Oxidation of Carbon Disulphide as the Sole Source of Energy for the Autotrophic Growth of Thiobacillus thioparus Strain TK

The ability of microorganisms to grow on carbon disulphide (CS,) as a sole source of carbon and energy appears to be very limited : none was obtained from enrichment culture and eight Thiobacillus species could not use it. Thiobacillus thioparus strain TK-m could grow autotrophically on either CS2 or carbonyl sulphide (COS) as sole substrates. Growth yield on CS2 was 7.9 f 0.9 g cell-carbon (mol CS2)-l, and yields on COS, thiosulphate or thiocyanate were in the range 5.6-6.1. COS was detected as an intermediate during growth on CS2, and there was quantitative conversion of the sulphur of CS2 to sulphate during growth. Aerobic oxidation of CS2 by suspensions of strain TK-m exhibited a K, of 16.5 p~ and a V,,, of 524 nmol 0 2 consumed min-l (mg organism-protein)-l. When incubated anaerobically with CS2, strain TK-m sequentially produced COS and H2S. CS2 oxidation is proposed to proceed by its sequential hydrolytic cleavage to COS then H2S, with release of all the carbon as C 0 2 , followed by oxidation of the sulphide to sulphate. This oxidation provides all the energy for growth, which is dependent on the autotrophic fixation of C 0 2 , apparently by means of ribulose bisphosphate carboxylase.