[Effect of Fe3+ ions on Thiobacillus ferrooxidans oxidation of ferrous oxide at various temperatures]

The inhibition of the rate of ferrous iron oxidation by Thiobacillus ferrooxidans with ferric ions was shown to depend on their concentration, the temperature of the medium, and the phase of the cultural growth. Ferrous iron oxidation was inhibited with ferric ions both at low (below 1.0 g/l) and high (ca. 10 g/l) concentrations, the process being temperature dependent: the rate of inhibition decreased with a fall of the temperature. The bacterium was most sensitive to unfavourable Fe3+ concentrations at 8-26 degrees C during the lag phase; Fe2+ oxidation was inhibited during the exponential phase of growth only at 26 degrees C. The Ki for Fe3+ at 27, 10 and 5 degrees C were 3.09-3.39, 11.4-22.8 and 46.0 g/l Fe3+, respectively. Therefore, the affinity of the enzyme for the inhibitor Fe3+ decreases with a fall of the temperature.