes is not fully understood to date. In this line, it was previously shown that tellurite-exposed cells displayed reduced activity of the α-ketoglutarate dehydrogenase complex (α-KGDH), which resulted in α-ketoglutarate (α-KG) accumulation. In this work, we assessed if α-KG accumulation in tellurite-exposed E. coli could also result from increased isocitrate dehydrogenase (ICDH) and glutamate dehydrogenase (GDH) activities, both enzymes involved in α-KG synthesis. Unexpectedly both activities were found to decrease in the presence of the toxicant, an observation that seems to result from the decreased transcription of icdA and gdhA genes (encoding ICDH and GDH, resp.). Accordingly, isocitrate levels were found to increase in tellurite-exposed E. coli. In the presence of the toxicant, cells lacking icdA or gdhA exhibited decreased reactive oxygen species (ROS) levels and higher tellurite sensitivity as compared to the wild type strain. Finally, a novel branch activity of ICDH as tellurite reductase is presented.

Topics: Escherichia coli; Isocitrate Dehydrogenase; Ketoglutarate Dehydrogenase Complex; Ketoglutaric Acids; Oxidation-Reduction; Oxidative Stress; Oxidoreductases; Reactive Oxygen Species; Tellurium; Transcription, Genetic

Glasses with chemical composition of (62-x) TeO(2)+25 ZnO+8 K(2)O+5 CaO+x Sm(2)O(3) (TZKCSmx; x=0.1, 0.5, 1.0, 1.5 mol%) were prepared by melt quenching technique. The absorption spectrum was recorded in the UV-visible and NIR regions. The oscillator strengths of absorption bands were obtained by measuring the area under the bands. Judd-Ofelt analysis has been carried out to estimate the host dependent J-O intensity Ω(λ) (λ=2, 4, 6) parameters by least squares fitting approach. Photoluminescence spectra recorded in the visible region revealed intense green, orange and red emission bands in all the glasses, corresponding to the (4)G(5/2)→(6)H(5/2), (4)G(5/2)→(6)H(7/2) and (4)G(5/2)→(6)H(9/2) transitions respectively. From the emission spectra and J-O intensity parameters, various radiative parameters were calculated from the excited (4)G(5/2) to the lower lying (6)H(J) (J=5/2, 7/2, 9/2, 11/2) multiplet. Quenching of luminescence with the increase of Sm(3+) ions concentration has been observed. Decay times of excited (4)G(5/2) state decrease with the increase of the Sm(3+) ions concentration. The energy transfer mechanism that leads to the quenching of (4)G(5/2) state lifetime has been discussed. Inokuti-Hirayama (I-H) model was used to evaluate various energy transfer parameters, which are the qualitative indicators for the interaction among Sm(3+) ions.

Topics: Absorption; Energy Transfer; Glass; Luminescence; Samarium; Spectrometry, Fluorescence; Spectrophotometry, Ultraviolet; Spectroscopy, Near-Infrared; Tellurium; Thermodynamics

Mid-infrared fiber optical parametric oscillators (MIR FOPOs) based on the degenerate four-wave mixing (DFWM) of tellurite photonic crystal fibers (PCFs) are proposed and modeled for the first time. Using the DFWM coupled-wave equations, numerical simulations are performed to analyze the effects of tellurite PCFs, single-resonant cavity, and pump source on the MIR FOPO performances. The numerical results show that: (1) although a longer tellurite PCF can decrease the pump threshold of MIR FOPOs to a few watts only, the high conversion-efficiency of MIR idler usually requires a short-length optimum PCF with low loss; (2) compared with the single-pass DFWM configurations of the MIR fiber sources published previously, the stable oscillation of signal light in single-resonant cavity can significantly promote the MIR idler output efficiency. With a suggested tellurite PCF as parametric gain medium, the theoretical prediction indicates that such a MIR FOPO could obtain a wide MIR-tunable range and a high conversion efficiency of more than 10%.

Topics: Amplifiers, Electronic; Computer Simulation; Computer-Aided Design; Equipment Design; Equipment Failure Analysis; Fiber Optic Technology; Infrared Rays; Light; Models, Theoretical; Numerical Analysis, Computer-Assisted; Oscillometry; Photons; Scattering, Radiation; Tellurium

Staphylococcus aureus CstR (CsoR-like sulfur transferase repressor) is a member of the CsoR family of transition metal sensing metalloregulatory proteins. Unlike CsoR, CstR does not form a stable complex with transition metals but instead reacts with sulfite to form a mixture of di- and trisulfide species, CstR2(RS-SR') and CstR2(RS-S-SR')n)n=1 or 2, respectively. Here, we investigate if CstR performs similar chemistry with related chalcogen oxyanions selenite and tellurite. In this work we show by high resolution tandem mass spectrometry that CstR is readily modified by selenite (SeO3(2-)) or tellurite (TeO3(2-)) to form a mixture of intersubunit disulfides and selenotrisulfides or tellurotrisulfides, respectively, between Cys31 and Cys60'. Analogous studies with S. aureus CsoR reveals no reaction with selenite and minimal reaction with tellurite. All cross-linked forms of CstR exhibit reduced DNA binding affinity. We show that Cys31 initiates the reaction with sulfite through the formation of S-sulfocysteine (RS-SO3(2-)) and Cys60 is required to fully derivatize CstR to CstR2(RS-SR') and CstR2(RS-S-SR'). The modification of Cys31 also drives an allosteric switch that negatively regulates DNA binding while derivatization of Cys60 alone has no effect on DNA binding. These results highlight the differences between CstRs and CsoRs in chemical reactivity and metal ion selectivity and establish Cys31 as the functionally important cysteine residue in CstRs.

Topics: Amino Acid Sequence; Bacterial Proteins; Chromatography, Liquid; Cross-Linking Reagents; Crystallography, X-Ray; Cysteine; DNA, Bacterial; Fluorescence Polarization; Kinetics; Molecular Sequence Data; Molecular Weight; Mutant Proteins; Mycobacterium tuberculosis; Peptides; Protein Binding; Sodium Selenite; Spectrometry, Mass, Electrospray Ionization; Staphylococcus aureus; Sulfides; Tandem Mass Spectrometry; Tellurium

The effects of selenite and tellurite on the mammalian enzyme lipoamide dehydrogenase were compared. Selenite acts as a substrate of lipoamide dehydrogenase in a process requiring the presence of lipoamide. In contrast, tellurite is a potent inhibitor, effective in the low micromolar range. The inhibitory effect of tellurite on lipoamide dehydrogenase is partially reverted by dithiothreitol indicating the participation of the thiol groups of the enzyme. Tellurite, but not selenite, stimulates the diaphorase activity of lipoamide dehydrogenase. In a mitochondrial matrix protein preparation, which contains lipoamide dehydrogenase, an inhibitory action similar to that observed on the purified enzyme was also elicited by tellurite. Human embryonic kidney cells (HEK 293 T) treated with tellurite show a partial inhibition of lipoamide dehydrogenase. In addition to the toxicological implications of tellurium compounds, the reported results suggest that tellurite and its derivatives can be used as potential tools for studying biochemical reactions.

Topics: Animals; Dihydrolipoamide Dehydrogenase; Enzyme Activators; HEK293 Cells; Humans; Oxidation-Reduction; Sodium Selenite; Sulfhydryl Compounds; Swine; Tellurium

Pathogen resistance to antibiotics is a rapidly growing problem, leading to an urgent need for novel antimicrobial agents. Unfortunately, development of new antibiotics faces numerous obstacles, and a method that resensitizes pathogens to approved antibiotics therefore holds key advantages. We present a proof of principle for a system that restores antibiotic efficiency by reversing pathogen resistance. This system uses temperate phages to introduce, by lysogenization, the genes rpsL and gyrA conferring sensitivity in a dominant fashion to two antibiotics, streptomycin and nalidixic acid, respectively. Unique selective pressure is generated to enrich for bacteria that harbor the phages carrying the sensitizing constructs. This selection pressure is based on a toxic compound, tellurite, and therefore does not forfeit any antibiotic for the sensitization procedure. We further demonstrate a possible way of reducing undesirable recombination events by synthesizing dominant sensitive genes with major barriers to homologous recombination. Such synthesis does not significantly reduce the gene's sensitization ability. Unlike conventional bacteriophage therapy, the system does not rely on the phage's ability to kill pathogens in the infected host, but instead, on its ability to deliver genetic constructs into the bacteria and thus render them sensitive to antibiotics prior to host infection. We believe that transfer of the sensitizing cassette by the constructed phage will significantly enrich for antibiotic-treatable pathogens on hospital surfaces. Broad usage of the proposed system, in contrast to antibiotics and phage therapy, will potentially change the nature of nosocomial infections toward being more susceptible to antibiotics rather than more resistant.

Topics: Anti-Bacterial Agents; Bacteria; Bacteriophages; DNA Gyrase; Drug Resistance, Bacterial; Genes, Bacterial; Genes, Dominant; Lysogeny; Nalidixic Acid; Recombinant Proteins; Ribosomal Proteins; Selection, Genetic; Streptomycin; Tellurium

To unveil the metabolic impact of tellurite in the bacterial cell, the effect of this toxicant on the expression and activity of key enzymes of the Escherichia coli glycolytic pathway was analyzed. E. coli exposure to tellurite results in: (i) increased glucose consumption, which was paralleled by an increased expression of the glucose transporter-encoding gene ptsG, (ii) augmented phosphoglucoisomerase activity and pgi transcription, (iii) decreased activity of the enzymatic regulators phosphofructokinase and pyruvate kinase. In spite of these observations, increased intracellular pyruvate, phosphoenol pyruvate and phosphorylated sugars was observed. E. coli lacking key glycolytic enzymes was considerably more sensitive to tellurite than the parental, isogenic, wild type strain. Taken together, these results suggest that increasing the availability of key metabolites (pyruvate, phosphoenol pyruvate, NADPH), required to respond to tellurite mediated-stress, E. coli shifts the carbon flux towards the pentose phosphate pathway thus facilitating the functioning of the Entner-Doudoroff pathway and/or the glycolytic productive phase.

Topics: Escherichia coli; Glucose; Glycolysis; Oxidative Stress; Pentose Phosphate Pathway; Reactive Oxygen Species; Tellurium

Triply ionized thulium/thulium--ytterbium doped/codoped TeO2-Pb3O4 (TPO) glasses have been fabricated by classical quenching method. The upconversion emission spectra in the Tm3+/Tm3+-Yb3+ doped/codoped glasses upon excitation with a diode laser lasing at ∼980 nm has been studied. Effect of the addition of the Yb3+ on the upconversion emission intensity in the visible and near infrared regions of the Tm3+ doped in TPO glass has been studied and the processes involved explored.

Topics: Glass; Lead; Oxides; Spectrum Analysis; Tellurium; Thulium; Ytterbium

We demonstrate theoretically and experimentally that it is feasible to draw the microstructured fiber with longitudinally varying diameter (FLVD) whose diameter varies sharply in a short fiber length. It is elucidated that during the fiber drawing process the tension is linearly proportional to the natural logarithm of the fiber drawing speed. As a result, the tension is not so sensitive to the fiber diameter. Moreover, this sensitivity can be decreased by using a large diameter ratio of preform to fiber. Owing to the low sensitivity the FLVD with diameter varying sharply in a short fiber length can be drawn directly from the preform. Additionally we show that the microstructural geometry of FLVD does not depend on the varying diameter. The deformation in microstructural geometry is determined by the fiber segment with the smallest diameter. We fabricate a FLVD of which the diameter decreases by 75% in a fiber length of 10 cm. By using this fiber we demonstrate the 600-1800 nm supercontinuum (SC) generation and the 532 nm second harmonic generation pumped by a picosecond fiber laser. The SC spectra by the conventional fibers with the largest and the smallest diameters of the FLVD are also shown, respectively. The comparisons show that the FLVD has the broadest SC spectrum due to its high nonlinearity, varying dispersion, and high damage threshold.

Topics: Feasibility Studies; Fiber Optic Technology; Manufactured Materials; Models, Theoretical; Optical Fibers; Tellurium; Tensile Strength

Broadband and anisotropic light emission from rare-earth doped tellurite thin films is demonstrated using Er3+-TeO2 photonic crystals (PhCs). By adjusting the PhC parameters, photoluminescent light can be efficiently coupled into vertical surface emission or lateral waveguide propagation modes. Because of the flexibility of light projection direction, Er3+-TeO2 is a potential broadband light source for integration with three-dimensional photonic circuits and on-chip biochemical sensors.

Topics: Anisotropy; Crystallization; Luminescence; Luminescent Measurements; Membranes, Artificial; Photons; Tellurium

We present a microstructured fiber whose 9 µm diameter core consists in three concentric rings made of three active glasses having different rare earth oxide dopants, Yb3+/Er3+, Yb3+/Tm3+ and Yb3+/Pr3+, respectively. Morphological and optical characterization of the optical fiber are presented. The photoluminescence spectrum is investigated for different pumping conditions using a commercial 980 nm laser diode. Tuning of the RGB (or white light) emission is demonstrated not only by adjusting the pump power but also by using an optical iris as spatial filter which, thanks to the microstructured core, also acts as a spectral filter.

Topics: Equipment Design; Equipment Failure Analysis; Fiber Optic Technology; Glass; Lighting; Materials Testing; Miniaturization; Tellurium

We report on the spectroscopic properties of Pr(3+)-doped boro-phosphate, boro-germo-silicate and tellurite glasses. The stimulated absorption and emission cross sections were estimated. Only one emission at 596 nm and 605 nm is observed in Pr(3+)-doped boro-phosphate and boro-germo-silicate glasses, respectively, while three emissions at 605 nm, 612 nm and 645 nm are observed in Pr(3+)-doped tellurite glass when excited at 467 nm. The fluorescence lifetime at 600 nm in Pr(3+)-doped boro-phosphate, boro-germo-silicate and tellurite glasses is 137 μs, 73 μs and 51 μs, respectively. The emissions from Pr(3+)-doped boro-phosphate, boro-germo-silicate and tellurite glasses show different decay behaviors and can be well explained by multiphonon relaxation theory.

Topics: Glass; Phosphates; Praseodymium; Silicates; Spectrophotometry; Tellurium

We investigated the ~2 μm spectroscopic and lasing performance of Tm(3+) and Tm(3+)-Ho(3+) co-doped tungsten tellurite glass single mode fibers with a commercial 800 nm laser diode. The double cladding single mode (SM) fibers were fabricated by using rod-in-tube method. The propagation loss of the fiber was ~2.5 dB/m at 1310 nm. The spectroscopic properties of the fibers were analyzed. A 494 mW laser operating at ~1.9 μm was achieved in a Tm(3+) doped 20 cm long fiber, the slope efficiency was 26%, and the laser beam quality factor M(2) was 1.09. A 35 mW ~2.1 μm laser output was also demonstrated in a 7 cm long of Tm(3+)-Ho(3+) co-doped tungsten tellurite SM fiber.

Topics: Equipment Design; Equipment Failure Analysis; Fiber Optic Technology; Glass; Lasers, Semiconductor; Tellurium; Tungsten

The emergence of antibiotic-resistant pathogenic bacteria during the last decades has become a public health concern worldwide. Aiming to explore new alternatives to treat antibiotic-resistant bacteria and given that the tellurium oxyanion tellurite is highly toxic for most microorganisms, we evaluated the ability of sub lethal tellurite concentrations to strengthen the effect of several antibiotics. Tellurite, at nM or µM concentrations, increased importantly the toxicity of defined antibacterials. This was observed with both gram negative and gram positive bacteria, irrespective of the antibiotic or tellurite tolerance of the particular microorganism. The tellurite-mediated antibiotic-potentiating effect occurs in laboratory and clinical, uropathogenic Escherichia coli, especially with antibiotics disturbing the cell wall (ampicillin, cefotaxime) or protein synthesis (tetracycline, chloramphenicol, gentamicin). In particular, the effect of tellurite on the activity of the clinically-relevant, third-generation cephalosporin (cefotaxime), was evaluated. Cell viability assays showed that tellurite and cefotaxime act synergistically against E. coli. In conclusion, using tellurite like an adjuvant could be of great help to cope with several multi-resistant pathogens.

Topics: Ampicillin; Anti-Bacterial Agents; Cefotaxime; Chloramphenicol; Drug Synergism; Escherichia coli; Microbial Sensitivity Tests; Microbial Viability; Tellurium; Tetracycline

The tellurium oxyanion tellurite is toxic to most organisms because of its ability to generate oxidative stress. However, the detailed mechanism(s) how this toxicant interferes with cellular processes have yet to be fully understood. As part of our effort to decipher the molecular interactions of tellurite with living systems, we have evaluated the global metabolism of α-ketoglutarate a known antioxidant in Escherichia coli. Tellurite-exposed cells displayed reduced activity of the KG dehydrogenase complex (KGDHc), resulting in increased intracellular KG content. This complex's reduced activity seems to be due to decreased transcription in the stressed cells of sucA, a gene that encodes the E1 component of KGDHc. Furthermore, it was demonstrated that the increase in total reactive oxygen species and superoxide observed upon tellurite exposure was more evident in wild type cells than in E. coli with impaired KGDHc activity. These results indicate that KG may be playing a pivotal role in combating tellurite-mediated oxidative damage.

Topics: Dihydrolipoamide Dehydrogenase; Electron Transport Complex I; Escherichia coli; Escherichia coli Proteins; Ketoglutarate Dehydrogenase Complex; Ketoglutaric Acids; Multienzyme Complexes; NADH, NADPH Oxidoreductases; Oxidative Stress; Reactive Oxygen Species; Tellurium; Transcription, Genetic

Bacterial thiopurine methyltransferases (bTPMTs) can favour resistance towards toxic tellurite oxyanions through a pathway leading to the emission of a garlic-like smell. Gene expression profiling completed by genetic, physiological and electron microscopy analyses was performed to identify key bacterial activities contributing to this resistance process. Escherichia coli strain MG1655 expressing the bTPMT was used as a cell model in these experiments. This strain produced a garlic-like smell which was found to be due to dimethyl telluride, and cell aggregates in culture media supplemented with tellurite. Properties involved in aggregation were correlated with cell attachment to polystyrene, which increased with tellurite concentrations. Gene expression profiling supported a role of adhesins in the resistance process with 14% of the tellurite-regulated genes involved in cell envelope, flagella and fimbriae biogenesis. Other tellurite-regulated genes were, at 27%, involved in energy, carbohydrate and amino acid metabolism including the synthesis of antioxidant proteins, and at 12% in the synthesis of transcriptional regulators and signal transduction systems. Escherichia coli mutants impaired in tellurite-regulated genes showed ubiquinone and adhesins synthesis, oxidative stress response, and efflux to be essential in the bTPMT resistance process. High tellurite resistance required a synergistic expression of these functions and an efficient tellurium volatilization by the bTPMT.

Topics: Adhesins, Bacterial; Drug Resistance, Bacterial; Enzyme Inhibitors; Escherichia coli; Gene Expression Profiling; Gene Expression Regulation, Bacterial; Gene Knockout Techniques; Genes, Bacterial; Methylation; Methyltransferases; Mutation; Oxidation-Reduction; Oxidative Stress; Tellurium

We report the first demonstration of superbroadband emission extending from 1.30 to 1.68 μm in praseodymium(Pr(3+))-erbium(Er(3+)) codoped fluorotellurite glasses under 488 nm excitation. This superbroad near-infrared emission is contributed by the Pr(3+): (1)D(2)→(1)G(4) and Er(3+): (4)I(13/2)→(4)I(15/2) transitions which lead to emissions located at 1.48 and 1.53 μm, respectively. The quenching of the Pr(3+) emission resulted from the cross relaxation [(1)D(2), (3)H(4)]→[(1)G(4), (3)F(3,4)] was effectively compensated by the codoping of Er(3+). The results suggest that, other than the heavy-metal and transition-metal elements of active bismuth (Bi), nickel (Ni), chromium (Cr), etc., Pr(3+)-Er(3+) codoped system is a promising alternative for the broadband near-infrared emission covering the expanded low-loss window.

Topics: Energy Transfer; Fluorine; Glass; Infrared Rays; Materials Testing; Tellurium

To identify copper homeostasis genes in Rhodobacter capsulatus, we performed random transposon Tn5 mutagenesis. Screening of more than 10,000 Tn5 mutants identified tellurite resistance gene trgB as a so far unrecognized major copper tolerance determinant. The trgB gene is flanked by tellurite resistance gene trgA and cysteine synthase gene cysK2. While growth of trgA mutants was only moderately restricted by tellurite, trgB and cysK2 mutants were severely affected by tellurite, which implies that viability under tellurite stress requires increased cysteine levels. Mutational analyses revealed that trgB was the only gene in this chromosomal region conferring cross-tolerance towards copper. Expression of the monocistronic trgB gene required promoter elements overlapping the trgA coding region as shown by nested deletions. Neither copper nor tellurite affected trgB transcription as demonstrated by reverse transcriptase PCR and trgB-lacZ fusions. Addition of tellurite or copper gave rise to increased cellular tellurium and copper concentrations, respectively, as determined by inductively coupled plasma-optical emission spectroscopy. By contrast, cellular iron concentrations remained fairly constant irrespective of tellurite or copper addition. This is the first study demonstrating a direct link between copper and tellurite response in bacteria.

Topics: Copper; Cysteine Synthase; Drug Resistance, Bacterial; Genes, Bacterial; Iron; Microbial Viability; Mutagenesis, Insertional; Mutation; Rhodobacter capsulatus; Tellurium

Antimony telluride has a low thermoelectric figure of merit (ZT < ∼0.3) because of a low Seebeck coefficient α arising from high degenerate hole concentrations generated by antimony antisite defects. Here, we mitigate this key problem by suppressing antisite defect formation using subatomic percent sulfur doping. The resultant 10-25% higher α in bulk nanocrystalline antimony telluride leads to ZT ∼ 0.95 at 423 K, which is superior to the best non-nanostructured antimony telluride alloys. Density functional theory calculations indicate that sulfur increases the antisite formation activation energy and presage further improvements leading to ZT ∼ 2 through optimized doping. Our findings are promising for designing novel thermoelectric materials for refrigeration, waste heat recovery, and solar thermal applications.

Topics: Antimony; Crystallization; Energy Transfer; Macromolecular Substances; Materials Testing; Molecular Conformation; Nanostructures; Particle Size; Sulfur; Surface Properties; Tellurium; Temperature; Thermal Conductivity

The dissimilatory metal-reducing bacterium, Shewanella oneidensis MR-1, reduced tellurite (Te(IV), TeO(3)(2-)) to elemental tellurium under anaerobic conditions resulting in the intracellular accumulation of needle shaped crystalline Te(0) nanorods. Fatty acid analyses showed that toxic Te(IV) increased the unsaturated fatty acid composition of the lipid components of the cell membrane, implying a deconstruction of the integrity of the cellular membrane structure. The current results suggest that dissimilatory metal reducing bacteria such as S. oneidensis MR-1 may play an important role in recycling toxic tellurium elements, and may be applied as a novel selective biological filter via the accumulation of industry-applicable rare materials, Te(0) nanorods, in the cell.

Topics: Biodegradation, Environmental; Environmental Pollutants; Nanotubes; Oxidation-Reduction; Shewanella; Tellurium

The mode of action of the bacterial ter cluster and TelA genes, implicated in natural resistance to tellurite and other xenobiotic toxic compounds, pore-forming colicins and several bacteriophages, has remained enigmatic for almost two decades. Using comparative genomics, sequence-profile searches and structural analysis we present evidence that the ter gene products and their functional partners constitute previously underappreciated, chemical stress response and anti-viral defense systems of bacteria. Based on contextual information from conserved gene neighborhoods and domain architectures, we show that the ter gene products and TelA lie at the center of membrane-linked metal recognition complexes with regulatory ramifications encompassing phosphorylation-dependent signal transduction, RNA-dependent regulation, biosynthesis of nucleoside-like metabolites and DNA processing. Our analysis suggests that the multiple metal-binding and non-binding TerD paralogs and TerC are likely to constitute a membrane-associated complex, which might also include TerB and TerY, and feature several, distinct metal-binding sites. Versions of the TerB domain might also bind small molecule ligands and link the TerD paralog-TerC complex to biosynthetic modules comprising phosphoribosyltransferases (PRTases), ATP grasp amidoligases, TIM-barrel carbon-carbon lyases, and HAD phosphoesterases, which are predicted to synthesize novel nucleoside-like molecules. One of the PRTases is also likely to interact with RNA by means of its Pelota/Ribosomal protein L7AE-like domain. The von Willebrand factor A domain protein, TerY, is predicted to be part of a distinct phosphorylation switch, coupling a protein kinase and a PP2C phosphatase. We show, based on the evidence from numerous conserved gene neighborhoods and domain architectures, that both the TerB and TelA domains have been linked to diverse lipid-interaction domains, such as two novel PH-like and the Coq4 domains, in different bacteria, and are likely to comprise membrane-associated sensory complexes that might additionally contain periplasmic binding-protein-II and OmpA domains. We also show that the TerD and TerB domains and the TerY-associated phosphorylation system are functionally linked to many distinct DNA-processing complexes, which feature proteins with SWI2/SNF2 and RecQ-like helicases, multiple AAA+ ATPases, McrC-N-terminal domain proteins, several restriction endonuclease fold DNases, DNA-binding domains and a type-VI

Topics: Adenosine Triphosphatases; Colicins; Coliphages; Crystallography, X-Ray; DNA Repair; DNA-Binding Proteins; DNA, Bacterial; Drug Resistance, Bacterial; Escherichia coli; Escherichia coli Proteins; Lipids; Membrane Proteins; Metals; Operon; Phosphorylation; Principal Component Analysis; Protein Interaction Domains and Motifs; Protein Structure, Tertiary; Signal Transduction; Stress, Physiological; Tellurium; Virus Inactivation

In this work, we report the experimental observation of supercontinua generation in two kinds of suspended-core microstructured soft-glass optical fibers. Low loss, highly nonlinear, tellurite and As2S3 chalcogenide fibers have been fabricated and pumped close to their zero-dispersion wavelength in the femtosecond regime by means of an optical parametric oscillator pumped by a Ti:Sapphire laser. When coupled into the fibers, the femtosecond pulses result in 2000-nm bandwidth supercontinua reaching the Mid-Infrared region and extending from 750 nm to 2.8 µm in tellurite fibers and 1 µm to 3.2 µm in chalcogenide fibers, respectively.

Topics: Equipment Design; Lasers; Light; Nonlinear Dynamics; Optical Fibers; Sulfides; Tellurium

A new way to suppress stimulated Brillouin scattering by using an all-solid chalcogenide-tellurite photonic bandgap fiber is presented in the paper. The compositions of the chalcogenide and the tellurite glass are As(2)Se(3) and TeO(2)-ZnO-Li(2)O-Bi(2)O(3). The light and the acoustic wave are confined in the fiber by photonic bandgap and acoustic bandgap mechanism, respectively. When the pump wavelength is within the photonic bandgap and the acoustic wave generated by the pump light is outside the acoustic bandgap, the interaction between the optical and the acoustic modes is very weak, thus stimulated Brillouin scattering is suppressed in the photonic bandgap fiber.

Topics: Chalcogens; Equipment Design; Equipment Failure Analysis; Light; Optical Fibers; Photons; Scattering, Radiation; Tellurium

By physical and chemical dehydration techniques, a group of Er3+-doped water-free fluorotellurite glasses with a composition of 60TeO2-30ZnF2-10NaF(TZNF60,mol%)+x Er2O3(wt%,x=0~1.5) were fabricated. Under 978 nm excitation, the 4I(11/2)→4I(13/2) emission of Er3+ ions in TZNF60-glass was investigated: τ(f) is of 1.07~1.93 ms and emission bandwidth is about 163 nm at 2.71 µm, which benefits from the absence of OH groups and the decreased phonon energy with the addition of fluorides. In contrast, 1.25Er-TZNF60 glass is proposed to be a promising material for mid-infrared fiber lasers at around 2.7 µm.

Topics: Equipment Design; Equipment Failure Analysis; Erbium; Fluorine; Glass; Lasers; Tellurium; Water

The tellurium oxyanion TeO(3)(2-) has been used in the treatment of infectious diseases caused by mycobacteria. However, many pathogenic bacteria show tellurite resistance. Several tellurite resistance genes have been identified, and these genes mediate responses to diverse extracellular stimuli, but the mechanisms underlying their functions are unknown. To shed light on the function of KP-TerD, a 20.5 -kDa tellurite resistance protein from a plasmid of Klebsiella pneumoniae, we have determined its three-dimensional structure in solution using NMR spectroscopy. KP-TerD contains a β-sandwich formed by two five-stranded β-sheets and six short helices. The structure exhibits two negative clusters in loop regions on the top of the sandwich, suggesting that KP-TerD may bind metal ions. Indeed, thermal denaturation experiments monitored by circular dichroism and NMR studies reveal that KP-TerD binds Ca(2+). Inductively coupled plasma-optical emission spectroscopy shows that the binding ratio of KP-TerD to Ca(2+) is 1:2. EDTA (ethylenediaminetetraacetic acid) titrations of Ca(2+)-saturated KP-TerD monitored by one-dimensional NMR yield estimated dissociation constants of 18  and 200 nM for the two Ca(2+)-binding sites of KP-TerD. NMR structures incorporating two Ca(2+) ions define a novel bipartite Ca(2)(+)-binding motif that is predicted to be highly conserved in TerD proteins. Moreover, these Ca(2+)-binding sites are also predicted to be present in two additional tellurite resistance proteins, TerE and TerZ. These results suggest that some form of Ca(2+) signaling plays a crucial role in tellurite resistance and in other responses of bacteria to multiple external stimuli that depend on the Ter genes.

Topics: Amino Acid Sequence; Bacterial Proteins; Binding Sites; Calcium; Calcium-Binding Proteins; Circular Dichroism; Drug Resistance, Bacterial; Klebsiella pneumoniae; Molecular Sequence Data; Nuclear Magnetic Resonance, Biomolecular; Protein Structure, Secondary; Protein Structure, Tertiary; Tellurium

The reduction of selenite (Se(IV)) and tellurite (Te(IV)) by Escherichia coli was significantly enhanced by various quinone redox mediators (lawsone, menadione, anthraquinone-2-sulfonate, and anthraquinone-2,6-disulfonate). In the presence of 0.2mM lawsone, over 99.1% Se(IV) and around 96.4% Te(IV) were reduced in 8 h, at average reduction rates of 9.1 and 7.6 mM g cell(-1) h(-1), respectively. Better mediated reduction of Se(IV) and Te(IV) were observed when lawsone concentration increased from 0.1 to 0.4 mM and cell concentration increased from 0.1 to 0.6 g l(-1), respectively. Transmission electron microscopy analysis revealed the formation of both intracellular and extracellular Se(0) nanospheres or Te(0) nanorods, and the presence of lawsone increased the formation and accumulation of extracellular precipitates. The efficient mediated microbial reduction of Se(IV)/Te(IV) may be exploited for pollution removal and biological nanomaterials production.

