monensin and tetronasin

Topics: Anti-Bacterial Agents; Ethers; Furans; Genes, Bacterial; Monensin; Multienzyme Complexes; Open Reading Frames; Pyrans; Streptomyces

Concentrations of Na(+), K(+) and Ca(2+) in the growth medium were varied within limits normally found in vivo to determine how cation concentrations affect the sensitivity of ruminal bacteria to the ionophores, monensin (a Na(+)/H(+) and K(+)/H(+) exchanger) and tetronasin (Ca(2+)/H(+)). High [Na(+)] (172 mM cf. 137 mM in control medium) enhanced the efficacy of monensin towards Eubacterium ruminantium 2388, Streptococcus bovis C277, Lactobacillus casei LB17 and Prevotella albensis M384. High [K(+)] (35 mM cf. 19 mM) alone caused a decreased potency of both ionophores, except with L. casei. Added Ca(2+) (7.4 cf. 2.8 mM) increased the potency of tetronasin when [Na(+)] was low. High [Na(+)] alone also potentiated the efficacy of tetronasin. Monensin caused intracellular [Na(+)] and [K(+)] to be decreased in the most sensitive of these organisms, E. ruminantium, whereas only intracellular [Ca(2+)] fell with tetronasin. The changes were small; however, Δp fell by only 20 mV after 2 h when ionophores caused immediate cessation of growth. ATP concentrations fell by 77% and 75% with monensin and tetronasin, respectively. Thus, altering cation concentrations might be used to potentiate the efficacy of ionophores, by increasing the rate of energy expenditure to maintain ionic homoeostasis in sensitive bacteria.

Topics: Animals; Bacteria; Calcium; Furans; Ionophores; Monensin; Potassium; Rumen; Sheep; Sodium

We report the use of RuCl3 as an "alkali metal sponge". This is a general and highly efficient method for generating protonated parent ions for a variety of compounds that usually do not show this ion in electrospray mass spectrometry. This technique is demonstrated to be highly useful in "cleaning up" spectra from multiply metallated ions, thereby substantially improving the signal-to-noise ratio.

Topics: beta-Cyclodextrins; Cyclodextrins; Furans; Ions; Monensin; Protons; Ruthenium Compounds; Spectrometry, Mass, Electrospray Ionization; Valinomycin

Four ionophores differing in cation selectivity were compared for their effect on microbial fermentation and biohydrogenation by ruminal bacteria in continuous culture. Monensin and nigericin are monovalent antiporters with selective binding affinities for Na+ and K+, respectively. Tetronasin is a divalent antiporter that binds preferentially with Ca2+ or Mg2+. Valinomycin is a monovalent uniporter and does not exchange K+ for H+. Steady-state concentrations of 2 micrograms/ml of monensin, nigericin, tetronasin, or valinomycin were maintained by constant infusion into fermenters. Molar percentages of acetate were lower, and those of propionate were higher, in the presence of monensin, nigericin, and tetronasin; all three ionophores also decreased CH4 production. Concentrations of valinomycin as high as 8 micrograms/ml had no effect on volatile fatty acids or CH4 production. Monensin, nigericin, and tetronasin inhibited the rate of biohydrogenation of linoleic acid. Continuous infusion of C18:2n-6 at a steady-state concentration of 314 micrograms/ml into fermenters receiving monensin, nigericin, or tetronasin resulted in lower amounts of stearic acid and higher amounts of oleic acid. Ionophores increased total C18:2 conjugated acids mainly because of an increase in the cis-9, trans-11-C18:2 isomer. If reflected in milk fat, ionophore-induced changes in ruminal lipids could enhance the nutritional qualities of milk.

Topics: Animals; Cattle; Fatty Acids, Volatile; Female; Fermentation; Furans; Hydrogenation; Ionophores; Methane; Monensin; Nigericin; Oleic Acid; Rumen; Stearic Acids; Valinomycin

The Gram-negative rumen bacteria Fibrobacter succinogenes S85, Prevotella ruminicola M384 and Veillonella parvula L59 were grown in media containing successively increasing concentrations of the ionophores, monensin and tetronasin. All three species became more resistant to the ionophore with which they were grown. Increased resistance to one ionophore caused increased resistance to the other, and cross-resistance to another ionophore--lasalocid--and an antibiotic--avoparcin. Recovery of tetronasin-resistant bacteria from the rumen of monensin-fed sheep increased and vice versa, indicating that similar cross-resistance occurred in vivo.

Topics: Animals; Anti-Bacterial Agents; Bacteroides; Colony Count, Microbial; Drug Resistance, Microbial; Fermentation; Furans; Gram-Negative Anaerobic Bacteria; Ionophores; Monensin; Rumen; Sheep; Veillonella

The ionophore antibiotics monensin and tetronasin have been reported to inhibit anaerobic fungi in vitro, and are suitable for animal use. In this study, their effectiveness in removing the anaerobic fungus Neocallimastix sp. LM1 from the rumen was investigated in vitro. Both antibiotics were fungistatic: tetronasin at 0.5 microgram/ml and monensin at 1.0 microgram/ml; exposure for 24 h did not inhibit subsequent growth after removal of the ionophore. The ionophores were fungicidal at much higher concentrations, 1 microgram/ml for tetronasin and 16 micrograms/ml for monensin. It seems likely that the combination of relatively high inhibitory dose and the fungistatic nature of monensin would explain difficulties in using this compound to eliminate anaerobic fungi from the rumens of experimental animals.

