Arsenic Bioremediation Potential of Arsenite Oxidizing Bacteria Isolated from Geogenic and Anthropogenically Contaminated Soil

The soil of many places of eastern India contains high amount of arsenic, due to several geogenic activities in this area. In the specific regions of the country where there is no such type of Geogenic activities, the soil is found to be almost free of arsenic. In such places where there are industries, the soil is being contaminated with the arsenic due to anthropogenic activities. One of such site which was selected for the study was in close vicinity to the textile industries in Jaipur, Rajasthan, India discharging their effluents having 423 μg/g arsenic. While the soil sample collected from the far eastern part of Tezpur Assam, India, contaminated by Geogenic sources contained 443μg/g arsenic. Four arsenite resistant bacterial strains were isolated from each of the samples. Strains SE-3 and TB-1 isolated from Jaipur and Tezpur, respectively showed highest minimum inhibitory concentration of 46.5mM and 38.7mM sodium arsenite. Based on 16S rDNA sequencing and nucleotide homology and Phylogenetics analysis strain, SE-3 was identified as Pseudomonas sp. SE-3 (accession no. KP730605) and TB-1 as Bacterium TB-1 (accession no KP866680). Complete oxidation of arsenite to less toxic form arsenate was observed in Pseudomonas sp. SE-3, while 64.6% by Bacterium TB-1. The arsenite oxidation was supported on the molecular level by confirming the presence of aox gene by PCR amplification. The enzyme activity of arsenite oxidase was also established. Arsenic hyper tolerant bacteria isolated from these soils having arsenite oxidizing ability show a promising way for the bioremediation of arsenic in contaminated soil.