Iron-oxidizing and leaching activities of sulphur-grown Thiobacillus ferrooxidans cells on other substrates: Effect of culture pH

The rate of iron (II) oxidation by sulphur-grown Thiobacillus ferrooxidans cells decreased when the pH of the original growth medium was lowered. This behaviour was observed even after shifting from the original growth pH to a higher pH. After being suspended in medium at a pH higher than the growth pH, sulphur-grown cells could leach covellite at a similar initial rate to iron-grown cells. Sulphur-grown cells exhibited a long lag phase when the original growth pH was low. These results were correlated with the number o f protons associated with the cell surface, rather than with cell hydrophob icity or cell capacity to attach to solid particles. Sulphur-grown cells gr own in very acidic media (without pH control) were not able to oxidize iron (II) or leach covellite even after shifting to a high pH.