Arsenic Removing Soil Indigenous Bacteria of Hyper Arsenic Contaminated Region in Bihar

Three arsenic hyper tolerant bacteria were isolated and identified as Acinetobacter calcoaceticus J1, Agrobacterium tumefaciens J2 and Bacillus cereus DAS3, with MICs (minimal inhibitory concentrations) were found 310, 300, 280 mM As(V) and 25, 3, 35 mM As(III), respectively. All the three isolates were found efficient in removing arsenic both As(V) as well as As(III) from the growth medium. Maximum removal of As(V) observed was 56.7% by DAS3 and of As(III) was 68% by J2. pH and nutrients strength of medium were found as factors to modulate the potential of As removal by bacteria. Maximum values of removal for As(V) was 64% by DAS3 on 20% dilution of medium and for As(III) was 76% by J2 at pH 8. Study of bacterial growth and chemical toxicity (DHA) had drawn picture of better arsenic [As(V) and As(III)] tolerance than other osmotic stress [NaCl or PEG 6000], indicating the existence of cross-protection between arsenic toxicity and arsenic generated osmotic stress.