Highly Cr(vi)-tolerant Staphylococcus simulans assisting chromate evacuation from tannery effluent

Chromium( ) contaminated sites have been targeted for studying highly chromate-resistant bacteria. From a total of 23 Cr( )-resistant bacteria isolated on Luria-Bertani agar medium supplemented with K CrO (1,500 μg/mL), only one strain UT8 ( ) was able to tolerate high concentration of chromate, i.e., up to 200 mg/mL in agar medium from tannery effluent. In acetate minimal medium (AMM), it showed maximum tolerance of up to 2,500 μg/mL. Cr( ) removal potential was 94.6% after 24 h (K CrO 1,500 μg/mL). Parametric conditions were optimized in AMM to attain maximum chromate removal. Exopolysaccharides extracted from bacterial cells exposed to chromate exhibited major absorption shifts from 2,500 to 500 cm revealed by Fourier transform infrared spectroscopy. Energy-disperse X-ray spectroscopy further confirmed the adsorption of oxyanions to the bacterial cells. Surface topography of the Cr( ) treated cells showed transformation into concave shape by scanning electron microscopy. The presence of resistance genes, i.e., chromate reductase ( ) and class I integrase ( ), further confirmed tolerance toward chromate. Microarray data analysis of transcriptional gene expression suggested upregulation of gene cluster under chromate exposure. Concisely, the present investigations revealed the potential of to be an effective candidate for chromate reclamation of wastewater. Chromate-resistant bacterium UT8 was isolated from tannery effluent. The cultural conditions for strain UT8 were optimized for maximum chromate removal and exopolymer production. SEM-EDS analysis of strain UT8 revealed variations under Cr( ) stress related to nonstress. The FTIR analysis of exopolymer under chromate stress indicated vibrational shifts for metal ion chelation.