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At least 19 recordsLinked to original sources

PubMed1992

DNA relatedness among some thermophilic members of the genus Methanobacterium: emendation of the species Methanobacterium thermoautotrophicum and rejection of Methanobacterium thermoformicicum as a synonym of Methanobacterium thermoautotrophicum.

DNA reassociation was used to determine levels of relatedness among four thermophilic Methanobacterium strains that are able to use formate and between these organisms and two representative strains of Methanobacterium thermoautotrophicum, strain delta HT (= DSM 1053T = ATCC 29096T) (T = type strain) and strain Marburg (= DSM 2133). Three homology groups were delineated, and these groups coincided with the clusters identified by antigenic fingerprinting. The first group, which had levels of cross hybridization that ranged from 73 to 99%, included M. thermoautotrophicum delta HT, Methanobacterium thermoformicicum Z-245, Methanobacterium sp. strain THF, and Methanobacterium sp. strain FTF. The second and third groups were each represented by only one strain, Methanobacterium sp. strain CB-12 and M. thermoautotrophicum Marburg, respectively (cross-hybridization levels, 13 to 30 and 29 to 33%, respectively). Our results indicate that the name M. thermoformicicum should be rejected as it is a synonym of M. thermoautotrophicum. The taxonomic positions of strains Marburg and CB-12 need further investigation.

Antigens, Bacterial↗

PubMed1998

The formylmethanofuran dehydrogenase isoenzymes in Methanobacterium wolfei and Methanobacterium thermoautotrophicum: induction of the molybdenum isoenzyme by molybdate and constitutive synthesis of the tungsten isoenzyme.

Formylmethanofuran dehydrogenase catalyzes the first step in methane formation from CO2 in methanogenic archaea. Methanobacterium wolfei and Methanobacterium thermoautotrophicum have been shown to contain two isoenzymes, a tungsten-containing isoenzyme (Fwd) and a molybdenum-containing isoenzyme (Fmd). We report here that in both thermophilic organisms the encoding genes are organized in a highly conserved fwdHFGDACB tungsten operon and in an fmdECB molybdenum operon. In both organisms, the tungsten isoenzyme was found to be constitutively transcribed, whereas the transcription of the molybdenum operon was induced by molybdate. Induction by molybdate was not significantly affected by tungstate.

Aldehyde Oxidoreductases↗

PubMed1989

Nucleotide sequence of the glyceraldehyde-3-phosphate dehydrogenase gene from the mesophilic methanogenic archaebacteria Methanobacterium bryantii and Methanobacterium formicicum. Comparison with the respective gene structure of the closely related extreme thermophile Methanothermus fervidus.

The genes for glyceraldehyde-3-phosphate dehydrogenase (gap genes) from the mesophilic methanogenic archaebacteria Methanobacterium formicicum and Methanobacterium bryantii were cloned and sequenced. The deduced amino acid sequences show 95% identity to each other and about 70% identity to the glyceraldehyde-3-phosphate dehydrogenase from the thermophilic methanogenic archaebacterium Methanothermus fervidus. Although the sequence similarity between the archaebacterial glyceraldehyde-3-phosphate dehydrogenase and the homologous enzyme of eubacteria and eukaryotes is low, an equivalent secondary-structural arrangement can be deduced from the profiles of the physical parameters hydropathy, chain flexibility and amphipathy. In order to find possible thermophile-specific structural features of the enzyme from M. fervidus, a comparative primary-sequence analysis was performed. Amino acid exchanges leading, to a stabilization of the main-chain conformation, could be found throughout the sequence of the thermophile enzyme. Striking features of the thermophile sequence are the preference for isoleucine, especially in beta-sheets, and a low arginine/lysine ratio of 0.54.

Amino Acids↗

PubMed1992

Enrichment of Thermophilic Propionate-Oxidizing Bacteria in Syntrophy with Methanobacterium thermoautotrophicum or Methanobacterium thermoformicicum.

