Urbanization drives the succession of antibiotic resistome and microbiome in a river watershed

Urbanization is a process of ecosystem evolution mediated by human activities. One of the main consequences is the alteration of antibiotic resistome and microbiome in aquatic environment, which may transfer from water to sediments and exert a long-term health concern to aquatic animals and even humans. However, the role of urbanization in shaping resistome and microbiome in water and sediments is largely unknown. Here, a typical watershed with a significant gradient of urbanization was selected, and the resistome and microbiome in both water and sediments were profiled. In water, the relative abundance of ARGs and bacterial diversity increased gradually along the urbanization, but were relatively stable in sediments. The abundance of potential multidrug-resistant bacteria in peri-urban and urban water were significantly higher than rural water, while in sediments, unique potential multidrug-resistant bacteria were detected at different urbanization levels. Population size was identified as the key factor shaping the ARGs profiles. Finally, environmental risk assessment based on the projection pursuit regression model suggested that the water in urban region had higher potential environmental risk of antibiotic resistance, in contrary to the sediments in rural and peri-urban regions. Our findings revealed distinct responses of water and sediment to urbanization in terms of antibiotic resistome and microbiome. This work provides important guide for hierarchically controlling ARGs dissemination in watershed.