Ferrous iron oxidation and leaching of copper ore with halotolerant bacteria in ore columns

Growth on ferrous iron of a new isolate of the acidophile Thiobacillus prosperus occurred with a substrate oxidation rate similar to that of Acidithiobacillus ferrooxidans. As well as similar capacities for iron oxidation, these species were shown to possess similar, but not identical, clusters of genes (the rus operon) that encode proteins likely to be involved in transfer of electrons from ferrous iron. Abundant rusticyanin was present in acidified, cell-free extracts of T. prosperus. In contrast to these similarities between the species, T. prosperus grew at a salt (NaCl) concentration several times that which prevented growth of A. ferrooxidans. A mixed culture of halotolerant bacteria maintained continuous ferrous iron oxidation in the presence of 5% w/v NaCl in solution percolating through ore in laboratory columns, and so enhanced ferric iron-dependent solubilization of copper.