Competitive Inhibition of Ferrous Iron Oxidation by Thiobacillus ferrooxidans by Increasing Concentrations of Cells.

The oxidation of ferrous iron (Fe) to ferric iron (Fe) with dioxygen (O(2)) by various strains of Thiobacillus ferrooxidans was studied by measuring the rate of O(2) consumption at various Fe concentrations and cell concentrations. The apparent K(m) values for Fe remained constant at different cell concentrations of laboratory strains ATCC 13661 and ATCC 19859 but increased with increasing cell concentrations of mine isolates SM-4 and SM-5. The latter results are explained by the competitive inhibition of the Fe-binding site of a cell by other cells in the reaction mixture. Possible mechanisms involving cell surface properties are discussed.