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 thiosulfateJtetrathionate oxidation activity.Thus it becomes evident that the inhibition of thiosulfate and tetrathionate oxidation is solely due to presence of ferrous iron.