Microcalorimetric studies of the growth of sulfate-reducing bacteria: comparison of the growth parameters of some Desulfovibrio species

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Abstract
The growth energetics of some species of Desulfovibrio were compared by measuring microcalorimetric and molar growth yield values. Lactate and pyruvate were used as energy sources for sulfate reduction. On lactate-sulfate media D. desulfuricans Norway, D. gigas and D. africanus exhibited molar growth yields of 4.1 .+-. 0.6, 3.7 .+-. 1.7 and 1.8 .+-. 0.1 g/mol, respectively; on pyruvate-sulfate media, the molar growth yields were higher (8.5 .+-. 0.8, 7.7 .+-. 1.6 and 3.5 .+-. 0.5 g/mol, respectively). D. africanus was thus the least efficient species in converting energy into cell material. The uncoupling of energy in this strain was obvious since its catabolic activities were high compared with those of 2 other strains. The enthalpy changes associated with lactate and pyruvate metabolism were -49 .+-. 0.7 and -70.2 .+-. 6.0 kJ/mol, respectively, for D. desulfuricans, -76.6 .+-. 1.8 and -91.2 .+-. 1.1 kJ/mol, respectively, for D. gigas, and -78.8 .+-. 7.2 and -88.0 .+-. 6.2 kJ/mol, respectively, for D. africanus. D. gigas and D. africanus produced only acetate, CO2 and H2S as metabolic end products. In addition to these normal end products, D. desulfuricans Norway produced a small amount of butanol. This butanol production was interpreted as reflecting a regulatory system of electron flow during the catabolism of both substrates. Such metabolism was comparable to that reported for D. vulgaris, which lost part of the reducing power of its energy sources through H2 evolution.