OXIDATION OF INORGANIC SULFUR COMPOUNDS BY WASHED CELL SUSPENSIONS OF THIOBACILLUS FERROOXIDANS

Abstract

Oxidation of various inorganic sulfur compounds by Thiobacillus ferrooxidans was studied, and conditions necessary for maximum respiration rates were established. Optimum oxidation of elemental sulfur occurred at pH 5.0 and gave a Qo₂(N) of 726; oxidation of thiosulfate gave a maximum Qo₂(N) of 514 at pH 4.0; tetra- and tri-thionate, when oxidized at pH 6.0, gave a maximum Qo₂(N) of 103 and 113, respectively. Polythionates accumulated during thiosulfate oxidation, but did not during oxidation of elemental sulfur. Metallic sulfide minerals were oxidized optimally as follows: chalcopyrite, pH 2.0, maximum Qo₂(N) 3200; bornite, pH 3.0, maximum Qo₂(N) 450; pyrite, pH 2.0, maximum Qo₂(N) 1600. Maximum temperature for oxidation of all inorganic sulfur compounds tested was 40 C.The effect of a variety of organic compounds on sulfur oxidation is presented.T. ferrooxidans requires growth adaptation on iron for maximum respiration on that substrate; however, sulfur oxidation is not inducible. Iron and sulfur can be oxidized simultaneously, giving a rate equal to the sum of the maximum rates of oxidation of the two substrates individually.