天然共代谢底物促进土壤中多氯联苯微生物降解机理研究

Polychlorinated biphenyls (PCBs) are typical persistent organic pollutants. They can be easily absorbed onto soil particles and are able to accumulate in soil after they are released into the environment. Thus, their potential hazard to soil environment can not be neglected. Microbial degradation is an important way for PCBs removal in soil. Lower chlorinated PCBs (Cl≤4) are degraded mainly by cometabolism. The degradation of PCBs can be significantly promoted by natural cometabolism substrates. However, the mechanism of microbial degradation of PCBs promoted by these compounds is still unclear. Therefore, this project will study the effect of the natural cometabolism substrates on growth and metabolism of microorganisms. Then the relationship between the molecular structure of the natural cometabolism substrates and their induction ability of enzymes, the response mechanism of PCBs-degrading enzymes to the natural cometabolism substrates, and the influence of the natural cometabolism substrates on microbial community structure in soil will be studied thoroughly. Finally, the possible mechanism of microbial degradation of PCBs in soil promoted by the natural cometabolism substrates will be revealed. The results will provide scientific basis for the screening of natural cometabolism substrates and the utilization of these compounds for the remediation of PCBs-contaminated soil.

多氯联苯(Polychlorinated biphenyls，PCBs)是一类持久性有机污染物，流入环境后易被土壤颗粒吸附而蓄积在土壤中，从而对土壤环境造成危害。微生物降解是土壤中PCBs削减的途径之一，其中低氯代PCBs（Cl≤4）主要通过共代谢的方式被微生物氧化分解。在土壤中添加天然共代谢底物能显著促进低氯代PCBs的降解。然而，天然共代谢底物究竟通过哪些具体机制促进PCBs降解，尚不明确。本项目通过考察天然共代谢底物对微生物生长代谢的影响、分析天然共代谢底物的分子结构与其酶诱导能力之间的关系、探究PCBs降解酶系对天然共代谢底物的响应机制及天然共代谢底物对土壤微生物群落结构的影响，揭示天然共代谢底物促进土壤中PCBs微生物降解的机理。项目研究结果将为筛选天然共代谢底物、科学利用天然共代谢底物修复PCBs污染土壤提供理论依据。

微生物降解是土壤中PCBs削减的途径之一。研究表明添加天然共代谢底物能促进低氯代PCBs的好氧生物降解。但天然共代谢底物究竟通过哪些具体机制促进PCBs降解，尚不明确。本项目通过考察天然共代谢底物对微生物生长繁殖的影响、分析天然共代谢底物对PCBs降解相关基因转录翻译的影响以及研究天然共代谢底物强化土壤中PCBs微生物降解的效果，揭示天然共代谢底物促进土壤中PCBs微生物降解的机理。. 本项目研究发现天然共代谢底物（薄荷酮、水芹烯、松油烯、双戊烯等）在低浓度时可刺激微生物生长繁殖，浓度升高时则逐渐抑制微生物生长繁殖，呈现出了明显的低剂量刺激效应。PCBs降解菌株SS1、SS2、HC3均含有bph基因，分别分布于其环状染色体和环状质粒之上，且部分基因有多个拷贝。天然共代谢底物薄荷酮、双戊烯和水杨酸可以明显促进菌株HC3中bph基因的转录，但这几种共代谢底物促进bph基因转录及翻译的能力是否具有普适性（在不同微生物之间）仍有待继续探究。共代谢底物可以通过促进bph基因转录而强化微生物对PCBs的降解，但在实际应用中，共代谢底物添加量过高会抑制PCBs的生物降解，而且与共代谢底物相比，土水比（影响传质水平）和RAMEB（影响PCBs生物有效性）是影响PCBs降解的主要因素。项目研究结果可为筛选天然共代谢底物、科学利用天然共代谢底物修复PCBs污染土壤提供理论依据。