Energy Coupling During Sulphur Compound Oxidation by Thiobacillus sp. Strain C

Abstract

The addition of either sulfide or thiosulfate to an aerobic suspension of a Thiobacillus was followed within 10 sec. by the synthesis of intracellular adenosine triphosphate (ATP). The ATP formation accompanying sulfide oxidation was strongly inhibited by 0[center dot]1 m[image]-2,4-dinitrophenol, but that accompanying thiosulfate oxidation was unaffected. The presence of carbon dioxide had no effect on ATP formation or on the steady-state concentration attained. 2,4-Dinitro-phenol did not significantly affect oxygen uptake nor the kinetics of thiosulfate oxidation but it inhibited carbon dioxide fixation with either sulfide or thiosulfate as substrate. It is concluded that sulfur-compound oxidation can be coupled to two different types of phosphorylation, only one of which is sensitive to 2,4-dinitrophenol. In the presence of 2,4-dinitrophenol and with thiosulfate as substrate, carbon dioxide fixation was not limited by the availability of ATP but might be limited by the availability of reduced nicotinamide adenine dinucleotides.