Hexavalent Chromium Reduction by Microbacterium oleivorans A1: A Possible Mechanism of Chromate -Detoxification and -Bioremediation

Background Hexavalent chromium (Cr(6+)) contamination is one of the mejor problems of environmental protection for its carcinogenic effect on human health. Remediation of Cr(6+) contaminated environment thus becomes highest priority. Methods A Gram positive tiny rod shaped chromate (Cr(6+)) reducing bacterium strain A1 was isolated from uranium ore collected from Jaduguda, East Singhbhum, Jharkhand. The strain was identified and characterized in terms of its potential to reduce more toxic Cr(6+) to its less toxic form for its application in bioremediation of Cr(6+) contaminated environments. Results 16S rRNA gene based phylogentic analysis identified the strain as Microbacterium oleivorans. Along with Cr(6+), the strain showed resistance to other heavy metals including Ag, Cu, Co, Hg, Ni and Zn also. Complete reduction of Cr(6+) (750 µM) was achieved within 84 h with optimum reduction at pH 9 and 30°C. Effect of different parameters including cell mass concentration, pH, induction with Cr(6+), SO4 = ion, heavy metals, etc. on Cr(6+) reduction were studied thoroughly at resting cell condition to study its potential towards Cr(6+) bioremediation. Chromate reductase gene (chrA) was detected within this strain. Conclusion Along with presence of appropriate genetic determinant, efficient Cr(6+) reduction ability of the strain indicated its potential for developing redox based Cr(6+) remediation system for varied concentrations of Cr6+ under a wide range of environmental conditions. Patent data have suggested the efficient application of Cr(6+) reducing bacteria in cleaning up of Cr(6+) contaminated environments.