The Oxidation of Inorganic Compounds of Sulphur by various Sulphur Bacteria

SUMMARY: Cultures of Thiobacillus thiooxidans, Th. thioparus, Th. novellus, Thiobacillus B (Waksman, 1922a), strains ‘T’ and ‘K’ (Trautwein, 1921) and Th. concretivorus, Thiobacillus X and the ‘M’ strains, organisms isolated from concrete (Parker, 1945, 1947), were examined to elucidate the mode of oxidation and to establish the identity of the organisms recently isolated from corroded concrete. Thiosulphate was oxidized by all these bacteria. Th. thiooxidans, Th. concretivorus and Thiobacillus X first converted it to tetrathionate and sulphate and then oxidized the tetrathionate to sulphate and free sulphuric acid. Thiobacillus X differed from the other two in that, owing to a lesser acid tolerance, some tetrathionate was found in the final products of oxidation. Th. thioparus converted thiosulphate to sulphate and sulphur, followed by partial oxidation of the sulphur to sulphuric acid. Th. novellus produced sulphate and sulphuric acid. Thiobacillus B, the ‘T’ and ‘K’ strains and the ‘M’ strains formed sulphate and tetrathionate with temporary increase in pH value; only Thiobacillus X oxidized tetrathionate, yielding sulphate and sulphuric acid. Elementary sulphur was oxidized by Th. thiooxidans, Th. concretivorus, Thiobacillus X and Th. thioparus; the rates of oxidation decreased in that order, and the only product was sulphuric acid. Hydrogen sulphide was oxidized only at low concentrations and only by Th. concretivorus and Thiobacillus X; sulphuric acid was the end-product, and elementary sulphur may have been an intermediate. Thiobacillus X differed from Th. thiooxidans in pH range for growth and from Th. thioparus in its method of oxidation of thiosulphate, tetrathionate and H2S. It appeared to fit earlier descriptions of Th. thioparus by Nathansohn (1902) and Beijerinck (1904) more closely than the strain described as Th. thioparus by Starkey (1934a). The ‘M’ strains were similar to Thiobacillus B and the ‘T’ and ‘K’ strains of Trautwein.