Oxidation of Thiosulphate By Intact Cells of Thiobacillus X: Effects of Some Experimental Conditions

Abstract

Low cell concentrations of Thiobacillus X (grown with low aeration) failed to oxidize thiosulfate to completion in air, and tetrathionate accumulated. The extent to which thiosulfate was oxidized was decreased in 100% oxygen and depended upon the substrate concentration. The rate of oxidation of thiosulfate in air by organisms grown with high aeration fell off progressively with time but little or no tetrathionate accumulated: 100% oxygen did not affect the extent to which thiosulfate was oxidized. Sulfite inhibited thiosulfate oxidation and was formed to a small extent during thiosulfate oxidation. During the oxidation of outer-labelled [S35]thiosulfate by Thiobacillus X, S35 became incorporated into the inner position of thiosulfate. Under all conditions studied, approximately two molecules of sulfate were formed from the inner sulfur of thiosulfate, for every one from the outer sulfur, in the early stages of thiosulfate oxidation. Some quantitative relationships between the products of oxidation of outer-labelled [S35]thiosulfate are described. A hypothesis is presented to account for these results.