[35S]thiosulphate oxidation by Thiobacillus strain C

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Abstract
Thiobacillus strain-C oxidized [S35] thiosulfate completely to sulfate. During thiosulfate oxidation [S35] sulfate was formed more rapidly from (S. S35O3)2- than from (S35.SO3)2-. S35 disappeared less rapidly from thiosulfate with (S35.SO3)2- as substrate than with (S.S35O3)2-. Thiosulfate labelled in both atoms was produced during (S35.SO3)2-oxidation, but not during (S.S35O3)2- oxidation. No S35 was precipitated as elementary sulfur either in the presence or absence of exogenous unlabelled sufur. During [S35]thiosulfate oxidation, appreciable quantities of [S35]trithionate accumulated and later disappeared. Other polythionates did not accumulate consistently. [S35]Thithionate was formed initially at a greater rate from (S.S35O3)2- than from (S35.S03)2-, but subsequently at a similar rate from each. Trithionate formed from (S.S35O3)2- was labelled only in the oxidized sulfur atoms, but that formed from (S35.SO3)2- was labelled in both oxidized and reduced atoms. The proportion of S35 in the oxidized atoms increased as more trithionate accumulated. The results eliminate some mechanisms of trithionate formation but are consistent both with a mechanism of thiosulfate oxidation based on an initial reductive cleavage of the molecule and with a mechanism in which thiosulfate undergoes an initial oxidative reaction.