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Abstract
The anionic requirement for the oxidation of ferrous ions by suspensions of Thiobacillus ferrooxidans was satisfied by selenate as well as sulphate. Selenate was toxic to the organism and suppressed growth in ferrous iron media, even in the presence of high concentrations of sulphate. After treatment with dilute hydrochloric acid at 0°C, T. ferrooxidans, which specifically required SO4 2− or SeO4 2− for iron oxidation, showed no activity in response to 12 other anions tested. However, after the introduction of SO4 2− or SeO4 2−, addition of anions such as TeO4 2−, WO4 2−, AsO4 3− or PO4 3− further enhanced the rate of iron oxidation. Under these conditions, Cl-, B4O7 2− and ClO3 - had no significant effect at low concentration, whereas Br-, NO3 - and MoO4 2− were inhibitory. These observations distinguish between a specific and a non-specific anionic requirement for the oxidation of ferrous ions by T. ferrooxidans. The specific requirement is satisfied only through the uptake of SO4 2− or SeO4 2− by the bacteria. The non-specific requirement is satisfied by any one of several anions, including SO4 2− and SeO4 2−, which are presumed to act as ligands for iron in solution.
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