ABSTRACT
Two genera of strictly anaerobic bacteria, Desulfovibrio and Desulfotomaculum, are capable of utilizing sulfate (or reduced products thereof) as terminal electron acceptor for catabolic oxidation processes. There is some evidence that the intracellular pH of sulfate reducing bacteria lies between 7 and 8. Since, however, the intracellular concentration of sulfite and the physiological electron donor are not known, it is impossible to decide which products are formed by bisulfite reductase in vivo. The formation of thiosulfate by the enzyme is dependent on the simultaneous presence of bisulfite. The presence of the thiosulfate-forming enzyme and of thiosulfate reductase in sulfate-reducing bacteria has been taken as evidence that dissimilatory sulfate reduction proceeds via trithionate and thiosulfate. It is therefore conceivable that both the thiosulfate-forming enzyme and thiosulfate reductase have a function only when the bacteria are growing in the presence of trithionate or thiosulfate.
