Dissimilatory Sulfate Reduction, Mechanistic Aspects

Abstract

Dissimilatory sulfate-reducing bacteria, belonging to the genera Desulfovibrio and Desulfotomaculum can carry out the process of anaerobic respiration by utilizing inorganic sulfate as a terminal electron acceptor. The overall process of dissimilatory sulfate reduction may be considered to occur in two phases. They are (1) the reduction of sulfate to bisulfite through the intermediate Compound, adenylyl sulfate (APS), and (2) the reduction of bisulfite to sulfide. The biochemistry of (1), with respect to the pathway by which sulfate is reduced to bisulfite, has been firmly established. The sequence of events and the intermediate involved were unequivocally determined. In contrast, the issue concerning the pathway of bisulfite reduction to sulfide is still unsettled. One view advocates a direct reduction of bisulfite to sulfide comparable to the mechanism ascribed to the assimilatory sulfite reductase. The other hypothesis supports the view that bisulfite is reduced to sulfide sequentially through a pathway containing trithionate and thiosulfate as intermediates. It is the purpose of this review to discuss the current status of the mechanistic aspects of sulfate reduction with emphasis placed on the bisulfite reduction process catalyzed by dissimilatory sulfate-reducing bacteria.