A COMBINED PATHWAY OF SULFUR COMPOUND DISPROPORTIONATION IN DESULFOVIVRIO DESULFURICANS

The fates of the two different sulfur atoms of the thiosulfate molecul e during anaerobic disproportionation by the sulfate-reducing bacteriu m Desulfovibrio desulfuricans were followed by isotope mass spectromet ry. During disproportionation, S-32-thiosulfate was preferentially met abolized, and the residual thiosulfate became enriched in S-34. The su lfate formed was isotopically heavier than the inner sulfur of the con sumed thiosulfate. Vice versa, the sulfide formed was isotopically lig hter than the outer sulfur of the consumed thiosulfate. These results indicate that thiosulfate is cleaved to intermediates that undergo fur ther disproportionation to sulfate and sulfide in a second step. These intermediates are probably elemental sulfur and sulfite. It is conclu ded that disproportionation of thiosulfate, sulfite and elemental sulf ur includes a combined pathway. (C) 1998 Federation of European Microb iological Societies. Published by Elsevier Science B.V. All rights res erved.