Selenite bioremediation by food-grade probiotic Lactobacillus casei ATCC 393: insights from proteomics analysis

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Microorganisms capable of converting toxic selenite into elemental selenium (Se0) are considered as an important and effective approach for bioremediation of Se contamination. In this study, we investigated the mechanism of reducing selenite to Se0 and forming Se nanoparticles (SeNPs) by food-grade probiotic Lactobacillus casei ATCC 393 (L. casei ATCC 393) through proteomics analysis. Proteomics analysis revealed that selenite induced a significant increase in the expression of glutaredoxin, oxidoreductase, and ATP binding cassette (ABC) transporter, which has the ability to transport glutathione (GSH) and selenite. Selenite treatment significantly increased the CydC and CydD (putative cysteine and glutathione importer, ABC transporter) mRNA expression level, GSH content and GSH reductase activity. Furthermore, supplementation with an additional GSH significantly increased the reduction rate of selenite, while GSH depletion significantly inhibited the reduction of selenite, indicating that GSH-mediated Painter-type reaction may be the main pathway of selenite reduction in L. casei ATCC 393. Moreover, nitrate reductase also participates in the reduction process of selenite, but it is not the primary factor.

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