摘要

       强蒸发作用下的盐分在土壤表层的累积是旱季的一种自然现象，尤其是在滩涂复垦的沿海地区。然而，盐积累对耐药基因（ARGs）和移动基因元件（MGEs）分布的影响尚不清楚。在本研究中，我们选取了一个经常观察到盐分积累的野生盐渍土，研究了ARGs和MGEs的垂直分布特征。结果表明，随着电导率（EC1:5）的降低，土壤中ARGs和MGEs的梯度从上到下逐渐增大，说明盐分对ARGs的衰减有一定的影响。竞争试验表明，ARGs对盐度梯度的响应减弱是由于ARG携带质粒的消除，而质粒携带菌株的相对适应度降低。此外，网络分析表明ARGs的衰减可能与放线菌的丰度降低有关。总的来说，本研究认为盐分作为一种非生物胁迫可以改变ARGs的分布，从而影响ARGs在环境中的传播。

       Salt accumulation on the surface of the soil layer driven by the strong evaporation is a natural phenomenon that usually happens in the dry season, particularly on the coastal lands reclaimed from tidal flats. However, the influence of salt accumulation on the distribution profile of antibiotic resistance genes (ARGs) and mobile gene elements (MGEs) remains unclear. In this study, we sampled a wild saline soil where the salt accumulation was frequently observed to investigate the vertical distribution profiles of ARGs and MGEs. The results showed that an increasing gradient of ARGs and MGEs was observed from the top to deep layer with the decreasing of electrical conductivity (EC1:5 values) indicating the salt-influenced attenuation of ARGs in the saline soil. The competing test suggested that the attenuation of ARGs in response to salinity gradient was attributable to the elimination of the ARG-harboring plasmids, due to the reduction of the relative fitness of plasmid-harboring strains. Additionally, the network analyses showed that the attenuation of ARGs might be associated with decreased abundance of Actinobacteria. Overall, this study identifies that salinity as an abiotic stress could re-shape the distribution of ARGs, which may influence the dissemination of ARGs in the environment.

        https://www.sciencedirect.com/science/article/pii/S0304389419304388?via%3Dihub