Thermophilic propionate-oxidizing, proton-reducing bacteria were enriched from the granular methanogenic sludge of a bench-scale upflow anaerobic sludge bed reactor operated at 55 degrees C with a mixture of volatile fatty acids as feed. Thermophilic hydrogenotrophic methanogens had a high decay rate. Therefore, stable, thermophilic propionate-oxidizing cultures could not be obtained by using the usual enrichment procedures. Stable and reproducible cultivation was possible by enrichment in hydrogen-pregrown cultures of Methanobacterium thermoautotrophicum DeltaH which were embedded in precipitates of FeS, achieved by addition of FeCl(2) to the media. The propionate-oxidizing bacteria formed spores which resisted pasteurization for 30 min at 90 degrees C or 10 min at 100 degrees C. Highly purified cultures were obtained with either M. thermoautotrophicum DeltaH or Methanobacterium thermoformicicum Z245 as the syntrophic partner organism. The optimum temperature for the two cultures was 55 degrees C. Maximum specific growth rates of cultures with M. thermoautotrophicum DeltaH were somewhat lower than those of cultures with M. thermoformicicum Z245 (0.15 and 0.19 day, respectively). Growth rates were even higher (0.32 day) when aceticlastic methanogens were present as well. M. thermoautotrophicum DeltaH is an obligately hydrogen-utilizing methanogen, showing that interspecies hydrogen transfer is the mechanism by which reducing equivalents are channelled from the acetogens to this methanogen. Boundaries of hydrogen partial pressures at which propionate oxidation occurred were between 6 and 34 Pa. Formate had a strong inhibitory effect on propionate oxidation in cultures with M. thermoautotrophicum. Inhibition by formate was neutralized by addition of the formate-utilizing methanogen or by addition of fumarate. Results indicate that formate inhibited succinate oxidation to fumarate, an intermediate step in the biochemical pathway of propionate oxidation.

Journal Article↗

PubMed1987

Purification and use of Methanobacterium wolfei pseudomurein endopeptidase for lysis of Methanobacterium thermoautotrophicum.

The pseudomurein-degrading enzyme from autolysates of Methanobacterium wolfei was purified approximately 500-fold to electrophoretic homogeneity by ion-exchange chromatography under anaerobic conditions. Analysis of the soluble cell wall fragments produced by the pure enzyme from a cell wall preparation of M. thermoautotrophicum indicated that it is a peptidase hydrolyzing the epsilon-Ala-Lys bond of pseudomurein. A partially purified preparation of pseudomurein endopeptidase was free of nuclease activity and thus proved useful for the preparation in high yields of undegraded chromosomal and plasmid DNA from M. thermoautotrophicum. The partially purified enzyme was also used for the preparation of protoplasts, which were stabilized by 0.8 M sucrose. Under growth conditions the protoplasts produced methane and increased up to 100-fold in size, but failed to regenerate a cell wall.

Endopeptidases↗

PubMed1994

Aspartate aminotransferase from a thermophilic formate-utilizing methanogen, Methanobacterium thermoformicicum strain SF-4: relation to serine and phosphoserine aminotransferases, but not to the aspartate aminotransferase family.

The primary structure of the aspartate aminotransferase (AspAT) of an archaebacterium, Methanobacterium thermoformicicum strain SF-4, has been determined by cloning and sequencing of the gene for the enzyme. The gene had a consensus promoter and a ribosome binding sequence of methanogens in the 5' untranslated region, followed by an open reading frame starting with ATG and terminating with TGA. The deduced amino acid sequence was identical with the partial amino acid sequences of the enzyme including the N-terminal sequence, and the deduced molecular weight of 41,684 was virtually identical to that reported earlier for this enzyme [Tanaka, T., Yamamoto, S., Taniguchi, M., Hayashi, H., Kuramitsu, S., Kagamiyama, H., & Oi, S. (1992) J. Biochem. 112, 811-815]. The gene was expressed in Escherichia coli by inserting it into an expression vector just downstream of the lacZ promoter, and this verified that the cloned gene really encodes the Methanobacterium AspAT. The primary structure of the Methanobacterium AspAT showed extremely low homology, 5%, with AspATs of eubacteria, eukaryotes, and a thermoacidophilic arachaebacterium, Sulfolobus solfataricus. On the other hand, the Methanobacterium AspAT showed remarkable amino acid sequence homology, 31.5%, with rat serine:pyruvate aminotransferase and, 13.5%, with E. coli phosphoserine aminotransferase. Thus, the Methanobacterium AspAT apparently belongs to subgroup IV of the aminotransferases [Mehta, P.K., Hale, T.I., & Christen, P. (1993) Eur. J. Biochem. 214, 549-561], but not to subgroup I, in which all the AspATs known so far are included.

