环境压力对城市河流细菌抗生素耐药性的选择及散播机制的研究

The urban river is a natural water to accept a variety of waste and recycled waters. It also accepts the emerging pollution of antibiotic resistant genes (ARGs) which result from the extensive use of antibiotics by human. The antibiotic resistance of bacteria will affect the river ecosystem and even threat to human health. It is worth asking how the aquatic environmental pressures caused by pollutants such as antibiotics and heavy metals select antibiotic resistance in the natural water and how they affect the dissemination of ARGs. In the proposed project, we will choose 3 waters with contaminated gradient disconnected by rubber dam as the experiment place in Ba River, Xi’an. The techniques of metagenomics and bacteria whole genome sequencing, gene transfer assay of ARGs and traditional methods for microbiology will be employed. The genotypes and phenotypes of the antibiotic resistance for 3 bacteria compartments from water column, sediment and intestinal tract of fish will be analyzed and compared. The selection of antibiotic resistance under environmental pressures from antibiotics, heavy metal and other ecological factors will be determined. The mechanism for the acquired antibiotic resistance for several dominant species of antibiotic resistant bacteria in water column will be explored. The potential gene transfer pathway of ARGs from bacteria of water column or sediment to intestinal tract bacteria of fish will be analyzed. The results of the proposed project will contribute to figure out the dissemination features for the bacteria antibiotic resistance under environmental pressures from all kind of pollutants in the natural ecosystem. The results will guide the prevention and control of ARGs pollution in water ecosystem.

城市河流作为接纳各种污水和再生水的自然水体，必然接收抗生素广泛使用所产生的抗生素耐药基因这种新污染，这种新污染将影响河流生态甚至危及人类健康。抗生素、重金属等污染物的排放造成的环境压力如何在水体中选择抗生素耐药性以及如何影响耐药基因的散播，值得关注。本项目拟选择由橡胶坝拦出的3段污染程度显著不同的灞河水体为研究场所，采用细菌宏基因组和全基因组技术、基因转移实验及传统微生物方法，分别对水、底泥和鱼肠道细菌耐药性的基因型和表现型进行分析和比较，确定抗生素、重金属等压力对细菌耐药性的选择方向，探讨水体中的优势种耐药性的获得机制，分析水体或底泥细菌中耐药基因转移至鱼类肠道细菌的可能途径。本项目所获得的结果将有助于认识自然水体中各类污染所造成的环境压力影响细菌耐药性散播的特点，为抗生素耐药基因的污染的防控提供指导。

抗生素的广泛使用与耐药基因的新型污染对水域生态及人类健康构成潜在风险，作为这些污染主要接纳者的城市河流并未有深入研究。本项目以橡胶坝拦出的3段不同污染程度的灞河水体为研究场所，采用宏基因组技术、全基因组技术以及荧光定量PCR技术分析水体、底泥和鱼肠道细菌耐药基因的基因型，使用传统微生物学方法对细菌的耐药表型进行分析，并将基因型与表型进行此较，确定抗生素、重金属等环境压力对细菌耐药性的选择方向，探究水体中优势种耐药性的获得机制，分析水体及底泥微生物中耐药基因传播至鱼类肠道的可能途径。获得的结果如下，河流自上游至下游环境压力的增加促进特定ARGs丰度的提高并且改变了ARGs的细菌宿主。同时，环境压力的增强还促进了ARGs从水体传播至鱼肠道，并且导致携带多种ARGs的潜在病原体出现。本项目还证明了抗生素残留促进了约氏不动杆菌耐药表型的出现。此外，约氏不动杆菌的基因组具有高度可塑性并且具有形成生物膜的能力，其形态影响抗生素的耐药策略。

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