Topics: Animals; Antifungal Agents; Fungi; Furans; Ionophores; Monensin; Rumen; Sheep

Bacteroides ruminicola M384 was grown in the presence of increasing concentrations of tetronasin, an ionophore that has been developed as a feed additive for ruminants. The resulting culture, B. ruminicola M384/TnR, was then maintained in medium containing 0.1 microgram tetronasin/ml. Growth of the parent strain was eliminated by the addition of 0.1 micrograms tetronasin/ml, but the growth rate of B. ruminicola M384/TnR, which grew more slowly than the parent strain, was unaffected by adding tetronasin. Bacteroides ruminicola M384/TnR retained its resistance to tetronasin even after repeated subculture in the absence of the ionophore, suggesting that a mutation had occurred. The absence of plasmids in individual colonies of B. ruminicola M384/TnR implied that the mutation was chromosomal. Bacteroides ruminicola M384/TnR was also more resistant to the ionophores monensin and lasalocid and, to a lesser degree, to the antibiotic avoparcin than B. ruminicola M384. Binding of [14C]tetronasin to B. ruminicola M384/TnR was lower than binding of the ionophore to the parent stain, and this difference was eliminated by washing cells with EDTA. The peptidolytic activity of B. ruminicola M384 towards triphenylalanine (Mr = 460) was unaffected in B. ruminicola M384/TnR, but the rate of breakdown tetraphenylalanine (Mr = 607) was decreased. This difference was also abolished by EDTA. It was concluded that growth of B. ruminicola in the presence of tetronasin resulted in a mutation affecting the permeability of the cell envelope, such that permeation of tetronasin and molecules of a similar size (Mr = 628) was decreased.

Topics: Animals; Anti-Bacterial Agents; Bacteroides; Cell Membrane Permeability; Chromosomes, Bacterial; Drug Resistance, Microbial; Furans; Glycopeptides; Ionophores; Lasalocid; Monensin; Mutation; Plasmids; Sheep

A continuous coculture of four ruminal bacteria, Megasphaera elsdenii, Selenomonas ruminantium, Streptococcus bovis, and Lactobacillus sp. strain LB17, was used to study the effects of the ionophores monensin and tetronasin on the changes in ruminal microbial ecology that occur during the onset of lactic acidosis. In control incubations, the system simulated the development of lactic acidosis in vivo, with an initial overgrowth of S. bovis when an excess of glucose was added to the fermentor. Lactobacillus sp. strain LB17 subsequently became dominant as pH fell and lactate concentration rose. Both ionophores were able to prevent the accumulation of lactic acid and maintain a healthy non-lactate-producing bacterial population when added at the same time as an excess of glucose. Tetronasin was more potent in this respect than monensin. When tetronasin was added to the culture 24 h after glucose, the proliferation of lactobacilli was reversed and a non-lactate-producing bacterial population developed, with an associated drop in lactate concentration in the fermentor. Rises in culture pH and volatile fatty acid concentrations accompanied these changes. Monensin was unable to suppress the growth of lactobacilli; therefore, in contrast to tetronasin, monensin added 24 h after the addition of glucose failed to reverse the acidosis. Numbers of lactobacilli and lactate concentrations remained high, whereas pH and volatile fatty acid concentrations were low.

Topics: Acidosis, Lactic; Animals; Cattle; Furans; Glucose; Hydrogen-Ion Concentration; In Vitro Techniques; Lactates; Lactic Acid; Monensin; Rumen; Sheep

The antimicrobial activity of the novel ionophore tetronasin (formerly ICI 139603) was compared with that of monensin for the growth of ruminal bacteria, protozoa, and an anaerobic fungus. The potency of tetronasin toward most bacteria and the fungus was an order of magnitude or more greater than that of monensin. Lactobacillus casei was 55 times more sensitive to tetronasin than to monensin, indicating a potential role for tetronasin in reversing lactic acidosis. Bacteria with a gram-positive ultrastructure were generally sensitive to the ionophores and unable to adapt to grow in their presence. The exception was the cellulolytic Ruminococcus flavefaciens, which adapted during successive cultivation on media with increasing ionophore concentrations to grow at 100-fold higher concentrations of tetronasin than were initially lethal to the organism. Gram-negative bacteria were more resistant and generally able to adapt to grow in the presence of both ionophores. An in vivo trial with cattle and in vitro growth experiments indicated that the effect of tetronasin on ciliate protozoa was minor. In vitro experiments measuring hydrogen production by Neocallimastix frontalis suggested that this fungus would be unable to survive in ruminants receiving tetronasin.

Topics: Animals; Bacteria; Cattle; Eukaryota; Fungi; Furans; Gram-Negative Bacteria; Gram-Positive Bacteria; Ionophores; Monensin; Rumen; Sheep