Amino Acid Sequence↗

PubMed2004

Methanobacterium aarhusense sp. nov., a novel methanogen isolated from a marine sediment (Aarhus Bay, Denmark).

Strain H2-LR(T), a 5-18 micro m long and 0.7 micro m wide filamentous, mesophilic, moderately halophilic, non-motile hydrogenotrophic methanogen, was isolated from marine sediment of Aarhus Bay, Denmark, 1.7 m below the sediment surface. On the basis of 16S rRNA gene comparison with sequences of known methanogens, strain H2-LR(T) could be affiliated to the genus Methanobacterium. The strain forms a distinct line of descent within this genus, with Methanobacterium oryzae (95.9 % sequence identity) and Methanobacterium bryantii (95.7 % sequence identity) as its closest relatives. The 16S rRNA-based affiliation was supported by comparison of the mcrA gene, which encodes the alpha-subunit of methyl-coenzyme M reductase. Strain H2-LR(T) grew only on H(2)/CO(2). The DNA G+C content is 34.9 mol%. Optimum growth temperature was 45 degrees C. The strain grew equally well at pH 7.5 and 8. No growth or methane production was observed below pH 5 or above pH 9. Strain H2-LR(T) grew well within an NaCl concentration range of 100 and 900 mM. No growth or methane production was observed at 1 M NaCl. At 50 mM NaCl, growth and methane production were reduced. Based on 16S rRNA gene sequence analysis, the isolate is proposed to represent a novel taxon within the genus Methanobacterium, namely Methanobacterium aarhusense sp. nov. The type strain is H2-LR(T) (=DSM 15219(T)=ATCC BAA-828(T)).

Base Composition↗

PubMed1982

Kinetics of Formate Metabolism in Methanobacterium formicicum and Methanospirillum hungatei.

The kinetics of formate metabolism in Methanobacterium formicicum and Methanospirillum hungatei were studied with log-phase formate-grown cultures. The progress of formate degradation was followed by the formyltetrahydrofolate synthetase assay for formate and fitted to the integrated form of the Michaelis-Menten equation. The K(m) and V(max) values for Methanobacterium formicicum were 0.58 mM formate and 0.037 mol of formate h g (dry weight), respectively. The lowest concentration of formate metabolized by Methanobacterium formicicum was 26 muM. The K(m) and V(max) values for Methanospirillum hungatei were 0.22 mM and 0.044 mol of formate h g (dry weight), respectively. The lowest concentration of formate metabolized by Methanospirillum hungatei was 15 muM. The apparent K(m) for formate by formate dehydrogenase in cell-free extracts of Methanospirillum hungatei was 0.11 mM. The K(m) for H(2) uptake by cultures of Methanobacterium formicicum was 6 muM dissolved H(2). Formate and H(2) were equivalent electron donors for methanogenesis when both substrates were above saturation; however, H(2) uptake was severely depressed when formate was above saturation and the dissolved H(2) was below 6 muM. Formate-grown cultures of Methanobacterium formicicum that were substrate limited for 57 h showed an immediate increase in growth and methanogenesis when formate was added to above saturation.

Journal Article↗

PubMed1984

Comparison of assimilatory organic nitrogen, sulfur, and carbon sources for growth of methanobacterium species.

Experiments document the ability of two species of autotrophic methanogens to assimilate and utilize organic substrates as the nutrient sulfur or nitrogen source and as a carbon source during growth on H(2)-CO(2). Methanobacterium thermoautotrophicum strain DeltaH and the mesophilic species Methanobacterium sp. strain Ivanov grew with glutamine as the nitrogen source or cysteine as the sulfur source. M. thermoautotrophicum also utilized urea as the nitrogen source and as a carbon precursor for methane and cell synthesis. Methanobacterium sp. strain Ivanov grew with methionine as the sulfur source. The growth rate of two different Methanobacterium species was lower on an organic N or S source than on ammonium or sulfide. S and C tracer studies demonstrated that amino acid or urea assimilation correlated with time and amount of growth. The rate of [S]cysteine incorporation was similar in strain DeltaH (34 nmol h mg of cells) and strain Ivanov (23 nmol h mg of cells). However, the rate of [C]acetate incorporation was dramatically different (17 versus 208 nmol h mg of cells in strains DeltaH and Ivanov, respectively). [C]acetate accounted for 1.3 and 21.2% of the total cell carbon synthesized by strains DeltaH and Ivanov, respectively. Amino acids and urea were mainly assimilated into the cell protein fraction, but accounted for less than 2.0% of the total cell carbon synthesized. The data suggest that a biochemical-genetic approach to understanding cell carbon synthesis in methanogens is feasible; mutants that are auxotrophic for either acetate, glutamine, cysteine, or methionine are suggested as future targets for genetic studies.

