Docking assisted mechanistic elucidation of bio conversion of hexavalent chromium by Serratia marcescens AJRR-22 that is effective yet long term sustainable in bio-geosphere

[Display omitted] •Characterization of a Cr (VI) tolerant strain of Serratia marcescens AJRR-22.•Determination of Cr (VI) resistance in AJRR-22 with subsequent physiological changes.•Confirmation of intracellular NADH dependent bio-reduction by molecular docking.•Elucidate sustainability of AJRR-22 as potential candidate for Cr (VI) bioremediation. Environmental accumulation of hexavalent chromium [Cr(VI)] in the food chain can induce detrimental effects on plants and animals, which calls for effective remediation strategies using biological entities. The bacterium isolated from an iron mine in Odisha, India, is identified asSerratia marcescensAJRR-22. This multi-metal tolerant strain is capable of bio-converting up to 350 mg/L Cr(VI) within 72 h of incubation. Observable electron dense precipitates in transmission electron microscopic images, data patterns in fluorescence microscopy and flow cytometry clearly reveal the chromate reduction ability of the strain. The molecular study is depicted by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopic analyses. Furthermore, a simulation study to estimate the interactions of chromium bound flavin reductasewith predicted docked complexes suggests significant negative Gibbs free energy and a low inhibition constant (Ki), signifying strong spontaneous binding of Cr(VI) to the enzyme, which makes the strain an efficient candidate for chromium bioremediation.