Interrelations between sulfate-reducing and methane-producing bacteria in bottom deposits of a fresh-water lake. II. Inhibition experiments

A possible substrate interrelationship between methane-producing and sulfate-reducing bacteria has been studied in bottom deposits of Lake Vechten. Inhibition of methanogenesis in mud samples by chlorine-containing analogues of methane resulted in accumulation of acetate. Fluoroacetate reduced the concentration of methane by about 75%. With carbon tetrachloride, accumulation of hydrogen gas was observed. These results indicate that acetate is the main precursor of methanogenesis in mud. After addition of β-fluorolactate, lactate accumulated and H₂S was no longer produced, which indicates that lactate is the main source of energy for sulfate reduction in mud. At the same time the concentration of methane increased possibly due to the lower concentration of H₂S, which has a toxic effect on methanogenesis. Experiments with intact mud cores provide evidence that the described phenomena occur also in situ.