Polarographic Evidence of the Production of Polythionates During the Bacterial Oxidation of Thiosulphate

Abstract

Summary: A polarographic technique and Starkey's alkali method have been applied to the qualitative analysis of thiosulphate, trithionate and pentathionate and to the quantitative analysis of tetrathionate in filtrates of bacterial cultures grown in an inorganic medium containing sodium thiosulphate. Five strains of autotrophic thiobacilli and one strain of a heterotrophic bacterium produced polythionates. During thiosulphate oxidation by two autotrophic strains which resembled Thiobacillus thioparus, tetrathionate, small amounts of trithionate, pentathionate and abundant elemental sulphur were produced and the pH fell from c. 7.0 to c. 3.0. In cultures of one of the three autotrophic strains which resembled T. thiocyanoxidans, about half as much tetrathionate, with even smaller amounts of trithionate and pentathionate, was found; abundant sulphur was precipitated and the pH fell to c. 4.0. In cultures of the two other strains resembling T. thiocyanoxidans, small amounts of tetrathionate were detected only occasionally; trithionate and pentathionate were not found, sulphur was deposited and the pH fell to c. 4.5. Much tetrathionate, as well as trithionate and pentathionate, were all readily identified in cultures of the heterotrophic organism; the pH rose to c. 8.7 and no sulphur was formed.