摘要

    最近的研究一致表明，在不使用抗生素的情况下，抗生素抗性基因（ARG）的丰度不断提高。有大量定量数据已将人为影响环境中升高的ARGs水平与重金属浓度相关联。但是，重金属促进环境细菌之间ARGs的增殖和水平基因转移的机制仍是未知的。这项研究验证了四种典型重金属（铜，镉，铅，锌）对质粒RP4介导的ARG在淡水微观世界中的共轭转移的影响。结果表明，包括Cu，Pb和Zn在内的典型重金属将促进质粒RP4的共轭转移，而Cu（5.0μg/ L）具有比对照组高16倍的最大共轭转移能力。在结合转移的微观世界中，分离出每种可培养的结合结合剂的种类，并通过抗生素敏感性测试评估其最小抑菌浓度（MIC）。 Cu的共轭转移增加的机制是Cu诱导细胞损伤，而Cd的共轭转移减少的原因是Cd增加了细胞外聚合物物质（EPS）的含量。这项研究证实，重金属铜通过细胞损伤效应促进了环境介导的质粒RP4的共轭转移，从而加速了ARGs的传播和增殖。方法

    Recent studies have consistently demonstrated increasing abundances of antibiotic resistance genes (ARGs) in the absence of antibiotic use. There is a large amount of quantitative data that has correlated the elevated ARGs levels with the concentrations of heavy metals in environments with anthropogenic impact. However, the mechanisms by which heavy metals facilitate the proliferation and horizontal gene transfer of ARGs among environmental bacteria were still unknown. This study validated effects of four typical heavy metals (Cu, Cd, Pb, Zn) on the plasmid RP4 mediated conjugative transfer of ARGs in freshwater microcosms. The results suggested that the typical heavy metals including Cu, Pb and Zn would promote conjugative transfer of the plasmid RP4, and Cu (5.0 μg/L) had the greatest ability to increase conjugative transfer by 16-fold higher than the control groups. In conjugative transfer microcosms, the species of each cultivable transconjugant were isolated, and their minimum inhibitory concentrations (MICs) were assessed via antibiotic susceptibility testing. The mechanism of the increased conjugative transfer of Cu was that Cu induced cell damage and the reduced conjugative transfer of Cd was that Cd increased the content of extracellular polymers substances (EPS). This study confirms that heavy metal Cu facilitates the conjugative transfer of environmental-mediated plasmid RP4 by cell damage effect, therefore accelerating the transmission and proliferation of ARGs.

    https://www.sciencedirect.com/science/article/abs/pii/S0048969720305659