Journal Article↗

PubMed1988

Enzyme-Linked Immunosorbent Assays for the Specific and Sensitive Quantification of Methanosarcina mazei and Methanobacterium bryantii.

Three microtitration plate enzyme-linked immunosorbent assays (ELISAs) have been developed: a competitive ELISA and a two-site (or indirect sandwich) ELISA for Methanosarcina mazei S6 and a two-site ELISA for Methanobacterium bryantii FR-2. The assays were sensitive, with limits of cell protein detection of 3 ng ml, 5 ng ml, and 50 ng ml, respectively, and showed good precision. The M. mazei assays used monoclonal antibodies and were entirely species specific, showing no cross-reaction with methanogens of other genera or with other species of the same genus. The Methanobacterium bryantii assay, which used two polyclonal antisera, showed only a slight cross-reaction with one other Methanobacterium species but no cross-reaction with methanogens of other genera. The use of the ELISAs for quantitative analysis of mixed cultures and of sewage sludge samples was investigated. Sludge diluted at 1:10 or more caused no significant interference in any of the three ELISAs. Various cultures of bacteria, methanogens, and nonmethanogens at a protein concentration of 50 mug ml showed no significant interference in the M. mazei competitive assay and the Methanobacterium bryantii two-site assay, although they did cause falsely low results in the M. mazei two-site assay.

Journal Article↗

PubMed1988

Cloning and physical mapping of RNA polymerase genes from Methanobacterium thermoautotrophicum and comparison of homologies and gene orders with those of RNA polymerase genes from other methanogenic archaebacteria.

The structural genes encoding the four largest subunits of RNA polymerase, A, B', B", and C, were physically mapped in Methanobacterium thermoautotrophicum Winter. The genes formed a cluster in the order B", B', A, C and had a common orientation. DNA hybridization experiments yielded different degrees of homology between RNA polymerase gene sequences of different species of Methanobacterium and Methanococcus voltae. No homology was detectable between Methanobacterium thermoautotrophicum and Methanosarcina barkeri. From Southern hybridization experiments in which probes of the four genes from Methanobacterium thermoautotrophicum Winter and restriction digests of the genomic DNAs of the different methanogens were used, a common gene order of the RNA polymerase genes could be deduced.

Archaea↗

PubMed1994

Na(+)-driven ATP synthesis in Methanobacterium thermoautotrophicum and its differentiation from H(+)-driven ATP synthesis by rhodamine 6G.

Rhodamine 6G (3 microM) effectively inhibited delta pH-driven ATP synthesis in Methanobacterium thermoautotrophicum while delta pNa-driven ATP synthesis was not affected by it. Rhodamine 6G inhibited Mg(2+)-stimulated ATPase activity of membrane vesicles prepared from these cells but the ATPase catalytic sector detached from the membrane was insensitive to this inhibitor. Methanogenesis-driven ATP synthesis at pH 6.8 of cells grown in the presence of 50 mM NaCl was inhibited by rhodamine 6G both in the presence of 5 mM and 50 mM NaCl. On the other hand, the methanogenesis-driven ATP synthesis at pH 8.0 of cells grown in the presence of 50 mM NaCl was slightly inhibited by rhodamine 6G in the presence of 5 mM NaCl and was not inhibited at all in the presence of 50 mM NaCl. The growth experiments have shown that cells of Methanobacterium thermoautotrophicum can grow under alkaline conditions even in the presence of rhodamine 6G and of high NaCl concentration when the growth media were inoculated with the cells which had been grown in the presence of 50 mM NaCl. These results indicate that sodium-motive force-driven ATP synthase in Methanobacterium thermoautotrophicum operates effectively in alkaline conditions and it might be the sole ATP synthesizing system when the proton-motive force-supported ATP synthesis is inhibited by rhodamine 6G.

Adenosine Triphosphatases↗

PubMed1994

Na(+)-driven ATP synthesis in Methanobacterium thermoautotrophicum and its differentiation from H(+)-driven ATP synthesis by rhodamine 6G.

