摘要

      尽管季节性是水生生态系统环境波动的关键驱动因素，但在流域尺度上，对控制抗生素抗性基因（ARGs）跨季节分布的因素的认识有限。本文采用高通量定量PCR技术，对厦门市亚热带河流生态系统中285种主要抗生素耐药的ARG进行了定量分析，揭示了它们的空间和季节分布规律，并描述了在低、高人为压力下的潜在机制。我们的结果表明，ARG丰富度和丰度的空间差异压倒了它们的季节性变化，只有能够产生抗磺胺和万古霉素的ARG在不同季节有显著差异。只有少量丰富的ARGs（19个ARGs）能占总ARGs丰度的70%以上，且在所有季节都能发现。夏季雨季ARG的数量明显高于其他季节，同时ARG共生网络的显著边缘数也较高。夏季降水对上游水体ARGs有较强的稀释作用，对下游水体ARGs有较强的富集作用。方差分块分析表明，环境对ARG剖面的解释力大于移动遗传因子（MGEs）、空间预测因子和降雨量。然而，转座酶基因绝对丰度与氨基糖苷类、氯霉素类、MLS类、多药类和四环素类耐药基因之间存在显著的相关性，推测MGEs在ARG分布中的作用。总的来说，我们的研究结果表明，通过考虑在空间和季节梯度上占主导地位的优先基因，可以更好地实现高动态生态系统中ARG的建模和管理。

        Although seasonality is a key driver of environmental fluctuation in aquatic ecosystems, there exists limited knowledge on the factors controlling the distribution of antibiotic resistance genes (ARGs) across seasons at a watershed scale. Here we used high-throughput quantitative PCR to quantify 285 ARGs conferring resistance to most major classes of antibiotics, reveal their spatial and seasonal distribution patterns, and depict the underlying mechanisms in a subtropical riverine ecosystem under low and high human pressures, in Xiamen city, southeast China. Our results showed that spatial differences in ARG richness and abundance overwhelmed their seasonal variations, with only ARGs that confer resistance to sulfonamide and vancomycin being significantly different across seasons. Only a few abundant ARGs (19 ARGs) could contribute to >70% of the total ARGs abundance and were found in all seasons. The significantly higher number of ARGs in the summer rainy period than other seasons coincided with high number of significant edges in ARG co-occurrence networks. Summer rainfall had strong dilution effect on ARGs in upstream waters and enrichment effect in downstream waters. The variance partitioning analysis indicated that the environment explained larger variance of ARG profiles than mobile genetic elements (MGEs), spatial predictors and the rainfall. Nevertheless, strong and significant correlations between transposase gene absolute abundance and aminoglycoside, chloramphenicol, MLS, multidrug and tetracycline classes of resistance genes inferred the role of MGEs on ARG distribution. Overall, our results imply that the modelling and management of ARGs in highly dynamic ecosystems could be better implemented by considering priority genes that dominate at spatial and seasonal gradients.

        https://www.sciencedirect.com/science/article/pii/S004896971931544X?via%3Dihub