Physiological properties of Acidithiobacillus ferrooxidans strains isolated from sulfide ore deposits in Kazakhstan

Abstract

Acidithiobacillus ferroxidans strains were isolated from acidophilic microbial communities of Kazakhstan sulfide ore deposits. Their biotechnologically important properties (optimal and maximal growth temperatures and resistance to NaCl) were determined. While temperature optima of the strains were the same (30-32 degrees C), temperature ranges were different. Thus, strain TFBK oxidized iron very poorly at 37 degrees C, while for strain TFV, the iron oxidation rate at this temperature was insignificantly lower than at lesser temperatures. NaCl inhibited the oxidative activity of both strains. Iron oxidation by strain TFV was inhibited at 5 g/L NaCl and was suppressed almost completely at 20 g/L. Iron oxidation by strain TFBK was inhibited by NaCl to a lesser degree, so that iron oxidation rate was relatively high at 10 g/L, while at 20 g/L NaCl the process was not suppressed completely, although the oxidation rate was low. Sulfur oxidation by these strains was less affected by NaCl than oxidation of ferrous iron. Sulfur oxidation by strain TFV was considerably inhibited only at 20 g/L NaCl, but was not suppressed completely. Sulfur oxidation by strain TFBK was more affected by NaCl. At 10 g/L NaCl the oxidation rate was much lower than at lower NaCl concentrations (sulfate concentrations after 6 days of oxidation at 5 and 10 g/L NaCl were -130 and -100 mM, respectively). While sulfur oxidation by strain TFBK was considerably inhibited at 10 and 20 g/L NaCl, similar to strain TFV it was not suppressed completely. Our results indicate the adaptation of the species A. ferrooxidans to a broad range of growth conditions.