Topics: Benzoquinones; Biodegradation, Environmental; Escherichia coli; Oxidation-Reduction; Sodium Selenite; Tellurium; Water Pollutants, Chemical; Water Purification

Tellurite (Tel) resistant enterohaemorrhagic Escherichia coli (EHEC) O157:H7 is a global pathogen. In strain EDL933 Tel resistance (Tel(R) ) is encoded by duplicate ter cluster in O islands (OI) 43 and 48, which also harbour iha, encoding the adhesin and siderophore receptor Iha. We identified five EHEC O157:H7 strains that differentiate into large (L) colonies and small (S) colonies with high and low Tel minimal inhibitory concentrations (MICs) respectively. S colonies (Tel-MICs ≤ 4 µg ml⁻¹) sustained large internal deletions within the Tel(R) OIs via homologous recombination between IS elements and lost ter and iha. Moreover, complete excision of the islands occurred by site-specific recombination between flanking direct repeats. Complete excision of OI 43 and OI 48 occurred in 1.81 × 10⁻³ and 1.97 × 10⁻⁴ cells in culture, respectively; internal deletion of OI 48 was more frequent (9.7 × 10⁻¹ cells). Under iron limitation that promotes iha transcription, iha-negative derivatives adhered less well to human intestinal epithelial cells and grew slower than did their iha-positive counterparts. Experiments utilizing iha deletion and complementation mutants identified Iha as the major factor responsible for these phenotypic differences. Spontaneous deletions affecting Tel(R) OIs contribute to EHEC O157 genome plasticity and might impair virulence and/or fitness.

Topics: Bacterial Adhesion; Cell Line, Tumor; Chromosomal Instability; DNA, Bacterial; Escherichia coli O157; Genomic Islands; Humans; Multigene Family; Phenotype; Sequence Analysis, DNA; Sequence Deletion; Tellurium; Virulence

This article reports on the development and spectral results of Eu(3+) and Tb(3+) ions doped cadmium lithium alumino fluoro boro tellurite (CLiAFBT) glasses in the following composition. 40TeO2-30B2O3-10CdO-10Li2O-10AlF3 (Hostglass) (40-x)TeO2-30B2O3-10CdO-10Li2O-10AlF3-xEu2O3 (40-x)TeO2-30B2O3-10CdO-10Li2O-10AlF3-xTb4O7 where x=0.25, 0.50, 0.75, 1.0, 1.25 mol%. Glass amorphous nature and thermal properties have been studied using the XRD and DSC profiles. From the emission spectra of Eu(3+):glasses, five emission transitions have been observed at 578 nm, 592 nm, 612 nm, 653 nm, 701 nm and are assigned to the transitions (5)D(0)→(7)F(0), (7)F(1,)(7)F(2), (7)F(3) and (7)F(4), respectively, with λ(exci)=392 nm ((7)F(0)→(5)L(6)). In case of Tb(3+):glasses, four emission transitions ((5)D(4)→(7)F(6,)(7)F(5), (7)F(4) and (7)F(3)) are observed at 488 nm, 543 nm, 584 nm and 614 nm, respectively, with λ(exci)=376 nm. Decay curves and energy level diagrams have been plotted to evaluate the life times and to analyze the emission mechanism.

Topics: Aluminum; Boron; Cadmium; Calorimetry, Differential Scanning; Europium; Fluorine; Glass; Ions; Lithium; Optical Phenomena; Photons; Spectrophotometry, Ultraviolet; Tellurium; Terbium; Thermodynamics; X-Ray Diffraction

The interactions of selenite and tellurite with cytosolic and mitochondrial thioredoxin reductases (TrxR1 and TrxR2) and glutathione reductases (GR) from yeast and mammalian sources were explored. Both TrxR1 and TrxR2 act as selenite and tellurite reductases. Kinetic treatment shows that selenite has a greater affinity than tellurite with both TrxR1 and TrxR2. Considering both k(cat) and K(m), selenite shows a better catalytic efficiency than tellurite with TrxR1, whereas with TrxR2, the catalytic efficiency is similar for both chalcogens. Tellurite is a good substrate for GR, whereas selenite is almost completely ineffective. Selenite or tellurite determine a large mitochondrial permeability transition associated with thiol group oxidation. However, with increasing concentrations of both chalcogens, only about 25% of total thiols are oxidized. In isolated mitochondria, selenite or tellurite per se does not stimulate H₂O₂ production, which, however, is increased by the presence of auranofin. They also determine a large oxidation of mitochondrial pyridine nucleotides. In ovarian cancer cells both chalcogens decrease the mitochondrial membrane potential. These results indicate that selenite and tellurite, interacting with the thiol-dependent enzymes, alter the balance connecting pyridine nucleotides and thiol redox state, consequently leading to mitochondrial and cellular alterations essentially referable to a disulfide stress.

Topics: Animals; Auranofin; Cell Line, Tumor; Cell Membrane Permeability; Female; Glutathione Reductase; Humans; Kinetics; Membrane Potential, Mitochondrial; Mitochondria, Liver; Ovarian Neoplasms; Oxidation-Reduction; Pyridines; Rats; Sodium Selenite; Substrate Specificity; Sulfhydryl Compounds; Tellurium; Thioredoxin-Disulfide Reductase; Yeasts

Optical absorption and photoluminescent properties of Ho(3+)/Yb(3+) co-doped tellurite and zinc halide tellurite glasses are investigated. The effect of zinc halides as modifier on the luminescence properties of above mentioned samples has been explored. Two intense upconversion emission bands centered at 546 ((5)F(4), (5)S(2)→(5)I(8)) and 660 ((5)F(5)→(5)I(8)) nm are observed when samples are excited by 976 nm radiation. Zinc halides act as quencher when 976 nm excitation source is used. The up and downconversion emission spectra are recorded with 532 nm excitation source also. In this case also, zinc halides do not show any improvement. The dependence of upconversion intensities on excitation power and temperature is discussed. The power dependence study shows a quadratic dependence of fluorescence intensity on the excitation power while decrement in emission intensity of different transitions at different rates is observed in temperature dependence study. The possible upconversion mechanisms are also discussed in order to understand the energy transfer between Yb(3+) and Ho(3+) ions.

Topics: Absorption; Chlorides; Energy Transfer; Fluorides; Glass; Holmium; Luminescence; Spectrum Analysis; Tellurium; Temperature; Ytterbium; Zinc Compounds

FTIR, UV-VIS and EPR spectra of manganese doped lead-tellurate glasses with composition xMnO·(100-x)[4TeO2·PbO2] where x=0, 1, 5, 10, 20, 30, 40mol% have been studied. The FTIR spectra show the formation of the Mn-O-Pb and Mn-O-Te bridging bonds by increasing of MnO concentration. The UV-VIS spectra show the Mn(+3) species exhibit pronounced absorption, which masks the Mn(+2) spin-forbidden absorption bands when Mn(+2) ions are in high concentrations in these glasses. The EPR spectra exhibit resonance signals characteristic of Mn(+2) ions. The resonance signal located at g≈2 is due to Mn(+2) ions in an environment close to octahedral symmetry, whereas the resonance at g≈4.3 and 3.3 are attributed to the rhombic surroundings of the Mn(+2) ions. The increase in the MnO content gives rise to absorption at g≈2.4 and the paramagnetic ions are involved in dinuclear manganese centers.

Topics: Electron Spin Resonance Spectroscopy; Glass; Lead; Manganese; Spectrophotometry; Spectroscopy, Fourier Transform Infrared; Tellurium

Topics: Diamond; Glass; Information Science; Materials Testing; Particle Size; Quantum Theory; Surface Properties; Tellurium

We previously described a marine, tellurite-resistant strain of the yeast Rhodotorula mucilaginosa that both precipitates intracellular Te0 and volatilizes methylated Te compounds when grown in the presence of the oxyanion tellurite. The uses of microbes as a "green" route for the production of Te0-containing nanostructures and for the remediation of Te-oxyanion wastes have great potential, and so a more thorough understanding of this process is required. Here, Te precipitation and volatilization catalyzed by R. mucilaginosa were examined in continuously aerated and sealed (low oxygen concentration) batch cultures. Continuous aeration was found to strongly promote Te volatilization while inhibiting Te0 precipitation. This differs from the results in sealed batch cultures, for which tellurite reduction to Te0 was found to be very efficient. We show also that volatile Te species may be degraded rapidly in medium and converted to the particulate form by biological activity. Further experiments revealed that Te0 precipitates produced by R. mucilaginosa can be further transformed to volatile and dissolved Te species. However, it was not clearly determined whether Te0 is a required intermediate for Te volatilization. Based on these results, we conclude that low oxygen concentrations will be the most efficient for production of Te0 nanoparticles while limiting the production of toxic volatile Te species, although the production of these compounds may never be completely eliminated.

Topics: Aerobiosis; Anaerobiosis; Drug Resistance, Fungal; Methylation; Oxidation-Reduction; Rhodotorula; Tellurium

A thermophilic, arsenate resistant bacterial strain was isolated from a geothermal field located in the area surrounding Monterotondo (Tuscany, Italy). Based on 16S rRNA gene analysis and recN comparisons the strain was identified as Geobacillus kaustophilus. Cells of the strain, designated A1, were rod-shaped, 2-3 μm long and reacted negatively to Gram staining, despite its taxonomic classification as a Gram positive microorganism. Strain A1 is a thermophilic spore-forming bacterium, and grows optimally at pH 6.5 and 55 °C. An arsenate MIC of 80 mM was determined for strain A1, and the close relative G. kaustophilus DSM 7263(T) showed similar levels of arsenate resistance. These observations were consistent with the presence of arsenic detoxification genes in the genome of G. kaustophilus HTA426. Furthermore, strain A1 growth was not inhibited by 5 mM antimonite and 15 mM arsenite, the highest tested concentrations. This is the first description of arsenic resistance in a Geobacillus strain and supports the hypothesis that members of the genus may have a role in the biogeochemical cycling of arsenic.

Topics: Antimony; Arsenates; Bacterial Proteins; Bacterial Typing Techniques; Base Sequence; Biodegradation, Environmental; Biofilms; Carbon; DNA Restriction Enzymes; DNA, Bacterial; DNA, Ribosomal; Drug Resistance, Bacterial; Geobacillus; Italy; Molecular Sequence Data; Phylogeny; RNA, Bacterial; RNA, Ribosomal, 16S; Sequence Analysis, DNA; Soil; Soil Microbiology; Tellurium

To investigate the presence of tellurite resistance (ter) gene cluster and its resistance in Escherichia coli 0157 strains collected by national foodborn disease surveillance system from 2005 to 2007.. The ter gene cluster was tested by PCR. Tellurite resistance was evaluated by plate dilution method.. Of the investigated 89 E. coli strains,the presence of ter gene cluster was found in 51 strains. They were separately from 41 of 42 E. coli O157: H7 strains,all of 6 strains of O157 : NM (non-mobile flicH7 positive) and only 3 of 41 O157: NM (flicH7 negative)/O157: hund strains. The 51 strains with ter gene cluster were resistance to the high level of potassium tellurite. The MIC was from 64-512 microg/ml. In contrast, the MIC of most of 38 strains without ter gene cluster was from 2-16 microg/ml. Only one strain was 128 microg/ml. 28 of 29 stx-positive E. coli isolates contained the ter gene cluster and had the high levels of tellurite resistance.. E. coli 0157 from food had the diversity levels of tellurite resistance. The presence of the ter gene cluster had significant associated with the high levels of tellurite resistance.

Topics: Drug Resistance, Bacterial; Escherichia coli O157; Escherichia coli Proteins; Food Microbiology; Microbial Sensitivity Tests; Multigene Family; Tellurium

The highly toxic oxyanion tellurite (TeO(3) (2-)) enters the cells of the facultative photosynthetic bacterium Rhodobacter capsulatus through an acetate permease. Here we show that actP gene expression is down-regulated by fructose and this in turn determines a strong decrease of tellurite uptake and a parallel increase in the cells resistance to the toxic metalloid (from a minimal inhibitory concentration of 8 μM up to 400 μM tellurite under aerobic growth conditions). This demonstrates that there exists a direct connection between the level of tellurite uptake and the sensitivity of the cells to the oxyanion.

Topics: Bacterial Proteins; Biological Transport; Down-Regulation; Fructose; Gene Expression Regulation, Bacterial; Membrane Transport Proteins; Rhodobacter capsulatus; Tellurium

A Pseudomonas strain (TeU), resistant to tellurite (TeO(2)(3)(-) and cadmium (Cd(2+)) ions, was isolated from heavy-metal-contaminated sediments by enrichment. Black precipitates, presumably the product of the reduction of tellurite, such as tellurium, occurred in cultures of the isolate after growth in medium containing tellurite. Quantitative determination of the TeO(2)(3)(-) concentration in the liquid culture demonstrated a decreased concentration of tellurite (to less than 100 µM) from initial concentrations of approximately 1,000 µM within 24 h of growth. Strain TeU was resistant to TeO(2)(3)(-) and Cd(2+) concentrations as high as 2,000 µM and 500 µM, respectively. Transposon mutagenesis of strain TeU resulted in mutants exhibiting Cd(2+) sensitivity (Strain BU21) and one with decreased ability to reduce tellurite (strain AU08). Strain BU21 was less tolerant to Cd(2+) (100 µM) compared with the wild-type strain TeU (500 µM) but was still able to reduce tellurite to 80% of that of strain TeU. Although strain AU08 possesses the ability for Cd(2+) resistance, it reduced less than 20% of the initial concentrations of tellurite compared with strain TeU. Genes encoding an HflKC complex and a putative metallopeptidase were associated with the bacterium's capacity for tellurite reduction and Cd resistance, respectively. The ability to reduce tellurite therefore may not be necessary for this bacterium's heavy metal and metalloid tellurite resisting ability.

Topics: Cadmium; Genes, Bacterial; Geologic Sediments; Metalloproteases; Mutagenesis; Phenotype; Pseudomonas; Tellurium

A solid-core tellurite glass fiber with 1.8 dB/m loss at 1.55 μm was made by using the built-in casting preform fabrication method and rod-in-tube fiber drawing technique. Pumping a 10 cm fiber piece with picosecond pulses of 3-5×10(12) W/cm(2), 0.1% of the fundamental power limited by the coherence length of 0.3-5 μm was converted into visible third-harmonic power tunable over a broad near-IR wavelength ranging from 1500 to 1680 nm. Frequency conversion from the mid-IR to near-IR was found to be even more efficient due to the longer coherence lengths of 12-20 μm in the wavelength range of 2200-2500 nm.

Topics: Glass; Infrared Rays; Optical Fibers; Optical Phenomena; Tellurium

The tellurite resistance operon has been found in a wide range of bacteria. We have previously identified the ter operon (terXYW and terZABCDEF) of the uropathogenic strain Escherichia coli KL53. In this study, we use an innovative approach to identify putative protein-protein interaction partners for one of the essential tellurite resistance proteins - TerB. We observe that N-terminus of TerB attaches to the periplasmic membrane, while the C-terminus is partly localized in the cytoplasm. Subsequently, by methods of in vivo cross-linking and mass-spectroscopic analysis, we have determined the proteins from both the membrane and cytoplasmic fractions, which can potentially interact with TerB.

Topics: Amino Acid Sequence; Cell Membrane; Cross-Linking Reagents; Cytoplasm; Drug Resistance, Bacterial; Escherichia coli Proteins; Gene Expression Regulation, Bacterial; Genes, Bacterial; Mass Spectrometry; Molecular Sequence Data; Protein Structure, Tertiary; Sequence Homology, Amino Acid; Subcellular Fractions; Tellurium; Uropathogenic Escherichia coli

The tellurium oxyanion tellurite induces oxidative stress in most microorganisms. In Escherichia coli, tellurite exposure results in high levels of oxidized proteins and membrane lipid peroxides, inactivation of oxidation-sensitive enzymes and reduced glutathione content. In this work, we show that tellurite-exposed E. coli exhibits transcriptional activation of the zwf gene, encoding glucose 6-phosphate dehydrogenase (G6PDH), which in turn results in augmented synthesis of reduced nicotinamide adenine dinucleotide phosphate (NADPH). Increased zwf transcription under tellurite stress results mainly from reactive oxygen species (ROS) generation and not from a depletion of cellular glutathione. In addition, the observed increase of G6PDH activity was paralleled by accumulation of glucose-6-phosphate (G6P), suggesting a metabolic flux shift toward the pentose phosphate shunt. Upon zwf overexpression, bacterial cells also show increased levels of antioxidant molecules (NADPH, GSH), better-protected oxidation-sensitive enzymes and decreased amounts of oxidized proteins and membrane lipids. These results suggest that by increasing NADPH content, G6PDH plays an important role in E. coli survival under tellurite stress.

Topics: Escherichia coli; Escherichia coli Proteins; Glucose-6-Phosphate; Glucosephosphate Dehydrogenase; NADP; Oxidative Stress; Reactive Oxygen Species; Tellurium

In this paper we calculated, for the first time to the best of our knowledge, the cross relaxation parameter of Tm(3+) ions in tellurite glasses over a wide range of concentrations: from 0.36 mol% up to 10 mol%. A new measurement approach based on emission spectra monitoring is proposed. This method is very simple and allows to measure even very highly doped samples. The obtained values of cross-relaxation parameter show a linear dependence with respect to dopant concentration over the full investigated interval, suggesting a dipole-dipole interaction process. The measured slope is 1.81x10(-17) cm(3) s(-1) mol%(-1).

Topics: Computer Simulation; Energy Transfer; Glass; Light; Models, Chemical; Refractometry; Scattering, Radiation; Tellurium; Thulium

A new ammonium vanadium tellurate, (NH(4))(2)[VO(2)](2)[TeO(4)(OH)(2)] (1), was hydrothermally synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, and TG analysis. Compound 1 crystallizes in the monoclinic system, space group P2(1)/n: a = 8.9112(18) A, b = 15.151(3) A, c = 15.187(3) A, beta = 97.91(3)(o), V = 2030.9(7) A(3), Z = 8, R1 (I > 2sigma(I)) = 0.0295, wR2 (all data) = 0.0631. The structure of 1 consists of infinite anionic chains, {[VO(2)](2)[TeO(4)(OH)(2)]}(2-), of edge-sharing VO(5) square pyramids and TeO(4)(OH)(2) octahedra. Two VO(5) square pyramids are joined together by sharing their edge to form a V(2)O(8) binuclear unit. The V(2)O(8) and TeO(4)(OH)(2) units are alternatively connected to each other by sharing their edges to complete infinite zigzag anionic {[VO(2)](2)[TeO(4)(OH)(2)]}(2-) chains. The structure contains an extended network of O-H...O hydrogen bonds between the chains. The network of intermolecular hydrogen bonding results in layers parallel to the ab plane. Ammonium cations are hydrogen-bonded either to the oxygen atoms of the anionic chains or to each other in a complex arrangement.

Topics: Crystallography, X-Ray; Hydrogen Bonding; Models, Molecular; Spectrophotometry, Infrared; Tellurium; Vanadium Compounds

The highly toxic oxyanion tellurite has to enter the cytoplasm of microbial cells in order to fully express its toxicity. Here we show that in the phototroph Rhodobacter capsulatus, tellurite exploits acetate permease (ActP) to get into the cytoplasm and that the levels of resistance and uptake are linked.

Topics: Acetates; Adenosine Triphosphatases; Anaerobiosis; Bacterial Proteins; Biological Transport; Cell Membrane Permeability; Colony Count, Microbial; Escherichia coli; Gene Expression Regulation, Bacterial; Genes, Bacterial; Ion Transport; Light; Membrane Transport Proteins; Microbial Sensitivity Tests; Oxidative Stress; Oxygen; Rhodobacter capsulatus; Tellurium

Vanadate-tellurate vitreous systems with composition (1-x)TeO(2).xV(2)O(5) where x=0.3 and 0.4 have been prepared by the conventional melt-quench method. The structural aspects have been investigated using FTIR spectroscopy and the density functional theory (DFT) calculations. The present study provides the interesting information concerning devitrification behavior of the vanadate-tellurate vitreous system which occur Te(2)V(2)O(9) crystalline phase. The structure of the heat-treated glasses was found to consist mainly of rings containing [TeO(3)], [TeO(4)], [VO(4)] and some [VO(5)] structural units.

Topics: Ceramics; Models, Chemical; Molecular Structure; Quantum Theory; Spectrophotometry, Infrared; Spectroscopy, Fourier Transform Infrared; Spectrum Analysis, Raman; Tellurium; Vanadates

The structural properties of the xTeO(2) x (1-x)B(2)O(3) glasses (x = 0.6; 0.7) were investigated by FT-IR spectroscopy. From the analysis of the FTIR spectra, it is reasonable to assume that by the increasing of boron ions content, the tetrahedral [BO(4)] units are gradually replaced by the trigonal [BO(3)] units. The increase in the number of non-bridging oxygen atoms would decrease the connectivity of the glass network and will yield the depolymerization of the borate chains. The molecular structure and vibrational frequencies of the proposed structural models have been studied by exploring the density functional theory (DFT) calculations. The FTIR spectra of the xTeO(2) x (1-x)B(2)O(3) vitreous systems were compared with the calculated spectrum. This procedure allowed us to assign most of the observed IR bands.

Topics: Borates; Electrons; Glass; Models, Molecular; Spectroscopy, Fourier Transform Infrared; Tellurium; Thermodynamics

Data regarding tellurium (Te) toxicity are scarce. Studies on its metabolism, performed mainly in bacteria, underline a major role of reactive oxygen species (ROS). We investigated whether tellurite undergoes redox cycling leading to ROS formation and cancer cell death. The murine hepatocarcinoma Transplantable Liver Tumor (TLT) cells were challenged with tellurite either in the presence or in the absence of different compounds as N-acetylcysteine (NAC), 3-methyladenine, BAPTA-AM, and catalase. NAC inhibition of tellurite-mediated toxicity suggested a major role of oxidative stress. Tellurite also decreased both glutathione (GSH) and ATP content by 57 and 80%, respectively. In the presence of NAC however, the levels of such markers were almost fully restored. Tellurite-mediated ROS generation was assessed both by using the fluorescent, oxidation-sensitive probe dichlorodihydrofluorescein diacetate (DCHF-DA) and electron spin resonance (ESR) spectroscopy to detect hydroxyl radical formation. Cell death occurs by a caspase-independent mechanism, as shown by the lack of caspase-3 activity and no cleavage of poly(ADP-ribose)polymerase (PARP). The presence of gamma-H2AX suggests tellurite-induced DNA strand breaking, NAC being unable to counteract it. Although the calcium chelator BAPTA-AM did show no effect, the rapid phosphorylation of eIF2alpha suggests that, in addition to oxidative stress, an endoplasmic reticulum (ER) stress may be involved in the mechanisms leading to cell death by tellurite.

Topics: Adenosine Triphosphate; Animals; Carcinoma, Hepatocellular; Caspase 3; Cell Death; Cell Line, Tumor; Glutathione; Humans; Liver Neoplasms; Mice; Oxidative Stress; Reactive Oxygen Species; Tellurium

The role of charge density matching was investigated in the formation of templated vanadium tellurites under mild hydrothermal conditions. Reactions were conducted using a fixed NaVTeO(5):amine ratio in an ethanol/water solution to isolate the effects of amine structure. The use of 1,4-diaminobutane, 1,3-diaminopropane, and piperazine resulted in three distinct vanadium tellurite connectivities, [V(2)Te(2)O(10)](n)(2n-) chains, [V(2)TeO(8)](n)(2n-) layers, and [V(2)Te(2)O(10)](n)(2n-) layers, respectively. Charge density matching with the protonated amines is the primary influence over the structure of each vanadium tellurite anion, as quantified by molecular surface area and geometric decomposition methods. Electron localization functions were calculated using the Stuttgart tight-binding linear muffin-tin orbital, atomic sphere approximation code, to visualize the location and relative size, shape, and orientation of the stereoactive lone pair in the tellurite groups. [C(4)H(14)N(2)][V(2)Te(2)O(10)]: a = 5.649(5) A, b = 6.348(5) A, c = 9.661(5) A, alpha = 84.860(5) degrees , beta = 85.380(5) degrees , gamma = 81.285(5) degrees , triclinic, P1 (No. 2), Z = 1.

Topics: Crystallography, X-Ray; Models, Molecular; Stereoisomerism; Tellurium; Vanadium

We have characterized a novel pleiotropic role for CymR, the master regulator of cysteine metabolism. We show here that CymR plays an important role both in stress response and virulence of Staphylococcus aureus. Genes involved in detoxification processes, including oxidative stress response and metal ion homeostasis, were differentially expressed in a DeltacymR mutant. Deletion of cymR resulted in increased sensitivity to hydrogen peroxide-, disulfide-, tellurite- and copper-induced stresses. Estimation of metabolite pools suggests that this heightened sensitivity could be the result of profound metabolic changes in the DeltacymR mutant, with an increase in the intracellular cysteine pool and hydrogen sulfide formation. Since resistance to oxidative stress within the host organism is important for pathogen survival, we investigated the role of CymR during the infectious process. Our results indicate that the deletion of cymR promotes survival of S. aureus inside macrophages, whereas virulence of the DeltacymR mutant is highly impaired in mice. These data indicate that CymR plays a major role in virulence and adaptation of S. aureus for survival within the host.

Topics: Animals; Cell Line; Copper; Cystine; Disulfides; Female; Gene Deletion; Genes, Bacterial; Homeostasis; Hydrogen Peroxide; Macrophages; Mice; Mice, Inbred BALB C; Oxidants; Oxidative Stress; Staphylococcal Infections; Staphylococcus aureus; Tellurium; Up-Regulation; Virulence

In this paper, we report the physical and spectroscopic properties of Er(3+), Sm(3+) and Er(3+):Sm(3+) ions codoped barium fluorotellurite (BFT) glasses. Different Stokes and anti-Stokes emissions were observed under 532 nm and 976 nm laser excitations. Energy transfer from Er(3+) ion to Sm(3+) ion was confirmed on the basis of luminescence intensity variation and decay curve analysis in both the cases. Under green (532 nm) excitation emission intensity of Sm(3+) ion bands improves whereas on NIR (976 nm) excitation new emission bands of Sm(3+) ions were observed in Er:Sm codoped samples. Ion interactions and the different energy transfer parameters were also calculated.

Topics: Barium; Energy Transfer; Erbium; Glass; Kinetics; Luminescence; Samarium; Spectrum Analysis; Tellurium; Thermogravimetry

A fast, simple, and reliable chemical method for tellurite quantification is described. The procedure is based on the NaBH(4)-mediated reduction of TeO(3)(2-) followed by the spectrophotometric determination of elemental tellurium in solution. The method is highly reproducible, is stable at different pH values, and exhibits linearity over a broad range of tellurite concentrations.

Topics: Culture Media; Oxidation-Reduction; Reproducibility of Results; Spectrophotometry; Tellurium

Neodymium doped zinc-tellurite glasses of composition TeO(2)-ZnO-Na(2)O-Li(2)O have been prepared and characterized for their thermal, structural and optical properties. Differential thermal analysis revealed reasonably good forming tendency of the glass composition. FTIR spectra were used to analyze the functional groups present in the glass. Judd-Ofelt intensity parameters were derived from the absorption spectrum and used to calculate the radiative lifetime, branching ratio and stimulated emission cross-section for (4)F(3/2)-->(4)I(9/2, 11/2, 13/2) transitions. The quantum efficiency of the (4)F(3/2) level is comparable to the typical values obtained for the Nd(2)O(3)-doped glasses. The decay properties for higher concentration of Nd(2)O(3) were analyzed using Inokuti-Hirayama model to investigate the non-radiative relaxation of the (4)F(3/2) emitting level. The experimental values of branching ratio and saturation intensity of (4)F(3/2)-->(4)I(11/2) transition and calculated spectroscopic quality factor indicate the favourable lasing action in these glasses.

Topics: Alkalies; Crystallization; Glass; Models, Chemical; Neodymium; Optical Phenomena; Refractometry; Spectroscopy, Fourier Transform Infrared; Tellurium; Time Factors; Transition Temperature; Zinc

Despite a century of research and increasing environmental and human health concerns, the mechanistic basis of the toxicity of derivatives of the metalloid tellurium, Te, in particular the oxyanion tellurite, Te(IV), remains unsolved. Here, we provide an unbiased view of the mechanisms of tellurium metabolism in the yeast Saccharomyces cerevisiae by measuring deviations in Te-related traits of a complete collection of gene knockout mutants. Reduction of Te(IV) and intracellular accumulation as metallic tellurium strongly correlated with loss of cellular fitness, suggesting that Te(IV) reduction and toxicity are causally linked. The sulfate assimilation pathway upstream of Met17, in particular, the sulfite reductase and its cofactor siroheme, was shown to be central to tellurite toxicity and its reduction to elemental tellurium. Gene knockout mutants with altered Te(IV) tolerance also showed a similar deviation in tolerance to both selenite and, interestingly, selenomethionine, suggesting that the toxicity of these agents stems from a common mechanism. We also show that Te(IV) reduction and toxicity in yeast is partially mediated via a mitochondrial respiratory mechanism that does not encompass the generation of substantial oxidative stress. The results reported here represent a robust base from which to attack the mechanistic details of Te(IV) toxicity and reduction in a eukaryotic organism.

Topics: Drug Resistance, Fungal; Gene Deletion; Oxidation-Reduction; Oxidative Stress; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Selenomethionine; Sodium Selenite; Sulfates; Tellurium

Nisin is a class I bacteriocin (lantibiotic), which is employed by the food and veterinary industries and exhibits potent activity against numerous pathogens. However, this activity could be further improved through the targeting and inhibition of factors that contribute to innate nisin resistance. Here we describe a novel locus, lmo1967, which is required for optimal nisin resistance in Listeria monocytogenes. The importance of this locus, which is a homologue of the tellurite resistance gene telA, was revealed after the screening of a mariner random mutant bank of L. monocytogenes for nisin-susceptible mutants. The involvement of telA in nisin resistance was confirmed through an analysis of a nonpolar deletion mutant. In addition to being 4-fold-more susceptible to nisin, the ΔtelA strain was also 8-fold-more susceptible to gallidermin and 2-fold-more susceptible to cefuroxime, cefotaxime, bacitracin, and tellurite. This is the first occasion upon which telA has been investigated in a Gram-positive organism and also represents the first example of a link being established between a telA gene and resistance to cell envelope-acting antimicrobials.

