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PubMedDate not supplied

[Effect of inorganic electron acceptors on the bacterial formation of methane from cellulose].

The effect of nitrate, nitrogen oxide, sulphate, oxidized iron and manganese on the methane fermentation of cellulose was studied with the enrichment bacterial culture. The action of these oxidants on the enrichment culture growing on cellulose was compared to that on a pure methanosarcina culture in order to find out which stage of methane formation from cellulose was inhibited. Nitrate at the concentration of 2 g NaNO3 and more per litre of the medium inhibited the whole process of fermentation; at the concentration less than 2 g/l the production of methane was inhibited, and cellulose decomposition was accompanied with denitrification. Sulphate at the concentration of 2 g MgSO4 per litre had no effect on the formation of methane but the process was inhibited by the product of its reduction, i. e. sulphiade. Cellulose decomposition could be accompanied with sulphate reduction if sulphide produced in the process of the reduction were removed from the medium. In this case as well as in the presence of ferric iron, the production of methane was inhibited due to competition for the reducing agent.

Cellulose↗

PubMedDate not supplied

[Mechanism of methane oxidation by intact cells of obligate methylotrophs].

Ethane and propane were found to be competitive inhibitors of methane oxidation. Obligate methylotrophs can oxidize ethane only in the presence of methane, i.e. co-oxidation of ethane takes place. Studies on the kinetics of simultaneous oxidation of ethane and methane have shown that their oxidation is catalysed by one and the same enzyme system, within one and the same enzyme active site; therefore, the absolute substrate specificity is absent. The reactions of methane and ethane oxidation are coupled since ethane can be oxidized only after the reduced coenzyme had been provided by the reaction of methane oxidation.

Ethane↗

PubMed1978

Tetrakis(acetoxymercuri)methane: a polymetallic reagent for labeling sulfur in nucleic acids.

Tetrakis(acetoxymercuri)methane binds to the sulfur atom of 6-thioguanosine and also to the 4-thiouridine residue of Escherichia coli tRNAVal. A 4:1 complex is formed between 6-thioguanosine and tetrakis(acetyoxymercuri)methane. Addition of 3 equivalents of N,N-dimethyl-2-amino-ethanethiol hydrochloride to tetrakis(acetoxymercuri)methane effectively blocks three of the four mercury atoms, rendering the compound monofunctional toward 6-thioguanosine. Under appropriate conditions, tetrakis(acetyoxymercuri)methane, in the presence or absence of N,N-dimethyl-2-amino-ethanethiol hydrochloride, binds to the 4-thiouridine residue in E. coli tRNAVal without forming intermolecular crosslinks. These results suggest that tetrakis(acetoxymercuri)methane will be a useful polymetallic reagent for labeling sulfur sites in polynucleotides. It may also prove to be a valuable reagent for preparing heavy metal derivatives of proteins for x-ray crystallographic study.

Chemical Phenomena↗

PubMed2025

Diversity and distribution of the lanthanome in aerobic methane-oxidising bacteria.

BACKGROUND: Lanthanides (Ln) play important and often regulatory roles in the metabolism of methylotrophs, including methanotrophs, particularly through their involvement in methanol oxidation. However, the diversity, distribution, and ecological relevance of Ln-associated proteins (the lanthanome) in aerobic methane-oxidising bacteria (MOB) remain underexplored. This study investigates the lanthanome using genome, plasmid, and proteome data, alongside metatranscriptome data from methane-rich lake sediments. RESULTS: We surveyed 179 genomes spanning Proteobacterial, Verrucomicrobial, and Actinobacterial MOBs to examine the distribution of Ln-dependent methanol dehydrogenases (MDHs) and Ln transport proteins. Distinct lineage-specific patterns were observed: XoxF5 was the most widespread MDH variant in Proteobacteria, while XoxF2 was restricted to Verrucomicrobia. Transporter systems also showed distinct patterns, with LanM restricted to Alphaproteobacteria, LanPepSY and LanA confined to Gammaproteobacteria, and LutH-like receptors broadly distributed across all lineages. Homologues of these genes were also detected on plasmids, indicating potential for horizontal gene transfer. In Lake Washington sediment metatranscriptomes, lanthanome transcripts were detected, with Proteobacteria as dominant contributors. Notably, a large fraction of xoxF transcripts were affiliated with non-MOB Methylophilaceae, consistent with known cooperative interactions with MOB. Using Methylosinus trichosporium OB3b as a model, we assessed methane oxidation and proteomic responses to soluble CeCl3 and a mixed-lanthanide ore. Lag phases were prolonged in the presence of lanthanides, particularly with ore, but methane oxidation rates converged across treatments after acclimation. Proteomic analysis revealed extensive condition-specific responses, with 724 proteins differentially expressed in Ore treatment compared to 60 under CeCl3. XoxF3 and XoxF5 were upregulated while MxaF and its accessory proteins were downregulated, consistent with the "lanthanide switch". Notably, LanM was not expressed despite being encoded, whereas LutH-like receptor was downregulated under both treatments, likely reflecting regulatory control to prevent excess metal uptake. Additional upregulation of a TonB-dependent receptor and ABC transporter suggests a potential lanthanophore-mediated uptake strategy. CONCLUSION: This study highlights the diversity and ecological activity of Ln-binding and transport systems in MOBs, their plasmid localisation and potential mobility, and their distinct regulation under different Ln sources. The strong proteomic response to complex ore underscores the physiological flexibility of MOBs in coping with natural lanthanide forms. These findings provide a framework for ecological studies and candidate targets for biotechnological applications in methane bioconversion and sustainable lanthanide recovery from complex materials.

