Arsenate bioremediation by <i>Bacillus pumilus </i> through <i> cis-</i> acting of both arB and subtilisin genes

Abstract

Accumulation of arsenate in the natural environment causes serious environmental problems. Hence, the main goal of the present study was to isolate arsenic-resistant bacteria capable of removing arsenic from the environment. Screening of 30 bacterial isolates, isolated from arsenate-contaminated soil, revealed a highly resistant strain, which could tolerate up to 2g L^-1 of arsenate. This strain was identified as <i>Bacillus pumilus</i> based on the partial sequences of 16S rRNA. Molecular tools, such as, differential display-PCR, cloning and sequencing were used to screen and identify genes that can be involved in arsenate bioremoval. Differential display for scanning the most abundant of induced/suppressed genes at different sodium arsenate concentrations of the bacterial genome indicated the significant induction of the two genes, arsenical pump membrane protein <i>(arB)</i> and subtilisin. It was noticed that the <i>arB</i> gene was up regulated at high arsenate concentrations, while subtilisin gene was induced at low concentrations. The results showed that <i>arB</i> gene and subtilisin were working together for reducing the arsenate effect through its hydrolysis by β-galactosidase enzyme. The study gives significant insight about the expected mechanism of both two genes for remediating arsenate-polluted ecosystems.