固定菌群强化降解土壤中氯苯的生物膜作用机制

Decontamination of chlorobenzene in soil is of worldwide concern. Our previous results showed that the degradation efficiency of 1,2,4-trichlorobenzene (TCB) - a model compound for chlorobenzenes - in soil by an immobilized microbial community (as a biofilm) was higher than that by both the single strain and the non-immobilized community. This project, from the perspective of quorum sensing in biofilm, is aimed at finding out why the immobilized microbial community shows the highest degradation efficiency. The degrading bacteria (Bordetella sp.) and the community immobilized on clay particles will be used in the research; fluoresence in-situ hybridization, coupled with confocol laser scanning microscope, will be used to record bacterial immobilization on clay particles with a view to understanding the biofilm formation process. A transportation experiment and section technique will be combined to investigate bacteria reproduction and release in soil from the immobilized micriobial community, the immobilized single strain and the planktonic micriobial community so as to clarify the influence of quorum sensing on bacterial colonization in soil. Degradation of TCB will be quantified by isotopic tracer technique; Ultra Performance Liquid Chromatography will be applied to monitor the production of sensing signal - acylhomoserine lactones (AHLs) - during the degradation of TCB. These results will be combined with the adsorption/desorption of AHLs on clay and dissipation of AHLs in soil to illustrate the function of quorum sensing on the enhancement of TCB degradation. The influence of quorum sensing in biofilm on the enhanced degradation of chlorobenzenes in soil by an immobilized microbial community will be elucidated for possible application - of immobilized microorganisms - in the remediation of cholorbenzene-contaminated soil.

针对氯苯土壤污染，以1,2,4-三氯苯（TCB）为代表，在前期研究（黏土颗粒固定菌群降解土壤中TCB效率比游离菌群和固定单菌都高）基础上，从生物膜群体感应着手，研究固定菌群强化降解土壤中氯苯的生物膜作用机制。以黏土颗粒固定降解菌（博德特氏菌）与降解菌群为研究对象，采用荧光原位杂交-电镜耦合技术记录载体中细菌的吸附固定，探明生物膜形成过程；采用迁移实验结合切片技术，研究固定菌群、固定单菌与游离菌群在土壤中的繁殖与释放特征，阐明生物膜群体感应对土壤中降解菌定殖行为影响规律；通过同位素示踪对比分析固定菌群、固定单菌与游离菌群降解TCB效率，超高效液相色谱监测降解过程中感应物质-酰基高丝氨酸内酯（AHLs）的生成动态，结合AHLs在载体中的吸附/解吸及其在土壤中的消解动力学，揭示生物膜群体感应促进TCB降解规律；综上阐明固定菌群高效降解土壤中氯苯的机理，为固定化微生物修复氯苯污染土壤提供理论基础。

随着我国工业的快速发展，持久性有机污染物污染土壤面积不断扩大，开展污染土壤修复与治理已成为我国生态环境保护的重要内容。微生物降解是消除土壤中持久性有机污染物的最主要途径，然而，在实际应用中，功能微生物接种到土壤后，往往难以与土著微生物竞争，甚至被土著微生物捕食等，阻碍了生物修复技术的应用。针对该科学问题，以氯苯为代表，在前期研究基础上，研究了固定菌群强化降解土壤中氯苯的生物膜作用机制。以黏土颗粒固定降解菌（博德特氏菌）与降解菌群为研究对象，采用荧光原位杂交-电镜耦合技术记录了载体中细菌的吸附固定，探明了生物膜的形成过程；利用是否去除降解菌的胞外聚合物进行降解培养实验，揭示了生物膜的组分-胞外聚合物在污染物的传质与降解过程中的作用规律与机制；通过同位素示踪对比分析了固定菌群与游离菌群降解三氯苯的效率，酶联免疫监测了降解过程中信号分子—酰基高丝氨酸内酯的生成动态，揭示了生物膜信号分子与污染物降解的相关关系；并采用FT-ICR-MS对信号分子及其降解产物进行了结构鉴定，解析其降解转化途径，结合信号分子在载体中的吸附与分布规律及其消解动力学，揭示了生物膜促进三氯苯降解规律，综上阐明了固定菌群高效降解土壤中氯苯的机理，为固定化微生物修复氯苯污染土壤提供理论基础。