The Specificity of the Anionic Requirement for Iron Oxidation by Thiobacillus ferrooxidans

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Abstract
The anionic requirement for the oxidation of Fe2+ by suspensions of T. ferrooxidans was satisfied by selenate and sulfate. Selenate was toxic to the organism and suppressed growth in Fe2+ media, even in the presence of high concentrations of sulfate. After treatment with dilute HCl at 0.degree. C, T. ferrooxidans, which specifically required SO42- or SeO42- for Fe oxidation, showed no activity in response to 12 other anions tested. After the introduction of SO42- or SeO42-, addition of anions such as TeO42-, WO42-, AsO43- or PO43- further enhanced the rate of Fe oxidation. Under these conditions, Cl-, B4O72- and ClO3- had no significant effect at low concentration, whereas Br-, NO3- and MoO42- were inhibitory. These observations distinguish between a specific and a non-specific anionic requirement for the oxidation of Fe2+ by T. ferrooxidans. The specific requirement is satisfied only through the uptake of SO42- by the bacteria. The non-specific requirement is satisfied by any 1 of several anions, including SO42- and SeO42-, which are presumed to act as ligands for Fe in solution.