Dissimilatory Sulfate Reduction, Energetic Aspects

Abstract

Several strict anaerobic prokaryotes are capable of using sulfate as electron acceptor for catabolic oxidation processes. In doing so sulfate is reduced to H₂S (Fig. 1). Respiration with sulfate as acceptor is termed dissimilatory sulfate reduction, bacteria capable of sulfate respiration are classifled as sulfate-reducing bacteria. Seven genera have been described: Desulfovibrio (Postgate and Campbell, 1966), Desulfotomaculum (Campbell and Postgate, 1965), Desulfobulbus, Desulfobacter, Desulfococcus, Desulfosarcina, and Desulfonema (Widdel, 1980). In this paper it will be discussed whether the dissimilatory reduction of sulfate to H₂S is coupled with the net synthesis of ATP from ADP and P_i, or whether the reduction of sulfate serves only as an electron sink, the function of which is to enable ATP synthesis via substrate level phosphorylation (SLP). It is shown that dissimilatory sulfate reduction is coupled with the net synthesis of ATP. Results are presented from which the stoichiometry of coupling and the mechanism of coupling can be deduced. The treatise begins with a short summary of what was known when the investigation was started. Detailed reviews on the subject have appeared by Postgate (1979), LeGall and Postgate (1973), Peck (1974), Siegel (1975), Thauer et al. (1977), and Thauer and Badziong (1980). For original literature the reader is referred to these reviews.