摘要
      抗生素耐药性基因（ARGs）是一个众所周知的环境问题。然而，关于ARGs在经历季节性水文变化的深层淡水水库中的命运和运输，尤其是在颗粒附着（PA）和自由生活（FL）生活方式的背景下，知识有限。在这里，使用高通量定量PCR检测了中国南方水口水库四个季节PA和FL生活方式的ARG谱，代表了两种水文现象（垂直混合和热分层）。结果表明，季节性水文动力学对于影响PA和FL的ARGs以及ARGs在两种生活方式之间的转变至关重要。PA和FL中的ARG谱很可能是通过水平基因转移形成的。然而，在季节水文动力学下，它们对物理化学（如营养物质和溶解氧）的变化表现出不同的反应。粒子关联生态位（PAN）指数显示，94个非保守ARG（即对PA和FL没有偏好），23个和16个保守ARG分别偏好PA和FL的生活方式。分层水文条件下保守ARGs的急剧下降表明季节性影响了PA和FL生活方式之间的ARGs转变。值得注意的是，保守型ARG（PA或FL生活方式）在其首选生活方式中与细菌OTU的关系比其同类更密切，这表明生活方式依赖性ARG富集。总之，这些发现增强了我们对ARG生活方式的理解，以及季节性水文变化在控制典型深层淡水生态系统中生活方式之间的ARG转变中的作用。
Abstract
Antibiotic resistance genes (ARGs) are a well-known environmental concern. Yet, limited knowledge exists on the fate and transport of ARGs in deep freshwater reservoirs experiencing seasonal hydrological changes, especially in the context of particle-attached (PA) and free-living (FL) lifestyles. Here, the ARG profiles were examined using high-throughput quantitative PCR in PA and FL lifestyles during four seasons representing two hydrological phenomena (vertical mixing and thermal stratification) in the Shuikou Reservoir (SR), Southern China. The results indicated that seasonal hydrological dynamics were critical for influencing the ARGs in PA and FL and the transition of ARGs between the two lifestyles. ARG profiles both in PA and FL were likely to be shaped by horizontal gene transfer. However, they exhibited distinct responses to the physicochemical (e.g., nutrients and dissolved oxygen) changes under seasonal hydrological dynamics. The particle-association niche (PAN) index revealed 94 non-conservative ARGs (i.e., no preferences for PA and FL) and 23 and 16 conservative ARGs preferring PA and FL lifestyles, respectively. A sharp decline in conservative ARGs under stratified hydrologic suggested seasonal influence on the ARGs transition between PA and FL lifestyles. Remarkably, the conservative ARGs (in PA or FL lifestyle) were more closely related to bacterial OTUs in their preferred lifestyle than their counterparts, indicating lifestyle-dependent ARG enrichment. Altogether, these findings enhanced our understanding of the ARG lifestyles and the role of seasonal hydrological changes in governing the ARG transition between the lifestyles in a typical deep freshwater ecosystem.

https://www.sciencedirect.com/science/article/pii/S2666498422000795