摘要

    尽管抗生素抗性基因（ARGs）在各种水生生态系统中的发生和分布已经得到了很好的研究，但对细菌ARGs的组成、动态生物学过程和机制的认识仍然是有限的。本文采用高通量方法对中国东南部城市厦门，一个亚热带流域城市化过程中的细菌ARG和可操作分类单元（OTUs）进行了5年的空间格局检测。在流域尺度上，OTU轮廓呈现方向性变化，而ARG轮廓则表现出高度的稳定性或随时间的随机变化。与上游和中游相比，下游水体中ARGs的丰度、绝对丰度、标准化丰度和多样性均显著升高。我们的结果揭示了在ARG和OTU轮廓上呈现明显的城乡差异，这两个轮廓分别受确定性和随机分配过程的控制。随着沿江城市建筑面积的增加，ARG轮廓的生物学过程由随机性向确定性转变。在下游水体中，细菌ARG轮廓比细菌OTUs更稳定。此外，我们的研究结果表明，人类主导的环境（如土地利用）和可移动基因元件（MGEs）在ARG轮廓的形成和动力学方面都发挥了重要作用。总的来说，这是对河流下游地区包括城市发展在内的广泛的人文景观相互作用的回应，这些作用在中国亚热带沿海城市中普遍存在，并且可以改变沿城乡梯度的ARG轮廓动力学过程。因此，在河流流域城市化过程中，以减少ARGs威胁为目标的管理行为应该首先要考虑周边城市化水平和人类活动的方式和程度。我们的研究结果还表明由于细菌功能和分类学的脱钩，这两个方面应该分开研究。

    Although the occurrence and distribution of antibiotic resistance genes (ARGs) in various aquatic ecosystems are well explored, understanding of the ecological processes and mechanisms governing the composition and dynamics of bacterial ARGs still remains limited across space and time. Here, we used high-throughput approaches to detect spatial patterns of bacterial ARGs and operational taxonomic units (OTUs) in an urbanizing subtropical watershed, Xiamen, southeast China over a five-year period. At watershed scale, the OTU profiles were undergoing a directional change, but the ARG profiles showed a high stability or stochastic change over time. Compared with the upstream and midstream, the richness, absolute abundance, normalized abundance and diversity of ARGs were significantly higher in the downstream waters. Our results revealed a clear rural-urban disparity in ARG and OTU profiles which were mainly governed by deterministic and stochastic assembly processes, respectively. With the increase of urban building area along the river, the ecological processes of ARG profiles shifted from stochastic to deterministic. In downstream waters, the bacterial ARG profiles were much more stable than bacterial OTUs. Further, our results indicated that both human-dominated environment (e.g., land use) and mobile genetic elements (MGEs) played an important role in shaping the ARG profiles and dynamics. Overall, this was a response to spatially extensive human-landscape interactions that included urban development in the river downstream region, which were common across subtropical coastal cities of China and can alter the ARG profile dynamics along rural-urban gradient. Therefore, watershed management actions aiming at reducing threats posed by ARGs in urbanizing watershed should first consider the surrounding urbanization level and the mode and intensity of human activity. Our findings also imply that due to the decoupling of bacterial function and taxonomy, both aspects should be studied separately.

     https://www.sciencedirect.com/science/article/pii/S016041201933171X