Interspecies hydrogen transfer in co-cultures of methanol-utilizing acidogens and sulfate-reducing or methanogenic bacteria

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Abstract
The metabolism of methanol by acidogenic bacteria (Butyribacterium methylotrophicum, Sporomusa ovata and Acetobacterium woodii) was studied in pure culture and in defined mixed cultures with sulfate-reducing bacteria (Desulfovibrio vulgaris) or methanogenic bacteria (Methanobrevibacter arboriphilus strain AZ). In the mixed cultures, less acids (acetate and/or butyrate) were formed per unit methanol converted than in pure cultures. In these mixed cultures, a significant production of sulfide or methane was observed despite the inability of the sulfate reducer and the methanogen to use methanol as an energy substrate. These results are explained in terms of interspecies hydrogen transfer between the acidogens (converting part of the methanol to 1 CO2 and 3 H2) and the Desulfovibrio or Methanobrevibacter species. The bioenergetic aspects of this process and its ecological implications are discussed.