Involvement of Formate as an Intespecies Electron Carrier in a Syntrophic Acetate-Oxidizing Anaerobic Microorganism in Coculture with Methanogens

概要

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To determine whether formate is involved in interspecies electron transfer between substrate-oxidizing bacteria and hydrogenotrophic microorganisms under anaerobil conditions, a syntrophic acetate-oxidizing bacterium Thermacetogenium phaeum strain PB was cocultured either with a formate/H_2-utilizing methanogen strain TM (designated as PB/TM coculture)(, or an H_2-utilizing methanogen strain ΔH (designated as PB/ΔH coculture). Acetate oxidation and subsequent methanogenesis in PB/TM coculture were found to be significantly faster than in PB/ΔH coculture. Formate dehydrogenase and hydrogenase were both detected in strains PB and TM. H_2 partial pressures in the PB/TM coculture were kept lower (20 to 40 Pa) than those of the PB/ΔH coculture (40 to 60 Pa) during the exponential growth phase. Formate was also detected in both PB/TM and PB/ΔH cocultures, and the concentration of formate was maintained at a lower level in the PB/TM coculture (5 to 9 μM) than in the PB/ΔH coculture. Thermodynamic calculations revealed that the concentrations of both H_2 and formate severely affect the syntrophic oxidation of acetate. These results strongly indicate that not only H_2 but also formate may be involved in interspecies electron transfer.
社団法人日本生物工学会の論文
2001-03-25