重金属和抗生素复合污染的微生物生态效应及其对硝化细菌群落作用机制

With the development of modern industry and agriculture, joint pollution of traditional and emerging pollutants was found in soil environment. According to environmental pollution in China, typical soils (red soil, brown soil and cinnamon soill) were chosen, with traditional contaminants - heavy metals (Cu and Zn) and emerging contaminants - antibiotics (tetracyclines and macrolides) as test chemicals in this project. The research focused on the ecological effects of the bioavailability of heavy metals and antibiotics and their metabolites in joint pollution soil combined by heavy metals and antibiotics, as well as their molecular mechanism of the nitrifiying bacteria. Methods including analytical chemistry, molecular biology and bioinformatics methods were applied to study the ecological effects on microbial community structure, function and the key material circulation functional genes. The community structure of nitrifiying bacteria and nitrogen forms in soil were investigated to clarify the molecular mechanism of the nitrogen cycle in response to the joint pollution combined by heavy metals and antibiotics. The ecological effects of bioavailability of heavy metals and antibiotics and their metabolites in co-comtamination soil and their impact on microbial nitrogen cycle were revealed, providing a scientific basis for accurate evaluation of complex environmental pollution risks and ecological mechanisms of the nitrogen cycle.

随着现代工农业的快速发展，大量新型污染物进入环境，形成传统污染物与新型污染物复合污染。根据我国土壤污染现状，以红壤、棕壤和褐土为代表性土壤，重金属（Cu和Zn）和抗生素（四环素类和大环内酯类）为研究对象，研究重金属和抗生素复合污染中有效态的重金属和抗生素及其代谢产物联合作用对土壤微生物的生态效应，及其对硝化细菌群落作用的分子机理。采用分析化学、分子生物学和生物信息学等方法，系统研究复合污染对土壤微生物群落结构、代谢途径和物质循环功能基因的生态效应及其机理，深入研究复合污染对硝化细菌群落结构和功能的影响，结合土壤中氮素形态变化，阐明氮循环功能微生物对复合污染的分子响应机制，揭示复合污染中有效态重金属和抗生素及其代谢产物在土壤中转归的微生物生态效应，及其对氮循环微生物影响的内在联系，为准确评价复合污染生态环境风险及其对氮循环影响机制提供科学依据。

畜禽养殖业中饲料添加剂大量使用，会导致抗生素和重金属在土壤环境中大量积累。抗生素具有较多的极性官能团，容易和金属离子形成络合物产生复合污染，会对土壤生态环境安全构成威胁。本课题主要采取土培实验和大田实验的方法，以重金属和抗生素复合污染土壤为研究对象，通过传统方法结合实时定量PCR以及Illumina高通量测序法等分子生物学技术开展重金属和抗生素复合污染对土壤理化性质、土壤养分、土壤生物学特性、土壤微生物群落结构和功能多样性及土壤氮循环相关功能微生物多样性的联合毒性效应及其机理研究。研究表明：1）通过单一污染与复合污染盆栽实验发现，在农作物小麦不同生长期内，重金属单一污染与复合污染对土壤硝化细菌群落丰度都随着污染浓度增加逐渐降低，而抗生素单一污染却是随着污染浓度增加呈现抑制-刺激的现象。同时对比分析单一和复合污染土壤中不同形态氮的浓度水平、脲酶活性及土壤微生物碳源利用能力，初步揭示了抗生素和重金属复合污染的联合效应机理；2）通过复合污染大田实验发现，四环素类抗生素的残留量最高，环境风险较大，结合土壤中重金属和抗生素及其代谢产物的分布特征、不同形态氮的变化、土壤生物学功能、土壤微生物结构多样性以及土壤氮循环功能细菌多样性的变化，阐明了不同有效态的重金属、抗生素及抗生素代谢产物对土壤微生物多样性的影响机理。本研究初步揭示了复合污染对氮循环的影响机理，为开展土壤生态环境风险评价和土壤环境治理提供了科学参考。