Topics: Anti-Bacterial Agents; Bacitracin; Bacterial Proteins; Bacteriocins; Cefuroxime; Cell Wall; Drug Resistance, Multiple, Bacterial; Listeria monocytogenes; Nisin; Peptides; Tellurium

The soluble tellurium oxyanion, tellurite, is toxic for most organisms. At least in part, tellurite toxicity involves the generation of oxygen-reactive species which induce an oxidative stress status that damages different macromolecules with DNA, lipids and proteins as oxidation targets. The objective of this work was to determine the effects of tellurite exposure upon the Escherichia coli pyruvate dehydrogenase (PDH) complex. The complex displays two distinct enzymatic activities: pyruvate dehydrogenase that oxidatively decarboxylates pyruvate to acetylCoA and tellurite reductase, which reduces tellurite (Te(4+)) to elemental tellurium (Te(o)). PDH complex components (AceE, AceF and Lpd) become oxidized upon tellurite exposure as a consequence of increased carbonyl group formation. When the individual enzymatic activities from each component were analyzed, AceE and Lpd did not show significant changes after tellurite treatment. AceF activity (dihydrolipoil acetyltransferase) decreased ~30% when cells were exposed to the toxicant. Finally, pyruvate dehydrogenase activity decreased >80%, while no evident changes were observed in complex's tellurite reductase activity.

Topics: Escherichia coli; Oxidation-Reduction; Oxidative Stress; Oxidoreductases; Protein Carbonylation; Pyruvate Dehydrogenase Complex; Tellurium

In Er(3+)/Yb(3+) codoped Na(2)O-ZnO-PbO-GeO(2)-TeO(2) (NZPGT) glass fiber, a clear and compact green upconversion amplified spontaneous emission (ASE) trace is observed, and the NZPGT glasses are proved to be a desirable candidate in fabricating low-phonon energy fiber. Intense green upconversion luminescence of Er(3+), balanced green and red upconversion emissions of Ho(3+), and dominant three-photon blue upconversion fluorescence of Tm(3+) have been represented. By varying the excitation power of 974 nm wavelength laser diode, a series of green and white fluorescences have been achieved in Tm(3+)/Er(3+)/Yb(3+) and Tm(3+)/Ho(3+)/Yb(3+) triply doped glass systems, respectively. These results reveal that high-intensity blue, green, and white upconversion ASE fluorescences, which can be adopted for lighting in minimally invasive photodynamic therapy and minimally invasive surgery, are reasonable to be expected in rare-earth doped NZPGT glass fibers.

Topics: Equipment Design; Erbium; Germanium; Humans; Ions; Luminescence; Metals; Microscopy, Fluorescence; Minimally Invasive Surgical Procedures; Photochemotherapy; Photons; Spectrometry, Fluorescence; Spectrum Analysis, Raman; Tellurium; Time Factors

We report on the first demonstration of an optical waveguide amplifier in phospho-tellurite glass providing net gain at 1.5 μm. The device was fabricated using a high repetition rate femtosecond laser and exhibited internal gain across 100-nm bandwidth covering the entire C + L telecom bands.

Topics: Amplifiers, Electronic; Equipment Design; Equipment Failure Analysis; Glass; Lasers; Phosphorus; Refractometry; Tellurium

Aerobic oxygenation of diaryl tellurides under photosensitized conditions is investigated. Unlike Ph(2)S and Ph(2)Se, reaction of diaryl tellurides with singlet oxygen proceeds smoothly to yield diaryl telluroxides and the corresponding tellurones. The product distribution is largely affected by the substrate and the reaction conditions. In particular, the photooxygenation of bulky diaryl tellurides principally produces tellurones. The results of a series of trapping experiments suggest that the diaryl telluroxides can capture transient intermediates such as Me(2)S(+)OO(-) and Ar(2)Te(+)OO(-), generated in the singlet oxygen oxidation of chalcogenides, to yield diaryl tellurones, and therefore it may be the most potent precursors of the tellurones.

Topics: Crystallography, X-Ray; Light; Models, Molecular; Molecular Structure; Oxygen; Tellurium

Tellurium (Te) is widely used in industry because of its unique chemical and physical properties, and has recently become a part of everyday life as a component of phase-change optical magnetic disks. However, the recovery of Te from the environment has not been discussed yet. In this regard, we evaluated the potential use of Indian mustard (Brassica juncea), a selenium (Se) accumulator, for the phytoremediation of Te. The Indian mustard plant was exposed to selenate and tellurate and the concentrations of Se and Te and the chemical species in the plant were determined. The Indian mustard plant accumulated less Te than Se, and the amount of Te accumulated in the plant was approximately 1/69 of that of Se. Although the incorporation of selenate was reduced by increasing sulfate concentration in the medium, the incorporation of Te was not affected by it, suggesting that this plant was able to discriminate tellurate from selenate in the roots. Three Te species were detected in the plant. The major species was tellurate. The other two species were not identical to available Te standards and thus could not be identified. Consequently, the Indian mustard plant is inappropriate for the phytoremediation of Te because it can strictly distinguish tellurate from selenate.

Topics: Biodegradation, Environmental; Mustard Plant; Selenic Acid; Selenium Compounds; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry; Tellurium

We report multicolor upconversion emissions including the blue-violet, green, and red lights in a Tm 3+/Er3+codoped tellurite glass photonic microwire between two silica fiber tapers. A silica fiber is tapered until its evanescent field is exposed and then angled-cleaved at the tapered center to divide the tapered fibers into two parts. A tellurite glass is melted by a gas flame to cluster into a sphere at the tip of one tapered fiber. The other angled-cleaved tapered fiber is blended into the melted tellurite glass. When the tellurite glass is melted, the two silica fiber tapers are simultaneously moving outwards to draw the tellurite glass into a microwire in between. The advantage of angled-cleaving on fiber tapers is to avoid cavity resonances in high index photonic microwire. Thus, the broadband white light can be transmitted between silica fibers and a special optical property like high intensity upconversion emission can be achieved. A cw 1064 nm Nd:YAG laser light is launched into the Tm 3+/Er3+ codoped tellurite microwire through a silica fiber taper to generate the multicolor upconversion emissions, including the blue-violet, green, and red lights, simultaneously.

Topics: Color; Equipment Design; Equipment Failure Analysis; Fiber Optic Technology; Lighting; Miniaturization; Photons; Silicon Dioxide; Tellurium

Raman spectroscopy has been used to study the tellurite minerals spiroffite and carlfriesite, which are minerals of formula type A(2)(X(3)O(8)) where A is Ca(2+) for the mineral carlfriesite and is Zn(2+) and Mn(2+) for the mineral spiroffite. Raman bands for spiroffite observed at 721 and 743 cm(-1), and 650 cm(-1) are attributed to the nu(1) (Te(3)O(8))(2-) symmetric stretching mode and the nu(3) (Te(3)O(8))(2-) antisymmetric stretching modes, respectively. A second spiroffite mineral sample provided a Raman spectrum with bands at 727 cm(-1) assigned to the nu(1) (Te(3)O(8))(2-) symmetric stretching modes and the band at 640cm(-1) accounted for by the nu(3) (Te(3)O(8))(2-) antisymmetric stretching mode. The Raman spectrum of carlfriesite showed an intense band at 721 cm(-1). Raman bands for spiroffite, observed at (346, 394) and 466 cm(-1) are assigned to the (Te(3)O(8))(2-)nu(2) (A(1)) bending mode and nu(4) (E) bending modes. The Raman spectroscopy of the minerals carlfriesite and spiroffite are difficult because of the presence of impurities and other diagenetically related tellurite minerals.

Topics: Manganese; Mexico; Minerals; Spectrophotometry, Infrared; Spectrum Analysis, Raman; Tellurium; Zinc

Bioremediation of toxic nonmetal and metalloid oxyanions is of great interest. In this study, among 148 bacterial isolates from two types of polluted water, strain STG-83 showed maximum oxyanion reduction and resistance ability. Sequencing of the 16S rDNA gene of STG-83 showed that the strain is closely related to Bacillus pumilus and morphological and biochemical tests confirmed the result. The strain was nitrate negative, but it could reduce half of tellurite in solution containing 1-mM concentration and completely reduced selenite and selenate in solutions containing 1-mM concentrations. Both reduction to elemental form and volatilization occurred in case of all oxyanions tested, according to hydride generation atomic absorption spectroscopy and proton induced X-ray emission analytical methods. The strain was able to tolerate remarkably high concentrations of selenite (640 mM), selenate (320 mM), and tellurite (1250 microM); and tolerance to tellurite increased in presence of selenite and selenate. Biochemical tests and zymogram of extracted culture solutions on gel electrophoresis showed that the strain was nitrate negative and therefore nitrate did not interfere with reduction of other oxyanions. Thus, the strain opens up good opportunities for the bioremediation of polluted waters in natural environment, since nitrate usually inhibits or decelerates reduction of the mentioned toxic oxyanions.

Topics: Anions; Bacillus; Biodegradation, Environmental; Nitrates; Selenic Acid; Selenium Compounds; Sodium Selenite; Tellurium; Water Pollutants, Chemical; Water Purification

Pseudomonas pseudoalcaligenes KF707 is naturally resistant to the toxic metalloid tellurite, but the mechanisms of resistance are not known. In this study we report the isolation of a KF707 mutant (T5) with hyperresistance to tellurite. In order to characterize the bacterial response and the pathways leading to tolerance, we utilized Phenotype MicroArray technology (Biolog) and a metabolomic technique based on nuclear magnetic resonance spectroscopy. The physiological states of KF707 wild-type and T5 cells exposed to tellurite were also compared in terms of viability and reduced thiol content. Our analyses showed an extensive change in metabolism upon the addition of tellurite to KF707 cultures as well as different responses when the wild-type and T5 strains were compared. Even in the absence of tellurite, T5 cells displayed a "poised" physiological status, primed for tellurite exposure and characterized by altered intracellular levels of glutathione, branched-chain amino acids, and betaine, along with increased resistance to other toxic metals and metabolic inhibitors. We conclude that hyperresistance to tellurite in P. pseudoalcaligenes KF707 is correlated with the induction of the oxidative stress response, resistance to membrane perturbation, and reconfiguration of cellular metabolism.

Topics: Cytoplasm; Drug Resistance, Bacterial; Magnetic Resonance Spectroscopy; Metabolomics; Microbial Viability; Pseudomonas pseudoalcaligenes; Sulfhydryl Compounds; Tellurium

Tellurites may be subdivided according to formula and structure. There are five groups based upon the formulae: (a) A(XO(3)), (b) A(XO(3)).xH(2)O, (c) A(2)(XO(3))(3).x(2)O, (d) A(2)(X(2)O(5)) and (e) A(X(3)O(8)). Raman spectroscopy has been used to study mackayite and quetzalcoatlite are examples of tellurites containing OH units Raman bands for mackayite observed at 732, 782 and 579, 635cm(-1) are assigned to the nu(1) (Te(2)O(5))(2-) symmetric stretching and nu(3) (Te(2)O(5))(2-) antisymmetric stretching modes. The Raman spectral profile of quetzalcoatlite is more complex with a considerable number of overlapping bands. Two bands may be resolved at 719 and 754cm(-1) which may be attributed to nu(1) (Te(2)O(5))(2-) symmetric stretching mode. The two Raman bands of quetzalcoatlite at 602 and 606cm(-1) are accounted for by the nu(3) (Te(2)O(5))(2-) antisymmetric stretching mode. Raman bands for mackayite, observed at 306, 349, 379 and 424, 436cm(-1) are assigned to the (Te(2)O(5))(2-) nu(2) (A(1)) bending mode and nu(4) (E) bending modes. This research shows that Raman spectroscopy may be applied to tellurite minerals successfully.

Topics: Minerals; Spectrophotometry, Infrared; Spectrum Analysis, Raman; Tellurium

Tellurites may be subdivided according to formula and structure. There are five groups based upon the formulae (a) A(XO3); (b) A(XO3).xH2O; (c) A2(XO3)3.xH2O; (d) A2(X2O5) and (e) A(X3O8). Rodalquilarite, a tellurite mineral of type (a) has been studied using Raman spectroscopy. Observed from the spectra was the presence of protons, an essential stabilising element for the minerals structure and stability. The tellurite ion should show a maximum of six bands. The free tellurite ion shows C3v symmetry and has four modes, 2A1 and 2E. Three Raman bands at 726, 755 and 780 cm(-1) are assigned to the nu1 (TeO3)2- symmetric stretching mode and the two bands at 610 and 642 cm(-1) are attributed to the nu3 (TeO3)2- antisymmetric stretching mode. The two bands at 321 and 345 cm(-1) and the two bands at 449 and 473 cm(-1) are assigned to the (TeO3)2-nu2 (A1) bending mode and (TeO3)2-nu4 (E) bending mode. Raman bands observed at 2341, 2796 and 2870 cm(-1) are attributed to OH stretching vibrations caused by interaction between the protons and the oxygen of the tellurite units. The values for these OH stretching vibrations provide hydrogen bond distances of 2.550 (6) A (2341 cm(-1)), 2.610 (3) A (2796 cm(-1)) and 2.623 (2) A (2870 cm(-1)) which are comparatively short for secondary minerals.

Topics: Iron Compounds; Minerals; Spectrum Analysis, Raman; Tellurium

We isolated a moderately halophilic bacterium with high level of tolerance to two toxic oxyanions, selenite and tellurite, from hypersaline soil in Garmsar, Iran. 16s rRNA sequence analysis revealed that the isolate, strain MAM, had 98% similarity with Halomonas elongate, and is closely related to other species of the genus Halomonas. We observed that the tolerance to tellurite and its removal increased significantly when both selenite and tellurite were added to the culture media, suggesting a positive synergism of selenite on tellurite tolerance and removal. We applied a proteomic approach to study the proteome response of Halomonas sp. strain MAM to selenite, tellurite, and selenite + tellurite. Out of approximately 800 protein spots detected on 2-DE gels, 208 spots were differentially expressed in response to at least one of treatments. Of them, 70 CBB stained spots were analyzed by MALDI TOF/TOF mass spectrometry, leading to identification of 36 proteins. Our results revealed that several mechanisms including fatty acid synthesis, energy production, cell transport, oxidative stress detoxification, DNA replication, transcription and translation contributed in bacterial response and/or adaptation. These results provided new insights into the general mechanisms on the tolerance of halophilic bacteria to these two toxic oxyanions and the use of them for bioremediation of contaminated saline soils and wastes discharge sites.

Topics: Acetyl-CoA Carboxylase; Bacterial Proteins; Biodegradation, Environmental; Electrophoresis, Gel, Two-Dimensional; Halomonas; Phylogeny; Proteome; Proteomics; Sodium Selenite; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Stress, Physiological; Tellurium

A gram-positive bacterium (designated as strain TeW) that is highly resistant to tellurite was isolated from sediment. The bacterium can grow in the presence of up to 2,000 micromol/L of potassium tellurite (K2TeO3). Reduction of K2TeO3 to tellurium was indicated by the blackening of the growth medium. No lag in growth was observed when cells unexposed to tellurite were transferred to the growth medium containing K2TeO3, indicating that resistance to tellurite was not inducible. Up to 50 and 90% of the metalloid oxyanion tellurite (TeO(3)(2-)) was removed from the medium by strain TeW during growth in nonstatic (shaking) and static (without shaking) conditions, respectively. The bacterium was identified as a Paenibacillus sp. according to its morphology, physiology, and 16S rDNA sequence homology.

Topics: Geologic Sediments; Gram-Positive Endospore-Forming Bacteria; Metals, Heavy; Phylogeny; Tellurium

There are few appropriate single-copy genetic tools for most Burkholderia species, and the high level of antibiotic resistance in this genus further complicates the development of genetic tools. In addition, the utilization of resistance genes for clinically important antibiotics is prohibited for the bioterrorism agents Burkholderia pseudomallei and Burkholderia mallei, necessitating the development of additional nonantibiotic-based genetic tools. Three single-copy systems devoid of antibiotic selection based on two nonantibiotic selectable markers, tellurite resistance (Tel(r)) and Escherichia coli aspartate-semialdehyde dehydrogenase (asd(Ec)), were developed to facilitate genetic manipulation in Burkholderia species. These systems include one mariner transposon, a mini-Tn7-derived site-specific transposon, and six FRT reporter fusion vectors based on the lacZ, gfp, and luxCDABE reporter genes. Initially, we showed that the random mariner transposon pBT20-Deltabla-Tel(r)-FRT efficiently transposed within Burkholderia cenocepacia, Burkholderia thailandensis, B. pseudomallei, and B. mallei. We then utilized the mini-Tn7-Tel(r)-based transposon vector (mini-Tn7-Tel(r)-betBA) and a transposase-containing helper plasmid (pTNS3-asd(Ec)) to complement the B. thailandensis DeltabetBA mutation. Next, one of the FRT-lacZ fusion vectors (pFRT1-lacZ-Tel(r)) was integrated by Flp (encoded on a helper plasmid, pCD13SK-Flp-oriT-asd(Ec)) to construct the B. thailandensis DeltabetBA::FRT-lacZ-Tel(r) reporter fusion strain. The betBA operon was shown to be induced in the presence of choline and under osmotic stress conditions by performing beta-galactosidase assays on the B. thailandensis DeltabetBA::FRT-lacZ-Tel(r) fusion strain. Finally, we engineered B. thailandensis DeltabetBA::FRT-gfp-Tel(r) and DeltabetBA::FRT-lux-Tel(r) fusion strains by utilizing fusion vectors pFRT1-gfp-Tel(r) and pFRT1-lux-Tel(r), respectively. The induction of the betBA operon by choline and osmotic stress was confirmed by performing fluorescent microscopy and bioluminescent imaging analyses.

Topics: Anti-Bacterial Agents; Artificial Gene Fusion; Aspartate-Semialdehyde Dehydrogenase; Bacterial Proteins; Burkholderia; Choline; DNA Transposable Elements; DNA, Bacterial; Drug Resistance, Bacterial; Escherichia coli Proteins; Gene Deletion; Gene Expression Profiling; Gene Expression Regulation, Bacterial; Genes, Reporter; Genetic Complementation Test; Molecular Biology; Molecular Sequence Data; Operon; Osmotic Pressure; Selection, Genetic; Sequence Analysis, DNA; Tellurium

The tellurium oxyanion tellurite is toxic for most organisms and it seems to alter a number of intracellular targets. In this work the toxic effects of tellurite upon Escherichia coli [4Fe-4S] cluster-containing dehydratases was studied. Reactive oxygen species (ROS)-sensitive fumarase A (FumA) and aconitase B (AcnB) as well as ROS-resistant fumarase C (FumC) and aconitase A (AcnA) were assayed in cell-free extracts from tellurite-exposed cells in both the presence and absence of oxygen. While over 90 % of FumA and AcnB activities were lost in the presence of oxygen, no enzyme inactivation was observed in anaerobiosis. This result was not dependent upon protein biosynthesis, as determined using translation-arrested cells. Enzyme activity of purified FumA and AcnB was inhibited when exposed to an in vitro superoxide-generating, tellurite-reducing system (ITRS). No inhibitory effect was observed when tellurite was omitted from the ITRS. In vivo and in vitro reconstitution experiments with tellurite-damaged FumA and AcnB suggested that tellurite effects involve [Fe-S] cluster disabling. In fact, after exposing FumA to ITRS, released ferrous ion from the enzyme was demonstrated by spectroscopic analysis using the specific Fe(2+) chelator 2,2'-bipyridyl. Subsequent spectroscopic paramagnetic resonance analysis of FumA exposed to ITRS showed the characteristic signal of an oxidatively inactivated [3Fe-4S](+) cluster. These results suggest that tellurite inactivates enzymes of this kind via a superoxide-dependent disabling of their [4Fe-4S] catalytic clusters.

Topics: Aconitate Hydratase; Aerobiosis; Anaerobiosis; Escherichia coli; Ferrous Compounds; Fumarate Hydratase; Hydro-Lyases; Intramolecular Oxidoreductases; Iron-Sulfur Proteins; Spectrum Analysis; Superoxides; Tellurium

In this paper we explore the TeO(2)-Bi(2)O(3)-BaO glass family with varied TeO(2) concentration for Raman gain applications, and we report, for the first time, the peak Raman gain coefficients of glasses within this glass family extrapolated from non-resonant absolute Raman cross-section measurements at 785 nm. Estimated Raman gain coefficients show peak values of up to 40 times higher than silica for the main TeO(2) bands. Other optical properties, including index dispersion from the visible to the long wave Infrared (LWIR) are also summarized in this paper.

Topics: Algorithms; Barium; Bismuth; Glass; Manufactured Materials; Reproducibility of Results; Sensitivity and Specificity; Spectrum Analysis, Raman; Tellurium

Selenium is an essential trace element incorporated as selenocysteine in 25 human selenoproteins. Among them are thioredoxin reductases (TrxR) and glutathione peroxidases, all central proteins in the regulation of the cellular thiol redox state. In this paper the effects of selenite and tellurite treatment in human cancer cells are reported and compared. Our results show that both selenite and tellurite, at relatively low concentrations, are able to increase the expression of mitochondrial and cytosolic TrxR in cisplatin-sensitive (2008) and -resistant (C13*) phenotypes. We further investigated the cellular effects induced by selenite or tellurite in combination with the specific TrxR inhibitor auranofin. Selenite pretreatment induced a dramatic increase in auranofin cytotoxicity in both resistant and sensitive cells. Investigation of TrxR activity and expression levels as well as the cellular redox state demonstrated the involvement of TrxR inhibition and redox changes in selenite and auranofin combined action.

Topics: Adenocarcinoma; Auranofin; Cell Death; Cell Line, Tumor; Cisplatin; Drug Resistance, Neoplasm; Enzyme Inhibitors; Female; Gene Expression Regulation, Neoplastic; Humans; Lung Neoplasms; Ovarian Neoplasms; Sodium Selenite; Tellurium; Thioredoxin-Disulfide Reductase

Endface reflectivities (ERs) of optical nanowires are investigated using three-dimensional finite-difference time-domain simulations. Typical ERs of both free-standing and substrate-supported silica, tellurite, PMMA and semiconductor nanowires or nanofibers are obtained. Unlike in conventional waveguides such as optical fibers, ERs of nanowires are usually considerably lower when operated in single mode. Dependences of ER on the diameter and the refractive index of the nanowire, and the wavelength of the guided light are also investigated. These results are helpful for estimating and understanding ERs in optical nanowires with diameters close to or smaller than the wavelengths of the light, and may offer valuable references for practical applications such as nanowire or nanofiber-based resonators and lasers.

Topics: Computer Simulation; Equipment Design; Fiber Optic Technology; Imaging, Three-Dimensional; Light; Nanotechnology; Nanowires; Optical Fibers; Optics and Photonics; Scattering, Radiation; Semiconductors; Silicon Dioxide; Tellurium

Tellurite glass microstructure fibers with a 1 microm hexagonal core were fabricated successfully by accurately controlling the temperature field in the fiber-drawing process. The diameter ratio of holey region to core (DRHC) for the fiber can be adjusted freely in the range of 1-20 by pumping a positive pressure into the holes when drawing fiber, which provides much freedom in engineering the chromatic dispersion. With the increase of DRHC from 3.5 to 20, the zero dispersion wavelengths were shifted several hundred nanometers, the cutoff wavelength due to confinement loss was increased from 1600 nm to 3800 nm, and the nonlinear coefficient gamma was increased from 3.9 to 5.7 W(-1)/m. Efficient visible emissions due to third harmonic generation were found for fibers with a DRHC of 10 and 20 under the 1557 nm pump of a femtosecond fiber laser. One octave flattened supercontinuum spectrum was generated from fibers with a DRHC of 3.5, 10 and 20 by the 1064 nm pump of a picosecond fiber laser. To the best of our knowledge, we have for the first time fabricated a hexagonal core fiber by soft glass with such a small core size, and have demonstrated a large influence of the holey region on the dispersion, nonlinear coefficient and supercontinuum generation for such fiber.

Topics: Eyeglasses; Gases; Lasers; Models, Statistical; Optical Fibers; Optics and Photonics; Pressure; Tellurium; Time Factors

Two serial Dy(3+)-doped and Dy(3+), Tm(3+)-codoped (100-x)(0.8GeS(2).0.2Ga(2)S(3)).xCdI(2) (0Dy(3+): 6H 11/2 energy transfer efficiency and intensified the mid-infrared emissions. The emission cross sections (sigma emi) of the 2900 and 4300 nm fluorescences were estimated to be 1.68 x 10(-20) and 1.20 x 10(-20)cm(2) respectively for the 0.2 wt% Dy(3+) and 0.5 wt% Tm(3+) codoped 64 GeS(2).16 Ga(2)S(3).20 CdI(2) glass. These novel chalcohalide glasses are promising candidate materials for fiber-amplifiers and mid-infrared laser devices.

Topics: Cadmium Compounds; Dysprosium; Gallium; Germanium; Glass; Halogens; Iodides; Luminescence; Optics and Photonics; Spectrometry, Fluorescence; Spectrophotometry; Spectrophotometry, Infrared; Spectrophotometry, Ultraviolet; Sulfur; Tellurium; Thulium

Upconversion (UC) emissions in UV/blue region have been observed in Nd(3+) doped tellurite glass on 532 nm excitation. The UC bands have been observed at 360, 387, 417 and 452 nm due to the (4)D(3/2)-->(4)I(9/2), (4)D(3/2)-->(4)I(11/2), (4)D(3/2)-->(4)I(13/2) and (4)D(3/2)-->(4)I(15/2) transitions, respectively and they show two photon character. The effect of BaCO(3), BaF(2) and BaCl(2) glass modifiers on the UC efficiency has been studied and Judd-Ofelt intensity parameters have been calculated and compared. The BaCl(2) modified glass showed maximum UC intensity among the three modifiers and this enhancement in UC intensity has been related to the reduction in average phonon frequency of the glass sample. Heat treatments of the BaF(2) and BaCl(2) modified samples also show enhancement in UC intensity while the BaCO(3) modified sample has no such effect. Lifetime of the (4)D(3/2) level has been measured to understand the mechanism responsible for UC emission. Temperature dependent fluorescence studies have been done on the (4)F(3/2), (4)F(5/2) and (2)S(3/2) emitting levels and results show that Nd(3+) doped tellurite glass can be used as a temperature sensor.

Topics: Hot Temperature; Luminescent Measurements; Neodymium; Optics and Photonics; Spectrometry, Fluorescence; Tellurium

The effects of potassium tellurite on growth and survival of rho(+) and rho(0) Saccharomyces cerevisiae strains were investigated. Both rho(+) and rho(0) strains grew on a fermentable carbon source with up to 1.2 mM K(2)TeO(3), while rho(+) yeast cells grown on a non-fermentable carbon source were inhibited at tellurite levels as low as 50 muM suggesting that this metalloid specifically inhibited mitochondrial functions. Growth of rho(+) yeast cells in the presence of increasing amount of tellurite resulted in dose-dependent blackening of the culture, a phenomenon not observed with rho(0) cultures. Transmission electron microscopy of S. cerevisiae rho(+) cells grown in the presence of tellurite showed that blackening was likely due to elemental tellurium (Te(0)) that formed large deposits along the cell wall and small precipitates in both the cytoplasm and mitochondria.

Topics: Carbon; Fermentation; Microscopy, Electron, Transmission; Mitochondria; Oxidation-Reduction; Saccharomyces cerevisiae; Tellurium

Nanowires of lead telluride (PbTe) were patterned on glass surfaces using lithographically patterned nanowire electrodeposition (LPNE). LPNE involved the fabrication by photolithography of a contoured nickel nanoband that is recessed by approximately 300 nm into a horizontal photoresist trench. Cubic PbTe was then electrodeposited from a basic aqueous solution containing Pb(2+) and TeO(3)(2-) at the nickel nanoband using a cyclic deposition/stripping potential program in which lead-rich PbTe was first deposited in a negative-going potential scan and excess lead was then anodically stripped from the nascent nanowire by scanning in the positive direction to produce near stoichiometric PbTe. Repeating this scanning procedure permitted PbTe nanowires 60-400 nm in width to be obtained. The wire height was controlled over the range of 20-100 nm based upon the nickel film thickness. Nanowires with lengths exceeding 1 cm were prepared in this study. We report the characterization of these nanowires using X-ray diffraction, transmission electron microscopy and electron diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). The surface chemical composition of PbTe nanowires was monitored by XPS as a function of time during the exposure of these nanowires to laboratory air. One to two monolayers of a mixed Pb and Te oxide are formed during a 24 h exposure. The electrical conductivity of PbTe nanowires was strongly affected by air oxidation, declining from an initial value of 2.0(+/-1.5) x 10 (4) S/m by 61% (for nanowires with a 20 nm thickness), 55% (for 40 nm), and 12% (for 60 nm).

Topics: Crystallization; Electric Conductivity; Lead; Macromolecular Substances; Materials Testing; Molecular Conformation; Nanotechnology; Nanotubes; Particle Size; Surface Properties; Tellurium; Titanium

We investigated the influence of self-diffraction effect on femtosecond cross pump-probe optical Kerr shutter (OKS) measurements for fast response and slow response materials, respectively. In the slow response material of CS(2), a fast response resulted from self-diffraction effect was observed in the time-resolved OKS signals, and the signal intensity showed different pump power dependences at different delay time. For the fast response material of bismuth oxide (BI) glass, the pump power dependence of OKS signals varied when the polarization angle was varied. The pump power dependences of OKS signals for the both materials showed that, the OKS signals resulted mainly from laser induced birefringence effect at low pump powers, and the contribution of self-diffraction effect to OKS signals was enhanced with increasing the pump power.

Topics: Chalcogens; Equipment Design; Glass; Infrared Rays; Lasers; Microscopy, Electron, Scanning; Optical Devices; Optical Fibers; Optics and Photonics; Refractometry; Spectroscopy, Near-Infrared; Tellurium

Continuous-wave and Q-switched lasing from a Tm(3+)/Ho(3+) codoped tellurite fiber is reported. An Yb(3+)/Er(3+)-doped silica fiber laser operating at 1.6 microm was used as an in-band pump source, exciting the Tm(3+) ions into the (3)F(4) level. Energy is then nonradiatively transferred to the upper laser level, the (5)I(7) state of Ho(3+). The laser transition is from the (5)I(7) level to the (5)I(8) level, and the resulting emission is at 2.1 microm. For continuous wave operation, the slope efficiency was 62% and the threshold 0.1 W; the maximum output demonstrated was 0.16 W. Mechanical Q switching resulted in a pulse of 0.65 microJ energy and 160 ns duration at a repetition rate of 19.4 kHz.

Topics: Equipment Design; Glass; Holmium; Ions; Lasers; Light; Luminescent Measurements; Silicon Dioxide; Tellurium; Thulium; Time Factors

We demonstrate superluminal propagation of optical pulses with amplification in optical fibers based on stimulated Brillouin scattering. A triple gain peak configuration is used for the generation of narrowband anomalous dispersion in 2 m tellurite glass fiber, where the group index change as much as -1.19 is achieved with 6.9 dB amplification in 34 ns Gaussian pulses, leading to the group index of 0.84.

