The influence of the redox potential (Eh) of incubation medium on the
methanogenesis of resting cultures of the thermophilic methanogenic ba
cteria Methanosarcina thermophila TS-2 and Methanobacterium thermophil
um M was studied. Both cultures produced methane at Eh values from +10
0 to -400 mV. The values of Eh optimal for methanogenesis were differe
nt for these methanogens and depended on the carbon and energy source.
With the redox potential of the medium being changed toward negative
or positive suboptimal values, the production of methane persisted, al
though at a slower rate. The ability of methanogens to alter the redox
potential of the medium is probably determined by the composition of
the redox chains associated with methanogenesis and energy production.