耐盐菌Staphylococcus sp. YZ-1和Bacillus cereus CC-1的Cr(VI)脱毒特性与机理

背景]高盐含铬废水的去除过程中,Cr(Ⅵ)还原菌是研究者关注的重点,但目前对耐盐菌株的Cr(Ⅵ)脱毒特性及机理的分析仍较少。目的]比较两株耐盐菌株的Cr(Ⅵ)移除特性,并区分Cr(Ⅵ)耐受机制的差异;通过基因组测序分析,从基因层面推测铬耐受相关基因;构建铬还原菌的混菌体系,考察两者对去除污染物的协同作用。方法]从青海茶卡盐湖分离耐盐菌Staphylococcus sp.YZ-1,与Bacillus cereus CC-1进行基础特性和Cr(Ⅵ)去除性能的比较,并通过全基因组序列的分析验证特性测试的结果。结果]两株菌都具有铬移除特性,但CC-1的铬移除效率更高,在初始Cr(Ⅵ)浓度为0.1 mmol/L情况下,CC-1能在12h内移除95.3%的Cr(Ⅵ),而YZ-1只能移除40.1%。在进一步实验中发现YZ-1只能对Cr(Ⅵ)进行还原,将其转化为可溶的有机态Cr(Ⅲ),而CC-1能同时对Cr(Ⅵ)进行还原和吸附。全基因组分析发现YZ-1具有编码外排泵蛋白的基因和编码NAD(P)H氧化还原酶的基因,而CC-1具有编码铬转运蛋白ChrA和细胞色素C氧化还原酶的基因。两株菌的混菌体系在处理含Cr(Ⅵ)、Te(Ⅳ)的废水时,菌群能将还原产物聚集成团并沉淀到底部。结论]菌株YZ-1和CC-1均为耐盐铬还原菌,但YZ-1中的铬还原酶为诱导型酶,CC-1则为组成型酶。基因组数据分析鉴别出两者可能同时存在多种铬耐受机制相关编码基因。混合菌群可以结合YZ-1的自絮凝特性和两者均有的Te(Ⅳ)/Cr(Ⅵ)还原活性,具有潜在的实用价值。

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

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.