INHIBITION OF THIOSULFATE AND TETRATHIONATE OXIDATION BY FERROUS IRON IN THIOBACILLUS-FERROOXIDANS

Thiosulfate and tetrathionate oxidation activity of Thiobacillus ferrooxidans were found to be absent in iron-grown cells as well as in the cells grown anaerobically on elemental sulfur. While the thiosulfate oxidase activity was absent in the cell-free extract of the above cells, the activity of rhodanese was present irrespective of the culture condition of T ferrooxidans. It is thus conceivable that rhodanese is not involved in thiosulfate metabolism. During growth in presence of ferrous sulfate plus elemental sulfur, the thiosulfate/tetrathionate oxidation activity was absent till the oxidation of ferrous iron was complete and the cells harvested only in the latter period acquired the thiosulfate/tetrathionate oxidation activity. Thus it becomes evident that the inhibition of thiosulfate and tetrathionate oxidation is solely due to presence of ferrous iron.