Bacterial bio-mobilization and -sequestration of arsenic in contaminated paddy fields of West Bengal, India

Abstract

One hundred and forty nine bacterial strains were isolated from arsenic contaminated paddy field soil of West Bengal following enrichment upon As(III), As(V) and control plates. The maximum tolerable concentration (MTC) of the bacterial population isolated towards As(V) and As(III) was found to be 600 mM and 10 mM, respectively. Eight isolates with varying MTC values were chosen to study their As ad-/ab-sorption abilities to form a consortium for bioremedial application to As contaminated soil. The As(III) or As(V) ab-/ad-sorption abilities of the chosen isolates positively correlated to their respective As(III) or As(V) MTC values. Phylogenetic analyses of the isolates affiliate them to be the members of genera Bacillus, Paenibacillus, Staphylococcus and Ralstonia. A consortium comprising the eight chosen isolates were incubated under eight microcosm conditions with combinations of flooded or non-flooded, sterile or non-sterile soils with low (6.1 mg/kg) or moderately high (19.5 mg/kg) As concentrations. The consortium revealed an overall appreciable activity of As mobilization and sequestration with best cellular As accumulation under non-flooded low As concentration soil incubation. While the microcosm with highly contaminated soil allowed best microbial As sequestration under flooded condition when incubated solely in sterile soil. Bacterial sequestration and removal of the toxic metalloid may find important implications in As bioremediation in agricultural fields hence, reducing the bioavailability of this toxic element for further translocation into the crop. The study, thereby, provides a novel insight for potential use of the consortia in bioremediating As contaminated soil through microbial biosequestration approach.