Topics: Equipment Design; Equipment Failure Analysis; Fiber Optic Technology; Glass; Optical Fibers; Refractometry; Scattering, Radiation; Signal Processing, Computer-Assisted; Tellurium

We report broad bandwidth, mid-IR supercontinuum generation using a sub-cm (8 mm) length of highly nonlinear tellurite microstructured photonic crystal fiber (PCF). We pump the fiber at telecommunication wavelengths by using 1550 nm, 100 fs pulses of energy E=1.9 nJ. When coupled in the PCF, these pulses result in a supercontinuum (SC) bandwidth of 4080 nm extending from 789 to 4870 nm measured at 20 dBm below the peak spectral power. This bandwidth is comparable or in excess of previously reported spectra for other nonlinear glass fiber formulations despite the significantly shorter fiber length. In addition, besides offering a convenient pump wavelength, short fiber lengths enable smoother SC spectra, lower dispersion, and reduced material absorption at longer wavelengths making the use of this PCF particularly interesting.

Topics: Crystallization; Equipment Design; Glass; Lasers; Light; Microscopy, Confocal; Optics and Photonics; Photons; Spectrophotometry, Infrared; Tellurium

Tellurites may be subdivided according to formula and structure. There are five groups based upon the formulae (a) A(XO3), (b) A(XO3).xH2O, (c) A2(XO3)3.xH2O, (d) A2(X2O5) and (e) A(X3O8). Raman spectroscopy has been used to study rajite and denningite, examples of group (d). Minerals of the tellurite group are porous zeolite-like materials. Raman bands for rajite observed at 740, and 676 and 667 cm(-1) are attributed to the nu1 (Te2O5)(2-) symmetric stretching mode and the nu3 (TeO3)(2-) antisymmetric stretching modes, respectively. A second rajite mineral sample provided a more complex Raman spectrum with Raman bands at 754 and 731 cm(-1) assigned to the nu1 (Te2O5)(2-) symmetric stretching modes and two bands at 652 and 603 cm(-1) are accounted for by the nu3 (Te2O5)(2-) antisymmetric stretching mode. The Raman spectrum of dennigite displays an intense band at 734 cm(-1) attributed to the nu1 (Te2O5)(2-) symmetric stretching mode with a second Raman band at 674 cm(-1) assigned to the nu3 (Te2O5)(2-) antisymmetric stretching mode. Raman bands for rajite, observed at (346, 370) and 438 cm(-1) are assigned to the (Te2O5)(2-)nu2 (A1) bending mode and nu4 (E) bending modes.

Topics: Crystallization; Geology; Mexico; Minerals; New Mexico; Oxides; Spectrophotometry, Infrared; Spectrum Analysis, Raman; Tellurium; Zeolites; Zinc

We report the fabrication of a large mode area tellurite holey fiber from an extruded preform, with a mode area of 3000microm(2). Robust single-mode guidance at 1.55microm was confirmed by both optical measurement and numerical simulation. The propagation loss was measured as 2.9dB/m at 1.55microm. A broad and flat supercontinuum from 0.9 to 2.5microm with 6mW output was obtained with a 9cm length of this fiber.

Topics: Computer Simulation; Computer-Aided Design; Equipment Design; Equipment Failure Analysis; Fiber Optic Technology; Glass; Models, Theoretical; Nonlinear Dynamics; Tellurium

We report on fs-laser micromachining of active waveguides in a new erbium-doped phospho-tellurite glass by means of a compact cavity-dumped Yb-based writing system. The spectroscopic properties of the glass were investigated, and the fs-laser written waveguides were characterized in terms of passive as well as active performance. In particular, internal gain was demonstrated in the whole C+L band of optical communications (1530- 1610 nm).

Topics: Amplifiers, Electronic; Computer Simulation; Computer-Aided Design; Equipment Design; Equipment Failure Analysis; Erbium; Glass; Lasers; Models, Theoretical; Optics and Photonics; Phosphorus; Tellurium

A novel and disposable microchip (K-kit) with SiO(2) nano-membranes was developed and used as a specimen kit for in situ imaging of living organisms in an aqueous condition using transmission electron microscopy (TEM) without equipment modification. This K-kit enabled the successful TEM observation of living Escherichia coli cells and the tellurite reduction process in Klebsiella pneumoniae. The K. pneumoniae and Saccharomyces cerevisiae can stay alive in K-kit after continuous TEM imaging for up to 14 s and 42 s, respectively. Besides, different tellurite reduction profiles in cells grown in aerobic and anaerobic environments can be clearly revealed. These results demonstrate that the K-kit developed in this paper can be useful for observing living organisms and monitoring biological processes in situ.

Topics: Bacteria; Cell Survival; Feasibility Studies; Fungi; Klebsiella pneumoniae; Microchip Analytical Procedures; Microscopy, Electron, Transmission; Microtechnology; Nanoparticles; Tellurium; Water

To compare rhamnose MacConkey agar supplemented with cefixime and tellurite (CT-RMac) and tryptone bile X-glucuronide (TBX) agars as isolation media for Vero cytotoxin-producing Escherichia coli (VTEC) serogroup O26 from animal faeces.. Nine VTEC O26 were isolated from sheep faeces; out of which six were isolated only on CT-RMac and one was isolated only on TBX. One hundred and twelve VTEC O26 were isolated from calf faeces; out of which 97% were from CT-RMac and 52% were from TBX. In a study of E. coli O26 strains, 84% of VT-positive O26 did not ferment rhamnose when compared with 16% of VT-negative O26. VT-positive (19%) and VT-negative (39%) E. coli O26 strains did not grow on CT-RMac agar.. It is important to consider that VTEC O26 strains either may ferment rhamnose or may be sensitive to the CT supplement of CT-RMac agar.. This work compares CT-RMac and TBX agars as isolation medium for VTEC O26 from Scottish animal faeces and highlights that VTEC O26 may be missed if only CT-RMac agar is used.

Topics: Agar; Animals; Cattle; Cefixime; Culture Media; Feces; Fermentation; Rhamnose; Sheep; Shiga-Toxigenic Escherichia coli; Tellurium

We report spectroscopic and bulk laser performance characteristics for Tm(3+)-doped tellurite glasses when used as gain media operating around 1.9 microm. Two glass hosts studied are TZN and TZNG and their performances have been compared. In each case, well-characterized cw laser performance was obtained and this has been related to detailed spectroscopic measurements of the important lasing parameters of the laser transitions around 1900 nm when pumped at 793 nm. The maximum output power achieved was 124 mW from the TZNG sample with an associated slope efficiency of 28 % with a tuning range of 135 nm. Efficiency and loss analyses yielded a calculated maximum attainable efficiency of 48 % in Tm(3+):TZN compared to 28 % for the TZNG host.

Topics: Computer-Aided Design; Equipment Design; Equipment Failure Analysis; Glass; Infrared Rays; Lasers; Reproducibility of Results; Sensitivity and Specificity; Spectrum Analysis; Tellurium

Among the 49 strains of moderately halophilic bacteria isolated from the salty environments of Iran, a Gram-positive coccus designated as strain QW6 showed high capacity in the removal of toxic oxyanions of tellurium in a wide range of culture medium factors including pH (5.5-10.5), temperature (25-45 degrees C), various salts including NaCl, KCl, and Na(2)SO(4) (0.5-4 M), selenooxyanions (2-10 mM), and at different concentrations of potassium tellurite (0.5-1 mM) under aerobic condition. Phenotypic characterization and phylogenetic analyses based on 16S rDNA sequence comparisons indicated that this strain was a member of the genus Salinicoccus. The maximum tellurite removal was exhibited in 1.5M NaCl at 35 degrees C, while the activity reduced by 53% and 47% at 25 and 45 degrees C, respectively. The optimum pH for removal activity was shown to be 7.5, with 90% and 83% reduced removal capacities at the two extreme values of 5.5 and 10, respectively. The impact of different concentrations of selenooxyanions (2-10 mM) on tellurite removal by strain QW6 was evaluated. The ability of strain QW6 in the removal of tellurite in the presence of 6mM selenite increased by 25%. The concentration of toxic potassium tellurite in the supernatant of the bacterial culture medium decreased by 99% (from 0.5 to 0.005 mM) after 6 days and the color of the medium changed to black due to the formation of less toxic elemental tellurium.

Topics: Aerobiosis; Culture Media; DNA, Bacterial; DNA, Ribosomal; Genes, rRNA; Hydrogen-Ion Concentration; Iran; Molecular Sequence Data; Phylogeny; RNA, Bacterial; RNA, Ribosomal, 16S; Sequence Analysis, DNA; Sequence Homology, Nucleic Acid; Sodium Chloride; Sodium Selenite; Soil Microbiology; Staphylococcaceae; Tellurium; Temperature

The facultative phototroph Rhodobacter capsulatus takes up the highly toxic oxyanion tellurite when grown under both photosynthetic and respiratory growth conditions. Previous works on Escherichia coli and R. capsulatus suggested that tellurite uptake occurred through a phosphate transporter. Here we present evidences indicating that tellurite enters R. capsulatus cells via a monocarboxylate transport system. Indeed, intracellular accumulation of tellurite was inhibited by the addition of monocarboxylates such as pyruvate, lactate and acetate, but not by dicarboxylates like malate or succinate. Acetate was the strongest tellurite uptake antagonist and this effect was concentration dependent, being already evident at 1 microM acetate. Conversely, tellurite at 100 microM was able to restrict the acetate entry into the cells. Both tellurite and acetate uptakes were energy dependent processes, since they were abolished by the protonophore FCCP and by the respiratory electron transport inhibitor KCN. Interestingly, cells grown on acetate, lactate or pyruvate showed a high level resistance to tellurite, whereas cells grown on malate or succinate proved to be very sensitive to the oxyanion. Taking these data together, we propose that: (a) tellurite enters R. capsulatus cells via an as yet uncharacterized monocarboxylate(s) transporter, (b) competition between acetate and tellurite results in a much higher level of tolerance against the oxyanion and (c) the toxic action of tellurite at the cytosolic level is significantly restricted by preventing tellurite uptake.

Topics: Acetic Acid; Biological Transport, Active; Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; Enzyme Inhibitors; Lactic Acid; Malates; Monocarboxylic Acid Transporters; Potassium Cyanide; Pyruvic Acid; Rhodobacter capsulatus; Succinic Acid; Tellurium

This paper reports on the optical spectroscopic properties and thermal stability of Er3+-doped antimony-borosilicate glasses for developing 1.5 microm optical amplifiers. Upon excitation at 980 nm laser diode, an intense 1.5 microm infrared fluorescence has been observed with the maximum full width at half maximum (FWHM) of 90 nm for Er3+-doped antimony-borosilicate glasses. The emission cross-section and the lifetime of the 4I13/2 level of Er3+ ions are 6.3 x 10(-21) cm2 and 0.30 ms, respectively. It is noted that the product of the emission cross-section and FWHM of the glass studied is as great as 567 x 10(-21) cm2 nm, which is comparable or higher than that of bismuthate and tellurite glasses.

Topics: Antimony; Bismuth; Calorimetry, Differential Scanning; Erbium; Glass; Ions; Models, Chemical; Optics and Photonics; Silicates; Spectrophotometry; Tellurium; Temperature

A new method was developed for the speciation of inorganic tellurium species in seawater by inductively coupled plasma-MS (ICP-MS) following selective magnetic SPE (MSPE) separation. Within the pH range of 2-9, tellurite (Te(IV)) could be quantitatively adsorbed on gamma-mercaptopropyltrimethoxysilane (gamma-MPTMS) modified silica-coated magnetic nanoparticles (MNPs), while the tellurate (Te(VI)) was not retained and remained in solution. Without filtration or centrifugation, these tellurite-loaded MNPs could be separated easily from the aqueous solution by simply applying external magnetic field. The Te(IV) adsorbed on the MNPs could be recovered quantitatively using a solution containing 2 mol/L HCl and 0.03 mol/L K2Cr2O7. Te(VI) was reduced to Te(IV) by L-cysteine prior to the determination of total tellurium, and its assay was based on subtracting Te(IV) from total tellurium. The parameters affecting the separation were investigated systematically and the optimal separation conditions were established. Under the optimal conditions, the LOD obtained for Te(IV) was 0.079 ng/L, while the precision was 7.0% (C = 10 ng/L, n = 7). The proposed method was successfully applied to the speciation of inorganic tellurium in seawater.

Topics: Magnetics; Mass Spectrometry; Nanoparticles; Organosilicon Compounds; Seawater; Silanes; Silicon Dioxide; Solid Phase Extraction; Spectrophotometry, Atomic; Tellurium

Energy transfer excited upconversion emission in Nd3+/Pr3+-codped tellurite glass have been studied on pumping with 800 nm wavelength. The upconversion emission bands from Pr3+ ion are observed at the 488, 524, 546, 612, 647, 672, 708 and 723 nm due to the (3P0 + 3P1)-->3H4, 3P1-->3H5, 3P0-->3H5, 3P0-->3H6, 3P0-->3F2, 3P1-->3F3, 3P0-->3F3 and 3P0-->3F4 transitions, respectively. The addition of ytterbium ions (Yb3+) on the upconversion emission intensity is also studied and result shows an eight times enhancement in the upconversion intensity at 488 nm from Pr3+ ions. The pump power and concentration dependence studies are also made. It is found that Yb3+ ions transfer its excitation energy to Nd3+ from which it goes to Pr3+. No direct transfer to Pr3+ is seen. This is verified by codoping Nd3+ and Pr3+ into the host.

Topics: Color; Energy Transfer; Glass; Ions; Neodymium; Praseodymium; Spectrophotometry; Tellurium; Ytterbium

Klebsiella pneumoniae (KP), a Gram-negative bacterium, is a common cause of hospital-acquired bacterial infections worldwide. Tellurium (Te) compounds, although relatively rare in the environment, have a long history as antimicrobial and therapeutic agents. In bacteria, tellurite (TeO(3) (-2)) resistance is conferred by the ter (Te(r)) operon (terZABCDEF). Here, on the basis of 2593 restraints derived from NMR analysis, we report the NMR structure of TerB protein (151 amino acids) of KP (KP-TerB), which is mainly composed of seven alpha-helices and a 3(10) helix, with helices II to V apparently forming a four-helix bundle. The ensemble of 20 NMR structures was well-defined, with a RMSD of 0.32 +/- 0.06 A for backbone atoms and 1.11 +/- 0.07 A for heavy atoms, respectively. A unique property of the KP-TerB structure is that the positively and negatively charged clusters are formed by the N-terminal positively and C-terminal negatively charged residues, respectively. To the best of our knowledge, the protein sequence and structures of KP-TerB are unique.

Topics: Bacterial Proteins; Drug Resistance, Bacterial; Klebsiella pneumoniae; Models, Molecular; Nuclear Magnetic Resonance, Biomolecular; Protein Structure, Secondary; Tellurium

A three-core tellurite glass fiber having different combinations of rare earth oxide dopants in each core has been fabricated using shaped die-extrusion. Three cores, doped with Ho(3+)-Tm(3+)-Yb(3+), Er(3+)-Ce(3+), and Tm(3+)-Yb(3+) respectively, exhibited visible upconversion (blue, green and red) and infrared emissions at 1.4 microm, 1.5 microm, 1.9 microm and 2.05 microm when pumped at a wavelength of 980 nm. The prospects for multi-band amplifiers and lasers are discussed.

Topics: Computer-Aided Design; Equipment Design; Equipment Failure Analysis; Metals, Rare Earth; Optical Fibers; Reproducibility of Results; Sensitivity and Specificity; Tellurium

The B2O3 was introduced into the Er3+ doped TeO2-ZnO-Na2O glass to increase the phonon energy of the host. The effect of B2O3 on the non-radiative rate of the 4I11/2-->4I13/2 transition of Er3+, the lifetime of the 4I11/2 and 4I13/2 levels, the green and red upconversion emissions intensity, and the 4I13/2-->4I15/2 emission intensity was discussed. The results show that the phonon energy of boro-tellurite glass is close to that of germanate glass and is quite smaller than that of borate glass. The lifetime of 4I11/2 level and the upconversion emissions decrease with increasing B2O3 concentration. The higher OH group concentration presented in the boro-tellurite glass may shorten the lifetime of 4I13/2 level and also reduce the quantum efficiency of 4I13/2-->4I15/2 emission. The future dehydrating procedures are suggested to enhance the efficiency of amplification at 1.5 microm band.

Topics: Boron Compounds; Erbium; Glass; Luminescent Measurements; Spectroscopy, Fourier Transform Infrared; Tellurium

The compositional and concentration dependence of luminescence of the (4)F(3/2)-->(4)I(J) (J=13/2, 11/2 and 9/2) transitions in four Nd(3+)-doped tellurite based glasses has been studied. The free-ion energy levels obtained for 60TeO(2)+39ZnO(2)+1.0Nd(2)O(3) (TZN10) glass have been analysed using the free-ion Hamiltonian model and compared with similar results obtained for Nd(3+):glass systems. The absorption spectrum of TZN10 glass has been analysed using the Judd-Ofelt theory. Relatively longer decay rates have been obtained for Nd(3+)-doped phosphotellurite glasses. The emission characteristics of the (4)F(3/2)-->(4)I(11/2) transition, of the Nd(3+):TZN10 glass, are found to be comparable to those obtained for Nd(3+):phosphate laser glasses. The non-exponential shape of the emission decay curves for the (4)F(3/2)-->(4)I(11/2) transition is attributed to the presence of energy transfer processes between the Nd(3+) ions.

Topics: Fluorescence; Glass; Ions; Neodymium; Spectrometry, Fluorescence; Tellurium

The highly toxic oxyanion tellurite (TeO3(2-)) is a well known pro-oxidant in mammalian and bacterial cells. This work examines the effects of tellurite on the redox state of the electron transport chain of the facultative phototroph Rhodobacter capsulatus, in relation to the role of the thiol:disulfide oxidoreductase DsbB. Under steady-state respiration, the addition of tellurite (2.5 mM) to membrane fragments generated an extrareduction of the cytochrome pool (c- and b-type hemes); further, in plasma membranes exposed to tellurite (0.25 to 2.5 mM) and subjected to a series of flashes of light, the rate of the QH2:cytochrome c (Cyt c) oxidoreductase activity was enhanced. The effect of tellurite was blocked by the antibiotics antimycin A and/or myxothiazol, specific inhibitors of the QH2:Cyt c oxidoreductase, and, most interestingly, the membrane-associated thiol:disulfide oxidoreductase DsbB was required to mediate the redox unbalance produced by the oxyanion. Indeed, this phenomenon was absent from R. capsulatus MD22, a DsbB-deficient mutant, whereas the tellurite effect was present in membranes from MD22/pDsbB(WT), in which the mutant gene was complemented to regain the wild-type DsbB phenotype. These findings were taken as evidence that the membrane-bound thiol:disulfide oxidoreductase DsbB acts as an "electron conduit" between the hydrophilic metalloid and the lipid-embedded Q pool, so that in habitats contaminated with subinhibitory amounts of Te(IV), the metalloid is likely to function as a disposal for the excess reducing power at the Q-pool level of facultative phototrophic bacteria.

Topics: Cell Membrane; Cytochrome c Group; Gene Expression Regulation, Bacterial; Light; Oxidation-Reduction; Oxidoreductases; Rhodobacter capsulatus; Tellurium

Up-conversion luminescence characteristics under 975 nm excitation have been investigated with Tb3+/Tm3+/Yb3+ triply doped tellurite glasses. Here, green (547 nm: (5)D(4)-->(7)F(4)) and red (660 nm: (5)D(4)-->(7)F(2)) up-conversion (UC) luminescence originating from Tb3+ is observed strongly, because of the quadratic dependences of emission intensities on the excitation power. Especially, the UC luminescence was intensified violently with the energy transfer from the Tm3+ ions involves in the Tb3+ excitation. To the Tb3+/Tm3+/Yb3+ triply doped glass system, a novel up-conversion mechanism is proposed as follows: the energy of (3)G(4) level (Tm3+) was transferred to (5)D(4) (Tb(3+)) and the 477-nm UC luminescence of Tm3+ was nearly quenched.

Topics: Glass; Ions; Luminescence; Spectrophotometry; Tellurium; Terbium; Thulium; Time Factors; Ytterbium

Quantum yields for multichannel transition emissions have been determined in Sm3+-doped heavy metal tellurite glass under the pumping of blue lighting emitting diode for the first time. To achieve this goal, the necessary fluorescence spectra were measured and calibrated in an integrating sphere, which was connected to a CCD detector with a 400 microm-core optical fiber. The spectral power distribution of the sample under the blue LED pumping was derived from the measured spectra firstly, and then the quantum yields for the visible emissions of Sm3+ were calculated based on the distribution and the total quantum yields in visible region is 7.55%. For accurate measurements, integrating sphere method is proved to be a reliable and reproducible way to characterize luminescence and laser materials.

Topics: Glass; Luminescence; Metals, Heavy; Photons; Quantum Theory; Samarium; Tellurium

Lactobacillus reuteri inhibits Staphylococcus aureus growth on Baird-Parker agar. This activity required the presence of tellurite and was not shared with other lactic acid bacteria or an L. reuteri mutant defective in cystine metabolism. Secreted products generated from L. reuteri cystine metabolism and thiols were shown to augment tellurite toxicity.

Topics: Agar; Bacterial Proteins; Bacteriological Techniques; Culture Media; Cystine; Limosilactobacillus reuteri; Staphylococcus aureus; Sulfhydryl Compounds; Tellurium

Optical properties of Tm(3+) and Er(3+) and Tm(3+)+Er(3+) codoped tellurite glass have been studied using different wavelengths from a Ti-Sapphire laser as excitation source. The energy transfer from one rare earth to other on excitation with different wavelengths has been studied. The Judd-Ofelt theory has been used to calculate various optical parameters suitable for laser oscillation.

Topics: Aluminum Oxide; Chemistry; Chemistry, Physical; Erbium; Glass; Lasers; Lithium; Models, Chemical; Oscillometry; Spectrophotometry, Infrared; Spectroscopy, Near-Infrared; Tellurium; Temperature; Titanium

Certain toxic elements support the metabolism of diverse prokaryotes by serving as respiratory electron acceptors for growth. Here, we demonstrate that two anaerobes previously shown to be capable of respiring oxyanions of selenium also achieve growth by reduction of either tellurate [Te(VI)] or tellurite [Te(IV)] to elemental tellurium [Te(0)]. This reduction achieves a sizeable stable-Te-isotopic fractionation (isotopic enrichment factor [epsilon] = -0.4 to -1.0 per ml per atomic mass unit) and results in the formation of unique crystalline Te(0) nanoarchitectures as end products. The Te(0) crystals occur internally within but mainly externally from the cells, and each microorganism forms a distinctly different structure. Those formed by Bacillus selenitireducens initially are nanorods ( approximately 10-nm diameter by 200-nm length), which cluster together, forming larger ( approximately 1,000-nm) rosettes composed of numerous individual shards ( approximately 100-nm width by 1,000-nm length). In contrast, Sulfurospirillum barnesii forms extremely small, irregularly shaped nanospheres (diameter < 50 nm) that coalesce into larger composite aggregates. Energy-dispersive X-ray spectroscopy and selected area electron diffraction indicate that both biominerals are composed entirely of Te and are crystalline, while Raman spectroscopy confirms that they are in the elemental state. These Te biominerals have specific spectral signatures (UV-visible light, Raman) that also provide clues to their internal structures. The use of microorganisms to generate Te nanomaterials may be an alternative for bench-scale syntheses. Additionally, they may also generate products with unique properties unattainable by conventional physical/chemical methods.

Topics: Anaerobiosis; Bacillus; Electron Transport; Epsilonproteobacteria; Microscopy, Electron; Nanoparticles; Spectrophotometry, Ultraviolet; Spectrum Analysis, Raman; Tellurium

Tellurite-containing media are widely used for the screening and isolation of Shiga toxin-producing Escherichia coli (STEC) O157:H7, but tellurite resistance among non-O157 STEC is poorly characterized. Therefore, we investigated 202 STEC strains representing 61 different serotypes from humans, animals or food for the presence of ter genes by PCR and their correlation with tellurite resistance, by assessing growth on cefixime-tellurite sorbitol MacConkey agar. All strains were screened for terC, terE and terF as markers for the ter gene cluster. Of the 202 strains, 127 contained terC and terE and were tellurite-resistant, but only 121 of these also contained terF. All 72 non-sorbitol-fermenting O157:H7 and O157:NM (non-motile) strains contained terC, terE and terF and expressed tellurite resistance. In contrast, all eight sorbitol-fermenting STEC O157:NM were terC-, terE- and terF-negative and tellurite-sensitive. Among non-O157 STEC, terC, terE and terF were found in all seven O145:NM, four O111:H8/NM, 17 of 18 O26:H11/NM and in 21 strains of 14 other serotypes. The strong correlation between the presence of ter genes and the ability to grow on tellurite-containing media suggest that the ter genes encode tellurite resistance in the vast majority of these strains. The presence of the ter gene cluster was significantly (P<0.00001) associated with the presence of eae genes. We conclude that the use of tellurite-containing media in screening for STEC will allow the detection of STEC O26, O111, O145 and non-sorbitol-fermenting O157, but most strains (in this study 74.3%) from other serotypes will be missed.

Topics: Adhesins, Bacterial; Animals; Cattle; Cefixime; Culture Media; DNA-Binding Proteins; Drug Resistance, Bacterial; Escherichia coli Infections; Escherichia coli O157; Escherichia coli Proteins; Food Microbiology; Genes, Bacterial; Goats; Hemolytic-Uremic Syndrome; Humans; Meat; Milk; Multigene Family; Shiga Toxin; Tellurium

Vaults are barrel-shaped ribonucleoprotein particles that are abundant in certain tumors and multidrug resistant cancer cells. Prokaryotic relatives of the major vault protein, MVP, have not been identified. We used sequence analysis and molecular modeling to show that MVP and the toxic anion resistance protein, TelA of Rhodobacter sphaeroides strain 2.4.1, share a novel fold that consists of a three-stranded antiparallel beta-sheet. Because of this strong structural correspondence, we examined whether mammalian cell vaults respond to tellurite treatment. In the presence of the oxyanion tellurite, large vault aggregates, or vaultosomes, appear at the cell periphery in 15 min or less. Vaultosome formation is temperature-dependent, reversible, and occurs in normal human umbilical vein endothelial cells as well as transformed HeLa cervical cancer cells. Vaultosome formation is not restricted to tellurite and occurs in the presence of other toxic oxyanions (selenate, selinite, arsenate, arsenite, vanadate). In addition, vaultosomes form independently from other stress-induced ribonucleoprotein complexes, stress granules and aggresomes. Vaultosome formation is therefore a unique cellular response to an environmental toxin.

Topics: Amino Acid Sequence; Bacterial Proteins; Biopolymers; Cell Line, Transformed; Cytoplasmic Structures; Cytoskeleton; Endothelial Cells; HeLa Cells; Humans; Microtubules; Models, Molecular; Molecular Sequence Data; Poly(ADP-ribose) Polymerases; Prokaryotic Cells; Protein Structure, Quaternary; Rhodobacter sphaeroides; Ribonucleoproteins; Tellurium; Vault Ribonucleoprotein Particles

We report on 2.0-microm emission characteristic and energy transfer of Ho3+-doped tellurite glass sensitized by Tm3+ upon excitation of a conventional 808 nm laser diode. The Judd-Ofelt strength parameters, spontaneous radiative transition probabilities and radiative lifetime of Ho3+ have been calculated from the absorption spectra by using the Judd-Ofelt theory. Significant enhancement of 2.0-microm emission of Ho3+ has been observed with increasing Tm3+ doping up to 0.7 mol%. The energy transfer coefficient of the forward Tm3+-->Ho3+ is approximately 17 times larger than that of the backward Tm3+<--Ho3+ energy transfer. Our result indicates that the maximum gain of 2.0-microm emission, assigned to the transition of (5)I7-->(5)I8 of Ho3+, might be achieved from the tellurite glass at the concentration of 0.5 mol% of Tm2O3 and 0.15 mol% of Ho2O3. The high gain coefficient and quantum efficiency (1.16) along with the large value of the product of the stimulated emission cross-section and the measured radiative lifetime (4.12 x 10(-27) m(2)s) of the Ho3+/Tm3+-codoped tellurite glasses might find potential applications in efficient 2.0-microm laser.

Topics: Algorithms; Cations; Chemical Phenomena; Chemistry, Physical; Energy Transfer; Fluorescence; Holmium; Lasers; Oxides; Spectrometry, Fluorescence; Spectrophotometry, Infrared; Spectrophotometry, Ultraviolet; Tellurium; Thulium; Tungsten; Zinc Oxide

A simple capillary zone electrophoretic method for the determination of biospherically important oxyanions of selenium (Se) and tellurium and another Se-containing anion, selenocyanate, has been developed. The method uses direct UV absorption detection. Time course experiments with time slices as short as 6 min are possible. This method's detection limits and linear range compare well with other methods involving samples containing complex biological matrices. The metalloid-containing anions examined were selenocyanate, selenite, selenate, tellurite, and tellurate. We applied this method to live cultures of two different bacteria in two different growth media in time course experiments following the changes in metalloid-containing anion concentrations. The results show that this method is a useful means of following the biological processing of these analytes in bacterial cultures.

Topics: Bacillus; Culture Media; Cyanates; Electrophoresis, Capillary; Microbiological Techniques; Oxidation-Reduction; Pseudomonas fluorescens; Selenic Acid; Selenium Compounds; Sensitivity and Specificity; Sodium Selenite; Spectrophotometry; Tellurium

Systems of iron tellurite glasses were prepared by melt quenching with compositions of [85%TeO2+5%Fe2O3+10%TMO], where transition metal oxides (TMO) are TiO2, V2O5, MnO, CoO, NiO and CuO. Furthermore, the main structural units of these samples have been characterized by means of Raman spectra (150-1200 cm(-1)) as well as wavenumber predictions by means of Gaussian 98 ab initio calculations for the proposed site symmetries of TeO4(4-) triagonal bipyramid (C2v) and Te2O7(6-) bridged tetrahedra (Cs and C1). Aided by normal coordinate analysis, calculated vibrational frequencies, Raman scattering activities, force constants in internal coordinates and potential energy distributions (PEDs), revised vibrational assignments for the fundamental modes have been proposed. The main structural features are correlated to the dominant units of triagonal bipyramid (tbp) or bridged tetrahedral (TeO3+1 binds to TeO3 through TeOTe bridge; corner sharing). Moreover, the Raman spectra of the investigated tellurites reflect a structural change from tbp (coordination number is four) to triagonal pyramidal (coordination number is three).

Topics: Glass; Metals; Oxides; Spectrum Analysis, Raman; Tellurium; Transition Elements

Er3+/Yb3+ co-doped TeO2-B2O3-Nb2O5-ZnO (TBN) glasses were prepared. The absorption spectra and upconversion luminescence spectra of TBN glasses were measured and analyzed. The upconversion emission bands centered at 530, 546 and 658 nm were observed under the excitation at 975 nm, corresponding to the transitions of 2H11/2-->4I15/2, 4S3/2-->4I15/2 and 4F9/2-->4I15/2 respectively. The ratio of red emission to green emission increases with an increasing of Yb3+ ions concentration. According to the quadratic dependence on excitation power, the possible upconversion mechanisms and processes were discussed.