Horizontal gene transfer↗

PubMed2026

Electron shuttles facilitate methane-dependent arsenate reduction in paddy soils.

Methane-dependent arsenate reduction (M-AsR) occurs widely in paddy soils and can substantially enhance arsenic mobilization, posing potential ecological risks. However, the role of electron shuttles in this process remains poorly understood. In this study, we investigated the influence of anthraquinone-2,6-disulfonate (AQDS) on M-AsR in paddy soils. Fourteen-day incubation showed that 1 mmol/L AQDS facilitated 50.88 % of arsenate reduction and 31.31 % of methane oxidation. Quantitative polymerase chain reaction analysis revealed that AQDS significantly increased the abundance of functional genes associated with arsenate reduction (arrA, arsC) and anaerobic methane oxidation (mcrA) (P < 0.05). Microbial community analysis revealed that AQDS addition enriched Cloacibacterium, Sphingorhabdus, and Methylocystis, while decreasing the relative abundance of Methylobacter and Methylomonas. These findings indicate that electron shuttles facilitate M-AsR by modulating functional microbial populations, providing valuable insights into arsenic biogeochemistry and the coupled cycling of methane and arsenic in paddy soils.

Methane↗

PubMed1975

Some cultural and physiological aspects of methane-utilizing bacteria.

A number of different methane-utilizing bacteria are described and compared with isolates of other investigators. The strains can be divided into three groups based on pigmentation, cell morphology and internal membrane structures. The oxidation of hydrocarbons, alcohols, aldehydes, fatty acids, methyl ethers and sugar phosphates by these bacteria was studied. There was much similarity between strains within the same group. Differences between groups as regards oxidative properties could be detected, but these were mainly quantitative and could not be used as taxonomical criteria. In addition, the inhibition of methane oxidation by metabolites and enzyme inhibitors was investigated. Formaldehyde proved to be the most active of the organic compounds tested. Iodoacetic acid inhibited both methane and methanol oxidation at concentrations of 0.03 M or above. Of the inorganic compounds, KCN completely suppressed methane oxidation at 5 times 10(-4) M and to more than 90% at 5 times 10(-5) M.

Alcohols↗

PubMed1978

Coenzyme M and methylcobalamin in methane biosynthesis: results of model studies.

Coenzyme M (2-mercaptoethanesulfonate, HS-CH2CH2SO3-) reacts with methylcobalamin nonenzymatically in the pH-range between 6 and 14 to yield the S-methyl derivative (CH3-S-CH2CH2SO3-). In addition, and also at lower pH, methane is produced by reductive cleavage of the Co-C bond. With methylcobaloximes as the methyl group donors, methane production predominates, with insignificant S-methylation. The initial rates of methane production from methylcobaloximes with coenzyme M as the reductant correlate with the rates of methane production from these substrates with active cell extracts of Methanobacterium M.o.H.

Bacteria↗

PubMed1978

Conversion of choline methyl groups through trimethylamine into methane in the rumen.

1. Choline methyl groups were rapidly metabolized to trimethylamine by rumen micro-organisms. 2. Trimethylamine was further metabolized to methane, but this system was more easily saturated by an excess of substrate, so that trimethylamine accumulated in the rumen of the fed animal. 3. Although trimethylamine was the only intermediate isolated in the conversion of the methyl groups of choline into methane, methylamine also served as a substrate for methane production. 4. The methyl group of methionine was also converted into methane by rumen fluid, but the methyl groups of carnitine were not.

Animals↗

PubMed1979

Utilization of trimethylamine and other N-methyl compounds for growth and methane formation by Methanosarcina barkeri.

