2-chlorobiphenyl and 4-chlorobiphenyl

A bacterium classified as Achromobacter xylosoxidans strain IR08 by phenotypic typing coupled with 16S rRNA gene analysis was isolated from a soil contaminated with electrical transformer fluid for over sixty years using Aroclor 1221 as an enrichment substrate. The substrate utilization profiles revealed that IR08 could grow on all three monochlorobiphenyls (CBs), 2,4'- and 4,4'-dichlorobiphenyl as well as 2-chlorobenzoate (2-CBA), 3-CBA, 4-CBA, and 2,3-dichlorobenzoate. Unusually, growth was poorly sustained on biphenyl and benzoate. In growth experiments, IR08 degraded all CBs (0.27 mmol/L) in less than 96 h with concomitant stoichiometric release of inorganic chloride and growth yields were 2-3 times higher than those observed on biphenyl. In contrast to most of the chlorobiphenyl-degrading strains described in the literature, which are reported to form CBA, no metabolite was identified in the culture broth by HPLC analysis. When co-incubated with respective CBs and biphenyl, strain IR08 preferentially utilized the chlorinated analogues in less than 96 h while it took another 264 h before 90% of the initially supplied biphenyl could be degraded. The promotion of co-metabolic transformation of halogenated substrates by the inclusion of their non-halogenated derivatives may not therefore, result in universal benefits.

Topics: Bacteria; Benzoates; Biodegradation, Environmental; Biphenyl Compounds; Electricity; Incubators; Isomerism; Minerals; Soil; Soil Pollutants

Nine polychlorinated biphenyl (PCB) congeners (2-chlorobiphenyl, 3-chlorobiphenyl, 4-chlorobiphenyl, 2,3,4-trichlorobiphenyl, 2,2',5,5'-tetrachlorobiphenyl, 2,3',4,4',5-pentachlorobiphenyl, 3,3',4,4',5-pentachlorobiphenyl, 2,2',4,4',5,5'-hexachlorobiphenyl, and decachlorobiphenyl) were dechlorinated by the sodium dispersion method (SD) at low temperature (60 degrees C). The dechlorination of 4-chlorobiphenyl was the fastest among the three monochlorobiphenyls. As for the other six congeners, we investigated the major dechlorination pathways. Although reaction selectivity was not very sensitive to the position of the chlorine substituent, the chlorines at the para position were slightly easier to dechlorinate than those at the ortho or meta positions. The decomposition rate increased with the total numbers of chlorine substituents. A chlorine situated between two other chlorines showed a high reactivity. When the numbers of chlorines on each of the phenyl rings were different, the reactions occurred on the more substituted ring. In the degradation of 4-chlorobiphenyl at elevated temperature (160 degrees C), we investigated the structures of the polymerized products and whether all the organic chlorinated compounds degraded finally or not. As for the dimers, p-quarterphenyl (QP) and m,p-QP were detected but not o-QP, m-QP, o,p-QP, o,m-QP, or the mono- to tetra-chlorinated QPs. Compounds with a molecular weight of 534.4183 or 758.6713 were detected. They were considered to have C40H54 or C56H86 as their molecular formula. The compounds were most probably the polymerized products resulting from coupling of hexadecane or two hexadecanes and two phenylcyclohexadienes. It was thought the dechlorination and the polymerization were the main reactions. All of many detected compounds were hydrocarbons without chlorines, and no peaks originating from organic chlorinated compounds were observed by mass spectroscopic (MS) methods.

Topics: Biphenyl Compounds; Mass Spectrometry; Molecular Structure; Polychlorinated Biphenyls; Sodium; Temperature

We studied the aerobic degradation of eight PCB congeners which comprise from 70 to 85% of the anaerobic dechlorination products from Aroclor 1242, including 2-, 4-, 2,4-, 2,6-, 2,2'-, 2,4'-, 2,2', 4-, and 2,4,4'-chlorobiphenyl (CB), and the biodegradation of their mixtures designed to simulate anaerobic dechlorination profiles M and C. Strains Comamonas testosteroni VP44 and Rhodococcus erythreus NY05 preferentially oxidized a para-substituted ring, while Rhodococcus sp. RHA1, similar to well known strain Burkholderia sp. LB400, preferably attacked an ortho-chlorinated ring. Strains with ortho-directed attack extensively degraded 2,4'- and 2,4,4'-CB into 4-chlorobenzoate, while bacteria with para-directed attack transformed these congeners mostly into potentially problematic meta-cleavage products. The strains that preferentially oxidized an ortho-substituted ring readily degraded seven of the eight congeners supplied individually; only 2,6-CB was poorly degraded. Degradation of 2,2'- and 2,4,4'-CB was reduced when present in mixtures M and C. Higher efficiencies of degradation of the individual congeners and defined PCB mixtures M and C and greater production of chlorobenzoates were observed with bacteria that preferentially attack an ortho-substituted ring. PCB congeners 2,4'-, 2,2',4-, and 2,4,4'-CB can be used to easily identify bacteria with ortho-directed attack which are advantageous for use in the aerobic stage of the two-phase (anaerobic/aerobic) PCB bioremediation scheme.