Topics: Erbium; Fluorescence; Glass; Spectrophotometry; Tellurium; Ytterbium

Raman spectra of schmitterite measured at 298 and 77K are presented and discussed in detail and in part in comparison with published IR spectrum of synthetic schmitterite. U-O bond lengths in uranyls, calculated with the empirical relations R(U-O)=f[nu(1)(UO(2))(2+)]A and R(U-O)=f[nu(3)(UO(2))(2+)] A, are close to those inferred from the X-ray single crystal structure of synthetic schmitterite and agree also with the data for other natural and synthetic uranyl tellurites.

Topics: Minerals; Spectrum Analysis, Raman; Tellurium; Uranium Compounds

The siderophore of Pseudomonas stutzeri KC, pyridine-2,6-bis(thiocarboxylic acid) (pdtc), is shown to detoxify selenium and tellurium oxyanions in bacterial cultures. A mechanism for pdtc's detoxification of tellurite and selenite is proposed. The mechanism is based upon determination using mass spectrometry and energy-dispersive X-ray spectrometry of the chemical structures of compounds formed during initial reactions of tellurite and selenite with pdtc. Selenite and tellurite are reduced by pdtc or its hydrolysis product H(2)S, forming zero-valent pdtc selenides and pdtc tellurides that precipitate from solution. These insoluble compounds then hydrolyze, releasing nanometer-sized particles of elemental selenium or tellurium. Electron microscopy studies showed both extracellular precipitation and internal deposition of these metalloids by bacterial cells. The precipitates formed with synthetic pdtc were similar to those formed in pdtc-producing cultures of P. stutzeri KC. Culture filtrates of P. stutzeri KC containing pdtc were also active in removing selenite and precipitating elemental selenium and tellurium. The pdtc-producing wild-type strain KC conferred higher tolerance against selenite and tellurite toxicity than a pdtc-negative mutant strain, CTN1. These observations support the hypothesis that pdtc not only functions as a siderophore but also is involved in an initial line of defense against toxicity from various metals and metalloids.

Topics: Chemical Precipitation; Culture Media; Microbial Sensitivity Tests; Microscopy, Electron, Scanning; Oxidation-Reduction; Pseudomonas stutzeri; Pyridines; Selenium; Tellurium

This paper reports the discovery of anaerobic respiration on tellurate by bacteria isolated from deep ocean (1,543 to 1,791 m) hydrothermal vent worms. The first evidence for selenite- and vanadate-respiring bacteria from deep ocean hydrothermal vents is also presented. Enumeration of the anaerobic metal(loid)-resistant microbial community associated with hydrothermal vent animals indicates that a greater proportion of the bacterial community associated with certain vent fauna resists and reduces metal(loid)s anaerobically than aerobically, suggesting that anaerobic metal(loid) respiration might be an important process in bacteria that are symbiotic with vent fauna. Isolates from Axial Volcano and Explorer Ridge were tested for their ability to reduce tellurate, selenite, metavanadate, or orthovanadate in the absence of alternate electron acceptors. In the presence of metal(loid)s, strains showed an ability to grow and produce ATP, whereas in the absence of metal(loid)s, no growth or ATP production was observed. The protonophore carbonyl cyanide m-chlorophenylhydrazone depressed metal(loid) reduction. Anaerobic tellurate respiration will be a significant component in describing biogeochemical cycling of Te at hydrothermal vents.

Topics: Anaerobiosis; Animals; Annelida; Gram-Negative Anaerobic Bacteria; Oxidation-Reduction; Oxygen Consumption; Pacific Ocean; Polychaeta; Seawater; Sodium Selenite; Symbiosis; Tellurium

We present the tellurite bioassay (Te-Assay) as an alternative approach for quantification of cell viability. The Te-Assay was developed to pre-screen environmental samples for potential bacterial toxicants in which the reduction of tellurite to tellurium is used as a metabolic marker; black phenotype development only occurs in metabolically competent bacteria capable of reducing tellurite (TeO(3)(2-)) to elemental tellurium. The black and white phenotypes equate to nonsignificant or significant impediment of normal metabolic processes, thus permitting the rapid visual assessment of the relative toxicity of environmental samples. Bacterial inocula were exposed in 96-well plates to arrays of diluted analytes or environmental samples before addition of a tellurite to assess cell health/viability. Toxicity was quantified as the analyte concentration at which a 50% reduction in blackness occurred (IC(50)) compared to control wells containing no added analyte. No proprietary strains or reagents are required for Te-Assay, in which characterised strains or recent environmental isolates performed equally well. Strain selection was independent of tellurite-resistance provided that tellurite was reduced intracellularly by active non-growing cells.

Topics: Bacteria; Biological Assay; Color; Environmental Pollution; Microbial Viability; Oxidation-Reduction; Phenotype; Tellurium

O-Acetylserine (thiol)-lyase (cysteine synthase) was purified from Azospirillum brasilense Sp7. After hydrolysis of the purified protein, amino acid sequences of five peptides were obtained, which permitted the cloning and sequencing of the cysK gene. The deduced amino acid sequence of cysteine synthase exhibited homology with several putative proteins from Alpha- and Gammaproteobacteria. Azospirillum brasilense Sp7 cysK exhibited 58% identity (72% similarity) with Escherichia coli K12 and Salmonella enterica serovar Typhimurium cysteine synthase proteins. An E. coli auxotroph lacking cysteine synthase loci could be complemented with A. brasilense Sp7 cysK. The 3.0-kb HindIII-EcoRI fragment bearing cysK contained two additional ORFs encoding a putative transcriptional regulator and dUTPase. Insertional disruption of the cysK gene did not produce a cysteine auxotroph, indicating that gene redundancy in the cysteine biosynthetic or other biosynthetic pathways exists in Azospirillum, as already described in other bacteria. Nitrogen fixation was not altered in the mutant strain as determined by acetylene reduction. However, this strain showed an eight-fold reduction in tellurite resistance as compared to the wild-type strain, which was only observed during growth in minimal medium. These data confirm earlier observations regarding the importance of cysteine metabolism in tellurite resistance.

Topics: Azospirillum brasilense; Base Sequence; Carbon-Oxygen Lyases; Chromatography; Cloning, Molecular; Drug Resistance, Fungal; Genetic Complementation Test; Mutation; Oxidation-Reduction; Phenotype; Tellurium

We have found and sequenced a significant part of the previously described tellurite resistance determinant on mini-Mu derivative pPR46, named pNT3B, originally cloned from a large conjugative plasmid pTE53, found in Escherichia coli. This plasmid contains genes essential for tellurite resistance, together with the protective region bearing genes terX, Y, W, and the conserved spacing region bearing several ORFs of unknown function. Computer analysis of obtained sequence revealed a close similarity to the formerly described ter operons found on the Serratia marcescens plasmid R478 and the chromosome of Escherichia coli O157:H7. This finding confirms the presence of a whole region on the large conjugative plasmid that pTE53 originated from a uropathogenic E. coli strain, and suggests its possible role in horizontal gene transfer, resulting in the development of new pathogenic E. coli strains.

Topics: Computational Biology; Culture Media; Drug Resistance, Bacterial; Escherichia coli O157; Gene Transfer, Horizontal; Humans; Microbial Sensitivity Tests; Molecular Sequence Data; Open Reading Frames; Operon; Plasmids; Tellurium

Five strains of Gram-negative, rod, curved rod and spiral-shaped bacteria were isolated from the vicinity of deep ocean hydrothermal vents along the Main Endeavour Segment of the Juan de Fuca Ridge in the Pacific Ocean. All strains showed remarkable resistance to high levels of toxic metalloid oxyanions, and were capable of reducing the oxyanions tellurite and selenite to their less toxic elemental forms. Phylogenetic analysis of four strains identified these isolates as close relatives of the genus Pseudoalteromonas within the class Gammaproteobacteria. Pseudoalteromonas agarivorans was the closest relative of strains Te-1-1 and Se-1-2-redT, with, respectively, 99.5 and 99.8% 16S rDNA sequence similarity. Strain Te-2-2T was most closely related to Pseudoalteromonas paragorgicola, with 99.8% 16S rDNA sequence similarity. The DNA G+C base composition was 39.6 to 41.8 mol%, in agreement with other members of the genus Pseudoalteromonas. However, the isolates showed important morphological and physiological differences from previously described species of this genus, with one group forming rod-shaped bacteria typical of Pseudoalteromonas and the other forming vibrioid- to spiral-shaped cells. Based on these differences, and on phylogenetic data, we propose the creation of the new species Pseudoalteromonas telluritireducens sp. nov., with strain Se-1-2-redT (DSMZ = 16098T = VKM B-2382T) as the type strain, and Pseudoalteromonas spiralis sp. nov., with strain Te-2-2T (DSMZ = 16099T = VKM B-2383T) as the type strain.

Topics: Base Sequence; DNA, Bacterial; Molecular Sequence Data; Phylogeny; Pseudoalteromonas; Sodium Selenite; Tellurium

Reactive oxygen species damage intracellular targets and are implicated in cancer, genetic disease, mutagenesis, and aging. Catalases are among the key enzymatic defenses against one of the most physiologically abundant reactive oxygen species, hydrogen peroxide. The well-studied, heme-dependent catalases accelerate the rate of the dismutation of peroxide to molecular oxygen and water with near kinetic perfection. Many catalases also bind the cofactors NADPH and NADH tenaciously, but, surprisingly, NAD(P)H is not required for their dismutase activity. Although NAD(P)H protects bovine catalase against oxidative damage by its peroxide substrate, the catalytic role of the nicotinamide cofactor in the function of this enzyme has remained a biochemical mystery to date. Anions formed by heavy metal oxides are among the most highly reactive, natural oxidizing agents. Here, we show that a natural isolate of Staphylococcus epidermidis resistant to tellurite detoxifies this anion thanks to a novel activity of its catalase, and that a subset of both bacterial and mammalian catalases carry out the NAD(P)H-dependent reduction of soluble tellurite ion (TeO(3)(2-)) to the less toxic, insoluble metal, tellurium (Te(o)), in vitro. An Escherichia coli mutant defective in the KatG catalase/peroxidase is sensitive to tellurite, and expression of the S. epidermidis catalase gene in a heterologous E. coli host confers increased resistance to tellurite as well as to hydrogen peroxide in vivo, arguing that S. epidermidis catalase provides a physiological line of defense against both of these strong oxidizing agents. Kinetic studies reveal that bovine catalase reduces tellurite with a low Michaelis-Menten constant, a result suggesting that tellurite is among the natural substrates of this enzyme. The reduction of tellurite by bovine catalase occurs at the expense of producing the highly reactive superoxide radical.

Topics: Amino Acid Sequence; Animals; Catalase; Cattle; Drug Resistance, Bacterial; Escherichia coli; Genes, Bacterial; In Vitro Techniques; Kinetics; Liver; Mutation; NAD; NADP; Oxidoreductases; Recombinant Proteins; Staphylococcus epidermidis; Substrate Specificity; Superoxides; Tellurium

The novel Er(3+) single-doped and Er(3+)/Yb(3+) co-doped tellurite glasses were prepared. The effect of Yb(2)O(3) concentration on absorption spectra, emission spectra and upconversion spectra of glasses were measured and investigated. The emission intensity, fluorescence full width at half maximum (FWHM) and upconversion luminescence of Er(3+) go up with the increasing concentration of Yb(3+) ions. The maximum FWHM of (4)I(13/2) --> (4)I(15/2) transition of Er(3+) is approximate 77 nm for 1.41 x 10(21)ions/cm(3) concentration of Yb(3+)-doped glass. The visible upconversion emissions at about 532, 546 and 659 nm, corresponding to the (2)H(11/2) --> (4)I(15/2), (4)S(3/2) --> (4)I(15/2) and (4)F(9/2) --> (4)I(15/2) transitions of Er(3+), respectively, were simultaneously observed under the excitation at 970 nm. Subsequently, the possible upconversion mechanisms and important role of Yb(3+) on the green and red emissions were discussed and compared. The results demonstrate that this kind of tellurite glass may be a potentially useful material for developing potential amplifiers and upconversion optical devices.

Topics: Erbium; Glass; Luminescent Measurements; Oxides; Phosphatidylethanolamines; Spectrophotometry; Tellurium; Thulium; Ytterbium

The spectral properties of Er3+/Yb3+ codoped tungsten-tellurite (WT) glasses have been investigated. The measured absorption spectra are analyzed by Judd-Ofelt theory. The compositional change of intensity parameter omega2 is attributed to the change in the covalency between the Er3+ and oxygen ions, the asymmetry in the local structures around the Er3+ ions can be neglected. The lifetimes of 4I(13/2) level of Er3+ in WT glasses are measured and comparable with other TeO2-based glasses. The stimulated emission cross-section is calculated based on McCumber theory. The fluorescence full width at half maximum (FWHM) and the emission cross-section (sigma(peak)) of the 4I(13/2) --> 4I(15/2) transition of Er3+ in different glass hosts have been compared. The suitability of such WT glasses as host materials for 1.5 microm broadband amplification is discussed.

Topics: Cations; Erbium; Glass; Spectrum Analysis; Tellurium; Tungsten; Ytterbium

Cells of the facultative photosynthetic bacterium Rhodobacter capsulatus (MT1131 strain) incubated with 10 microg ml-1 of the toxic oxyanion tellurite (TeO2-(3)) exhibited an increase in superoxide dismutase activity. The latter effect was also seen upon incubation with sublethal amounts of paraquat, a cytosolic generator of superoxide anions (O2-), in parallel with a strong increase in tellurite resistance (TeR). A mutant strain (CW10) deficient in SenC, a protein with similarities to peroxiredoxin/thiol:disulfide oxidoreductases and a homologue of mitochondrial Sco proteins, was constructed by interposon mutagenesis via the gene transfer agent system. Notably, the absence of SenC affected R. capsulatus resistance to periplasmic O2- generated by xanthine/xanthine oxidase but not to cytosolic O2- produced by paraquat. Further, the absence of SenC did not affect R. capsulatus tellurite resistance. We conclude that: (1) cytosolic-generated O2- enhances TeR of this bacterial species; (2) small amounts of tellurite increase SOD activity so as to mimic the early cell response to oxidative stress; (3) SenC protein is required in protection of R. capsulatus against periplasmic oxidative stress; and finally, (4) SenC protein is not involved in TeR, possibly because tellurite does not generate O-2 at the periplasmic space level.

Topics: Bacterial Proteins; Colony Count, Microbial; Drug Resistance, Bacterial; Gene Deletion; Mutagenesis, Insertional; Oxidative Stress; Paraquat; Photosynthetic Reaction Center Complex Proteins; Rhodobacter capsulatus; Superoxide Dismutase; Tellurium

Ytterbium-sensitized erbium-doped oxide-halide tellurite and germanate-niobic-lead glasses have been synthesized by conventional melting method. Intense green and red emissions centered at 525, 546 and 657 nm, corresponding to the transitions 2H11/2-->4I15/2, 4S3/2-->4I15/2 and 4F9/2-->4I15/2, respectively, were simultaneously observed at room temperature in these glasses. The quadratic dependence of the 525, 546 and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs. Tellurite glass showed a weaker up-conversion emission than germanate-niobic-lead glass, which is inconsistent with the prediction from the difference of maximum phonon energy between tellurite and germanate-niobic-lead glasses. In this paper, Raman spectroscopy was employed to investigate the origin of the difference in up-conversion luminescence in the two glasses. Compared with phonon side-band spectroscopy, Raman spectroscopy extracts more information including both phonon energy and phonon density. Our results reveal that the phonon density and the maximum phonon energy of host glasses are both important factors in determining the up-conversion efficiency.

Topics: Erbium; Germanium; Glass; Ions; Lead; Luminescence; Niobium; Spectrum Analysis, Raman; Tellurium; Temperature; Ytterbium

Shewanella oneidensis MR-1 reduces selenite and tellurite preferentially under anaerobic conditions. The Se(0) and Te(0) deposits are located extracellularly and intracellularly, respectively. This difference in localization and the distinct effect of some inhibitors and electron acceptors on these reduction processes are taken as evidence of two independent pathways.

Topics: Aerobiosis; Anaerobiosis; Bacteriological Techniques; Culture Media; Microscopy, Confocal; Microscopy, Electron; Oxidation-Reduction; Shewanella; Sodium Selenite; Tellurium

The Er3+/Yb3+-codoped 70TeO2-5Li2O-10B2O3-15GeO2 glass was prepared. The thermal stability, absorption spectra, emission spectra and up-conversion spectra were measured and investigated. The Judd-Ofelt analysis based on absorption spectra was performed in order to determine the Judd-Ofelt intensity parameters Omega(t) (t = 2, 4, 6), spontaneous emission probability, radiative lifetime and branching ratios of several Er3+ transitions. It was found that this studied glass has good thermal stability, broad fluorescence full width at half maximum (FWHM), large stimulated emission cross-section and strong up-conversion emissions at about 532, 546 and 659 nm, corresponding to the 2H(11/2)-->4I(15/2), 4S(3/2)-->4I(15/2) and 4F(9/2)-->4I(15/2) transitions of Er3+, respectively under the excitation at 970 nm. The results suggest that this Er3+/Yb3+-codoped germano-tellurite glass may be a potentially useful material for developing potential amplifiers and up-conversion optical devices.

Topics: Cations, Monovalent; Erbium; Germanium; Glass; Lithium; Spectrometry, Fluorescence; Tellurium; Temperature; Ytterbium

The absorption and fluorescence spectra of Pr(3+) doped in tellurite glass has been recorded and analyzed in terms of Judd-Ofelt theory. The lifetime of (3)P(0) and (3)P(1) levels has been measured. Fluorescence quenching has been observed for higher concentrations of Pr(3+) ion. The temperature dependence of the fluorescence intensity and the lifetime of the (3)P(0) level has been investigated and found that they decrease with the increase of the temperature.

Topics: Calorimetry; Glass; Praseodymium; Spectrometry, Fluorescence; Spectrophotometry; Tellurium; Thermodynamics

To obtain efficient blue upconversion laser glasses, upconversion luminescence and mechanisms of Tm(3+)/Yb(3+)-codoped oxyhalide tellurite glasses were investigated under 980 nm excitation. The results showed that upconversion blue and red emission intensities of Tm(3+) first increase, reach its maximum at Tm(2)O(3)%=0.1 mol %, and then decrease with increasing Tm(2)O(3) content. The effect of Tm(2)O(3) content on upconversion intensity is discussed, and possible effect mechanisms are evaluated. The investigated results were conducing to increase upconversion luminescence efficiency of Tm(3+).

Topics: Glass; Kinetics; Luminescent Measurements; Oxides; Spectrometry, Fluorescence; Tellurium; Thermodynamics; Ytterbium

Topics: Anti-Bacterial Agents; Cefixime; DNA, Bacterial; Drug Resistance, Multiple, Bacterial; Environmental Monitoring; Escherichia coli; India; Microbial Sensitivity Tests; Plasmids; Rivers; Sorbitol; Tellurium

Pederin belongs to a group of antitumor compounds found in terrestrial beetles and marine sponges. It is used by apparently all members of the rove beetle genera Paederus and Paederidus as a chemical defense against predators. However, a recent analysis of the putative pederin biosynthesis (ped) gene cluster strongly suggests that pederin is produced by bacterial symbionts. We have sequenced an extended region of the symbiont genome to gain further insight into the biology of this as-yet-unculturable bacterium and the evolution of pederin symbiosis. Our data indicate that the symbiont is a very close relative of Pseudomonas aeruginosa that has acquired several foreign genetic elements by horizontal gene transfer. Besides one functional tellurite resistance operon, the region contains a genomic island spanning 71.6 kb that harbors the putative pederin biosynthetic genes. Several decayed insertion sequence elements and the mosaic-like appearance of the island suggest that the acquisition of the ped symbiosis genes was followed by further insertions and rearrangements. A horizontal transfer of genes for the biosynthesis of protective substances could explain the widespread occurrence of pederin-type compounds in unrelated animals from diverse habitats.

Topics: Animals; Bacteria; Bacterial Proteins; Coleoptera; Drug Resistance, Bacterial; Gene Transfer, Horizontal; Molecular Sequence Data; Multigene Family; Pyrans; Sequence Analysis, DNA; Symbiosis; Tellurium

The gram-positive human pathogen Staphylococcus aureus is often isolated with media containing potassium tellurite, to which it has a higher level of resistance than Escherichia coli. The S. aureus cysM gene was isolated in a screen for genes that would increase the level of tellurite resistance of E. coli DH5alpha. The protein encoded by S. aureus cysM is sequentially and functionally homologous to the O-acetylserine (thiol)-lyase B family of cysteine synthase proteins. An S. aureus cysM knockout mutant grows poorly in cysteine-limiting conditions, and analysis of the thiol content in cell extracts showed that the cysM mutant produced significantly less cysteine than wild-type S. aureus SH1000. S. aureus SH1000 cannot use sulfate, sulfite, or sulfonates as the source of sulfur in cysteine biosynthesis, which is explained by the absence of genes required for the uptake and reduction of these compounds in the S. aureus genome. S. aureus SH1000, however, can utilize thiosulfate, sulfide, or glutathione as the sole source of sulfur. Mutation of cysM caused increased sensitivity of S. aureus to tellurite, hydrogen peroxide, acid, and diamide and also significantly reduced the ability of S. aureus to recover from starvation in amino acid- or phosphate-limiting conditions, indicating a role for cysteine in the S. aureus stress response and survival mechanisms.

Topics: Culture Media; Cysteine; Cysteine Synthase; Drug Resistance, Bacterial; Heat-Shock Response; Humans; Mutation; Staphylococcus aureus; Sulfur; Tellurium

This study compares Staphylococcus aureus ATCC 29213 and Pseudomonas aeruginosa ATCC 27853 biofilm and planktonic cell susceptibility to the selenium and tellurium oxyanions selenite (SeO3(2-)), tellurate (TeO4(2-)), and tellurite (TeO3(2-)). P. aeruginosa planktonic and biofilm cultures reduced the selenium and tellurium oxyanions to orange and black end-products (respectively) and were equally tolerant to killing by these metalloid compounds. S. aureus planktonic cell cultures processed these metalloid oxyanions in a similar way, but the corresponding biofilm cultures did not. S. aureus biofilms were approximately two and five times more susceptible to killing by tellurate and tellurite (respectively) than the corresponding planktonic cultures. Our data indicate that the means of reducing metalloid oxyanions may differ between the physiology displayed in biofilm and planktonic cultures of the same bacterial strain.

Topics: Animals; Biofilms; Culture Media; Drug Resistance, Bacterial; Metals, Heavy; Oxidation-Reduction; Plankton; Pseudomonas aeruginosa; Sodium Selenite; Staphylococcus aureus; Tellurium

Escherichia coli JM109 cells, expressing the genes encoded in a 3.8-kb chromosomal DNA fragment from Geobacillus stearothermophilus V, produced volatile organotellurium compounds which were released into the headspace gas above liquid cultures when amended with tellurite anions in micromolar amounts. Headspace sampling was achieved using gas-syringe extraction or solid-phase microextraction using carboxen-polydimethysiloxane fibers. In addition to dimethyl telluride and dimethyl ditelluride, two new organometalloidal compounds were detected using gas chromatograph with mass spectrometric or fluorine-induced chemiluminescence detection. These compounds are methanetellurol and dimethyl tellurenyl sulfide. The significance of these findings with regard to the current knowledge about bacterial tellurite resistance is discussed.

Topics: Adaptation, Biological; Chromatography, Gas; Escherichia coli K12; Genes, Bacterial; Geobacillus stearothermophilus; Mass Spectrometry; Organometallic Compounds; Tellurium

Pseudomonas putida CR30RNS (pADPTel) is an antibiotic-resistant strain with a recombinant plasmid that confers resistance to tellurite and the ability to catabolize atrazine. The survival of this strain as well as its ability to transfer genes for atrazine degradation and tellurite resistance to indigenous soil bacteria were tested in both fallow soil and canola (Brassica napus) rhizosphere by the use of parallel field and laboratory releases. Culturable CR30RNS (pADPTel) were enumerated in field and microcosm soils at 7- to 14-day intervals over 49 d. Strain CR30RNS (pADPTel) survived for up to 7 weeks in microcosm soils at a density of 10(4) CFU/g soil, whereas in field soils the population declined to 10(3) CFU/g soil by the fourth week. In contrast, when CR30RNS (pADPTel) was introduced into the soil as a seed coating of canola (B. napus 'Karoo'), the bacterium established at higher cell densities in the rhizosphere (10(6)-10(5) CFU/g fresh root mass), with no subsequent decrease in numbers. The presence of selective pressure (i.e., atrazine) had no significant effect on the survival of CR30RNS (pADPTel) in either field or microcosm soils. One year postinoculation field sites were examined for the presence of CR30RNS (pADPTel) and no evidence of culturable parental cells was observed when samples were plated onto selective media. However, the atzC and telAB gene segments were amplified from the field soils at that time. Under laboratory conditions, indigenous soil bacteria were capable of receiving and expressing the engineered plasmid construct at frequencies ranging from 1 to 10(-3) transconjugants per donor. However, no plasmid transfer to indigenous soil bacteria was detected in the field or microcosm soils regardless of the presence of canola rhizosphere and (or) the application of atrazine. Our results show that the survival and population size of P. putida CR30RNS (pADPTel) might be sufficient for degradation of environmental pollutants but that the transfer frequency was too low to be detected under the conditions of this study.

Topics: Agriculture; Brassica napus; Conjugation, Genetic; Drug Resistance, Bacterial; Ecosystem; Gene Transfer, Horizontal; Plant Roots; Plasmids; Pseudomonas putida; Recombination, Genetic; Soil; Soil Microbiology; Tellurium

Blue up-conversion luminescence properties in Tm3+ -doped lead chloride tellurite glasses have been studied under 980 nm excitation. The intense blue and relatively weak red emissions centered at 476 and 649 nm corresponding to the transitions 1G4 --> 3H6 and 1G4 --> 3H4 of Tm3+, respectively, are simultaneously observed at room temperature. The effect of PbCl2 on up-conversion intensity is observed and discussed, and possible up-conversion mechanisms are evaluated. The intense blue up-conversion luminescence of Tm3+ -doped lead chloride tellurite glasses may be a potentially useful material for developing up-conversion optical devices.

Topics: Cations; Chlorides; Glass; Lead; Luminescent Measurements; Spectrum Analysis, Raman; Tellurium; Temperature; Thulium; Ytterbium

This work examines the effects of potassium tellurite (K2TeO3) on the cell viability of the facultative phototroph Rhodobacter capsulatus. There was a growth mode-dependent response in which cultures anaerobically grown in the light tolerate the presence of up to 250 to 300 microg of tellurite (TeO3(2-)) per ml, while dark-grown aerobic cells were inhibited at tellurite levels as low as 2 microg/ml. The tellurite sensitivity of aerobic cultures was evident only for growth on minimal salt medium, whereas it was not seen during growth on complex medium. Notably, through the use of flow cytometry, we show that the cell membrane integrity was strongly affected by tellurite during the early growth phase (< or =50% viable cells); however, at the end of the growth period and in parallel with massive tellurite intracellular accumulation as elemental Te0 crystallites, recovery of cytoplasmic membrane integrity was apparent (> or =90% viable cells), which was supported by the development of a significant membrane potential (Deltapsi = 120 mV). These data are taken as evidence that in anaerobic aquatic habitats, the facultative phototroph R. capsulatus might act as a natural scavenger of the highly soluble and toxic oxyanion tellurite.

Topics: Anaerobiosis; Cell Membrane Permeability; Culture Media; Electron Transport; Flow Cytometry; Light; Membrane Potentials; Microbial Sensitivity Tests; Rhodobacter capsulatus; Tellurium

Here we compare the physiological state of Escherichia coli exposed to tellurite or selenite by using the noninvasive technique of phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy. We studied glucose-fed Escherichia coli HB101 cells containing either a normal pUC8 plasmid with no tellurite resistance determinants present or the pTWT100 plasmid which contains the resistance determinants tehAB. No differences could be observed in intracellular ATP levels, the presence or absence of a transmembrane pH gradient, or the levels of phosphorylated glycolytic intermediates when resistant cells were studied by 31P NMR in the presence or absence of tellurite. In the sensitive strain, we observed that the transmembrane pH gradient was dissipated and intracellular ATP levels were rapidly depleted upon exposure to tellurite. Only the level of phosphorylated glycolytic intermediates remained the same as observed with resistant cells. Upon exposure to selenite, no differences could be observed by 31P NMR between resistant and sensitive strains, suggesting that the routes for selenite and tellurite reduction within the cells differ significantly, since only tellurite is able to collapse the transmembrane pH gradient and lower ATP levels in sensitive cells. The presence of the resistance determinant tehAB, by an as yet unidentified detoxification event, protects the cells from uncoupling by tellurite.

Topics: Adenosine Triphosphate; Drug Resistance, Bacterial; Escherichia coli; Escherichia coli Proteins; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Phosphorus Isotopes; Sodium Selenite; Tellurium

It is known that many agents influence the capacity of cells to produce reactive oxygen species. However, assaying these agents, both those that stimulate and those that inhibit reactive oxygen production, can be complicated and time consuming. Here, a method is described in which two different cocktails are employed to stimulate luminol-dependent chemiluminescence (LDCL). These cocktails are comprised of luminol, with either sodium selenite [IV] (SEL) or tellurite [IV] (TEL) (where IV and VI refer to the 4+ or 6+ oxidation state of selenium or tellurium salts, respectively), morpholinosidonimine (SIN-1), serum albumin and Co(2+), called the SIN-1a (with selenite) and SIN1b (with tellurite) cocktails, respectively; or luminol with glucose oxidase (GO), sodium selenite [IV] and Co(2+), called the GO cocktail. The cocktails functioned best in Hank's balanced salt solution (HBSS) containing 1% glucose at pH 7.4, incubated at approximately 22 degrees C. Within 30-60 s there was a burst of luminescence, which lasted for 7-10 min. In 100% ethanol, the SIN-1 cocktails also generated LDCL to 70% of that produced in HBSS. Neither selenite [VI], seleno-cystine, seleno-methionine, nor the selenium-containing drug, ebselen, could replace SEL. Moreover, the effects of the NO-donor, SIN-1, could not be replicated by the oxyradical generators, xanthine-xanthine oxidase or hypochlorous acid. Only low levels of luminescence were generated by combinations of the peroxyl radical generator, 2,2'-azobis-2-amidinopropane dihydrochloride (AAPH) with either SEL or TEL. It is suggested that light emission induced by the SIN1 cocktail results from the oxidation of SEL [IV] to the [VI] state, possibly due to the generation of mixtures of superoxide, peroxide, peroxynitrite and also of unidentified oxidant species, catalyzed by CoCo(2+). However, the involvement of hydroxyl radicals in LDCL could not be confirmed by use of either dimethyl thiourea or by electron spin resonance (ESR). LDCL induced by the two cocktails is strongly reduced by phosphates, EDTA, deferoxamine, CuCo(2+), MnCo(2+), as well as by the "classical" antioxidants superoxide dismutase (SOD), ascorbate, vitamin E, uric acid or thiols. It is suggested that these chemiluminescence cocktail systems can be used to determine the total anti-oxidant capacities of biological fluids and commercially available anti-oxidants.

