摘要
      尽管人们越来越意识到抗生素耐药性基因（ARGs）在环境中传播，但在经历季节性水文变化的深层淡水生态系统中，关于ARGs在颗粒附着（PA）和自由生活（FL）生活方式中的命运和运输仍存在知识差距。在这里，我们使用高通量定量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，这四个季节代表了两个水文季节（即垂直混合和热分层）。结果表明，季节性水文动力学对于影响PA和FL组分中的ARGs以及ARGs在两种生活方式之间的转变至关重要。尽管PA和FL ARG谱可能是由水平基因转移形成的，但PA和FL AR对季节性水文动力学引起的物理化学物质（如营养物质和溶解氧）的变化有不同的反应。粒子相关生态位（PAN）指数显示，有94个非保守型ARG（即对PA和FL没有偏好），23个保守型ARGs倾向于PA生活方式，16个保守型AR倾向于FL生活方式。分层季节中保守ARG数量的急剧下降表明，ARG在两种生活方式之间发生了依赖水文动力学的转变。值得注意的是，与对应的生活方式相比，保守的ARG（PA或FL生活方式）在其偏好的生活方式中与细菌OTU的关系更密切，这表明生活方式依赖于ARG的富集。总之，这些发现增强了我们对季节性水文变化在深水生态系统中不同大小ARGs传播中的作用的理解。
Abstract
Despite the growing awareness of antibiotic resistance genes (ARGs) spreading in the environment, there is a knowledge gap on the fate and transport of ARGs in particle-attached (PA) and free-living (FL) lifestyles in deep freshwater ecosystems experiencing seasonal hydrological changes. Here, we examined the ARG profiles using high-throughput quantitative PCR in PA and FL lifestyles at four seasons representing two hydrological seasons (i.e., vertical mixing and thermal stratification) in the Shuikou Reservoir (SR), Southern China. The results indicated that seasonal hydrological dynamics were critical for influencing ARGs in PA and FL fractions, and the transition of ARGs between the two lifestyles. Although both PA and FL ARG profiles were likely to be shaped by horizontal gene transfer, PA and FL ARGs had different responses to the changes in physico-chemicals (e.g., nutrients and dissolved oxygen) caused by seasonal hydrological dynamics. The particle-associated niche (PAN) index revealed that there were 94 non-conservative ARGs (i.e., no preferences for PA and FL), 23 conservative ARGs that preferred PA lifestyle, and 16 conservative ARGs for FL lifestyle. A sharp decline in the number of conservative ARGs in stratified seasons suggests a hydrological dynamics-dependent transition of ARGs between two lifestyles. Remarkably, the conservative ARGs (in PA or FL lifestyle) were more closely related to bacterial OTUs in their preferred lifestyle compared to their counterpart lifestyle, suggesting a lifestyle-dependent ARG enrichment. Altogether, these findings enhance our understanding of the role of seasonal hydrological changes in the dissemination of ARGs in different size fractions in deep aquatic ecosystems.

https://www.biorxiv.org/content/10.1101/2022.06.11.495731v1.abstract