Abstract
SUMMARY: A newly isolated strain (c) of Thiobacillus thioparus is described. The organism oxidizes thiosulphate, sulphide, tetrathionate or trithionate to sulphate; carbon dioxide fixation is coupled to the oxidation of each of these compounds. Concentrations of arsenate, 2,4-dinitrophenol, and other inhibitors of oxidative phosphorylation, inhibit carbon dioxide fixation without appreciably affecting oxygen uptake. Carbon dioxide fixation coupled to sulphide oxidation is more sensitive to arsenate and 2,4-dinitrophenol inhibition than that coupled to thiosulphate oxidation. This result is consistent with the suggestion that thiosulphate oxidation is linked to a substrate phosphorylation which is relatively insensitive to inhibition by 2,4-dinitrophenol and arsenate.