Enhanced Detoxification of Arsenic Under Carbon Starvation: A New Insight into Microbial Arsenic Physiology

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Abstract
Nutrient availability in nature influenced the microbial ecology and behavior present in existing environment. In this study, we have focused on isolation of arsenic-oxidizing cultures from arsenic devoid environment and studied effect of carbon starvation on rate of arsenite oxidation. In spite of the absence of arsenic, a total of 40 heterotrophic, aerobic, arsenic-transforming bacterial strains representing 18 different genera were identified. Nineteen bacterial species were isolated from tannery effluent and twenty-one from tannery soil. A strong co-relation between the carbon starvation and arsenic oxidation potential of the isolates obtained from the said niche was observed. Interestingly, low carbon content enhanced the arsenic oxidation ability of the strains across different genera in Proteobacteria obtained. This represents the impact of physiological response of carbon metabolism under metal stress conditions. Enhanced arsenic-oxidizing ability of the strains was validated by the presence of aio gene and RT-PCR, where 0.5- to 26-fold up-regulation of arsenite oxidase gene in different genera was observed. The cultures isolated from tannery environment in this study show predominantly arsenic oxidation ability. This detoxification of arsenic in lack of carbon content can aid in effective in situ arsenic bioremediation.

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