摘要
      加速的城市化促进了城市流域成为抗生素耐药性基因（ARGs）的重要库；然而，流域尺度上ARGs的生物地理模式和驱动机制仍不清楚。在这里，我们研究了温带不同季节人类密集型流域（包括城市、河流和湖泊系统）中ARGs的动态分布，并通过结构方程模型揭示了形成ARGs动态的关键因素。在沉积物和地表水中检测到高多样性和丰度的ARGs，其中氨基糖苷类、β-内酰胺酶和多药耐药基因占主导地位。PCoA在两个阶段之间表现出明显的ARGs变化。季节变化和区域功能对ARGs的分布模式产生了重大影响。在冬季检测到更多样化的ARG，而在春季和夏季观察到更高的ARG丰度。根据SourceTracker分析和ARGs指标，城市系统的ARGs污染水平最高，主要来自废水和人类/动物粪便。值得注意的是，流域恢复可以显著缓解ARGs污染状况，并改善水环境中的生物多样性。网络分析确定了几个中枢ARG和细菌属，这有助于推断携带ARG的潜在细菌宿主。此外，ARGs指标为追踪ARGs来源提供了见解。SEM表明，在人类活动强度高的地区，生物可利用的重金属和营养物质可以极大地影响ARGs的动态，而在受人类影响较小的地区，微生物群落和MGE主导着ARGs命运。应更加重视控制重金属和营养物质，以遏制ARGs的传播。总的来说，这项研究强调了ARGs的环境命运，并为缓解人类密集型流域的ARGs污染提供了新的策略。
Abstract
Accelerated urbanization has promoted urban watersheds as important reservoirs of antibiotic resistance genes (ARGs); yet the biogeographical patterns and driving mechanisms of ARGs at the watershed scale remain unclear. Here, we examined the dynamic distribution of ARGs in a human-intensive watershed (including city, river and lake systems) over different seasons in a temperate region, as well as revealed the key factors shaping ARGs dynamics through structural equation models (SEMs). High diversity and abundance of ARGs were detected in sediments and surface water, with aminoglycoside, beta-lactamase and multidrug resistance genes dominating. PCoA showed distinct ARGs variations between the two phases. Seasonal changes and regional functions had significant impacts on the distribution patterns of ARGs. More diverse ARGs were detected in winter, while higher ARGs abundances were observed in spring and summer. The city system showed the highest level of ARGs contamination and was mainly derived from wastewater and human/animal feces based on SourceTracker analysis and ARGs indicators. Notably, watershed restoration could significantly mitigate the ARGs pollution status and improve biodiversity in the aquatic environment. Network analysis identified several hub ARGs and bacterial genera, which helped to infer potential bacterial hosts carrying ARGs. Furthermore, ARGs indicators provided insights to trace ARGs sources. SEMs indicated that bioavailable heavy metals and nutrients can greatly shape ARGs dynamics in regions with high-intensity human activities, while the microbial community and MGEs dominate the fate of ARGs in less human-impacted regions. More attention should be given to control heavy metals and nutrients to curb the spread of ARGs. Overall, this study highlights the environmental fate of ARGs and provides novel strategies to mitigate ARGs pollution in the human-intensive watershed.

https://www.sciencedirect.com/science/article/abs/pii/S0043135422007904