摘要

       强烈蒸发导致土壤层表面盐分积累是一种自然现象，通常发生在旱季，特别是在从滩涂开垦的沿海土地上。然而，盐分积累对抗生素抗性基因 (ARG) 和移动基因元件 (MGE) 分布的影响仍不清楚。在这项研究中，我们对经常观察到盐分积累的野生盐渍土进行了采样，以研究 ARGs 和 MGEs 的垂直分布剖面。结果表明，随着电导率（EC1:5 值）的降低，ARGs 和 MGEs 的梯度从顶层到深层逐渐增加，表明盐渍土中 ARGs 受盐影响衰减。竞争性测试表明，由于携带质粒的菌株的相对适应性降低，ARG 响应盐度梯度的衰减可归因于携带 ARG 的质粒的消除。此外，网络分析表明，ARG 的衰减可能与放线菌丰度的降低有关。总体而言，这项研究确定盐度作为一种非生物胁迫可以重塑 ARGs 的分布，这可能会影响 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