Methanosarcina barkeri

About: Methanosarcina barkeri is a research topic. Over the lifetime, 703 publications have been published within this topic receiving 32151 citations.

Conversion of Cellulose to Methane and Carbon Dioxide by Triculture of Acetivibrio cellulolyticus, Desulfovibrio sp., and Methanosarcina barkeri.

Abstract: The fermentation of cellulose by monocultures of Acetivibrio cellulolyticus and cocultures of A. cellulolyticus-Methanosarcina barkeri, A. cellulolyticus-Desulfovibrio sp., and A. cellulolyticus-M. barkeri-Desulfovibrio sp. was studied. The monoculture produced ethanol, acetate, H(2), and CO(2). More acetate and less ethanol was formed by the cocultures than by the monoculture. Acetate was utilized by M. barkeri in coculture with A. cellulolyticus after a lag period, whereas ethanol was metabolized by the sulfate reducer only under conditions of low H(2) partial pressure, i.e., when cocultured with A. celluloyticus-M. barkeri or when grown together with the methanogen. Only the three-component culture carried out the rapid conversion of cellulose to CO(2) and methane. Furthermore, this culture hydrolyzed the most cellulose-85% of that initially present. This amount was increased to 90% by increasing the population of M. barkeri in the triculture. Methane production was also increased, and a quicker fermentation rate was achieved.

Hydrogen production by methanogens under low-hydrogen conditions

Abstract: Hydrogen production was studied in four species of methanogens (Methanothermobacter marburgensis, Methanosaeta thermophila, Methanosarcina barkeri, and Methanosaeta concilii) under conditions of low (sub-nanomolar) ambient hydrogen concentration using a specially designed culture apparatus. Transient hydrogen production was observed and quantified for each species studied. Methane was excluded as the electron source, as was all organic material added during growth of the cultures (acetate, yeast extract, peptone). Hydrogen production showed a strong temperature dependence, and production ceased at temperatures below the growth range of the organisms. Addition of polysulfides to the cultures greatly decreased hydrogen production. The addition of bromoethanesulfonic acid had little influence on hydrogen production. These experiments demonstrate that some methanogens produce excess reducing equivalents during growth and convert them to hydrogen when the ambient hydrogen concentration becomes low. The lack of sustained hydrogen production by the cultures in the presence of methane provides evidence against "reverse methanogenesis" as the mechanism for anaerobic methane oxidation.

Electron-transport-driven sodium extrusion during methanogenesis from formaldehyde and molecular hydrogen by Methanosarcina barkeri

Abstract: Methanogenesis from formaldehyde or formaldehyde + H2, as carried out by Methanosarcina barkeri, was strictly dependent on sodium ions whereas methane formation from methanol + H2 or methanol + formaldehyde was Na+-independent. This indicates that the reduction of formaldehyde to the formal redox level of methanol exhibits a Na+ requirement. During methanogenesis from formaldehyde, a ΔpNa in the range of -62 mV to -80 mV was generated by means of a primary, electron-transport-driven sodium pump. This could be concluded from the following results obtained on cell suspensions of M. barkeri. 1 The addition of proton conductors or inhibitors of the Na+/H+ antiporter had no effect on sodium extrusion. 2 During methanogenesis from formaldehyde + H2 a ΔΨ of -60 mV to -70 mV was generated even in the presence of proton conductors. 3 ATPase inhibitors, applied in the presence of proton conductors, had no effect on primary sodium extrusion or generation of a ΔΨ. Evidence for a Na+-translocating ATPase could not be obtained.

Electron and Proton Flux for Carbon Dioxide Reduction in Methanosarcina barkeri During Direct Interspecies Electron Transfer.

Abstract: Direct interspecies electron transfer (DIET) is important in diverse methanogenic environments, but how methanogens participate in DIET is poorly understood. Therefore, the transcriptome of Methanosarcina barkeri grown via DIET in co-culture with Geobacter metallireducens was compared with its transcriptome when grown via H2 interspecies transfer (HIT) with Pelobacter carbinolicus. Notably, transcripts for the F420H2 dehydrogenase, Fpo, and the heterodisulfide reductase, HdrABC, were more abundant during growth on DIET. A model for CO2 reduction was developed from these results in which electrons delivered to methanophenazine in the cell membrane are transferred to Fpo. The external proton gradient necessary to drive the otherwise thermodynamically unfavorable reverse electron transport for Fpo-catalyzed F420 reduction is derived from protons released from G. metallireducens metabolism. Reduced F420 is a direct electron donor in the carbon dioxide reduction pathway and also serves as the electron donor for the proposed HdrABC-catalyzed electron bifurcation reaction in which reduced ferredoxin (also required for carbon dioxide reduction) is generated with simultaneous reduction of CoM-S-S-CoB. Expression of genes for putative redox-active proteins predicted to be localized on the outer cell surface was higher during growth on DIET, but further analysis will be required to identify the electron transfer route to methanophenazine. The results indicate that the pathways for electron and proton flux for CO2 reduction during DIET are substantially different than for HIT and suggest that gene expression patterns may also be useful for determining whether Methanosarcina are directly accepting electrons from other extracellular electron donors, such as corroding metals or electrodes.