两株多环芳烃降解菌协同对菲-镉污染的去除特性

Synergistic removal of phenanthrene and cadmium by two polycyclic aromatic hydrocarbon-degrading bacteria

摘要:

【目的】从污染土壤中分离筛选一株多环芳烃降解菌，并探究其与Pseudomonas aeruginosa B6-2构建的混菌体系对菲-镉复合污染的修复效能，以及微生物代谢特性对不同镉浓度赋存的响应特性，以期为复合污染的生物修复提供优良菌株资源及应用技术参考。【方法】采用富集驯化、筛选纯化方法得到一株多环芳烃降解菌，通过生理生化特征和16S rRNA基因序列分析进行鉴定。利用高效液相色谱法和电感耦合等离子体质谱法评估不同镉浓度赋存下各反应体系对菲和镉的去除效能；通过菌体细胞形态的扫描电镜观测及菌株代谢活性检测，探讨镉胁迫对菲生物降解过程的影响机制。【结果】筛选得到一株具有重金属耐受性和多环芳烃高效降解菌SZ-3，经鉴定为节杆菌属；降解菌协同体系(M)具有良好的菲降解效能和抗镉胁迫优势。镉胁迫浓度为0.5、10mg/L时，M对菲和镉的去除率分别高于85%、80%；镉胁迫浓度为25、50mg/L时，2种污染物的去除率均大于65%。扫描电镜分析表明，镉胁迫导致菌体表面粗糙且出现不同程度变形，菌体间黏附性和聚集性提高。反应周期内，邻苯二酚1,2-双加氧酶活性与电子传递体系活性随镉浓度增加而降低，两者变化与菲降解速率变化一致。【结论】Arthrobacter sp. SZ-3是一株PAHs高效降解菌，能与Pseudomonas aeruginosa B6-2协同高效修复菲-镉复合污染，随着初始镉胁迫浓度增加，混菌协同对目标污染物去除的优势显著。

关键词:复合污染;菲;重金属;协同去除;微生物修复;镉胁迫

Abstract:

[Objective] A polycyclic aromatic hydrocarbon (PAH)-degrading strain was isolated from the soil contaminated by PAHs. This strain was mixed with Pseudomonas aeruginosa B6-2 to construct a mixed bacterial system for remediation of the soil or liquid co-contaminated by phenanthrene and cadmium. We investigated the remediation efficiency and the response characteristics of microbial metabolism to Cd at different concentrations, aiming to provide bacterial resources and technology reference for the bioremediation of combined pollution. [Methods] The PAH-degrading strain was screened via enrichment, domestication, isolation, and purification and then identified by physio-biochemical tests and 16S rRNA gene sequence analysis. High performance liquid chromatography and inductively coupled plasma mass spectrometry were employed to evaluate the removal efficiency of phenanthrene and cadmium at different cadmium concentrations. Furthermore, the effects of cadmium stress on phenanthrene biodegradation were analyzed on the basis of cell morphology observed by scanning electron microscopy and metabolic activity. [Results] A novel strain SZ-3 with heavy metal tolerance and high PAH-degrading ability was screened out and identified as Arthrobacter. The mixed system (M) of the two degrading bacteria had high phenanthrene-degrading efficiency and resistance to cadmium stress. The removal rates of M for phenanthrene and cadmium were higher than 85% and 80%, respectively, at the cadmium concentrations of 0.5 mg/L and 10 mg/L. When the cadmium concentrations were 25 mg/L and 50 mg/L, M showed the removal rates higher than 65% for the two pollutants. Cadmium stress increased the surface roughness, led to different degrees of cell deformation, and strengthened the adhesion and aggregation between cells. Both catechol 1,2-dioxygenase activity and electron transport system activity decreased with the increase in cadmium concentration during the reaction cycle, which was consistent with the variation of phenanthrene degradation rate. [Conclusion] Arthrobacter sp. SZ-3 is a strain with high PAH-degrading efficiency, which, together with P. aeruginosa B6-2, can efficiently remediate the soil co-contaminated by phenanthrene and cadmium. The two strains demonstrated significant synergistic effect on the removal of target pollutants.

Key words:co-contamination;phenanthrene;heavy metals;synergistic removal;microbial remediation;cadmium stress