Topics: Anaerobiosis; Aroclors; Bacteria, Aerobic; Biodegradation, Environmental; Biphenyl Compounds; Burkholderia; Chlorine; Comamonas; Environmental Pollutants; Fatty Acids, Unsaturated; Oxidation-Reduction; Polychlorinated Biphenyls; Rhodococcus

Chlorobenzoates (CBA) arise as intermediates during the degradation of polychlorinated biphenyls (PCBs) and some chlorinated herbicides. Since PCBs were produced as complex mixtures, a range of mono-, di-, and possibly trichloro-substituted benzoates would be formed. Chlorobenzoate degradation has been proposed to be one of the rate-limiting steps in the overall PCB-degradation process. Three hybrid bacteria constructed to have the ability to completely mineralise 2-, 3-, or 4-monochlorobiphenyl respectively, have been studied to establish the range of mono- and diCBAs that can be utilised. The three strains were able to mineralise one or more of the following CBAs: 2-, 3-, and 4-monochlorobenzoate and 3,5-dichlorobenzoate. No utilisation of 2,3-, 2,5-, 2,6-, or 3,4-diCBA was observed, and only a low concentration (0.11 mM) of 2,4-diCBA was mineralised. When the strain with the widest substrate range (Burkholderia cepacia JHR22) was simultaneously supplied with two CBAs, one that it could utilise plus one that it was unable to utilise, inhibitory effects were observed. The utilisation of 2-CBA (2.5 mM) by this strain was inhibited by 2,3-CBA (200 microM) and 3,4-CBA (50 microM). Although 2,5-cba and 2,6-cba were not utilised as carbon sources by strain jhr22, they did not inhibit 2-cba utilisation at the concentrations studied, whereas 2,4-cba was co-metabolised with 2-cba. The utilisation of 2-, 3-, and 4-chlorobiphenyl by strain JHR22 was also inhibited by the presence of 2,3- or 3,4-diCBA. We conclude that the effect of the formation of toxic intermediates is an important consideration when designing remediation strategies.

Topics: Biodegradation, Environmental; Biphenyl Compounds; Burkholderia cepacia; Chlorobenzoates; Culture Media; Pseudomonas; Pseudomonas putida

Cocultures consisting of strains converting chlorobiphenyls to the respective benzoates or catechols and of chlorobenzoate degraders were investigated for the mineralization of chlorobiphenyls. Stable mixed cultures were obtained with 4-chlorobiphenyl, while those with 2-chloro- or 3-chlorobiphenyl were found to be unstable and released only low yields of chloride. When both sets of enzyme sequences were combined in one organism, Pseudomonas cepacia strain JH230, by conjugative transfer of genes of the biphenyl degradation sequence, the total degradation of 2-chloro-, 3-chloro-, 4-chloro-, 2,4-dichloro-, and 3,5-dichlorobiphenyl was achieved.

Topics: Aroclors; Benzoates; Biodegradation, Environmental; Biphenyl Compounds; Catechols; Hybridization, Genetic; Kinetics; Pseudomonas

Pseudomonas putida strain SU83, harbors the pBS311 plasmid coding for the degradation of biphenyl, 2- and 4-chlorbiphenyl, meta- and paratoluylate. The insertional mutants of the plasmid obtained by the transposon Tn5 insertion were isolated. One of the mutants was used for cloning of the biphenyl degradation genes. The plasmid pBS311:: Tn5 DNA was inserted into the BamHI site of the plasmid pBR322 and cloned. 11 recombinants of 354 tested were treated with 0.1% solution of 2,3-dioxybiphenyl. One of them has acquired the yellow colour testifying to conversion of 2,3-dioxyphenyl to "2-hydroxy-6-keto-6-phenylhexa-2,4-diene acid. The recombinant plasmid pBS312 from this clone is 10.5 kb in size, the size of the insert being 6.2 kb. Escherichia coli SU185 cells harbouring pBS312 are able to support metacleavage of 2,3-dioxybiphenyl, 3-methylcatechol and catechol, but not of 4-methylcatechol. The results suggest the cloned fragment to contain a gene for 2,3-dioxybiphenyl-1,2-dioxygenase, the third enzyme for biphenyl catabolism.

Topics: Biodegradation, Environmental; Biphenyl Compounds; Genes, Bacterial; Plasmids; Pseudomonas; Toluidines

In vitro rat hepatic microsomal metabolism of the monochlorobiphenyls (MCBs) 2-, 3- and 4-chlorobiphenyl, has been investigated as a model for the metabolism of polychlorinated biphenyl pollutants. MCB metabolism was catalyzed by cytochrome P-450, as indicated by a dependence on NADPH and O(2), inhibition by 2-diethylaminoethyl-2,2-diphenylpropylacetate (SKF 525-A), metyrapone and CO, and the formation of type I difference spectra, on the addition of MCBs to microsomes. All MCBs yielded a 4'-monohydroxy MCB as the major metabolite, as determined by mass and nuclear magnetic resonance spectroscopy, dechlorination to 4-hydroxybiphenyl, and high-pressure liquid chromatography retention times. Minor monohydroxy and dihydroxy metabolites were also produced from the MCBs. The regioselectivity of control cytochrome P-450 for metabolism of MCBs at the 4' position was not altered by preinduction of cytochrome P-450 with 2,4,2',4'-tetrachlorobiphenyl (TCB) or cytochrome P-448 with 3,4,3', 4'-TCB. 2-Chlorobiphenyl was metabolized only by control and induced cytochrome P-450; 3- and 4-chlorobiphenyl were metabolized by control and by induced cytochrome P-450 and P-448. Thus, the regioselectivity of metabolism of MCBs is independent of the chlorine position or the form of the induced cytochrome involved, but the extent of metabolism of polychlorinated biphenyls (PCBs) is determined by induction of the hepatic cytochromes P-450.

Topics: Animals; Biphenyl Compounds; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Kinetics; Liver; Male; Mass Spectrometry; Microsomes, Liver; Rats; Rats, Wistar