Rhodamine 6G (3 microM) effectively inhibited delta pH-driven ATP synthesis in Methanobacterium thermoautotrophicum while delta pNA-driven ATP synthesis was not affected by it. Rhodamine 6G inhibited Mg(2+)-stimulated ATPase activity of membrane vesicles prepared from these cells but the ATPase catalytic sector detached from the membrane was insensitive to this inhibitor. Methanogenesis-driven ATP synthesis at pH 6.8 of the cells grown in the presence of 50 mM NaCl was inhibited by rhodamine 6G both in the presence of 5 mM and 50 mM NaCl. On the other hand, the methanogenesis-driven ATP synthesis at pH 8.0 of cells grown in the presence of 50 mM NaCl was slightly inhibited by rhodamine 6G in the presence of 5 mM NaCl and was not inhibited at all in the presence of 50 mM NaCl. The growth experiments have shown that cells of Methanobacterium thermoautotrophicum can grow under alkaline conditions even in the presence of rhodamine 6G and of high NaCl concentration when the growth media were inoculated with the cells which had been grown in the presence of 50 mM NaCl. These results indicate that sodium-motive force-driven ATP synthase in Methanobacterium thermoautotrophicum operates effectively at alkaline conditions and it might be the sole ATP synthesizing system when the proton motive force-supported ATP synthesis is inhibited by rhodamine 6G.

Adenosine Triphosphatases↗

PubMed1995

The presence of H+ and Na(+)-translocating ATPases in Methanobacterium thermoautotrophicum and their possible function under alkaline conditions.

Two ATPases with different apparent molecular masses of approx. 500 kDa and 400 kDa were identified in the EDTA extract of the cell membranes of Methanobacterium thermoautotrophicum. Western blotting with polyclonal antiserum reactive with beta-subunit of mitochondrial ATPase from rat liver and yeast was used for further analysis of these ATPases. A strong crossreactivity with a single protein band with an apparent molecular weight of about 53 kDa (similar to beta-subunit of F-type ATPase from other sources) was found in protein extracts of whole cells of Methanobacterium thermoautotrophicum strains delta H and Marburg, as well as of Methanospirillum hungatei. This indicates the presence of F-type ATPase in methanogens. ATP synthesis driven by membrane potential which was generated by artificially-imposed delta pH in the presence of protonophorous uncoupler and sodium ions was stimulated by bafilomycin A1, an inhibitor of V- and A-type ATPases, as well as by harmaline, an inhibitor of Na+/H+ antiporter. These results indicate that cells of Methanobacterium thermoautotrophicum strain delta H contain the F-type ATP synthase which is Na(+)-translocating in addition to V- or A-type ATP synthase which is H(+)-translocating.

Adenosine Triphosphate↗

PubMed2000

Phylogenetic analysis of 18 thermophilic Methanobacterium isolates supports the proposals to create a new genus, Methanothermobacter gen. nov., and to reclassify several isolates in three species, Methanothermobacter thermautotrophicus comb. nov., Methanothermobacter wolfeii comb. nov., and Methanothermobacter marburgensis sp. nov.

Using a combination of 16S rRNA analysis and antigenic fingerprinting consisting of new and published data, the phylogenetic position of 18 thermophilic isolates currently classified as Methanobacterium species was reinvestigated. The results were verified by independent methods, including, where applicable, plasmid and phage typing. Comparative analysis of 16S rRNA data for 30 strains belonging to the order Methanobacteriales strongly suggested that mesophilic and thermophilic Methanobacterium isolates are distantly related and should be assigned to separate genera. For the thermophilic strains the genus Methanothermobacter was initially proposed by Boone, Whitman and Rouvière. Furthermore, the results support a reclassification of 15 isolates in three species within the proposed genus: (i) Methanothermobacter thermautotrophicus comb. nov., containing eight isolates, six of which are able to utilize formate (type strain deltaHT); (ii) Methanothermobacter wolfeii comb. nov., containing four formate-utilizing isolates (type strain DSM 2970T); (iii) Methanothermobacter marburgensis sp. nov., containing three obligately autotrophic isolates (type strain MarburgT). Of the nine isolates formerly referred to as Methanobacterium thermoformicicum, six were reclassified as Methanothermobacter thermautotrophicus and three as Methanothermobacter wolfeii.

