The reductive reactions of Thiobacillus ferrooxidans on sulphur and selenium

Abstract An investigation into the sulphur oxidation of iron grown Thiobacillus ferrooxidans is reported. A new mechanism for sulphur catabolism in this obligate acidophile, involving the initial reduction of the substrate, is proposed. Evidence to support substrate reduction comes from the evolution of H₂S in both aerobic and anaerobic conditions (O₂ and Fe³⁺ acting as terminal electron acceptors, respectively) and a accurate trapping method of detection is described. Levels of sulphur reduction are such that a role in the full catabolism of sulphur can be envisaged. In addition, red selenium reduction was investigated and the bioenergetic implications for both substrates are discussed.