FIG 3.

Mutant studies. (a) Lack of ethanol metabolism and methane production in a coculture initiated with a pilA-deficient G. metallireducens strain. (b) Methane production in cocultures initiated with wild-type G. metallireducens or a strain deficient in the Gmet 1868 gene, which encodes a predicted extracellular cytochrome. (c) GAC stimulation of methane production in cocultures initiated with wild-type G. metallireducens and enabling methane production in cocultures initiated with either the PilA- or cytochrome (Gmet 1868)-deficient strains of G. metallireducens. All incubations were set up with a 5% (vol/vol) inoculum of each coculture partner.