Antigens, Archaeal↗

PubMed1993

Cloning, sequencing and immunological characterization of the corrinoid-containing subunit of the N5-methyltetrahydromethanopterin: coenzyme-M methyltransferase from Methanobacterium thermoautotrophicum.

A 3.5-kb EcoRI fragment of the Methanobacterium thermoautotrophicum chromosome contains five open reading frames, mtrA to mtrE. The deduced N-terminal amino acid sequence of mtrA is identical with 26 N-terminal amino acids of a corrinoid-containing membrane protein from Methanobacterium. Computer-aided analyses of mtrA predicts 237 amino acids with a molecular mass of 25,603 Da for its gene product. A hydropathy plot of this amino acid sequence indicates one hydrophobic helical conformation near the N-terminus of the peptide which represents a tentative membrane-spanning region. The main part of the protein, however, shows hydrophilic domains, suggesting a location outside the cytoplasmic membrane. These domains are probably accessible by monospecific polyclonal antibodies raised previously against the corrinoid-containing membrane protein. The immunogold-labeling technique revealed that the corrinoid-dependent membrane protein was detectable at the cytoplasmic face of the membranes and of vesicle preparations. No significant identity of the deduced amino acid sequence was found with sequences of several corrinoid-containing enzymes. In contrast to the hydrophilic gene product of mtrA, four other gene products from the gene cluster encode extremely hydrophobic proteins. The N-terminal sequences of mtrC and mtrD are identical with two peptides of the N5-methyltetrahydromethanopterin:coenzyme-M methyltransferase complex from Methanobacterium, indicating that the mtr genes encode this membrane protein.

Amino Acid Sequence↗

PubMed1995

Evidence for a defective prophage on the chromosome of Methanobacterium wolfei.

Evidence shows the presence on the chromosome of Methanobacterium wolfei of a defective prophage which, by DNA-DNA hybridization, is closely related to the virulent archaeophage psi M1 of Methanobacterium thermoautotrophicum Marburg. Partial sequencing of a M. wolfei 16S rRNA gene and phylogenetic analysis indicated that this organism is more closely related to other representatives of the genus Methanobacterium than to M. thermoautotrophicum Marburg. The chromosomal region of M. wolfei encoding the putative prophage was found to be deleted for two non-contiguous segments of the phage psi M1 genome and thus encompassed only 80 to 90% of the psi M1 DNA. The prophage region was mapped to a 30 kb restriction fragment on the physical map of the M. wolfei chromosome. A randomly chosen DNA fragment was cloned from phage psi M1 DNA, as was its homologous counterpart from the chromosome of M. wolfei. The 126-bp region present in both clones exhibited 100% sequence identity.

Bacteriophages↗

PubMed1972

Methanobacterium thermoautotrophicus sp. n., an anaerobic, autotrophic, extreme thermophile.

The isolation of a new methanogenic bacterium, Methanobacterium thermoautotrophicus sp. n., is described. Successful isolation required a medium containing inorganic salts, an atmosphere consisting of an 80:20 mixture of hydrogen-carbon dioxide, and incubation temperatures of 65 to 70 C. Isolates of M. thermoautotrophicus were gram-positive, nonmotile, irregularly curved rods which frequently formed long filaments. The organism was found to be an autotroph and a strict anaerobe, and to have a pH optimum of 7.2 to 7.6. The optimal temperature for growth was 65 to 70 C, the maximum being 75 C and the minimum about 40 C. The generation time at the optimum was about 5 hr. The deoxyribonucleic acid of M. thermoautotrophicus had a guanine plus cytosine (GC) content of 52 moles per cent, whereas Methanobacterium sp. strain M.O.H. had a GC content of 38%. When heated, intact ribosomes of Methanobacterium sp. strain M.O.H. were stable up to 55 C and had a T(m) of 73 C. In contrast, ribosomes of M. thermoautotrophicus were stable up to 75 C and had a T(m) of 82 C. Upon complete thermal denaturation, ribosomes of strain M.O.H. underwent a 59% hyperchromic shift, whereas those of the thermophile showed only a 20% increase in hyperchromicity. Methane formation in cell-free extracts of M. thermoautotrophicus was temperature-dependent and required hydrogen and carbon dioxide; methyl cobalamin served as a methyl donor, and addition of coenzyme M stimulated methanogenesis.

Anaerobiosis↗