Comparative study of inorganic arsenic resistance of several strains of Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans

The growth characteristics of several strains of Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans were studied in the presence of soluble inorganic arsenic(III) and (V) with regard to media pH changes, total bacterial populations and sulfur oxidation rates. Most of these bacteria could reach large populations and have strong sulfur oxidation activity in the absence of arsenic. However, in the presence of up to 120 mM arsenite or arsenate, different strains showed different inorganic arsenic resistance. A. thiooxidans LYS and A. ferrooxidans BY-3 were two of the best performers which showed high arsenite resistance: up to 80 mM and 60 mM, respectively. On the other hand, A. thiooxidans JY and A. ferrooxidans TKY-2 could adapt up to 120 mM and 100 mM arsenate, respectively. These bacteria strains may play key roles in the bioleaching of arsenopyrite or in the bio-oxidation pretreatment of arsenic-bearing refractory gold sulfide ores and concentrates.