Accumulation of Amorphous Cr(III)–Te(IV) Nanoparticles on the Surface of <i>Shewanella oneidensis</i> MR‑1 through Reduction of Cr(VI)

Industrial effluents constitute a major source of metal pollution of aquatic bodies. Moreover, due to their environmental persistence, toxic metal pollution is of special concern. Microbial reduction is considered a promising strategy for toxic metal removal among the several methods available for metal remediation. Here, we describe the coremediation of toxic Cr­(VI) and Te­(IV) by the dissimilatory metal reducing bacterium-<i>Shewanella oneidensis</i> MR-1. In the presence of both Cr­(VI) and Te­(IV), <i>S. oneidensis</i> MR-1 reduced Cr­(VI) to the less toxic Cr­(III) form, but not Te­(IV) to Te(0). The reduced Cr­(III) ions complexed rapidly with Te­(IV) ions and were precipitated from the cell cultures. Electron microscopic analyses revealed that the Cr–Te complexed nanoparticles localized on the bacterial outer membranes. K-edge X-ray absorption spectrometric analyses demonstrated that Cr­(III) produced by <i>S. oneidensis</i> MR-1was rapidly complexed with Te­(IV) ions, followed by formation of amorphous Cr­(III)–Te­(IV) nanoparticles on the cell surface. Our results could be applied for the simultaneous sequestration and detoxification of both Cr­(VI) and Te­(IV) as well as for the preparation of nanomaterials through environmental friendly processes.