BUTYRATE OXIDATION BY SYNTROPHOSPORA-BRYANTII IN COCULTURE WITH DIFFERENT METHANOGENS AND IN PURE CULTURE WITH PENTENOATE AS ELECTRON-ACCEPTOR

Syntrophospora bryantii degraded butyrate in co-culture with methanoge ns that can use both H-2 and formate for growth, but not in co-culture with methanogens that metabolize only H-2, suggesting that in suspend ed cultures formate may be a more important electron carrier in the sy ntrophic degradation of butyrate than H-2. Syntrophic butyrate oxidati on was inhibited by the addition of 20 mM formate or the presence of 1 30 kPa H-2. In the absence of methanogens, S. bryantii is able to coup le the oxidation of butyrate to acetate with the reduction of pentenoa te to valerate. Under these conditions, up to 300 Pa H-2 was measured in the gas phase and up to 0.3 mM formate in the liquid phase. S. brya ntii was unable to grow syntrophically with the aceticlastic methanoge n Methanothrix soehngenii. However in triculture with Methanospirillum hungatei and Methanothrix soehngenii, S. bryantii degraded butyrate f aster than in a biculture with only M. hungatei. Hydrogenase and forma te dehydrogenase activities were demonstrated in cell-free extracts of S. bryantii.