Methanosarcina barkeri

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

Methanogenesis from sucrose by defined immobilized consortia. [Escherichia coli; Acetobacterium woodii; Desulfovibrio vulgaris; Methanosarcina barkeri; Methanobacterium formicicum]

Abstract: A bacterial consortium capable of sucrose degradation primarily to CH/sub 4/ and CO/sub 2/ was constructed, with acetate as the key methanogenic precursor. In addition, the effect of agar immobilization on the activity of the consortium was determined. The primary fermentative organism, Escherichia coli, produced acetate, formate, H/sub 2/, and CO/sub 2/ (known substrates for methanogens), as well as ethanol and lactate, compounds that are not substrates for methanogens. Oxidation of the nonmethanogenic substrates, lactate and ethanol, to acetate was mediated by the addition of Acetobacterium woodii and Desulfovibrio vulgaris. The methanogenic stage was accomplished by the addition of the acetophilic methanogen Methanosarcina barkeri and the hydrogenophilic methanogen Methanobacterium formicicum. Results of studies with low substrate concentrations (0.05 to 0.2% (wt/vol)), a growth-limiting medium, and the five-component consortium indicated efficient conversion (40%) of sucrose carbon to CH/sub 4/. Significant decreases in yields of CH/sub 4/ and rates of CH/sub 4/ production were observed if any component of the consortium was omitted. Approximately 70% of the CH/sub 4/ generated occurred via acetate. Agar-immobilized cells of the consortium exhibited yields of CH/sub 4/ and rates of CH/sub 4/ production from sucrose similar to those of nonimmobilized cells. The rate of CH/sub 4/more » production decreased by 25% when cysteine was omitted from reaction conditions and by 40% when the immobilized consortium was stored for 1 week at 4/sup 0/C.« less

Interspecies Electron Transfer in environmental and engineered syntrophic systems

Abstract: Syntrophic Interspecies Electron Transfer (IET) has been observed in anoxic environments and mainly requires intermediates such as hydrogen or formate as electron carriers. However direct IET (DIET) is also possible and requires that electrons are transferred via membrane-bound proteins or conductive appendages. Engineering of multiple artificial syntrophies was attempted to study these concepts. Growth of cultures proved very difficult due to long establishment times and slow adaptation. Three artificial syntrophies were confirmed by growth curves, chemical analysis, and microscopic analysis. These included a tri-culture of Syntrophobacter wolinii, Methanobrevibacter smithii and Methanosaeta concilii, degrading propionate, bidirectional co cultures with Shewanella oneidensis and Methanosarcina barkeri first growing on lactate and secondly on acetate with hydrous ferric oxide (HFO) or a carbon anode. Bidirectional syntrophies indicated that syntrophic associations can extend beyond those systems observed and isolated to date. This work also focused on the possibilities of stimulating and enhancing DIET in environmental cultures. A number of hypotheses were tested, including the presence of proton carrying buffers and increase in salinity. Since direct electron transport requires cation/proton transport, the presence of buffers such as phosphate should enhance rates where DIET dominates. This was tested by varying initial conductivity (1.5mS/cm, X10, X30) and total phosphate: chloride ratios (1:0, 1:1, 2:1, 1:2 and 0:1), in a square factorial analysis, during propionic acid oxidation and ethanol oxidation, with crushed anaerobic granules as inoculum. Microbial communities were analysed through 16S rRNA gene pyrosequencing and fluorescent in situ hybridisation (FISH). With propionic acid oxidation, key microbial shifts with increasing salinity were from Syntrophomonas sp to Syntrophobacter sp and Candidatus Cloacamonas sp within bacteria and Methanobacterium sp to Methanolinea sp. Results suggested an indirect IET (IIET) system. With ethanol, there was a higher percentage of Geobacter sp, capable of DIET, and Methanosaeta sp, especially at 1:1 and X10 conductivity where the best rate was recorded. Low methane yield was observed at X30 conductivity, likely due to the reduction of ethanol to higher organic acids. In both assays, responses were better at 1:1 ratio, with the best kinetic values recorded at X10 conductivity. Acclimatisation with propionic acid at high conductivities (X30), over 6 months was also tested to reduce the impact of salt shock. New granules were acclimatised at 1:0, 1:1 and 0:1 ratio. Activity was low at ratio 1:0 but improved at 1:1. Complete oxidation with KCl only was attributed to emerging Comamonas sp as presumptive oxidiser.n

(Anaerobie digestion; propionate; methanogenesis~ mixed culture; sulfide inhibition)

Abstract: 1. SUMMARY The association of Desulfobulbus sp. with Methanosarcina barkeri 227 was able to produce CH 4 from propionate in the presence of sulfate, if a sufficient amount of ferrous iron was added to the media in order to trap the soluble sulfides produced from-stllfate. In the absence of ferrous iront soluble sulfides inhibited the acetoclastic re­ action. Attempts to cultivate Desulfobulbus sp. with H 2 -utilising methanogenic bacteria in the absence of sulfate did noLsucceed.