Cr(VI) detoxification characteristics of salt-tolerant Staphylococcus sp. YZ-1 and Bacillus cereus CC-1

Abstract:

[Background] Cr(VI) reducing bacteria are important for bioremediation of high salinity Cr(VI) containing wastewater. However, Cr(VI) detoxification characteristics of salt-tolerant bacteria are little known. [Objective] Comparing the Cr(VI) removal performance and resistant mechanism of two salt-tolerant strains. Identifying the putative Cr(VI) resistance related genes from the result of genome sequencing. Constructing the microbial consortium of Cr(VI) reducing bacteria, and investigate the synergy effect on pollutant removal. [Methods] Staphylococcus sp. YZ-1 was isolated from Chaka salt lake in Qinghai province, and its Cr(VI) removal performance was compared with a previously identified strain Bacillus cereus CC-1. Genome sequencing was used to identify the putative Cr(VI) resistance related genes. [Results] Staphylococcus sp. YZ-1 and Bacillus cereus CC-1 both had Cr(VI) removal characteristics, but the latter was superior. When the Cr(VI) concentration was 0.1 mmol/L, Bacillus cereus CC-1 removed 95.3% Cr(VI) but Staphylococcus sp. YZ-1 only 40.1% in 12 hours. Strain YZ-1 reduced Cr(VI) to organic Cr(III) species, whereas CC-1 removed Cr(VI) through reduction and absorption. Genes encoding pump protein and NAD(P)H oxidoreductase were found in the genome of YZ-1, whereas genes encoding chromate transporter protein ChrA and cytochrome c oxidoreductase were found in the genome of CC-1. The mixture cultures of these strains could self-flocculate and carried the reduced Te0 as participation. The Cr(VI) reductase of YZ-1 was inducible enzyme, and the Cr(VI) reductase of CC-1 was constitutive enzyme. The related encoding genes of multiple Cr(VI) resistance mechanisms maid simultaneously in bacteria. [Conclusion] Staphylococcus sp. YZ-1 and Bacillus cereus CC-1 both are salt-tolerant Cr(VI) reducing bacteria. After mix culture of the two bacteria, the auto-aggregation and Te(IV) reducing performance of YZ-1 may extent the application of Cr(VI) resistant consortium in wastewater treatment.