Mechanism of arsenic resistance prevalent in Bacillus species isolated from soil and ground water sources of India

Abstract

Arsenic is a naturally occurring element and its contamination of soil and groundwater is a major threat to the environment and human health. The ubiquity of arsenic in the environment has led to the evolution of the arsenic defence mechanism in certain microbes. The present study highlights identical mechanisms of arsenic resistance in two bacterial strains, namely AG24 and AGM13, which were taken from two different ecosources and states of India. The phylogenetic analysis of the strains using 16S rDNA sequence revealed both strains to be under the genus ‘Bacillus’. Furthermore, arsC gene was amplified from the strains, cloned and sequenced. The homology of the sequences of the two strains, when compared with available database using BLASTn search, showed that the 300bp amplicons obtained in both strains possess a partial arsC gene sequence which codes for arsenate reductase, an enzyme involved in the reduction of arsenate to arsenite, which is then effluxed out of the cell. Nevertheless, atomic absorption spectroscopy and scanning electron microscopy analysis of both strains also strengthen the presence of the efflux mechanism. Thus, the presence of a similar mechanism of resistance in both strains suggests the possible role of lateral gene transfer from soil to water system and vice versa which is an alarming situation for global concern.