A number of N-methyl compounds, including several methylamines, creatine, sarcosine, choline, and betaine, were readily fermented by enrichment cultures yielding methane as a major product. Methylamine, dimethylamine, trimethylamine, and ethyldimethylamine were fermented by pure cultures of Methanosarcina barkeri; except for ethyldimethylamine, these amines are considered important substrates of this methanogenic microorganism. Creatine, sarcosine, choline, and betaine were fermented to methane only by mixed cultures. During growth of M. barkeri on methyl-, dimethyl-, or trimethylamine, methanol was not excreted into the medium. The fermentation of trimethylamine gave rise to an intermediary accumulation of methyl- and dimethylamine in the medium. An accumulation of methylamine during the fermentation of dimethylamine was not observed. Methane and ammonia were produced from the three methylamines by M. barkeri in amounts expected on the basis of the appropriate fermentation equations. The growth yield was 5.8 mg of cells (dry weight) per mmol of methane and was not dependent on the kind of methyl compound used as substrate.

Euryarchaeota↗

PubMed1977

Effect of sodium chloride on growth and methane production of methanogens.

The effect of up to 263.7 mM sodium chloride on the growth and methane production by pure cultures of Methanospirillum hungatii GP1, Methanobacterium MOH, Methanobacterium thermoautotrophicum, and an unidentified methanogen was studied. Growth and methane production by M. hungatii GP1 were not affected up to 97.3 mM NaCl but there was some inhibition of growth at higher concentrations. Growth of Methanobacterium MOH was independent of sodium chloride concentration within the range investigated. For the unidentified methanogen, optimum growth and methane production occurred at 15.2 mM NaCl, while growth of M. thermoautotrophicum was not affected by sodium chloride concentrations up to 15.2 mM. Concentrations over 15.2 mM were inhibitory to these two organisms. The 15 mM sodium chloride concentration used by some investigators appears suitable for isolation and cultivation of methanogens since all the organisms tested in this study exhibited good growth and methane production at this salt concentration.

Anaerobiosis↗

PubMedDate not supplied

[Microbiological oxidation of methane in the stratal waters of the Lower Volgian].

Methanotrophic bacteria are rather widely distributed in bed waters of oil and gas deposits in the Nizhneye Povolzhye. Their number reaches 250 cells per 1 ml of water. However, bacterial methane oxidation is active only in waters whose redox potential exceeds +250 mV. In a number of cases, microbial methane oxidation is limited by the absence of oxygen from bed waters. If air is added to samples of such water, methane dissolved in the water is oxidized by microorganisms at a high rate (2--451 X 10(-4) cm3 of methane per litre of water per day).

Geological Phenomena↗

PubMedDate not supplied

[The multiphase character of methane fermentation of cellulose].

An enrichment culture producing methane from cellulose was studied. The culture is a system of changing microbial populations realizing various pathways of methane formation. This change of microbial associations is expressed in three phases of growth; each phase is characterized by its maximum of methane production. The first maximum is related to accumulation and utilization of propionic acid. The second maximum is due to methane formation from acetate by Methanosarcina. One of the possible pathways regulating the methanogenous ecosystem is the action of concentrations of the main metabolites--glucose and the products of its fermentation.

Bacteria↗

PubMed2026

Ruminosignatures associated with methane emissions and feed efficiency across geographies and cattle breeds.

The cattle rumen microbiota represents a complex and dynamic ecosystem whose organization and relationship to host phenotypes are important for food security and environmental sustainability. We analyzed rumen microbiota profiles from 2496 cattle representing five breeds and production systems across five countries, identifying microbial co-abundance groups termed Ruminosignatures. We detected 14 distinct Ruminosignatures, including 2 observed across all populations dominated by Prevotella and UBA2810. Additional Ruminosignatures showed breed- and diet-specific patterns and collectively explained 96%-99% of variance in rumen microbial composition. Integrative cross-country analysis confirmed 10 out of 14 Ruminosignatures identified in cohort-specific analyses. Several Ruminosignatures were associated with methane emissions and feed efficiency traits and were partially under host genetic control, with heritability estimates ranging from 0.09 to 0.58. Structural equation modeling revealed consistent negative genetic and phenotypic correlations between the UBA2810-dominated Ruminosignature (RS_UBA2) and methane emissions across cohorts (rg = -0.40 to -0.65), with structural coefficients concordant in sign across all populations, supporting the expected direction of phenotypic response to selection on RS_UBA2. Meta-analysis confirmed positive associations of RS_UBA2 with average daily gain and negative associations with methane-related traits and feed conversion ratio. Functional genome-based predictions suggested RS_UBA2 may reduce methanogenesis through alternative hydrogen utilization pathways competing with methanogenic archaea. Production system type influenced both Ruminosignature occurrence and relationships with host phenotypes, emphasizing the relevance of context-specific strategies for microbiome modulation. Our findings highlight the potential of the Ruminosignatures framework for microbiome-informed breeding programs aimed at improving feed efficiency while reducing the environmental impact of cattle production.