Topics: Antioxidants; Cobalt; Electron Spin Resonance Spectroscopy; Glucose Oxidase; Light; Luminescent Measurements; Luminol; Molsidomine; Serum Albumin, Bovine; Sodium Selenite; Tellurium

Judd-Ofelt analysis of Sm(3+) ions doped in a tellurite glass has been accomplished. Fluorescence and life-time measurements have been carried out using Ar(+) laser and excimer laser. Stark splitting has been observed in the upper and lower levels in fluorescence. The life-time of 4G(5/2) level as a function of Sm(3+) concentration has been measured. Concentration quenching and the mechanism responsible for the same have been found.

Topics: Samarium; Spectrometry, Fluorescence; Spectrophotometry; Tellurium

Tellurite resistance (Te(r)) is widespread in nature and it is shown here that the natural resistance of Proteus mirabilis to tellurite is due to a chromosomally located orthologue of plasmid-borne ter genes found in enteric bacteria. The P. mirabilis ter locus (terZABCDE) was identified in a screen of Tn5lacZ-generated mutants of which one contained an insertion in terC. The P. mirabilis terC mutant displayed increased susceptibility to tellurite (Te(s)) and complementation with terC carried on a multicopy plasmid restored high-level Te(r). Primer extension analysis revealed a single transcriptional start site upstream of terZ, but only with RNA harvested from bacteria grown in the presence of tellurite. Northern blotting and reverse transcriptase-PCR (RT-PCR) analyses confirmed that the ter operon was inducible by tellurite and to a lesser extent by oxidative stress inducers such as hydrogen peroxide and methyl viologen (paraquat). Direct and inverted repeat sequences were identified in the ter promoter region as well as motifs upstream of the -35 hexamer that resembled OxyR-binding sequences. Finally, the 390 bp intergenic promoter region located between orf3 and terZ showed no DNA sequence identity with any other published ter sequences, whereas terZABCDE genes exhibited 73-85 % DNA sequence identity. The ter operon was present in all clinical isolates of P. mirabilis and Proteus vulgaris tested and is inferred for Morganella and Providencia spp. based on screening for high level Te(r) and preliminary PCR analysis. Thus, a chromosomally located inducible tellurite resistance operon appears to be a common feature of the genus Proteus.

Topics: Bacterial Proteins; Drug Resistance, Bacterial; Gene Expression Regulation, Bacterial; Humans; Hydrogen Peroxide; Molecular Sequence Data; Operon; Paraquat; Proteus mirabilis; Sequence Analysis, DNA; Tellurium

To improve enrichment and isolation of Escherichia coli O157:H7, this study evaluated increased incubation temperature and cefixime-tellurite (CT) on five strains of each of the following bacteria, E. coli, Hafnia alvei, Enterobacter spp., Citrobacter freundii and E. coli O157:H7, and two strains of E. coli O157:nH7. These were grown in pure culture in LST broth with varying cefixime-tellurite concentrations. A range of incubation temperatures from 37 to 46 degrees C was investigated for the inhibition of cohabitant microorganisms. Minced beef, spiked with E. coli O157:H7 and cohabitant microorganisms was investigated. Increased incubation temperature (42 degrees C) and treatment with half of the prescribed amount of cefixime-tellurite by BAM for SMAC agar in enrichment step were the most effective in selectively growing E. coli O157:H7. The results show that E. coli O157:H7 is more resistant to these two conditions than the other cohabitant bacteria.

Topics: Animals; Anti-Bacterial Agents; Cattle; Cefixime; Citrobacter freundii; Consumer Product Safety; Dose-Response Relationship, Drug; Enterobacter; Escherichia coli; Escherichia coli O157; Food Microbiology; Hafnia alvei; Meat Products; Tellurium; Temperature

Spectroscopic properties of Ho3+ doped tellurite glass (1 mol.% of Ho3+) have been studied. The absorption and fluorescence spectra have been recorded and analysed using the Judd-Offelt theory. The analysis indicates that Ho doped tellurite glasses can show lasing on the 5F4 (5S2)-5I8 transition (548.0 nm).

Topics: Glass; Holmium; Spectrometry, Fluorescence; Spectrophotometry; Tellurium

The uptake by light-grown cells of Rhodobacter capsulatus of the highly toxic metalloid oxyanion tellurite (TeO(3)(2-)) was examined. We show that tellurite is rapidly taken up by illuminated cells in a process which is inhibited by the protonophore carbonyl cyanide-p-trifluoromethoxyphenyl-hydrazone (FCCP) and by the K(+)/H(+) exchanger nigericin. Notably, the light-driven membrane potential (Delta psi) is enhanced by K(2)TeO(3)> or =200 microM. Further, tellurite uptake is largely insensitive to valinomycin, strongly repressed by the sulfhydryl reagent N-ethylethylmaleimide (NEM) and competitively inhibited by phosphate. We conclude that tellurite is transported into cells by a Delta pH-dependent, non-electrogenic process which is likely to involve the phosphate transporter (PiT family).

Topics: Biological Transport; Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; Electrochemistry; Ethylmaleimide; Kinetics; Light; Membrane Potentials; Nigericin; Onium Compounds; Organophosphorus Compounds; Oxygen; Proton-Motive Force; Rhodobacter capsulatus; Tellurium; Valinomycin

The genome of Pseudomonas putida KT2440 encodes an unexpected capacity to tolerate heavy metals and metalloids. The availability of the complete chromosomal sequence allowed the categorization of 61 open reading frames likely to be involved in metal tolerance or homeostasis, plus seven more possibly involved in metal resistance mechanisms. Some systems appeared to be duplicated. These might perform redundant functions or be involved in tolerance to different metals. In total, P. putida was found to bear two systems for arsenic (arsRBCH), one for chromate (chrA), four to six systems for divalent cations (two cadA and two to four czc chemiosmotic antiporters), two systems for monovalent cations: pacS, cusCBA (plus one cryptic silP gene containing a frameshift mutation), two operons for Cu chelation (copAB), one metallothionein for metal(loid) binding, one system for Te/Se methylation (tpmT) and four ABC transporters for the uptake of essential Zn, Mn, Mo and Ni (one nikABCDE, two znuACB and one mobABC). Some of the metal-related clusters are located in gene islands with atypical genome signatures. The predicted capacity of P. putida to endure exposure to heavy metals is discussed from an evolutionary perspective.

Topics: Arsenicals; Cadmium; Chromates; Chromosomes, Bacterial; Computational Biology; Copper; Drug Tolerance; Gene Order; Genes, Bacterial; Genome, Bacterial; Homeostasis; Manganese; Metals, Heavy; Molybdenum; Nickel; Operon; Pseudomonas putida; Sodium Selenite; Tellurium; Zinc

Strains of Escherichia coli causing enterohemorrhagic colitis belonging to the O157:H7 lineage are reported to be highly related. Fifteen strains of E. coli O157:H7 and 1 strain of E. coli O46:H(-) (nonflagellated) were examined for the presence of potassium tellurite resistance (Te(r)). Te(r) genes comprising terABCDEF were shown previously to be part of a pathogenicity island also containing integrase, phage, and urease genes. PCR analysis, both conventional and light cycler based, demonstrated that about one-half of the Te(r) E. coli O157:H7 strains (6 of 15), including the Sakai strain, which has been sequenced, carried a single copy of the Te(r) genes. Five of the strains, including EDL933, which has also been sequenced, contained two copies. Three other O157:H7 strains and the O46:H(-) strain did not contain the Te(r) genes. In strains containing two copies, the Te(r) genes were associated with the serW and serX tRNA genes. Five O157:H7 strains resembled the O157 Sakai strain whose sequence contained one copy, close to serX, whereas in one isolate the single copy was associated with serW. There was no correlation between Te(r) and the ability to produce Shiga toxin ST1 or ST2. The Te(r) MIC for most strains, containing either one or two copies, was 1,024 micro g/ml, although for a few the MIC was intermediate, 64 to 128 micro g/ml, which could be increased to 512 micro g/ml by pregrowth of strains in subinhibitory concentrations of potassium tellurite. Reverse transcriptase PCR analysis confirmed that in most strains Te(r) was constitutive but that in the rest it was inducible and involved induction of terB and terC genes. Only the terB, -C, -D, and -E genes are required for Te(r). The considerable degree of homology between the ter genes on IncH12 plasmid R478, which originated in Serratia marcescens, and pTE53, from an E. coli clinical isolate, suggests that the pathogenicity island was acquired from a plasmid. This work demonstrates diversity among E. coli O157:H7 isolates, at least as far as the presence of Te(r) genes is concerned.

Topics: Drug Resistance, Bacterial; Escherichia coli O157; Reverse Transcriptase Polymerase Chain Reaction; Shiga Toxin; Tellurium

Cytotoxicity of tellurite to cultured HeLa cells was examined by cell viability, lactate dehydrogenase (LDH) assay, and tellurite uptake. The experimental results show that the toxicity of tellurite depends on its concentrations and exposure time. HeLa cells exposed to tellurite for 2 h at 9.1 x 10(-4) to 4.5 x 10(-3) mmol/L did not exhibit cytotoxic effects as measured by cell viability. Exposure to tellurite for 24 h at the same concentrations markedly reduced the cell viability to 57% of the control during the first 5 minutes. Additionally, HeLa cells incubated at 2.7 x 10(-2) to 0.27 mmol/L of tellurite for 2 h retained 53% to 67% of cell viability. Even after 24 h exposure, the HeLa cells incubated at 9.1 x 10(-4) to 4.5 x 10(-2) mmol/L of tellurite still retained 57% to 66% of cell viability. Furthermore, tellurite toxicity was also demonstrated in supernatant of the culture at 37 degrees C by LDH assay. It was found that exposure to tellurite for 90 minutes did not stimulate LDH activity. However, tellurite uptake seems to be more sensitive than the cell viability and LDH activity release tests, as it significantly increases with the increasing of exposure time.

Topics: Cell Survival; Dose-Response Relationship, Drug; HeLa Cells; Humans; L-Lactate Dehydrogenase; Tellurium

Deep-ocean hydrothermal-vent environments are rich in heavy metals and metalloids and present excellent sites for the isolation of metal-resistant microorganisms. Both metalloid-oxide-resistant and metalloid-oxide-reducing bacteria were found. Tellurite- and selenite-reducing strains were isolated in high numbers from ocean water near hydrothermal vents, bacterial films, and sulfide-rich rocks. Growth of these isolates in media containing K(2)TeO(3) or Na(2)SeO(3) resulted in the accumulation of metallic tellurium or selenium. The MIC of K(2)TeO(3) ranged from 1,500 to greater than 2,500 micro g/ml, and the MIC of Na(2)SeO(3) ranged from 6,000 to greater than 7,000 micro g/ml for 10 strains. Phylogenetic analysis of 4 of these 10 strains revealed that they form a branch closely related to members of the genus Pseudoalteromonas, within the gamma-3 subclass of the Proteobacteria. All 10 strains were found to be salt tolerant, pH tolerant, and thermotolerant. The metalloid resistance and morphological, physiological, and phylogenetic characteristics of newly isolated strains are described.

Topics: Drug Resistance, Bacterial; Gammaproteobacteria; Marine Biology; Pacific Ocean; Phylogeny; Sodium Selenite; Tellurium; Water Microbiology

Absorption and fluorescence spectra of Eu3+ ions doped in a tellurite glass have been recorded and analysed. Judd-Ofelt analysis has been done in order to calculate the different optical parameters such as oscillator strength, Judd-Ofelt intensity parameters, stimulated emission cross-section, transition probability, branching ratio, radiative lifetime, etc. Lifetime measurements of the 5D0 level as a function of Eu3+ concentration have been used to explore the concentration quenching process. The mechanism of quenching is found to be of a dipole-dipole type.

Topics: Europium; Glass; Ions; Kinetics; Spectrometry, Fluorescence; Spectrophotometry; Tellurium

The utility of CT-SSMAC medium (sorbitol-salicin MacConkey medium containing cefixime and tellurite) for the isolation of Escherichia coli O157:H7 from raw vegetables was investigated. The colonies of all E. coli O157:H7 and O157:NM strains tested were colorless and beta-galactosidase-positive on CT-SSMAC medium. Furthermore, the number of colorless colonies on the CT-SSMAC medium was less than that on the sorbitol MacConkey medium containing cefixime and tellurite (CT-SMAC medium) from several raw vegetable samples. All colorless colonies grown on CT-SSMAC medium from raw vegetable samples were beta-galactosidase-negative. These findings suggest that the CT-SSMAC medium is useful for the isolation of E. coli O157:H7 from raw vegetable samples.

Topics: Agar; beta-Galactosidase; Cefixime; Cephalosporins; Colony Count, Microbial; Color; Culture Media; Escherichia coli O157; Tellurium; Vegetables

Tellurite (TeO3(2-)) is highly toxic to most microorganisms. The mechanisms of toxicity or resistance are poorly understood. It has been shown that tellurite rapidly depletes the reduced thiol content within wild-type Escherichia coli. We have shown that the presence of plasmid-borne tellurite-resistance determinants protects against general thiol oxidation by tellurite. In the present study we observe that the tellurite-dependent depletion of cellular thiols in mutants of the glutathione and thioredoxin thiol:redox system was less than in wild-type cells. To identify the type of low-molecular-weight thiol compounds affected by tellurite exposure, the thiol-containing molecules were analyzed by reverse phase HPLC as their monobromobimane derivatives. Results indicated that reduced glutathione is a major initial target of tellurite reactivity within the cell. Other thiol species are also targeted by tellurite, including reduced coenzyme A. The presence of the tellurite resistance determinants kilA and ter protect against the loss of reduced glutathione by as much as 60% over a 2 h exposure. This protection of glutathione oxidation is likely key to the resistance mechanism of these determinants. Additionally, the thiol oxidation response curves were compared between selenite and tellurite. The loss of thiol compounds within the cell recovered from selenite but not to tellurite.

Topics: Bacterial Proteins; Chromatography, High Pressure Liquid; Coenzyme A; Drug Resistance, Bacterial; Escherichia coli; Escherichia coli Proteins; Glutathione; Mutation; Oxidation-Reduction; Plasmids; Sodium Selenite; Sulfhydryl Compounds; Tellurium; Thioredoxins

Ultraviolet, visible (UV/VIS) and differential thermal analysis (DTA) measurements were carried out in order to investigate the optical and thermal properties of various 0.5 mol.% Tm2O3 containing (1 - x)TeO2 + xLiCl glasses in molar ratio. The samples were prepared by fusing the mixture of their respective reagent grade powders in a platinum cricuble at 750 degrees C for 30 min. DTA curves taken in the 23-600 degrees C temperature range with a heating rate of 10 degrees C/min reveal a change in the value of the glass transition temperature, Tg, while melting was not observed for the glasses containing LiCl content less than 50 mol.%. These glasses were found to be moisture-resistant. However, the glasses with LiCl content higher than 50 mol.%, in which a melting peak was observed at Tc = 401 degrees C, were moisture-sensitive. Absorption measurements in the UV/VIS region of the glasses without Tm2O3 content show that the Urbach cutoff occurs at about 320 nm and, is relatively independent of the LiCl content. Six absorption bands were observed in the Tm2O3 doped glasses corresponding to the absorption of the 1G4, 3F2, 3F3 and 3F4, 3H5 and 3H4 levels from the 3H6 ground level of Tm3+ ions. The spectra also show that the integrated absorption cross-section of each band depends on the glass composition. Judd-Ofelt theory was used to determine the Judd-Ofelt parameters as well as the radiative transition probabilities for the metastable levels of Tm3+ ions in (0.3)LiCl + (0.7) TeO2: 0.01 Tm2O3 glass which is moisture-resistant.

Topics: Crystallization; Differential Thermal Analysis; Glass; Lithium Chloride; Optics and Photonics; Spectrophotometry, Ultraviolet; Tellurium; Thulium

The aims of this study were to evaluate the performance of a new medium, desferrioxamine oxacillin tellurite egg-yolk mannitol salt agar (DOTEMSA) in detecting methicillin-resistant Staphylococcus aureus (MRSA) and then to compare this medium against the Public Health Laboratory Service (PHLS) recommendation of mannitol salt agar (Oxoid) with oxacillin (OMSA) and Baird-Parker medium with ciprofloxacin (BPC) for the isolation of MRSA. The individual selective agents contained in DOTEMSA were tested against isolates of coagulase-negative staphylococci (CNS) and the medium with all constituents was challenged with various bacteria. Routine screening specimens were plated out on OMSA, BPC and DOTEMSA and the plates were incubated and examined at 24 and 48 h. Tellurite, desferrioxamine and oxacillin each inhibited the majority of CNS isolates; only three (of 103) grew in the presence of all three agents. Sixty-two of 63 isolates of MRSA grew on DOTEMSA and 59 produced lipase. Most other bacteria were inhibited. In all, 184 MRSA isolates were isolated from 540 screening specimens. The sensitivity of OMSA, BPC and DOTEMSA was 42%, 81% and 51% at 24 h, and 60%, 89% and 89% at 48 h. At 48 h, the combination of BPC and DOTEMSA detected 99% of MRSA isolates. Seventy, 49 and one non-MRSA isolates needed investigation for each of the three media respectively. A proposed strategy for MRSA screening would use BPC and DOTEMSA, examining BPC at 24 h and both media at 48 h. Provisional reports could then be issued at 24 h on the basis of rapid agglutination tests to confirm isolates as S. aureus from BPC and at 48 h on the basis of typical colonies from DOTEMSA.

Topics: Cell Division; Coagulase; Culture Media; Deferoxamine; Enterobacteriaceae; Enterococcus; Humans; Mannitol; Methicillin Resistance; Oxacillin; Staphylococcus; Staphylococcus aureus; Streptococcus; Tellurium

Zinc tellurite glasses of compositions 19ZnO-80TeO2-1Ln2O3 with Ln = Eu, Er, Nd and Tm were prepared by melt quenching. The absorption spectra were measured and from the experimental oscillator strengths of the f-->f transitions the Judd-Ofelt parameters ohm(lambda) were obtained. The values of the ohm(lambda) parameters are in the range usually observed for oxide glasses. For Nd3+ and Er3+, luminescence spectra in the near infrared were measured and the stimulated emission cross sections sigma(p) were evaluated for some laser transitions. The high values of sigma(p), especially for Nd3+, make them possible candidates for optical applications. Fluorescence line narrowing (FLN) spectra of the Eu3+ doped glass were measured at 20 K, and the energies of the Stark components of the 7F1 and 7F2 states were obtained. A crystal field analysis was carried out assuming a C2v site symmetry. The behaviour of the crystal field ratios B22/B20 and B44/B40 agrees reasonably well with the values calculated using the geometric model proposed by Brecher and Riseberg. The crystal field strength at the Eu3+ sites appears to be very low compared to other oxide glasses.

Topics: Biophysical Phenomena; Biophysics; Crystallography; Glass; Lanthanoid Series Elements; Spectrophotometry; Tellurium; Zinc Oxide

Preliminary studies showed that the periplasmic nitrate reductase (Nap) of Rhodobacter sphaeroides and the membrane-bound nitrate reductases of Escherichia coli are able to reduce selenate and tellurite in vitro with benzyl viologen as an electron donor. In the present study, we found that this is a general feature of denitrifiers. Both the periplasmic and membrane-bound nitrate reductases of Ralstonia eutropha, Paracoccus denitrificans, and Paracoccus pantotrophus can utilize potassium selenate and potassium tellurite as electron acceptors. In order to characterize these reactions, the periplasmic nitrate reductase of R. sphaeroides f. sp. denitrificans IL106 was histidine tagged and purified. The V(max) and K(m) were determined for nitrate, tellurite, and selenate. For nitrate, values of 39 micromol x min(-1) x mg(-1) and 0.12 mM were obtained for V(max) and K(m), respectively, whereas the V(max) values for tellurite and selenate were 40- and 140-fold lower, respectively. These low activities can explain the observation that depletion of the nitrate reductase in R. sphaeroides does not modify the MIC of tellurite for this organism.

Topics: Cupriavidus necator; Drug Resistance, Bacterial; Kinetics; Microbial Sensitivity Tests; Nitrate Reductases; Nitrates; Oxidation-Reduction; Paracoccus; Paracoccus denitrificans; Periplasm; Rhodobacter sphaeroides; Selenic Acid; Selenium Compounds; Tellurium

The cDNA for human squalene monooxygenase, a key enzyme in the committed pathway for cholesterol biosynthesis, was amplified from a human liver cDNA library and cloned, and the protein was expressed in Escherichia coli and purified. Kinetic analysis of the purified enzyme revealed an apparent K(m) for squalene of 7.7 microM and an apparent k(cat) of 1.1 min(-1). For FAD the apparent K(m) is 0.3 microM, consistent with a loosely bound flavin. The apparent K(m) for NADPH-cytochrome P450 reductase, the requisite electron transfer partner, is 14 nM. The amount of reductase needed for maximal activity is about threefold less than the amount of squalene monooxygenase present in the assay; thus, electron transfer to the monooxygenase is not likely to be rate limiting. Previous reports have implicated inhibition of this enzyme as the cause of a peripheral demyelination seen in weanling rats fed a diet containing tellurium. As no data were available for humans, the ability of a number of tellurium and related elemental compounds to inhibit the recombinant human enzyme was examined. Tellurite, tellurium dioxide, selenite, and selenium dioxide were inhibitory; the tellurium compounds were more potent than the selenium compounds, as indicated by their IC(50) values (17 and 37 microM, respectively). Kinetic analysis of the inhibition by tellurite suggests multiple sites of interaction with the enzyme in a noncompetitive manner with respect to squalene.

Topics: Amino Acid Sequence; Animals; Base Sequence; Candida albicans; Cloning, Molecular; DNA Primers; Enzyme Inhibitors; Flavin-Adenine Dinucleotide; Humans; Kinetics; Mice; Molecular Sequence Data; NADPH-Ferrihemoprotein Reductase; Open Reading Frames; Oxygenases; Rats; Recombinant Proteins; Selenium Compounds; Selenium Oxides; Sequence Alignment; Sequence Homology, Amino Acid; Sodium Selenite; Squalene; Squalene Monooxygenase; Tellurium

Culture on cefixime, tellurite, and sorbitol-MacConkey agar after HCl treatment facilitated the growth of 410 (94%) of 436 eae-positive Shiga toxin-producing Escherichia coli (STEC) strains and 17 (16%) of 107 eae-negative STEC strains. This selectivity was closely related to acid resistance in E. coli and tellurite resistance in eae-positive STEC strains.

Topics: Adhesins, Bacterial; Animals; Bacterial Outer Membrane Proteins; Bacterial Toxins; Carrier Proteins; Cattle; Culture Media; Drug Resistance, Microbial; Escherichia coli; Escherichia coli Infections; Escherichia coli Proteins; Humans; Hydrochloric Acid; Microbial Sensitivity Tests; Shiga Toxins; Tellurium; Virulence

The terminal oxidases of the respiratory chain of seven strains of gram-negative bacteria were shown to be involved in the reduction of tellurite. The rate of tellurite reduction correlated with the intensity of respiration. The inhibitors of terminal oxidases, carbon monoxide and cyanide, inhibited the reduction of tellurite. In Pseudomonas aeruginosa PAO ML4262 and P. aeruginosa PAO ML4262 (pBS 10), the respiratory chain was found to contain three types of cytochrome c, one of which (the carbon monoxide-binding cytochrome c) was involved in the reduction of tellurite. Agrobacterium tumefaciens VKM B-1219, P. aeruginosa IBPM B-13, and Escherichia coli G0-102bd++ cells contained oxidases aa3, bb3, and bd, respectively. The respiratory chain of other strains contained two oxidases: E. coli DH5alpha of bb3- and bd-type, and Erwinia carotovora VKM B-567 of bo3- and bd-type. All the strains under study reduced tellurite with the formation of tellurium crystallites. Depending on the position of the active center of terminal oxidases in the plasma membrane, the crystallites appeared either in the periplasmic space [P. aeruginosa PAO ML4262 and P. aeruginosa PAO ML4262 (pBS10)], or on the outer surface of the membrane (A. tumefaciens VKM B-1219 and P. aeruginosa IBPM B-13), its inner surface (E. coli G0-102bd++), or on both surfaces (E. coli DHaalpha and E. carotovora VKM B-567).

Topics: Cell Compartmentation; Electron Transport; Gram-Negative Bacteria; Oxidation-Reduction; Oxidoreductases; Oxygen Consumption; Periplasm; Species Specificity; Tellurium

8-hydroxyquinoline-beta-D-glucuronide (HQG) was used to improve the presumptive identification of Shiga toxin-producing Escherichia coli O157 (STEC O157) on sorbitol MacConkey agars (SMAC). Advantages of HQG are (i) that it is less expensive than 5-bromo-4-chloro-3-indoxyl-glucuronide; (ii) that it is visible in normal daylight and (iii) that it does not diffuse into the agar like 4-methylumbelliferryl-beta-D-glucuronide (MUG). Sixteen STEC O157 isolates, 91 bovine mastitis-associated E. coli isolates and 222 faecal E. coli isolates from apparently healthy cattle were used in this study. 4-methylumbelliferryl-beta-D-glucuronide detected beta-glucuronidase activity in more isolates than HQG (P < 0.05). On SMAC with HQG, cefixime and tellurite all STEC O157 isolates grew as cream-coloured colonies (100% sensitivity), whereas all non-STEC O157 E. coli except one grew either not at all or as purple or black colonies (99.7% specificity). No difference was found between faecal and mastitis isolates for the proportion of isolates that hydrolysed HQG or MUG or fermented sorbitol. However, significantly more mastitis isolates were able to grow in the presence of the cefixime-tellurite supplement. 8-Hydroxyquinoline-beta-D-glucuronide is a useful substrate for the identification of STEC O157 on SMAC.

Topics: Animals; Cattle; Culture Media; Escherichia coli O157; Feces; Female; Humans; Hydroxyquinolines; Mastitis; Meat; Sorbitol; Tellurium

A modified version of sorbitol MacConkey medium containing cefixime and tellurite (CT-SMAC medium) was produced by adding salicin and 4-methylumbelliferyl-beta-D-galactopyranoside to CT-SMAC medium; this medium was designated CT-SSMAC medium and was used to isolate Escherichia coli O157:H7 from radish sprouts. Of 101 non-E. coli bacteria isolated from radish sprouts that produced colorless colonies similar to colonies of E. coli O157:H7 grown on CT-SMAC medium, 92 (91%) formed colonies that were red to pink or were beta-galactosidase negative and colorless on CT-SSMAC medium. On the other hand, colonies of E. coli O157:H7 strains were colorless and beta-galactosidase positive on CT-SSMAC medium. Our results suggest that CT-SSMAC medium is more selective than CT-SMAC medium for isolating E. coli O157:H7.

Topics: Animals; Brassicaceae; Cattle; Cefixime; Culture Media; Escherichia coli O157; Feces; Humans; Tellurium

The tellurite-resistant Escherichia coli strain KL53 was found during testing of the group of clinical isolates for antibiotics and heavy metal ion resistance (Burian et al. 1990). Determinant of the tellurite resistance of the strain was located on the large conjugative plasmid pTE53 and cloned into pACYC184. Three different Ter clones harboring pLK2, pLK18 and pLK20 were isolated (Burian et al. 1998). The smallest functional Ter clone harboring pLK18 was chosen for further analysis. Plasmid pLK18 have been subcloned to obtain convenient DNA fragments for sequencing of tellurite-resistance determinant. Sequencing of this DNA fragments provided complete DNA sequence of the determinant, 5,250 bp in size. The sequence has been compared with nucleotide and protein databank (BLAST programs) and significant homology with the three known operons coding for tellurite resistance has been found (determinat on plasmid pR478 from Serratia marcescens, on plasmid pMER610 from Alcaligenes sp. and chromosomal tellurite resistance genes from Proteus mirabilis). We identified 5 ORFs coding for 5 genes named terB to terF. The clone harboring pLK18 was subjected to the transposition with Tn1737Km to disrupt determinant of the tellurite resistance. Plasmid DNA of several clones containing pLK18 with Tn1737Km was isolated to locate the target site of Tn1737Km. Analyses showed, the genes terB, terC, terD and terE are essential for conservation of the resistance whereas the gene terF is not important in this respect.

Topics: DNA, Bacterial; Drug Resistance; Escherichia coli; Humans; Plasmids; Sequence Analysis, DNA; Tellurium

TehATehB is a tellurite (TeO(2-)(3)) resistance determinant found on the Escherichia coli chromosome. Normally silent, it specifies a minimal inhibitory concentration (MIC) of 2 microg K(2)TeO(3)/ml unless upregulated or present on a multicopy plasmid which results in an MIC of 128 microg/ml. Both TehA and TehB have three cysteine residues. Oligonucleotide site-directed mutagenesis was carried out to systematically replace all six cysteine residues by alaninies. The results showed that cysteine residues in both TehA and TehB play a role in tellurite resistance: A single cysteine change had no effect, however increasing combinations of two or three cysteine substitutions demonstrated strong phenotypic effects with minimal inhibitory concentrations ranging from 16-64 microg K(2)TeO(3)/ml. A cysteine-free mutant in which all six cysteine residues were replaced by alanines maintained a MIC of 16 microg/ml. Further investigations on the role of cysteines in resistance were studied using thiol reactive reagents on the soluble subunit TehB. These studies confirmed that TehB is a dimer and undergoes a conformational change with tellurite and S-adenosyl-l-methionine binding. Studies using native and SDS denaturing PAGE under reducing and oxidizing conditions suggested that a cysteine in TehB is involved in binding tellurite.

Topics: Alanine; Alkylating Agents; Bacterial Proteins; Binding Sites; Cysteine; Dithionitrobenzoic Acid; Drug Resistance; Electrophoresis, Polyacrylamide Gel; Enzyme Inhibitors; Escherichia coli; Escherichia coli Proteins; Ethylmaleimide; Iodoacetamide; Iodoacetates; Ligands; Microbial Sensitivity Tests; Mutagenesis, Site-Directed; Phenotype; Plasmids; Protein Binding; Protein Conformation; Protein Denaturation; S-Adenosylmethionine; Sulfhydryl Reagents; Tellurium; Up-Regulation

The Escherichia coli chromosomal determinant for tellurite resistance consists of two genes (tehA and tehB) which, when expressed on a multicopy plasmid, confer resistance to K(2)TeO(3) at 128 microg/ml, compared to the MIC of 2 microg/ml for the wild type. TehB is a cytoplasmic protein which possesses three conserved motifs (I, II, and III) found in S-adenosyl-L-methionine (SAM)-dependent non-nucleic acid methyltransferases. Replacement of the conserved aspartate residue in motif I by asparagine or alanine, or of the conserved phenylalanine in motif II by tyrosine or alanine, decreased resistance to background levels. Our results are consistent with motifs I and II in TehB being involved in SAM binding. Additionally, conformational changes in TehB are observed upon binding of both tellurite and SAM. The hydrodynamic radius of TehB measured by dynamic light scattering showed a approximately 20% decrease upon binding of both tellurite and SAM. These data suggest that TehB utilizes a methyltransferase activity in the detoxification of tellurite.

