Cr(VI)-bioremediation mechanism of a novel strain Bacillus paramycoides Cr6 with the powerful ability to remove Cr(VI) from contaminated water

This research provided an excellent novel hexavalent chromium (Cr(VI))-removal bacterium, Bacillus para-mycoides Cr6, and investigated its removal mechanism from the perspective of molecular biology. Cr6 could resist up to 2500 mg/L Cr(VI), and the removal rate of 2000 mg/L Cr(VI) reached 67.3% under the optimal culture conditions of 220 r/min, pH 8 and 31 celcius. When the initial concentration of Cr(VI) was 200 mg/L, Cr6 had a removal rate of 100% within 18 h. The differential transcriptome analysis identified two key structural genes named bcr005 and bcb765 of Cr6, which were upregulated by Cr(VI). Their functions were predicted and further confirmed by bioinformatic analyses and in vitro experiments. bcr005 encodes Cr(VI)-reductase BCR005, and bcb765 encodes Cr(VI)-binding protein BCB765. Real-time fluorescent quantitative PCRs were performed, and the data illustrated a parallel pathway (one is Cr(VI) reduction, and the other is Cr(VI) immobilisation) of Cr6 to remove Cr(VI), which relies on the synergistic expression of the genes bcr005 and bcb765 induced by different concentrations of Cr(VI). In summary, a deeper molecular mechanism of Cr(VI) microorganism removal was elaborated; Bacillus paramycoides Cr6 was an exceptional novel Cr(VI)-removed bacterial resource, while BCR005 and BCB765 were two new-found efficient enzymes that have potential practical applications for sustainable microbial remediation of Cr-contaminated water.

Automated summary

This research discovered an exceptional novel bacterium, Bacillus para-mycoides Cr6, which is capable of removing hexavalent chromium (Cr(VI)). The study investigated the molecular biology behind its removal mechanism and identified two key genes, bcr005 and bcb765, that play a role in the removal process. These genes encode the Cr(VI)-reductase BCR005 and Cr(VI)-binding protein BCB765, respectively, and their synergistic expression is essential for Cr(VI) removal by Cr6. This research provides a deeper understanding of the molecular mechanism of Cr(VI) removal and highlights the potential practical applications of BCR005 and BCB765 enzymes in the remediation of Cr-contaminated water.