Evaluation of arsenic removal potential of arsenic resistant bacteria with the role of physiological and genomic factors

Abstract

Arsenic contamination in drinking ground water has reached an alarming situation in parts of Bengal Delta, India. Development of methods for removal of arsenic contamination from the drinking water will be of great importance for the mankind. The main objective of this study was to isolate and characterize arsenic resistant bacteria (ARB) from the surface water of Kabar Wetland (6.066±0.23 mg/L As) located in Begusarai district of Bihar province (25°35’N and 86°10’E), India. Bacteria were isolated from water sample by enrichment culture technique and based on their 16S rRNA gene sequences, isolates tolerating 150mM arsenate/As(V) were identified as <i>Paracoccus </i> sp strain NC-A and <i>Alcaligenes</i> <i>faecalis </i> strain NC-B, whereas isolate resistant to 30mM arsenite/As(III) was identified as <i>Stenotrophomonas </i> sp. strain NC-C<i>.</i> Bioinformatic analysis of genome of reference strains revealed the presence of different arsenic resistance (<i>ars</i>) genes. Arsenic removal efficiency of isolates was evaluated and it was observed that As(V) resistant strains of <i>Paracoccus </i> and <i>Alcaligenes</i> removed up to 84.5% and 93% arsenic, respectively from the external growth medium, whereas, As(III) resistant strain of <i>Stenotrophomonas</i> sp. removed 79.6% arsenic from the culture broth. The optimum pH, temperature and nutrient levels (peptone water) for arsenic removal by these isolates were 7.0, 35°C and (PW/60), respectively. These observations suggest that the strains described in this study are capable of removing arsenic from the dilute solutions, and hence being natural isolates, these strains can be easily used in the purification of arsenic contaminated water and thereby check the increasing arsenic toxicity in human food chain.