摘要

       城郊河流是城乡共生生态系统之间的重要界面之一，是环境中抗生素抗性基因（ARGs）的贮存库。为了防止城市近郊河流与人类之间的ARGs传播风险，有必要探索ARGs在环境中的分布和来源，以设计潜在的缓解策略。本文研究了北京市潮白河典型城郊河流沉积物中ARGs的特征和来源。应用高通量定量PCR技术检测了27个环境中常见的ARGs和2个整合子（intI1和intI2）。通过16srRNA基因测序确定细菌群落结构。同时，利用新近发现的DNA噬菌体crAssphage，追踪人类粪便污染对ARGs流行的贡献。结果表明，在潮白河底泥中广泛检测到目标ARGs。相对而言，下游的ARGs丰度高于上游，可能是沿河人类活动的梯度影响。值得注意的是，int1基因与河流沉积物中的大多数ARGs显著相关，可能是影响沉积物中ARGs形成的关键因素。然而，ARGs与选择性压力因子（包括抗生素和金属）之间没有显著相关性。在已鉴定的1039属中，大肠杆菌属、类杆菌属、弧菌属、氯单胞菌属和假单胞菌属是最丰富的微生物。基于crAssphage注释的微生物源跟踪表明，人类污水可能是河流沉积物中潜在的耐药菌源之一。本研究可提高我们对城市近郊河流中ARGs的认识，为城市近郊河流ARG污染控制提供管理参考。

        The peri-urban rivers are one of the critical interfaces between urban-rural symbiotic ecosystems and appear to be a reservoir of antibiotic resistance genes (ARGs) in the environment. To prevent the transmission risks of ARGs between peri-urban river and human, it is essential to explore the prevalence and source of ARGs in the environment for designing potential mitigation strategies. In this study, we focused on the characterization and source-tracking of ARGs in the sediments of a typical peri-urban river in Beijing, Chaobai River. Twenty-seven ARGs frequently reported in the environment, and two integrons (intI1 and intI2) were detected using high-throughput quantitative PCR. The profile of bacterial community was determined by performing 16S rRNA gene sequencing. Meanwhile, crAssphage, a novel recently-discovered DNA bacteriophage, was employed for tracking the contribution of human fecal pollution to the prevalence of ARGs. Results showed that the targeted ARGs were detected widely in the sediments of Chaobai River. Relatively, the abundances of ARGs in downstream were higher than those in the upstream, likely suggesting a gradient impact of anthropogenic activities along the river. Remarkably, the int1 gene was correlated significantly with most of the ARGs and might be the key factor influencing the shaping of ARGs in the river sediments. However, no significant correlations were observed between the ARGs and selective pressure factors, including antibiotics and metals. Of the identified 1039 genera, Escherichia-Shigella, Bacteroides, Arcobacter, Dechloromonas and Pseudomonas were the top most abundant organisms. Microbial source tracking based on the crAssphage annotation suggested that human sewage might be one of the potential sources of resistance bacteria in the river sediments. The study can advance our knowledge about ARGs in the peri-urban river and provides a management reference for ARG pollution control.

        https://www.sciencedirect.com/science/article/pii/S0048969719320753?via%3Dihub