KINETICS OF SULFUR OXIDATION BY THIOBACILLUS-FERROOXIDANS

Thiobacillus ferrooxidans ATCC 23270 was grown with elemental sulfur as the energy source. Substrate oxidation was measured using a Clark-type oxygen electrode. Whole cells demonstrated a broad pH optimum for sulfur oxidation between pH 2.0 and 8.0. The V(max) and K(s) for sulfur oxidation varied depending on pH. Sulfite was oxidized at 227 nmol O2/min/mg protein. Thiosulfate oxidation was slow, and tetrathionate oxidation was not detected. At a concentration of 2 mM, sodium azide completely inhibited sulfur, sulfite, and thiosulfate oxidation. Inhibition by N-ethylmaleimide, antimycin A, and 2-heptyl-4-hydroxyquinoline N-oxide varied with substrate.