摘要
      越来越多的证据表明，盐积累在介导抗生素抗性基因（ARGs）在土壤中传播中发挥着关键作用，而盐如何介导ARGs传播仍然未知。在此，通过同时考虑盐度胁迫和微生物反应策略的作用，探讨了低、中、高水平（Ne/Al–L、Ne/Al-M、Ne/Al-H）的中性或碱性（Ne/Al）盐对10种典型ARGs在土壤中传播的影响。在用Ne/Al–L和Al–M盐改良的土壤中，ARGs的传播可以忽略不计，并且ARGs和可移动遗传元素（MGE）的相对丰度降低。然而，Ne–M和Al–H盐有助于ARGs在土壤中的传播，ARGs和MGE的绝对和相对丰度显著增加。在Ne–H土壤中，尽管由于严重的氧化损伤，ARGs的绝对丰度急剧下降，但它们的相对丰度有所提高。ARGs转移的促进可能与细胞内活性氧的过度生成和参与SOS系统的DNA修复酶活性的增加有关。此外，包括群体感应和能量代谢在内的激活的细胞内保护反应在很大程度上为ARGs的传播提供了重要因素。在特定的耐盐细菌中，ARGs和过度表达的耐盐基因的共存进一步表明了盐胁迫对ARGs的选择。此外，由于对微生物的非生物胁迫和选择压力较低，碱性盐对ARGs进化的干扰小于中性盐。这项研究强调，土壤盐碱度可以剂量依赖性地重塑ARGs的传播和微生物的群落结构，这可能会增加ARGs在农业环境中的生态风险。
Abstract
Growing evidence points to the pivotal roles of salt accumulation in mediating antibiotic resistance genes (ARGs) spread in soil, whereas how salt mediates ARGs dissemination remains unknown. Herein, the effects of neutral or alkaline (Ne/Al) salt at low, moderate and high levels (Ne/Al–L, Ne/Al–M, Ne/Al–H) on the dissemination of ten typical ARGs in soils were explored, by simultaneously considering the roles of salinity stress and response strategies of microbes. In the soils amended with Ne/Al–L and Al–M salt, the dissemination of ARGs was negligible and the relative abundances of ARGs and mobile genetic elements (MGEs) were decreased. However, Ne–M and Al–H salt contributed to the dissemination of ARGs in soils, with the significantly increased absolute and relative abundances of ARGs and MGEs. In Ne–H soil, although the absolute abundance of ARGs declined drastically due to serious oxidative damage, their relative abundances were promoted. The facilitated ARGs transfer was potentially related to the excessive generation of intracellular reactive oxygen species and increased activities of DNA repair enzymes involved in SOS system. In addition, the activated intracellular protective response including quorum sensing and energy metabolism largely provided essential factors for ARGs dissemination. The co-occurrence of ARGs and over-expressed salt-tolerant genes in specific halotolerant bacteria further suggested the selection of salt stress on ARGs. Moreover, less disturbance of alkaline salt than neutral salt on ARGs evolution was observed, due to the lower abiotic stress and selective pressure on microbes. This study highlights that soil salinity-sodicity could dose-dependently reshape the dissemination of ARGs and community structure of microbes, which may increase the ecological risks of ARGs in agricultural environment.

https://www.sciencedirect.com/science/article/abs/pii/S0048969721073228