凤眼莲根际耐Cd、Zn细菌的分离鉴定及对Cd、Zn去除效果研究

从凤眼莲根系分离纯化出3株耐Cd和Zn的细菌R12、R15、R16。重金属耐受性实验证明3株菌均可以耐受10 mg·L~(-1)Cd~(2+)和30 mg·L~(-1)Zn~(2+)。通过16S rRNA基因测序和同源性分析,菌株R12、R15被鉴定为假单胞菌属(Pseudomonas),R16为寡养单胞菌属(Stenotrophomonas)。实验研究了菌株对重金属的去除效果,结果显示:单位质量的R12、R16对Cd和Zn的去除量均表现为随时间延长而增加,R15则表现为随时间延长先减小后增加,3株细菌对Cd和Zn的去除率均在36 h达到峰值。其中R16对Cd和Zn的去除效果最好,单位质量最大去除量分别为0.17 mg·kg~(-1)和2.71 mg·kg~(-1),最大去除率为41%和16%。凤眼莲-耐重金属微生物联合培养对Cd和Zn的富集影响结果发现,R12、R16影响凤眼莲对Cd的富集主要表现为抑制Cd进入凤眼莲根部,R15则表现为调节Cd进入凤眼莲根部及其在植株中的迁移。3株菌对凤眼莲富集Zn的影响主要表现为调控Zn在植株中的迁移。

Isolation and identification of Cd-and Zn-resistant bacteria in the rhizosphere of Eichhornia crassipes and their effects on Cd and Zn removal

Three Cd-and Zn-resistant bacteria strains(R12, R15, and R16) were isolated from the rhizosphere of Eichhornia crassipes. Heavy metal tolerance tests indicated that the strains could tolerate up to 10 mg·L^-1 and 30 mg·L^-1 of Cd²⁺ and Zn²⁺, respectively, and 16S rRNA sequence analyses identified isolates R12 and R15 as Pseudomonas and isolate R16 as Stenotrophomonas. The results on the effect of strains on the removal of heavy metals during 36 h showed that the amount of Cd and Zn removed by R12 and R16 increased with time, whereas that removed by R15 first decreased and then increased, and the amount of Cd and Zn removed by all the strains reached a maximum after 36 h. Among the three strains, R16 was the most capable of removing Cd and Zn, with maximum removal amounts of 0.17 mg·kg^-1 and 2.71 mg·kg^-1 Cd and Zn, respectively, and maximum removal rates of 41% and 16%. Furthermore, the co-culture of E. crassipes and the rhizosphere isolates on Cd-and Zn-enriched substrate indicated that R12 and R16 mainly affect the Cd enrichment of E. crassipes by inhibiting the entry of Cd ions into the roots, whereas R15 affected Cd enrichment by regulating both the entry of Cd ions into the roots and the migration of Cd ions inside plants. The three strains all affected Zn enrichment by regulating the migration of Zn ions inside the plants.