Topics: Amino Acid Sequence; Amino Acid Substitution; Bacterial Proteins; Drug Resistance, Microbial; Escherichia coli; Escherichia coli Proteins; Molecular Sequence Data; Mutation; Protein Binding; Protein Conformation; S-Adenosylmethionine; Sequence Alignment; Tellurium

Selenium is both an essential and a toxic trace element, and the range of concentrations between the two is extremely narrow. Although tellurium is not essential and is only rarely found in the environment, it is considered to be extremely toxic. Several hypotheses have been proposed to account for the toxic effects of selenite and tellurite. However, these potential mechanisms have yet to be fully substantiated. Through screening of an Escherichia coli luxAB transcriptional gene fusion library, we identified a clone whose luminescence increased in the presence of increasing concentrations of sodium selenite or sodium tellurite. Cloning and sequencing of the luxAB junction revealed that the fusion had occurred in a previously uncharacterized open reading frame, termed o393 or yhfC, which we have now designated gutS, for gene up-regulated by tellurite and selenite. Transcription from gutS in the presence of selenite or tellurite was confirmed by RNA dot blot analysis. In vivo expression of the GutS polypeptide, using the pET expression system, revealed a polypeptide of approximately 43 kDa, in good agreement with its predicted molecular mass. Although the function of GutS remains to be elucidated, homology searches as well as protein motif and secondary-structure analyses have provided clues which may implicate GutS in transport in response to selenite and tellurite.

Topics: Amino Acid Sequence; Bacterial Proteins; Base Sequence; Chromosome Mapping; Cloning, Molecular; DNA Transposable Elements; Escherichia coli; Gene Expression Regulation, Bacterial; Genes, Bacterial; Luminescence; Molecular Sequence Data; Mutagenesis, Insertional; Peptides; Recombinant Fusion Proteins; Sodium Selenite; Tellurium; Transcription, Genetic; Transferases

A potassium tellurite-resistance determinant was isolated from Bacillus stearothermophilus V and cloned in Escherichia coli. Transformed cells formed black colonies when grown on solid media containing permissive tellurite concentrations. The resistance determinant was contained in a B. stearothermophilus V chromosomal DNA fragment of 7 kb.

Topics: Cloning, Molecular; DNA, Bacterial; Drug Resistance; Escherichia coli; Gene Library; Genes, Bacterial; Geobacillus stearothermophilus; Oxidation-Reduction; Tellurium; Transformation, Genetic

The metallic group XVIa elements selenium and tellurium possess remarkably similar chemical properties. However, unlike selenium, tellurium is not an essential micronutrient and, indeed, induces both acute and chronic toxicity in a variety of species. Despite this, very little is known of the molecular mechanisms of toxicity of tellurium, particularly with respect to potential chemical interactions with selenium-containing components in the cell. In this work we describe a novel interaction of inorganic tellurite with hepatocellular selenoproteins, particularly with selenium-dependent glutathione peroxidase. The accumulation of (121Te)-tellurite into cultured primary rat liver hepatocytes was shown to be much more rapid than that of (75Se)-selenite on a molar basis. Neither the uptake of (121Te)-tellurite nor of (75Se)-selenite was affected by a large molar excess of the unlabelled counterpart, respectively. Interestingly, separation of the hepatocellular proteins on continuous pH denaturing gels demonstrated clear binding of radiolabelled tellurium to a number of protein bands, including one at 23 and one at 58 kDa, which corresponded to proteins readily labelled in cells treated with (75Se)-selenite. The binding of (121Te) to these proteins was insensitive to reduction with mercaptoethanol and not affected by pre-treatment of the cells with cycloheximide. When purified selenium-dependent glutathione peroxidase was treated directly with (121Te)-tellurite, the protein became labelled in an analogous manner to that achieved in intact cells. This was not affected by coincubation of the enzyme with (121Te)-tellurite and one or both of its substrates. Additionally, incubation of the peroxidase with tellurite effectively inhibited its ability to catalyse glutathione-dependent reduction of hydrogen peroxide. These data suggest that inorganic tellurite delivers tellurium to the intracellular milieu in a form capable of binding to some intracellular selenoproteins and at least in the case of glutathione peroxidase, cause inhibition of catalytic activity. The nature of the binding seems not to be due to the insertion of tellurocysteine into the protein and the insensitivity to reductive cleavage with mercaptoethanol seems to preclude the formation of stable telluro-selenides in the proteins. These data may offer alternative explanations for the established toxicity of tellurium via disruption of selenoprotein function, particularly by the induction of intracellula

Topics: Animals; Binding, Competitive; Cells, Cultured; Cycloheximide; Cytosol; Female; Glutathione Peroxidase; Liver; Protein Synthesis Inhibitors; Proteins; Radioisotopes; Rats; Rats, Sprague-Dawley; Selenium; Selenium Radioisotopes; Selenoproteins; Tellurium

Streptococcus pneumoniae is a Gram-positive bacterium which is naturally resistant to tellurite. In this study, we cloned and sequenced a homologue of the Escherichia coli tellurite resistance gene tehB from S. pneumoniae. It encoded a protein of 284 amino acids which is 86 residues longer than E. coli TehB, but similar in size to Haemophilus influenzae TehB and Eikenella corrodens hemagglutinin (Hag1) as well as homologues from Actinobacillus actinomycetemcomitans, Neisseria gonorrhoeae and Neisseria meningitidis. The S. pneumoniae TehB displayed 46-58% identity (52-68% similarity) to these proteins. The results in this study showed that the S. pneumoniae tehB alone not only conferred on E. coli high level resistance to tellurite, but also caused filamentous morphology in E. coli.

Topics: Amino Acid Sequence; Bacterial Proteins; Drug Resistance, Microbial; Escherichia coli; Escherichia coli Proteins; Genes, Bacterial; Microbial Sensitivity Tests; Molecular Sequence Data; Sequence Analysis, DNA; Streptococcus pneumoniae; Tellurium

The oxyanion of tellurium, tellurite (TeO3(2-)), is toxic to most micro-organisms, particularly gram-negative bacteria. The mechanism of tellurite toxicity is presently unknown. Many heavy metals and oxyanions, including tellurite, interact with reduced thiols (RSH). To determine if tellurite interaction with RSH groups is involved in the toxicity mechanism, the RSH content of Escherichia coli cultures was assayed. After exposure to tellurite, cells were harvested and lysed in the presence of the RSH-specific reagent 5,5'-dithiobis(2-nitrobenzoic acid). Upon exposure of tellurite-susceptible cells to TeO3(2-), the RSH content decreased markedly. Resistance to potassium tellurite (Te(r)) in gram-negative bacteria is encoded by plasmids of incompatibility groups IncFI, IncP alpha, IncHI2, IncHI3 and IncHII, as well as the tehAtehB operon from the E. coli chromosome. When cells harbouring a Te(r) determinant were exposed to TeO3(2-), only a small fraction of the RSH content became oxidized. In addition to tellurite-dependent thiol oxidation, the resistance of E. coli mutants affected in proteins involved in disulfide-bond formation (dsb) was investigated. Mutant strains of dsbA and dsbB were found to be hypersensitive to tellurite (MIC 0.008-0.015 microg K2TeO3 ml(-1) compared to wild-type E. coli with MICs of 1-2 microg K2TeO3 ml(-1)). In contrast, dsbC and dsbD mutants showed no hypersensitivity. The results suggest that hypersensitivity to tellurite is reliant on the presence of an isomerase activity and not the thiol oxidase activity of the Dsb proteins. The results establish that the Te(r) determinants play an important role in maintaining homeostasis of the intracellular reducing environment within gram-negative cells through specific reactions with either TeO3(2-) or thiol:tellurium products.

Topics: Bacterial Proteins; Drug Resistance, Microbial; Escherichia coli; Membrane Proteins; Microbial Sensitivity Tests; Oxidation-Reduction; Plasmids; Protein Disulfide-Isomerases; Sulfhydryl Compounds; Tellurium

Four Nudix hydrolase genes, ysa1 from Saccharomyces cerevisiae, orf209 from Escherichia coli, yqkg from Bacillus subtilis, and hi0398 from Hemophilus influenzae were amplified, cloned into an expression vector, and transformed into E. coli. The expressed proteins were purified and shown to belong to a subfamily of Nudix hydrolases active on ADP-ribose. Comparison with other members of the subfamily revealed a conserved proline 16 amino acid residues downstream of the Nudix box, common to all of the ADP-ribose pyrophosphatase subfamily. In this same region, a conserved tyrosine designates another subfamily, the diadenosine polyphosphate pyrophosphatases, while an array of eight conserved amino acids is indicative of the NADH pyrophosphatases. On the basis of these classifications, the trgB gene, a tellurite resistance factor from Rhodobacter sphaeroides, was predicted to designate an ADP-ribose pyrophosphatase. In support of this hypothesis, a highly specific ADP-ribose pyrophosphatase gene from the archaebacterium, Methanococcus jannaschii, introduced into E. coli, increased the transformant's tolerance to potassium tellurite.

Topics: Adenosine Triphosphatases; Amino Acid Sequence; Animals; Arsenate Reductases; Arsenite Transporting ATPases; Bacillus subtilis; Drug Resistance; Escherichia coli; Gene Library; Humans; Ion Pumps; Methanococcus; Molecular Sequence Data; Multienzyme Complexes; Pyrophosphatases; Rhodobacter sphaeroides; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Tellurium

The evolution over 30 years of a population of methicillin-resistant Staphylococcus aureus (MRSA) from a tertiary referral hospital was studied by phylogenetic analysis of SmaI-generated restriction fragment length polymorphisms (RFLPs). The results suggest that a new clone of MRSA appeared at the hospital in the early 1980s, which, although usually retaining its ancestral phage-type, developed four different RFLP pulsotypes in the next 16 years. This finding indicates that multiple RFLP patterns in MRSA do not necessarily represent multiple clones deriving from different mec gene transfer events. Such variation within a clone may be significant in the interpretation of RFLP patterns during outbreaks and emphasizes the need to use two typing methods in studies of such populations. Since the appearance of new clones of MRSA is a relatively rare event, cross-infection control is paramount in the prevention of MRSA dissemination.

Topics: Anti-Bacterial Agents; Australia; Bacteriophage Typing; Cross Infection; Culture Media; Deoxyribonucleases, Type II Site-Specific; Electrophoresis, Gel, Pulsed-Field; Gene Transfer Techniques; Hospitals; Humans; Methicillin Resistance; Microbial Sensitivity Tests; Molecular Epidemiology; Phylogeny; Polymorphism, Restriction Fragment Length; Reproducibility of Results; Staphylococcal Infections; Staphylococcus aureus; Staphylococcus Phages; Tellurium

The responses of Saccharomyces cerevisiae towards the oxyanions tellurite, selenite and chromate were investigated in order to establish the involvement of the yeast vacuole in their detoxification. Three mutants of S. cerevisiae with defective vacuolar morphology and function were used; mutant JSR180 delta 1 is devoid of any vacuolar-like structure while ScVatB and ScVatC are deficient in specific protein subunits of the vacuolar (V)-H(+)-ATPase. All the mutant strains showed increased sensitivity to tellurite and chromate compared to their parental strains. Such sensitivity of the mutants was associated with increased accumulation of tellurium and chromium. These results indicate that accumulation of both tellurium and chromium occurred mainly in the cytosolic compartment of the cell, with detoxification influenced by the presence of a functionally-active vacuole which may play a role in compartmentation as well as regulation of the cytosolic compartment for optimal expression of a detoxification mechanism, e.g. reduction. In contrast, the vacuolar-lacking mutant, JSR180 delta 1, and the defective V-H+ATPase mutant ScVatB displayed lower selenium accumulation than their parental strains. Additionally, the mutant strain ScVatB displayed a higher tolerance to selenite than the parental strain. This result suggests that accumulation of selenium occurs mainly in the vacuolar compartment of the cell with tolerance depending on the ability of the cytosolic component to reduce selenite to elemental selenium, which might, in turn, be related to activity of the V-H(+)-ATPase. These results are discussed in relation to vacuolar compartmentation and the significance of the vacuolar H(+)-ATPase in cytosolic homeostasis of H+ both of which may affect the accumulation, reduction, and tolerance to the tested metal(loids).

Topics: Chromates; Chromium; Drug Resistance, Microbial; Inactivation, Metabolic; Metals; Mutation; Proton-Translocating ATPases; Saccharomyces cerevisiae; Selenium; Sodium Selenite; Tellurium; Vacuolar Proton-Translocating ATPases; Vacuoles

A tellurite-resistance genetic determinant was isolated from the pea blight pathogen Pseudomonas syringae pathovar pisi by a shotgun strategy involving a tellurite-selective screening in Escherichia coli. A 1.65 kb tellurite resistance insert was obtained and analysed. It harbours a single complete and functional ORF encoding a deduced protein of 24, 445 Da. The deduced AA sequence shows significant similarities with the complete human thiopurine methyltransferase enzyme, a methyltransferase from Synechocystis and a methyltransferase-like sequence from Bordetella pertussis. The encoded thiopurine methyltransferase activity was demonstrated using a radiochemical microassay for the methylation of 6-mercaptopurine. This gene was detected in most P. syringae legume pathogens.

Topics: Amino Acid Sequence; Base Sequence; Drug Resistance, Microbial; Genes, Bacterial; Methyltransferases; Molecular Sequence Data; Pisum sativum; Pseudomonas; Restriction Mapping; Sequence Alignment; Tellurium

Resistance to the toxic compound potassium tellurite (Telr) has been employed as a selection marker built into a set of transposon vectors and broad-host-range plasmids tailored for genetic manipulations of Pseudomonas strains potentially destined for environmental release. In this study, the activated Telr determinants encoded by the cryptic telAB genes of plasmid RK2 were produced, along with the associated kilA gene, as DNA cassettes compatible with cognate vectors. In one case, the Telr determinants were assembled between the I and O ends of a suicide delivery vector for mini-Tn5 transposons. In another case, the kilA and telAB genes were combined with a minimal replicon derived from a variant of Pseudomonas plasmid pPS10, which is able to replicate in a variety of gram-negative hosts and is endowed with a modular collection of cloning and expression assets. Either in the plasmid or in the transposon vector, the Telr marker was combined with a 12-kb DNA segment of plasmid pWW0 of Pseudomonas putida mt-2 encoding the upper TOL pathway enzymes. This allowed construction of antibiotic resistance-free but selectable P. putida strains with the ability to grow on toluene as the sole carbon source through an ortho-cleavage catabolic pathway.

Topics: Base Sequence; DNA Primers; DNA, Bacterial; Drug Resistance, Microbial; Escherichia coli; Genetic Markers; Genetic Techniques; Molecular Sequence Data; Phenotype; Plasmids; Polymerase Chain Reaction; Pseudomonas; Pseudomonas putida; Replication Origin; Restriction Mapping; Tellurium

Bacillus stearothermophilus V is a naturally occurring Gram-positive rod which exhibits resistance to potassium tellurite. Crude extracts of this bacterium catalyse the NADH-dependent, protease-sensitive reduction of K2TeO3 in vitro. Two fractions which showed the ability to reduce potassium tellurite (H1 and H2) were obtained. Fraction H1 behaved as a macroaggregate exhibiting a very high molecular mass that could not be estimated accurately. Upon electrophoresis in polyacrylamide gels in the presence of SDS, however, it was resolved into three distinct bands of 60, 41 and 37.5 kDa. On the other hand, an M(r) of 121 was determined for fraction H2 by means of gel filtration and high-pressure liquid chromatography. In SDS-PAGE a unique protein band of 60 kDa was observed, suggesting that it is actually a dimer. Both fractions showed pH and temperature optima of 7.5 and 57 degrees C, respectively. Concentrations of 2.5 M NaCl or 0.35 mM SDS inhibited fraction H2 almost completely, while fraction H1 retained 20% of its activity under the same conditions. Concentrations of 5 mM EDTA caused the activity of both fractions to increase 2-fold. In addition to reducing tellurite, they were also able to reduce Na2SeO3 and Na2SO3 in vitro.

Topics: Edetic Acid; Geobacillus stearothermophilus; Hydrogen-Ion Concentration; Indicators and Reagents; Kinetics; Microbial Sensitivity Tests; Molecular Weight; Osmolar Concentration; Oxidation-Reduction; Oxidoreductases; Substrate Specificity; Tellurium; Temperature

Tellurite and selenate reductase activities were identified in extracts of Escherichia coli. These activities were detected on non-denaturing polyacrylamide gels using an in situ methyl viologen activity-staining technique. The activity bands produced from membrane-protein extracts had the same RF values as those of nitrate reductases (NRs) A and Z. Tellurite and selenate reductase activities were absent from membranes obtained from mutants deleted in NRs A and Z. Further evidence of the tellurite and selenate reductase activities of NR was demonstrated using rocket immunoelectrophoresis analysis, where the tellurite and selenate reductase activities corresponded to the precipitation arc of NR. Additionally, hypersensitivity to potassium tellurite was observed under aerobic growth conditions in nar mutants. The tac promoter expression of NR A resulted in elevated tellurite resistance. The data obtained also imply that a minimal threshold level of NR A is required to increase resistance. Under anaerobic growth conditions additional tellurite reductase activity was identified in the soluble fraction on non-denaturing gels. Nitrate reductase mutants were not hypersensitive under anaerobic conditions, possibly due to the presence of this additional reductase activity.

Topics: Drug Resistance, Microbial; Escherichia coli; Membranes; Mutation; Nitrate Reductase; Nitrate Reductases; Oxidoreductases; Subcellular Fractions; Substrate Specificity; Tellurium

A range of sensitivities exhibited by Escherichia coli O157 to cefixime and potassium tellurite are demonstrated. The sensitivity was shown by growth on cefixime tellurite sorbitol MacConkey agar and by the effect on the metabolic activity in glucuronate trimethylamine-oxide conductance broth. These antimicrobials are regularly used in the isolation of this pathogen from food and clinical specimens, and such sensitivity may lead to the reporting of false negative samples.

Topics: Cefixime; Cefotaxime; Escherichia coli O157; Microbial Sensitivity Tests; Tellurium

The ability of the facultative photoheterotroph Rhodobacter sphaeroides to tolerate and reduce high levels of tellurite in addition to at least 10 other rare earth metal oxides and oxyanions has considerable potential for detoxification and bioremediation of contaminated environments. We report the identification and characterization of two loci involved in high-level tellurite resistance. The first locus contains four genes, two of which, trgAB, confer increased tellurite resistance when introduced into the related bacterium Paracoccus denitrificans. The trgAB-derived products display no significant homology to known proteins, but both are likely to be membrane-associated proteins. Immediately downstream of trgB, the cysK (cysteine synthase) and orf323 genes were identified. Disruption of the cysK gene resulted in decreased tellurite resistance in R. sphaeroides, confirming earlier observations on the importance of cysteine metabolism for high-level tellurite resistance. The second locus identified is represented by the telA gene, which is separated from trgAB by 115 kb. The telA gene product is 65% similar to the product of the klaB (telA) gene from the tellurite-resistance-encoding kilA operon from plasmid RK2. The genes immediately linked to the R. sphaeroides telA gene have no similarity to other components of the kilA operon. R. sphaeroides telA could not functionally substitute for the plasmid RK2 telA gene, indicating substantial functional divergence between the two gene products. However, inactivation of R. sphaeroides telA resulted in a significant decrease in tellurite resistance compared to the wild-type strain. Both cysK and telA null mutations readily gave rise to suppressors, suggesting that the phenomenon of high-level tellurite resistance in R. sphaeroides is complex and other, as yet uncharacterized, loci may be involved.

Topics: Amino Acid Sequence; Chromosome Mapping; Cloning, Molecular; Conserved Sequence; Cosmids; Cysteine; Drug Resistance, Microbial; Evolution, Molecular; Genes, Bacterial; Molecular Biology; Molecular Sequence Data; Mutation; Paracoccus denitrificans; Plasmids; Rhodobacter sphaeroides; Sequence Homology, Amino Acid; Tellurium

The differences in the effects of inorganic Se (IV and VI) compounds and seleno-cystine [(CySe)2] on the Te (as Na2TeO3) uptake by the yeast, Saccharomyces cerevisiae, has been studied. Se, Te, Ag, Zn, Fe and Co contents of the cells were measured by instrumental neutron activation analysis. For the determination of the Ag content, the monostandard method was applied as the analytical method. The contents of other elements were determined by comparison with standards having similar amounts of the determined element as the sample. Results obtained show that an antagonist interaction occurs between SeO2 and Te. There was a significant increase in the concentrations of Se and Te when the yeast was incubated in the medium containing (CySe)2 and Te. (CySe)2 markedly increased the Ag content of cells, especially within the first 8 h of incubation. The low level of SeO2 in the medium are the exterior factor which produce an observable increase of the Ag concentration in the cells. The higher level of SeO2 in the medium causes a long-term marked increase in the Ag content of the cells. The uptake yield of Ag also increased in the presence of (NH4)2SeO4 in the medium. The Te supply produced a significant enhancement in the Ag content of the cells during the initial 8 h of incubation. The presence of Se and/or Te in the medium causes change in the intracellular Zn, Fe and Co levels.

Topics: Cystine; Metals; Neutron Activation Analysis; Organoselenium Compounds; Saccharomyces cerevisiae; Selenium Compounds; Silver; Tellurium

A region of the IncHI2 plasmid R478, encoding the phenotypes of tellurite resistance (Ter), phage inhibition (Phi), and colicin resistance (PacB), was cloned and sequenced. Analysis indicated seven open reading frames (ORFs), whose genes were designated terZ, -A, -B, -C, -D, -E, and -F. Five of these predicted ORFs (A to E) had extensive amino acid homology with the previously reported ORFs of the IncHI2 Ter operon from plasmid pMER610. There were domains of highly conserved amino acid residues within the group TerA, -D, -E, and -F and within TerD, -E, and -Z, but no consensus could be found among all five putative polypeptides. There were also regions of good identity and similarity between individual pairs of ORFs which was not reflected in the multiple alignments. The three phenotypes were expressed in Escherichia coli DH5 alpha by an 8.4-kb EcoRI insert subcloned from a cosmid of R478. The latter insert was clonable only as a double insertion with a 4.5-kb fragment, and forced deletion of the smaller fragment was lethal to cells. This lethality was not dependent on the cloned orientation of either fragment, suggesting that there is a trans-acting element in the 4.5-kb fragment. Tn1000 mutagenesis of one of the double-insert clones, pDT2575, showed that the phenotypes, including multiple colicin resistance, were genetically linked. Transpositions into terD, terC, and terZ reduced or abolished all phenotypes, while inserts into terE and terF had no effect on the phenotypes. Insertions in terA reduced phage inhibition levels only. The presence of the terZ and terF ORFs in pMER610 was confirmed, and derivatives of this plasmid mediated Phi, PacB, and Ter.

Topics: Amino Acid Sequence; Bacterial Proteins; Base Sequence; Cloning, Molecular; Colicins; Drug Resistance, Microbial; Escherichia coli; Genes, Bacterial; Molecular Sequence Data; Multigene Family; Mutagenesis, Insertional; Open Reading Frames; Phenotype; R Factors; Sequence Analysis, DNA; Sequence Homology, Amino Acid; T-Phages; Tellurium

A peripheral neuropathy characterized by a transient demyelinating/remyelinating sequence results when young rats are fed a tellurium-containing diet. The neuropathy occurs secondary to a systemic block in cholesterol synthesis. Squalene accumulation suggested the lesion was at the level of squalene expoxidase, a microsomal monooxygenase that uses NADPH cytochrome P450 reductase to receive its necessary reducing equivalents from NADPH. We have now demonstrated directly specificity for squalene epoxidase; our in vitro studies show that squalene epoxidase is inhibited 50% in the presence of 5 microM tellurite, the presumptive in vivo active metabolite. Under these conditions, the activities of other monooxygenases, aniline hydroxylase and benzo(a)pyrene hydroxylase, were inhibited less than 5%. We also present data suggesting that tellurite inhibits squalene epoxidation by interacting with highly susceptible -SH groups present on this monooxygenase. In vivo studies of specificity were based on the compensatory response to feeding of tellurium. Following tellurium intoxication, there was up-regulation of squalene epoxidase activity both in liver (11-fold) and sciatic nerve (fivefold). This induction was a specific response, as demonstrated in liver by the lack of up-regulation following exposure to the nonspecific microsomal enzyme inducer, phenobarbital. As a control, we also measured the microsomal monooxygenase activities of aniline hydroxylase and benzo(a)pyrene hydroxylase. Although they were induced following phenobarbital exposure, activities of these monooxygenases were not affected following tellurium intoxication, providing further evidence of specificity of tellurium intoxication for squalene epoxidase.

Topics: Aniline Hydroxylase; Animals; Benzopyrene Hydroxylase; Liver; NADPH-Ferrihemoprotein Reductase; Oxygenases; Peripheral Nervous System Diseases; Rats; Sciatic Nerve; Squalene Monooxygenase; Sulfhydryl Compounds; Tellurium

Rates of uptake of the TeO3(2-) oxyanion were investigated in Escherichia coli cells containing tellurite resistance determinants from both plasmid (RK2Ter, R478, pMER610, MIP233, pHH1508a, pMUR) and chromosomal (tehAB) sources. The uptake was investigated to determine whether or not reduced uptake or increased efflux is involved in the tellurite resistance mechanism. Reduced TeO3(2-) uptake generated by cultures harboring arsABC from the plasmid R773, which has been previously shown to be an oxyanion efflux transporter, was used as the standard. Uptake curves were found to be essentially identical among E. coli cultures harboring the tellurite resistance plasmids RK2Ter, pMER610, pHH1508a, and pMUR and cultures harboring tellurite-sensitive control plasmids. Cultures harboring clones of the tehAB operon from E. coli showed no change in the TeO3(2-) accumulation. Cultures harboring R478 demonstrated reduced uptake. However, a subclone containing only the tellurite resistance determinant displayed no reduced uptake. This suggests that there may be another determinant on R478 other than the primary tellurite resistance determinant that gives rise to TeO3(2-) efflux. These results demonstrate that neither reduced uptake nor increased efflux is responsible for the tellurite resistance in the resistance determinants investigated here.

Topics: Adenosine Triphosphatases; Arsenite Transporting ATPases; Biological Transport; Drug Resistance, Microbial; Escherichia coli; Ion Pumps; Multienzyme Complexes; Operon; R Factors; Tellurium

Inhibition of a Zn(2+)-glycerophosphocholine cholinephosphodiesterase by thiols or tellurites were examined mechanistically. Inactivation of the phosphodiesterase by thio-carboxylates, which was due to the removal of Zn2+ in the catalytic site, was enhanced by introduction of an amino group in the structure of thiols, suggesting the presence of an anionic site adjacent to a Zn2+ site. In support of the suggestion, it was found that thiols, associable with both a Zn2+ site and an anionic site, were more potent reversible inhibitors; dimethylaminoethanethiol (Ki, 17 microM), diethylaminoethanethiol (Ki, 1.2 microM) and thiocholine (Ki, 2.6 microM). Meanwhile, the inhibition of the phosphodiesterase by tellurites is ascribed to the binding of tellurite anions to a Zn2+ site, based on the protective action of tellurite anions against the inactivation of the enzyme by EDTA. Moreover, the inhibition of the phosphodiesterase by tellurites was prevented by phosphate ions, which expressed the protective effect against EDTA inactivation. In further support, it was observed that tellurite and thiocholine appeared to interact with active site in an additive manner, in contrast to a synergistic action between tellurites and quaternary ammonium compounds such as acetylcholine or choline.

Topics: Animals; Anions; Binding Sites; Brain; Cell Membrane; Kinetics; Mice; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Sulfhydryl Compounds; Tellurium; Zinc

The tehAtehB operon from the Escherichia coli chromosome (32.3 min) mediates resistance to potassium tellurite (K2TeO3) when expressed on a multicopy plasmid such as pUC8 (pTWT100). An MIC of 128 micrograms ml-1 is observed when tehAtehB is expressed in a wild-type host and grown on rich media. In this study, the tehAtehB determinant was transformed into mutants deficient in electron transport processes and/or thiol redox coupling within E. coli. These mutants included ubi, nad, cys, nar, trx, grx, gsh and sod. MICs of tehAtehB transformed into these mutants ranged from 1-16 micrograms K2TeO3 ml-1 compared to 0.03-2 micrograms ml-1 for strains transformed with a control plasmid. The tellurite-resistance determinant locus kilA cloned from the IncP alpha plasmid RK2Ter (pDT1558) was also investigated in these strains. This tellurite-resistance determinant showed little or no dependency on the host genotype. The ability of tehAtehB to mediate resistance in wild-type hosts is limited to rich medium. Rich medium may provide a key unidentified cofactor required by TehATehB that is not provided under minimal conditions. Again, the ability of the kilA determinant to mediate tellurite resistance was independent of medium conditions. These data suggest that either a reducing environment or electron-reducing equivalents are required for tehAtehB to mediate high levels of resistance to potassium tellurite. Therefore, the two resistance determinants studied here possess two very different biochemical mechanisms of resistance. Our data also suggest a mechanism for endogenous resistance to tellurite which involves nitrate reductase, superoxide dismutase, and thiol redox processes.

Topics: Culture Media; Cysteine; Drug Resistance, Microbial; Escherichia coli; Genes, Bacterial; Niacinamide; Nitrate Reductase; Nitrate Reductases; Operon; Oxidation-Reduction; Oxidative Stress; Oxidoreductases Acting on Sulfur Group Donors; Plasmids; Sulfhydryl Compounds; Tellurium; Ubiquinone

A tellurite resistance determinant, believed to have been cloned from the IncHII plasmid pHH1508a (E. G. Walter, J. H. Weiner, and D. E. Taylor, Gene 101:1-7, 1991), was shown instead to have originated from the chromosome of Escherichia coli K-12. The two genes, tehA and tehB, constitute an operon located in the terminus at approximately 32.3 min.

