Oxidation of sulfur compounds and electron transport in Thiobacillus denitrificans.

Abstract

Intact cells of Thiobacillus denitrificans catalyzed the oxidation of thiosulfate, sulfide and sulfite with nitrate or oxygen as the terminal acceptor. The anaerobic oxidation of thiosulfate, sulfide and sulfite was sensitive to the inhibitors of the flavoprotein system. Under aerobic conditions the oxidation of sulfide and sulfite was sensitive to these inhibitors but the thiosulfate oxidation was unaffected. Cyanide and azide inhibited the aerobic and anaerobic respiration when thiosulfate, sulfide or sulfite served as electron donors. The oxidation of thiosulfate by cell-free preparations was mediated by cytochromes of c, a and o-types. The cell-free extracts also catalyzed the oxidation of NADH and succinate, involving flavoproteins and b, c, a and o-type cytochromes. In addition, a cytochrome oxidase sensitive to cyanide and azide was also present.