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Desuljoribrio uulgcrris (Hildenborough) was grown on lactate with either a N,/C02 or a H 2 / C 0 2 gas phase. H, increased the growth yield on lactate and had a sparing effect on lactate utilization, without altering the growth rate or hydrogenase level. Growth on acetate plus CO, with H, as sole energy source did not require an extensive adaptation period. Addition of lactate to cultures growing on acetate and H,/C02 resulted in a switch from acetate to lactate utilization. In lactate-limited medium under H2/C02 biphasic growth was observed. Lactate was oxidized first with production of acetate, followed by a second phase of growth on the acetate. Under this condition H2 did not provide any supplementary energy during growth on lactate, as was evident from the ratio of lactate utilized to acetate produced.

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Desuljbvibrio vulgaris (Hildenborough) can grow on acetate plus C 0 2 as carbon source with Hz as the sole source of energy. The capability of sulphate reducers to oxidize H2 has been proposed as a major factor in the anaerobic corrosion of metals. Utilization by D . vulgaris of cathodic hydrogen from a mild steel electrode was demonstrated electrochemically and physiologically. D. uulgaris depolarized the metal electrode and growth on acetate under N2/C02 was dependent on the presence of the electrode. Although the highest corrosion rate was observed under aerobic conditions, D . vulgaris significantly increased the corrosion rate under anaerobic conditions.

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