Topics: Drug Resistance, Microbial; Escherichia coli; Operon; Restriction Mapping; Tellurium

A new aerobic gram-positive non-sporeforming bacillus has been isolated from infected genital hair of patients with white piedra in association with Trichosporon beigelii. This species has been characterised morphologically, nutritionally, by DNA base composition, cell-wall analysis and cellular fatty-acid profile on the basis of 14 isolates. The G+C content of DNA is 63.05 mol%. Cell walls possess meso-diaminopimelic acid (Type IV) and the sugars glucose, galactose, xylose and ribose; mycolic acids are not present. The species has a distinct colonial and microscopic morphology, is strongly proteolytic and produces methanethiol. These findings and the cellular fatty-acid profile are compatible with the genus Brevibacterium. A new species is proposed based on the following characters: colonial and microscopic growth and morphology; conditions for rod-to-coccus cycle; ribose utilisation; and tellurite reduction. The type strain has been named Brevibacterium mcbrellneri E2cr (ATCC 49030). The strong proteolytic properties may be the mechanism of pathogenesis.

Topics: Anti-Bacterial Agents; Base Composition; Brevibacterium; Cell Wall; DNA, Bacterial; Fatty Acids; Genitalia; Hair; Humans; Oxidation-Reduction; Piedra; Ribose; Tellurium; Terminology as Topic; Trichosporon

We have developed a simple method for the quantitative determination of tellurite in biological media. This assay is suitable for studying tellurite uptake in bacteria and overcomes the problems of older techniques which are time consuming and labor intensive. In earlier protocols diethyldithiocarbamate was reacted with tellurite and the resulting complex was extracted into organic solvents before spectrophotometric determination. In this study, diethyldithiocarbamate was incubated with tellurite at neutral pH to form a yellow colloidal solution. The absorbance of the aqueous yellow sol was used to determine tellurite concentrations in the range of 1 to 50 micrograms/ml (4 to 200 microM) without the need for solvent extraction.

Topics: Arsenic; Arsenites; Biological Transport; Ditiocarb; Escherichia coli; Hydrogen-Ion Concentration; Plasmids; Selenium; Spectrum Analysis; Tellurium

Human erythrocytes exposed to 0.1 mM tellurite (K2TeO3) in an isotonic buffered choline chloride medium for 15 min at 37 degrees C, washed, and incubated further in the absence of the chemical in the buffer, exhibited selective leakiness for potassium within minutes. The potassium efflux curve was sigmoidal, with an initially slow leakage followed by a sharp rise (first-order kinetics) and a plateau by 60 min. After 15 min, 30-50% of the total potassium concentration had leaked from the cells, although less than 1% lysis had occurred. The control cells incubated in buffer with no K2TeO3 exhibited no potassium leakage. The mean volume of the K2TeO3-treated erythrocytes increased and their median density decreased, indicating changes in the colloid osmotic state and physical characteristics of the cells. However, cells pretreated with K2TeO3 exhibited no significant change in glutathione (GSH) concentration and no membrane lipid peroxidation, unlike cells pretreated with t-butylhydroperoxide (Deuticke et al., Biochim. Bio phys. Acta, 899, 125-128, 1987). The enhanced potassium permeability of the K2TeO3-treated erythrocytes preceded the increase in cell volume, intracellular hydration, and a decrease in median density. We suggest that perturbation of the lipid-protein interaction in the membrane by the oxidant alters the potassium permeability and results in the selective leakage with eventual hemolysis.

Topics: Cell Membrane Permeability; Erythrocyte Membrane; Erythrocytes; Glutathione; Humans; In Vitro Techniques; Oxidants; Potassium; Tellurium

The tellurite resistance (Ter) determinant of the IncP alpha plasmid RK2Ter, a variant of RK2 (also called RP4), is located between the kilA and korA genes involved in plasmid replication control. Transcriptional and translational fusions were constructed between the gene for beta-galactosidase and the kilA and Ter genes by using the transpositional phage mini-Mu. These fusions indicated that the Ter genes are transcribed in the same direction as kilA and that transcription and translation of the cloned kilA gene are occurring and may not be lethal to the bacterial cell even in the absence of korA. The nucleotide sequence of this region was determined, and three open reading frames (ORFs) were identified. The first ORF codes for KilA, a 28-kDa hydrophilic protein. The second ORF, telA, codes for a hydrophilic protein of 42 kDa. The third ORF, telB, codes for a hydrophobic protein of 32 kDa. This protein appears to be located in the inner membrane of the bacterial cell, since fusions of TelB to alkaline phosphatase were obtained by using TnphoA. All three proteins were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after overproduction using the T7 RNA polymerase/promoter system. The same three proteins were produced when Tes and Ter derivatives of RP4 were expressed in an in vitro transcription-translation system. A single Ser-to-Cys missense mutation in telB was found to be responsible for mutation of RK2 to Ter.

Topics: Alkaline Phosphatase; Amino Acid Sequence; Bacterial Proteins; Base Sequence; Cloning, Molecular; DNA Transposable Elements; Drug Resistance, Microbial; Electrophoresis, Polyacrylamide Gel; Escherichia coli; Escherichia coli Proteins; Genes, Bacterial; Molecular Sequence Data; Open Reading Frames; Protein Biosynthesis; R Factors; Recombinant Fusion Proteins; Restriction Mapping; Tellurium; Transcription, Genetic

Escherichia coli AB1157, and the transconjugant AB1157 (pMJ600), were used to study the mechanism of tellurite resistance conferred by pMJ600, which contains the tellurite resistance determinant cloned from the IncHI-2 conjugative plasmid pMER610. The transconjugant can tolerate a 100-fold higher concentration of potassium tellurite [K2TeO3] than the plasmid-free strain. Both strains were found to accumulate tellurite irreversibly at equivalent rates, with elemental tellurium being deposited intracellularly, direct efflux of tellurite was not found to contribute to the resistance mechanism. However, under these conditions, growth, protein synthesis and oxygen uptake ceased in AB1157, but-were unaffected in the transconjugant. No NADH- or NADPH-linked reduction of tellurite was detected in crude cell extracts of either strain; however, cell extracts of both reduced tellurite at alkaline pH in the absence of any co-factors.

Topics: Drug Resistance, Microbial; Oxidation-Reduction; Plasmids; Tellurium

A new selective and differential agar medium, polymyxin-mannose-tellurite (PMT) agar was devised to differentiate easily colonies of Vibrio cholerae O1 from those of V. cholerae non-O1. The differentiation between colonies of the two vibrios is based on mannose-fermentation. Colonies of V. cholerae O1 on the agar are agglutinated with O1 antiserum of V. cholerae much more easily than those on thiosulfate-citrate-bile salts-sucrose (TCBS) agar.

Topics: Agar; Culture Media; Mannose; Polymyxins; Sensitivity and Specificity; Species Specificity; Tellurium; Vibrio cholerae

Cell-free extracts of Thermus thermophilus HB8 catalyze the in vitro, NADH-dependent reduction of potassium tellurite (K2TeO3). Three different protein fractions with tellurite-reducing activities were identified. Two exhibited high molecular weight and were composed of at least two different polypeptides. The protein in the third fraction was purified to homogeneity and had a single polypeptide chain of 53 to 54 kilodaltons, with an isoelectric point of 8.1. Each enzyme was thermostable, the temperature optimum was 75 degrees C, and 30 mM NaCl, 1.5 M urea, or 0.004% sodium dodecyl sulfate caused 50% inhibition of the enzymes. However, 2% Triton X-100 did not have an inhibitory effect. The enzymes were also able to catalyze the reduction of sodium selenite and sodium sulfite in vitro. NADH was replaceable by NADPH. Divalent cations, such as Ca2+ and Ba2+, had no effect on the activity, while similar concentrations of Zn2+, Ni2+, and Cu2+ abolished the activity. This reductase activity could enable these bacteria both to reduce K2TeO3 and to increase their tolerance toward this salt.

Topics: Chromatography, DEAE-Cellulose; Chromatography, Gel; Densitometry; Electrophoresis, Polyacrylamide Gel; Hot Temperature; Molecular Weight; Oxidation-Reduction; Oxidoreductases; Sodium Chloride; Substrate Specificity; Tellurium; Thermus

The tellurite resistance (Ter) determinant of RP4 is not normally expressed unless variants are selected on medium containing tellurite. The determinant was mapped in the variant plasmid RP4Ter by Tn7 insertion mutagenesis. Based on a 56.4-kilobase (kb) replicon, it covered the region from 56 kb, across the EcoRI site at 0 kb, to 1.5 kb.

Topics: Culture Media; DNA Restriction Enzymes; DNA Transposable Elements; DNA, Bacterial; Drug Resistance, Microbial; Escherichia coli; Mutation; R Factors; Tellurium

A large (greater than 250 kb) conjugative plasmid, pMER610, specifying resistance to tellurium and mercury was isolated from an Alcaligenes strain and transferred by conjugation to Escherichia coli AB1157. The acquisition of pMER610 by AB1157 increased the resistance to both telurite and tellurate by 100-fold. Expression of tellurite resistance by pMER610 and the cloned Ter determinant was inducible by prior exposure to tellurite at levels sub-toxic to the sensitive AB1157. Physical analysis of the cloned Ter fragment located the resistance determinant to a 3.55 kb region. Insertion of Tn 1000 (gamma delta) into this region produced two classes of sensitive mutations, fully sensitive and intermediate or hyposensitive, which map in adjacent regions and form two complementation groups. Maxicell analysis identified four polypeptides (15.5, 22, 23 and 41 kDa) expressed by the Ter clone. The 23 kDa polypeptide may not be required for resistance since tellurium-sensitive gamma delta insertion mutations were not detected in the 23 kDa coding region.

Topics: Alcaligenes; Cloning, Molecular; Drug Resistance, Microbial; Escherichia coli; Gene Expression Regulation; Genes, Bacterial; Genetic Complementation Test; Plasmids; Tellurium

Tellurite (TeO3(2-)) is highly toxic toward Escherichia coli (MIC, approximately 1 microgram ml-1). Mutants (Tel) that were resistant to low levels of TeO3(2-) (MIC, approximately 10 micrograms ml-1) and collaterally resistant to arsenate were isolated. These Tel mutants were unable to grow on media containing low levels of Pi, which supported growth of the parent strain. When grown at much higher Pi levels they exhibited depressed levels of the outer membrane phoE protein and the periplasmic phoS protein, as well as several other proteins indicative of Pi starvation. Tel mutants were markedly defective in 32Pi transport, and TeO3(2-) was shown to be a potent competitive inhibitor of 32Pi transport in the parent strain. The Tel phenotype could be complemented by an F' plasmid harboring the phoR, phoB, and phoA loci, and curing of the F' plasmid completely restored TeO3(2-) resistance. Of a variety of well-characterized Pi transport mutants, only phoB mutants were equally resistant to TeO3(2-), and susceptibility could also be restored in strains carrying an F' plasmid for the phoB region and lost once more after F' curing. The tel and phoB loci were equally cotransducible with lac. Tel mutants still synthesized alkaline phosphatase, the phoA gene product, after Pi starvation, suggesting that the phoB locus per se was not involved because phoB is a positive regulatory gene for phoA expression. The results indicate that TeO3(2-) is transported into E. coli by a phosphate transport system and that resistance to TeO3(2-) specifically selects for as yet uncharacterized mutants in the phoB-phoA region of the chromosome.

Topics: Alkaline Phosphatase; Bacteriophage lambda; Drug Resistance, Microbial; Escherichia coli; Mutation; Phosphates; Plasmids; Tellurium

The susceptibility of 326 clinical isolates of Pseudomonas aeruginosa to four metals was determined by agar dilution tests. Metal resistance was shown by 36% of the total isolates. The frequencies of resistance to individual ions were: mercuric, 31%; tellurite, 12%; arsenate, 10%; and chromate, 3%. The most frequent pattern was that of resistance to mercuric ions alone followed by mercury resistance associated with either tellurite, arsenate, or both. Resistance to more than one metal was found in 44% of metal-resistant isolates. The resistance to antibiotics was more frequent among metal-resistant isolates that in metal-sensitive isolates.

Topics: Arsenates; Chromates; Drug Resistance, Microbial; Humans; Mercuric Chloride; Metals; Potassium Compounds; Pseudomonas aeruginosa; Tellurium

Topics: Animals; Chick Embryo; Culture Techniques; Mitosis; Nerve Fibers; Nerve Tissue; Selenious Acid; Selenium; Telencephalon; Tellurium; Trigeminal Ganglion

Topics: Corynebacterium diphtheriae; Culture Media; Humans; Peptides; Tellurium

Six IncP plasmids were tested for their ability to generate tellurite-resistant variants by plating bacterial strains harbouring them on medium containing potassium tellurite. Four plasmids, three of subgroup IncP alpha and one not allocated, formed variants that could transfer tellurite-resistance at the same frequency as plasmid-determined drug resistance. This property was not shared by two examples of subgroup IncP beta.

Topics: Drug Resistance, Microbial; Escherichia coli; Plasmids; Tellurium

A total of 78 strains, representing 21 Vibrio species, were examined by using taurocholate-tellurite-gelatin agar (TTGA) medium and modified TTGA medium containing 4-methylumbelliferyl-beta-D-galactoside (150 micrograms/ml). Modified TTGA medium allowed for simple and direct detection of beta-D-galactosidase (beta-gal) activity. This feature, in conjunction with other differential characteristics of TTGA medium, gave improved differentiation of the vibrios tested. The modified TTGA medium allowed for easy differentiation of Vibrio cholerae (beta-gal+) from Vibrio parahaemolyticus (beta-gal-). The 4-methylumbelliferyl-beta-D-galactoside substrate is inexpensive and very stable. Incorporation into the agar did not affect the performance of TTGA as a differential medium. The assay for beta-gal activity with this substrate was specific and sensitive.

Topics: Agar; beta-Galactosidase; Galactosides; Gelatin; Humans; Hymecromone; Species Specificity; Taurocholic Acid; Tellurium; Vibrio

Klebsiella pneumoniae and Escherichia coli respond inversely toward P1 bacteriophage or TeO3(-2). Klebsiella pneumoniae is resistant to both antagonists and E. coli is sensitive. However, P1 cmts lysogens (P1 cmts resistant) of K. pneumoniae became sensitive to tellurite and when cured from P1 cmts regained resistance. Escherichia coli spontaneous mutants selected for resistance to either P1 or TeO3(-2) were collaterally resistant to the other. As well, TeO3(-3) enhanced the adsorption of P1 vir to both E. coli and K. pneumoniae. Several outer membrane proteins were enhanced in the K. pneumoniae lysogens and were reduced in E. coli lysogens; one of which was the same molecular weight (77 000) in both bacteria. When partially purified it enhanced the plaque efficiency of P1 vir. Lipopolysaccharide (LPS) from E. coli C600 inactivated P1 vir, but neither the P1 lysogens nor LPS derived from the lysogens inactivated P1 vir. Escherichia coli P1 lysogens produced only heptose-deficient LPS. It is suggested that both LPS and outer membrane protein(s) comprise the P1 receptor. TeO3(-2) may interact with one or both components.

Topics: Adsorption; Bacterial Outer Membrane Proteins; Bacteriophages; Escherichia coli; Klebsiella pneumoniae; Lipopolysaccharides; Lysogeny; Molecular Weight; Mutation; Tellurium

Potassium tellurite (K2TeO3) was found to be a potent antisickling agent that inhibited red cell sickling at concentrations less than 10 mumol/L. The inhibitory effect depended on the incubation time, with the effect increasing with longer incubation periods. Because tellurite causes swelling of red cells, and because the antisickling effect of tellurite correlated with the degree of red cell swelling, the antisickling effect of tellurite is assumed to be due to the decreased mean cell hemoglobin concentration. Swelling of red cells by tellurite was accelerated by the addition of reduced glutathione. Tellurite appears to be a new type of antisickling agent that interacts with the red cell membrane.

Topics: Antisickling Agents; Azepines; Drug Synergism; Erythrocyte Indices; Erythrocyte Membrane; Glutathione; Humans; Selenious Acid; Selenium; Tellurium

Selenium is known to form complexes with heavy metals in the blood and thus increase the retention time of the metals in several organs, especially in the reticulo-endothelial system. Selenium may similarly cause retention of mercury in the lung after metallic mercury (Hg0) inhalation. This study, comparing the effects of tellurium with those of selenium (both in group '6b' of the periodical system), showed that Te(IV) was as effective as Se(IV) and Se(VI) (all given in a dose of 10 mumol/kg body wt.) in retaining inhaled 203Hg0 (1.5 mumol/kg body wt.) in the lung (presumably 203Hg2+ after oxidation). Te(VI) had to be given in a dose of 100 mumol/kg body wt to produce the same effect. As in the lung, also in other organs tellurium caused a dose-dependent increase in mercury retention. At a dose level of 10 mumol Te(IV) per kg body wt. the mercury retention ratios (treated/control) were 140 for the lung and 8.6 for the whole body. The corresponding figures for Te(VI) (10, 30 and 100 mumol/kg body wt.) were 10, 73 and 120 and 3.7, 3.9 and 4.3, respectively. Retention of i.v. injected 203HgCl2 was increased by pre-administration of tellurium, again in a dose-dependent manner and Te(IV) being 3-10 times more effective than Te(VI). The kidney and the spleen were the dominant organs, as is the case after Se pretreatment. Anions of other elements, arsenite, arsenate, chromate, molybdate and wolframate (30 mumol/kg body wt.), did not affect the retention of 203Hg in lung or any other organ, or in the whole body after inhalation of 203Hg0. It is suggested that Te(IV) may easily be reduced to Te2- (in analogy with selenium) which may complex with Hg2+. The liability for Te(VI) to be reduced to Te2- appears to be approx. 10 times lower.

Topics: Administration, Intranasal; Animals; Drug Interactions; Kidney; Kinetics; Lung; Male; Mercury; Mice; Mice, Inbred C57BL; Selenium; Spleen; Tellurium; Tissue Distribution

The assimilation of selenite by Escherichia coli involves a transport process specific for this anion. Cystine, a repressor of sulfate and selenite uptake, when added to the growth medium, had no effect on selenite uptake; nor did sulfite inhibit assimilation of selenite. Cells grown aerobically in a basic salts medium transported selenite at an initial rate of 0.14 mumol . g-1 min-1 and a Vmax of 393.0 mumol. g-1 . min-1. In contrast, cells grown in a medium that contained the trace elements necessary for synthesis of the selenoenzyme formate dehydrogenase took up selenite at a significantly faster rate (initial rate = 0.27 mumol . g-1 . min-1, Vmax = 658.2 mumol . g-1 . min-1). Km values for the transport process in the two media, however, were found to be similar. The results suggest the existence of a metabolic pathway, specific for selenite, responsible for the incorporation of selenium into formate dehydrogenase.U

Topics: Biological Transport; Cystine; Escherichia coli; Kinetics; Selenious Acid; Selenium; Sulfates; Sulfites; Tellurium; Thiosulfates

Topics: Animals; Erythrocytes; Glucose; Glutathione; Hemolysis; In Vitro Techniques; Selenious Acid; Selenium; Sheep; Tellurium; Time Factors

Topics: Amobarbital; Animals; Anthraquinones; Anti-Bacterial Agents; Energy Metabolism; In Vitro Techniques; Mitochondria; Oxygen Consumption; Pyridines; Rotenone; Steroids; Tellurium

Observations were made on the value of certain selective media for isolation and identification of staphylococci from milk obtained from individual quarters and farm bulk tanks Aerobic fermentation of mannitol salt was unreliable for identification of coagulase positive strains. Coagulase positive strains tended to clump when grown in tryptose serum broth. Tellurite glycine agar plates were not entirely reliable for the selection of coagulase positive strains. Fibrinogen-tellurite-glycine plates were very useful for the isolation of staphylococci from milk in the presence of other microorganisms and for the simultaneous identification of coagulase positive strains. Plate coagulase tests utilizing fibrinogen tellurite glycine agar corresponded almost perfectly with conventional tube tests. Fibrinolytic strains were not uncommon and were found also among beta hemolysin producing coagulase positive strains.

Topics: Agar; Animals; Coagulants; Coagulase; Cultural Characteristics; Culture Media; Fermentation; Fibrinogen; Fibrinolysin; Food Contamination; Glycine; Hydrolases; Mannitol; Metabolism; Milk; Research; Staphylococcus; Tellurium

Five selective media for the detection and enumeration of coagulase-positive staphylococci were evaluated for their efficiency in the recovery of 17 strains of coagulase-positive staphylococci from foods. They were Staphylococcus Medium 110 (SM-110), tellurite-glycine-agar (TGA), egg-tellurite-glycine-pyruvate-agar (ETGPA), tellurite-egg-agar (TEA), and tellurite-polymyxin-egg yolk-agar (TPEY). Statistical analysis by the rank correlation method of the efficiency with which these media recovered staphylococci from pure 24-hr Brain Heart Infusion cultures revealed the following efficiencies in descending order: (i) TPEY, (ii) ETGPA, (iii) TGA, (iv) TEA, (v) SM-110. Growth of 17 strains of coagulase-negative cocci on these media showed the following approximate descending order of inhibition to these organisms: (i) ETGPA, (ii) TEA, (iii) SM-110, (iv) TGA, (v) TPEY. The appearance of colonies of the various coagulase-negative strains on each medium was studied for the degree to which they could be confused with colonies of coagulase-positive strains. Nineteen food contaminants, including Proteus vulgaris, Bacillus sp., Escherichia coli, Erwinia sp., fecal streptococci, and others, were also studied for similarities in appearance to staphylococci and for ability to grow on the selective media. The influence of five sterile food homogenates (frozen chicken and tuna pies, custard, smoked ham, and raw whole egg) on recovery of 1,500 enterotoxigenic staphylococci (three strains) per milliliter was determined by statistical analysis. Three main effects (culture, media, and food) and three interactions (media with food, food with cultures, and media with culture) were found to be significant. Recovery on TPEY was influenced less by food than the other selective media and showed optimal recovery ability from sterile custard, eggs, and ham. TGA recovered well from sterile chicken pie and custard, SM-110 from sterile custard, and TEA from sterile ham. None of the media was outstanding in recovering staphylococci from tuna pie. The ability of the five selective media to recover 1,500 enterotoxigenic staphylococci (three strains) per ml from three sterile foods in the presence of 10 strains of contaminating bacteria added at the 0, 10(5), and 10(6) levels per milliliter was also studied and analyzed statistically. Only three factors were significant under these conditions-cultures, foods, and the interaction of media with the level of added contamination. Efficiency of

Topics: Agar; Coagulase; Culture Media; Egg Yolk; Eggs; Food Contamination; Glycine; Hydrolases; Meat; Metabolism; Polymyxins; Pyruvates; Research; Staphylococcus; Tellurium

Topics: Amino Acids; Cyanides; Enzyme Inhibitors; Flavin-Adenine Dinucleotide; Glutamates; Glycine; Hydrogen-Ion Concentration; Leucine; Lysine; Methionine; NAD; Nitrogen; Ornithine; Oxidation-Reduction; Oxidoreductases; Pharmacology; Proteus; Proteus vulgaris; Research; Tellurium

In bacteria the exact location of a respiratory enzyme system comparable to that of the mitochondria of other cells has remained uncertain. On the one hand, the existence of particulate "bacterial mitochondria" has been advocated (Mudd); on the other hand, important enzymes of the respiratory chain were recovered in the cytoplasmic membranes associated with some granular material (Weibull). In order to gain insight into this question, sites of reducing activity were localized in thin sections of bacteria using the reduction of potassium tellurite as an indicator. When this salt was added to the culture medium of Bacillus subtilis, it turned out that in this Gram-positive organism the reduced product is strictly bound at two sites, and that the plasma membrane does not materially gain in electron opacity through deposition of the reduced product. The reduction product is found on or in the membranes of particular organelles, which may possibly be regarded as the mitochondrial equivalents in Gram-positive bacteria, and which are sometimes seen connected to the plasma membrane. The second location is in thin rod-like elements at the cell periphery, possibly the sites from which the flagella emerge.

Topics: Bacillus subtilis; Cell Biology; Cell Membrane; Cytoplasm; Cytoplasmic Granules; Electron Transport; Electrons; Enzymes; Histocytochemistry; Membranes; Microscopy; Microscopy, Electron; Mitochondria; Oxidation-Reduction; Research; Tellurium

In order to obtain information on the exact location of the respiratory enzyme chain in Gram-negative bacteria, an electron microscopic study was made of the sites of reducing activity of cells that had, in the living state, incorporated tellurite. In the test object Proteus vulgaris, the reduced tellurite was found to be deposited in bodies contiguous with the plasma membrane but different in structure from those described in the Gram-positive Bacillus subtilis (2). In fact, the bodies proved to consist of a conglomerate of elements which contained the strongly electron-scattering reduced tellurite and a delicately granular "matrix." A limiting membrane was not observed around these complexes. In serial sections details of the complexes are illustrated. Reduced tellurite was not deposited in the plasma membrane to any important degree. Since no other sites of deposition of the reduced product were revealed, it is assumed that the complexes represent the mitochondrial equivalents in the investigated organism. In addition, the bodies might function as the basal granules of the flagella.

Topics: Cell Biology; Cell Membrane; Cytoplasm; Cytoplasmic Granules; Electron Transport; Electrons; Enzymes; Flagella; Histocytochemistry; Microscopy; Microscopy, Electron; Mitochondria; Oxidation-Reduction; Proteus; Proteus vulgaris; Research; Tellurium

Topics: Bacillus; Carrier State; Corynebacterium diphtheriae; Diphtheria; Heterozygote; Tellurium; Tonsillectomy

Topics: Agar; Bile Acids and Salts; Cholera; Clinical Laboratory Techniques; Gelatin; Humans; Laboratories; Taurocholic Acid; Tellurium

Topics: Corynebacterium diphtheriae; Cystine; Diphtheria; Humans; Tellurium

Topics: Escherichia coli; Methionine; Selenious Acid; Selenium; Tellurium

Topics: Cell Death; Fluconazole; Mycobacteriophages; Mycobacterium bovis; Tellurium

Topics: Agar; Animals; Coagulase; Culture Media; Glycine; Milk; Research; Staphylococcus; Tellurium

Topics: Bacteriological Techniques; Biological Phenomena; Culture Media; Pasteurella; Physiological Phenomena; Potassium; Research; Tellurium; Yersinia pseudotuberculosis; Yersinia pseudotuberculosis Infections

Tucker, Fayne L. (University of Southern California, Los Angeles), John F. Walper, Milo Don Appleman, and Jerry Donohue. Complete reduction of tellurite to pure tellurium metal by microorganisms. J. Bacteriol. 83:1313-1314. 1962-The black precipitate produced in the presence of potassium tellurite by growing cells of Streptococcus faecalis N83 and Corynebacterium diphtheriae was shown, by X-ray diffraction analysis, to consist of metallic tellurium. The metal was not complexed, to any significant degree, with any organic material.

Topics: California; Corynebacterium diphtheriae; Enterococcus faecalis; Metals; Tellurium; X-Ray Diffraction

Woolfolk, C. A. (University of Washington, Seattle) and H. R. Whiteley. Reduction of inorganic compounds with molecular hydrogen by Micrococcus lactilyticus. I. Stoichiometry with compounds of arsenic, selenium, tellurium, transition and other elements. J. Bacteriol. 84:647-658. 1962.-Extracts of Micrococcus lactilyticus (Veillonella alcalescens) oxidize molecular hydrogen at the expense of certain compounds of arsenic, bismuth, selenium, tellurium, lead, thallium, vanadium, manganese, iron, copper, molybdenum, tungsten, osmium, ruthenium, gold, silver, and uranium, as well as molecular oxygen. Chemical and manometric data indicate that the following reductions are essentially quantitative: arsenate to arsenite, pentavalent and trivalent bismuth to the free element, selenite via elemental selenium to selenide, tellurate and tellurite to tellurium, lead dioxide and manganese dioxide to the divalent state, ferric to ferrous iron, osmium tetroxide to osmate ion, osmium dioxide and trivalent osmium to the metal, uranyl uranium to the tetravalent state, vanadate to the level of vanadyl, and polymolybdate ions to molybdenum blues with an average valence for molybdenum of +5. The results of a study of certain other hydrogenase-containing bacteria with respect to their ability to carry out some of the same reactions are also presented.

Topics: Arsenic; Arsenites; Hydrogen; Iron; Manganese; Metals; Micrococcus; Molybdenum; Oxidation-Reduction; Oxidoreductases; Selenium; Selenium Compounds; Silver; Tellurium; Veillonella

Topics: Amides; Culture Media; Sulfhydryl Compounds; Tellurium; Thioacetamide

A correlation was found to exist between tellurite and tetracycline resistance in the enterococci.

Topics: Anti-Bacterial Agents; Enterococcus; Humans; Streptococcus; Tellurium; Tetracycline; Tetracycline Resistance

Topics: Culture Media; Gelatin; Taurocholic Acid; Tellurium; Vibrio; Vibrio cholerae

Topics: Proteus; Proteus vulgaris; Tellurium

Topics: Indicators and Reagents; Staphylococcus; Tellurium

Topics: Corynebacterium diphtheriae; Cystine; Humans; Tellurium

Topics: Sodium Chloride; Sodium Chloride, Dietary; Sodium Dodecyl Sulfate; Tellurium; Vibrio cholerae

Topics: Agar; Fabaceae; Glycine; Micrococcus; Staphylococcus; Staphylococcus aureus; Tellurium

Topics: Blood; Candida; Candida albicans; Cell Differentiation; Communications Media; Culture Media; Humans; Tellurium; Tunica Media; Veins

Topics: Ascomycota; Candida; Candida albicans; Cell Division; Fungi; Humans; Morphogenesis; Selenious Acid; Selenium; Tellurium

Topics: Agar; Coagulase; Culture Media; Glycine; Micrococcus; Staphylococcus; Staphylococcus aureus; Tellurium

Topics: Body Temperature; Copper; Humans; Tellurium; Thermometers

Topics: Bacteria; Hot Temperature; Potassium; Tellurium

Topics: Gold; Oxidation-Reduction; Oxidoreductases; Tellurium

Topics: Corynebacterium diphtheriae; Humans; Tellurium; Tunica Media; Veins

Topics: Diphtheria; Humans; Poisoning; Tellurium

Topics: Bacillus; Mycobacterium tuberculosis; Streptomycin; Tellurium

Topics: Animals; Cattle; Culture Media; Mycobacterium bovis; Mycobacterium tuberculosis; Potassium; Tellurium; Tuberculosis

Topics: Diphtheria; Tellurium

Topics: Bacillus; Corynebacterium diphtheriae; Culture Media; Cystine; Diphtheria; Tellurium

Topics: Bacillus; Gram-Positive Bacteria; Lacticaseibacillus casei; Mycobacterium tuberculosis; Streptomycin; Tellurium

Topics: Bacteria; Culture Media; Diphtheria; Glucose; Humans; Microscopy; Tellurium

Topics: Agar; Diphtheria; Humans; Raffinose; Replantation; Tellurium

Topics: Corynebacterium; Corynebacterium diphtheriae; Diphtheria; Humans; Tellurium

Topics: Humans; Tellurium

Topics: Caseins; Corynebacterium diphtheriae; Diphtheria; Humans; Protein Hydrolysates; Tellurium

Topics: Bacteria; Corynebacterium diphtheriae; Culture Media; Diphtheria; Humans; Tellurium