Silver toxicity to ferrous iron and pyrite oxidation and its alleviation by yeast extract in cultures of Thiobacillusferrooxidans

Abstract

Ferrous-ion oxidation by Thiobacillusferrooxidans was inhibited by 10-6 M Ag+ while a slight inhibition of growth was apparent with 10-7 M Ag+. The threshold toxic concentration was the seme for four different test strains. While prolonged lag phases resulted from culture exposure to Ag+, Fe2+ oxidation rates after the onset of growth showed little variation under these conditions. Yeast extract (0.02%) partially alleviated the toxicity of silver-ion by reducing the lag periods. Pyrite oxidation by T.ferrooxidans and mixed cultures of acidophiles was tested at 8.3×10-7 to 8.3×10-5 M Ag+. Strong inhibition was apparent at 8.3×10-5 M Ag+ and little to no inhibition was observed at 8.3×10-7 M Ag+. © 1985 Kluwer Academic Publishers.