重金属胁迫对胞外聚合物的影响及与土壤中PAHs降解的关系

Microbial action is the core of bioremediation for polycyclic aromatic hydrocarbons (PAHs) contaminated soil, and the toxicity of heavy metals entering soil with PAHs to microorganisms affects EPS secretion and PAHs biodegradation. In the present project, EPS isolated from PAHs-degradation strains are selected as the research objectives, the adsorption, degradation and simulation experiment are carried out after Cu2+ and Pb2+ are introduced into PAHs contaminated soils. The secreting process, surface property and microstructure of EPS under heavy metals stress will be studied. Under heavy metals stress, the relationship of dioxygenase expression and protein profiling in PAHs-degradation strains and EPS to PAHs degradation are analyzed using molecular techniques, and the dioxygenase genes and proteins which play an important role in PAHs degradation will be indentifed. The co-metabolic degradation process of PAHs with EPS as cosubstrate, and the effect of EPS component on PAHs degradation will be illuminated. The effect of heavy metal-binding EPS on the desorption of PAHs from soil surfaces under heavy metals stress will be investigated. Base on these results, the project can provide support information for the migrating behavior of PAHs from soil surface to cell surface through EPS under heavy metals stress, and is of significance for further development of PAHs contaminated soil remediation.

微生物修复是多环芳烃（PAHs）污染土壤生物修复的核心技术，随PAHs进入土壤的重金属毒害微生物影响胞外聚合物（EPS）分泌，影响PAHs修复效果。本项目以PAHs高效降解菌EPS为研究对象，添加Cu2+、Pb2+到PAHs污染体系中进行吸附、降解与模拟实验，结合分子生物学手段，研究重金属胁迫对PAHs降解菌EPS产生过程、表面特性及微观结构的影响；分析重金属胁迫下PAHs降解菌细胞内及EPS中双加氧酶基因表达、相关蛋白特征与PAHs降解效果的关系，识别参与PAHs降解的关键加氧酶基因；阐明重金属胁迫下EPS共基质时微生物对PAHs的共代谢降解过程及EPS组分对PAHs降解效果的影响；探讨重金属结合态EPS对土壤表面PAHs的增溶作用。本项目研究成果为揭示重金属胁迫下土壤表面PAHs经EPS到细胞壁的迁移转化行为提供理论支持，为PAHs污染土壤修复理论与技术的进一步发展奠定基础。

自然环境中，随PAHs进入土壤的重金属毒害微生物影响EPS分泌过程，进而影响PAHs的修复效果。本项目以PAHs高效降解菌EPS为研究对象，添加重金属到PAHs污染体系中进行吸附与降解实验，借助分子生物学手段，研究重金属胁迫对PAHs降解菌EPS产生过程及表面特性的影响，分析重金属胁迫下 EPS 对 PAHs 降解的酶促作用、共基质代谢作用和增溶作用。研究发现，重金属胁迫促进毛霉对土壤芘的降解，且外加碳源时芘的降解率大小顺序：5%葡萄糖＞2%葡萄糖＞原体系；土壤pH值改变时，芘降解效果：pH值8.2＞pH值7.2＞pH值6.2。铜铅离子胁迫明显影响毛霉EPS的EPS产生量（TOC）、多糖成分含量、蛋白质含量、表面张力、乳化指数和Zeta电位的值（绝对值）等多项指标，EPS各项指标值随铜铅离子浓度（0-80 mg·L-1）增大而增加；当铜铅离子浓度大于80 mg·L-1时，除乳化指数外，其他指标值显著降低。重金属胁迫促进分枝杆菌向胞外EPS中释放加氧酶，且EPS影响菌体中的蛋白含量：去EPS后菌体<带EPS菌体；Pb2+胁迫下，辅助基质EPS和芘抑制液相体系中双加氧酶GP基因产生，但能提高分枝杆菌指数生长期对PAHs的降解能力；土壤中同时引入EPS和分枝杆菌，提高土壤中PAHs降解菌的生长及PAHs的降解效果。芘初始污染浓度、EPS浓度、体系温度均影响土壤中芘的解吸效果，重金属胁迫抑制EPS对污染土壤中芘的解吸效果。本项目研究结果揭示了重金属胁迫对微生物 EPS 产生及其转运 PAHs 过程的影响机制，有助于深入认识根际环境中微生物与 PAHs 相互作用关系，完善污染土壤的微生物修复机制，为 PAHs 污染土壤生物修复理论与技术进一步发展提供理论基础。