Abstract
The halotolerant acidophile Thiobacillus prosperus was shown to require chloride for growth. With ferrous iron as substrate, growth occurred at a rate similar to that of the well-studied acidophile Acidithiobacillus ferrooxidans. Previously, the salt (NaCl) requirement of T. prosperus was not clear and its growth on ferrous iron was described as poor. A subtractive hybridization of cDNAs from ferrous-iron-grown and sulfur-grown T. prosperus strain V6 led to identification of a cluster of genes similar to the rus operon reported to encode ferrous iron oxidation in A. ferrooxidans. However, the T. prosperus gene cluster did not contain a homologue of cyc1, which is thought to encode a key cytochrome c in the pathway of electron transport from ferrous iron in A. ferrooxidans. Rusticyanin, another key protein in ferrous iron oxidation by A. ferrooxidans, was present in T. prosperus at similar concentrations in cells grown on either ferrous iron or sulfur.