RESISTANCE TO HEAVY-METALS IN DIFFERENT STRAINS OF THIOBACILLUS-FERROOXIDANS

Ten different isolates of Thiobacillus ferrooxidans were studied with regard to their degree of resistance to the metals copper, nickel, ura nium, and thorium. Inhibitory concentrations for a particular metal we re those which showed a statistically-significant decrease in the amou nt of ferrous iron oxidized by the bacterium compared to an untreated control. The different isolates had different susceptibilities to the metals tested, and none of the metals had a stimulatory effect. Uraniu m and thorium were 20 to 40 times more toxic to ferrous iron oxidation than either copper or nickel.