Metabolic Studies of a Sulfate-Reducing Bacterium

The metabolic activity of a strain of Desulfovibrio which shows the characteristics of Desulfovibrio vulgaris, was studied in the presence of different combinations (of molar ratios) of lactate and sulfate, and further in presence of various other electron donors and electron acceptors. Growth rate, production of hydrogen sulfide and volatile metabolic products were the parameters used for checking the metabolic activity. Acetate and small amount of ethanol could be detected as volatile metabolic products in all experiments. The quantity of ethanol produced decreased with increase in growth of the bacterium, which indicates the production and then utilization of ethanol by the bacterium. The maximum production of hydrogen sulfide was detected at and above the molar ratio of lactate to sulfate 1: 1. When pyruvate with sulfate was used as substrate the growth rate was highest but the hydrogen sulfide production was lowest which could be due to the utilization of pyruvate without sulfate by the bacterium and thereby less sulfate reduction. Sulfite, as an electron acceptor could not support the growth of this strain. On ethanol with sulfate, the activity was low but on lactate with thiosulfate the activity was high.