Interactions of Acidithiobacillus ferrooxidans with Heavy Metals, Various Forms of Arsenic and Pyrite

Abstract

An arsenic resistant ferrous iron oxidizing bacterium Acidithiobacillus ferrooxidans (GenBank no. EF010878) was isolated from reactor leachate. The reactor leachate showed extreme environmental parameters. Ferrous iron concentrations of more than 60 g/L were found to be inhibitory in the presence and absence of arsenite. Ks values of 12.5 and 8.0 g/L ferrous sulphate and Vmax of 0.124 and 0.117 g/L/h/0.8 mg of protein were found in the presence and absence of arsenite respectively. At 14.9 g/L of arsenite and arsenate the culture showed 26.8 and 59.7 % ferrous iron oxidizing activity respectively. Amongst the metals studied, copper was found to be more toxic as compared to nickel and zinc. In the presence of 3.51 g/L nickel or 4.68 g/L zinc, about 30 % biooxidation activity was registered. In the pyrite oxidation study 87, 67 and 64 % of pyrite oxidation was found and 2.02, 3.19 and 5.96 g/L total iron was solubilized with 5, 10 and 20 g/L of pyrite respectively. The isolate was also able to oxidize refractory arsenopyrite gold ore and 0.531 g/L of arsenic was solubilized along with 0.872 g/L of soluble total iron. During this period the numbers of planktonic bacteria increased from 2.4 x 106 to 1.0 x 108 cells/mL.