PATHWAYS OF THE UTILIZATION OF INORGANIC SULPHUR COMPOUNDS IN THIOBACILLUS FERROOXIDANS

Abstract

During growth on ferrous-iron Thiobactllus ferrooxidans assimilated sulphate into cellular material. Sulphate was rapidly bound by the cells and activated into adenosine 5'-sulphatophosphate prior to its reduction to sulphite and sulphide. The sulphate activation was mediated by the ATP-sulphurylase enzyme. The heterotrophic strain of 7. ferrooxidans assimilated sulphate via the same route. Sulphate was not assimilated by the bacteria during growth on thiosulphate. Adenosine 3'- phosphate 5'-sulphatophosphate was not formed and APS-kinase activity not detected in T. ferrooxtdans grown on ferrous-iron, thiosulphate or glucose. Thiosulphate oxidation was preceded by its cleavage to sulphide and sulphite and the outer S-atom of thiosulphate was also incorporated into cellular material. Tetrathionate was formed from thiosulphate by the thiosulphate-oxidizing enzyme but this pathway was not studied any further. The thiosulphate-oxidizing enzyme activity was not detected in iron-grown 7m. ferrooxtdans. Enzymes mediating the oxidation of thiosulphate linked to oxidative and substrate-level phosphorylation were present in 7. ferrooxtdans grown autotrophically on ferrous-iron or thiosulphate or heterotrophically on glucose.