Animals↗

PubMed1977

The soluble methane mono-oxygenase of Methylococcus capsulatus (Bath). Its ability to oxygenate n-alkanes, n-alkenes, ethers, and alicyclic, aromatic and heterocyclic compounds.

1. Methane mono-oxygenase of Methylococcus capsulatus (Bath) catalyses the oxidation of various substituted methane derivatives including methanol. 2. It is a very non-specific oxygenase and, in some of its catalytic properties, apparently resembles the analogous enzyme from Methylomonas methanica but differs from those found in Methylosinus trichosporium and Methylomonas albus. 3. CO is oxidized to CO2. 4. C1-C8 n-alkanes are hydroxylated, yielding mixtures of the corresponding 1- and 2-alcohols; no 3- or 4-alcohols are formed. 5. Terminal alkenes yield the corresponding 1,2-epoxides. cis- or trans-but-2-ene are each oxidized to a mixture of 2,3-epoxybutane and but-2-en-1-ol with retention of the cis or trans configuration in both products; 2-butanone is also formed from cis-but-2-ene only. 6. Dimethyl ether is oxidized. Diethyl ether undergoes sub-terminal oxidation, yielding ethanol and ethanal in equimolar amounts. 7. Methane mono-oxygenase also hydroxylates cyclic alkanes and aromatic compounds. However, styrene yields only styrene epoxide and pyridine yields only pyridine N-oxide. 8. Of those compounds tested, only NADPH can replace NADH as electron donor.

Alkanes↗

PubMed1975

Oxidation of carbon monoxide and methane by Pseudomonas methanica.

The oxidation of carbon monoxide and methane by suspensions and ultrasonic extracts of Pseudomonas methanica was studied. A continuous assay for the oxidation of CO to CO2 was devised, using O2 and CO2 electrodes in combination. Stoicheiometries of CO-dependent CO2 formation, O2 consumption and NADH oxidation, and the partial stoicheiometries of methane-dependent NADH oxidation, suggest the involvement of a mono-oxygenase in these oxidations. Evidence is presented suggesting methane and CO oxidation are catalysed by a single enzyme system, distinct, at least in part, from the NADH oxidase present in extracts. Ethanol was able to provide the reductant necessary for CO oxidation by cell suspensions, though the metabolism of ethanol by P. methanica was found unlikely to result in substrate-level formation of NADH; the means whereby alcohol oxidation could supply reductant for the mono-oxygenase are discussed.

Ammonium Chloride↗

PubMed1976

Factors affecting rate of methane formation from acetic acid by enriched methanogenic cultures.

A stable enrichment culture converting acetic acid to methane was successfully obtained from a pear waste digester, using a synthetic substrate solution with acetic acid as the main carbon source. This enrichment culture converted up to 10 mmol of acetic acid per litre per day at 35 degrees C and did not use hydrogen or formic acid in appreciable amounts as substrate for methane production instead of, or in addition to, acetic acid. The rate of conversion of acetic acid to methane was maximum at temperature of 40-45 degrees C, at a pH of 6.5 to 7.1, and was adversely affected by exposure to air, reducing agents, and high salt concentrations. The rate of conversion was independent of acetic acid concentration between 0.2 and 100 mM, but dropped markedly at concentrations below 0.2 mM.

Acetates↗

PubMed1976

[Isotopic effect in enzymatic oxidation of methane].

The isotopic effect during oxidation of methane and deuteromethane by a suspension of Methylomonas rubrum cells, for which methane is the only source of carbon, was observed. The rate of CH4 oxidation is 12.5 times higher than that of CH4 oxidation. It is demonstrated that CD4 is a competitive inhibitor of CH4 oxidation. The results obtained suggest that the disruption of the C-H bond is the limiting step of enzymatic oxidation of methane.

Deuterium↗

PubMedDate not supplied

[Radioisotope method of determining the intensity of bacterial methane formation].

The rate of methane formation by bacteria was determined by the isotope tracer technique using labeled carbon in the form of bicarbonate. The rate of methane production in the ooze deposits of the Kuznechikha lake was calculated by this technique to constitute 7.46 to 7.70 cm3 CH4 per 1 litre per day. The rate of the process was shown to depend on the number of methane-producing bacteria.

Bacteria↗