Isolation and characterization of Cr(VI) reducing Mammaliicoccus sciuri jv5 from municipal solid waste dumpsite soils

Cr(VI) is one of the most widely used elements in various industrial sectors and, hence, extensively found as a toxicant in the ecosystem. The biotransformation of Cr(VI) via microorganisms is considered an ecofriendly approach for its detoxification. The present study focused on the isolation of an indigenous bacterium from municipal solid waste dumpsite soils with relatively higher Cr(VI) resistance (>1000 mg L−1 in broth) and a 97% reduction of Cr(VI) (100 mg L−1) under conditions of 37 °C, pH 7, and 120 rpm in 48 h. The biochemical and 16 S rRNA gene sequencing showed that the isolate exhibits 99% similarity with Mammaliicoccus sciuri. Partial reductase gene sequences were retrieved, showing 96% similarity to NADPH-dependent FMN reductases. Fourier transform infrared spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy showed the presence of Cr products on bacterial cells. X-ray photoelectron spectroscopic analysis confirmed the valence state of the residual Cr present as Cr(III). Furthermore, quantitative localization of reduced Cr products and transmission electron microscopic analysis confirmed the intracellular accumulation of the Cr(III). A multifaceted mechanism, including surface adsorption and bioaccumulation after biotransformation, confers a potential solid identity for the strain Mammaliicoccus sciuri jv5 toward Cr(VI) remediation in the Cr polluted environment niche.