摘要
      通常在汞污染的水生环境中发现丰富的抗生素抗性基因。这种现象部分归因于对汞和抗生素的共同耐药性、交叉耐药性和共同的调节反应。然而，目前尚不清楚汞是否以及如何影响可移动质粒介导的ARGs的偶联转移。在本研究中，我们发现环境相关浓度（0.001–0.5 mg L−1）的Hg2+促进了ARGs通过可移动质粒RP4从供体大肠杆菌HB101向受体大肠杆菌K12的偶联转移。暴露于Hg2+显著增加了活性氧的形成、丙二醛的产生、抗氧化酶活性和细胞膜通透性，同时降低了谷胱甘肽的浓度。扫描电子显微镜和透射电子显微镜显示细胞膜受到氧化损伤，这有利于结合转移。Hg2+抑制了负调控结合转移的全局调控基因（korA、korB和trbA）的表达，同时促进了参与交配对形成系统（trbBp和traF）以及DNA转移和复制系统（trfAp和traJ）的正调控基因的表达。尽管高Hg2+浓度（1.0 mg L−1）抑制了ARGs的结合转移，但我们的研究结果表明，Hg2+在环境相关浓度下有助于ARGs在水生环境中的传播。这项研究提高了我们对汞污染的水生环境中ARGs传播的理解。
Abstract
Abundant antibiotic resistance genes (ARGs) are typically found in mercury (Hg)-contaminated aquatic environments. This phenomenon is partly attributed to the co-resistance, cross-resistance, and shared regulatory responses to Hg and antibiotics. However, it remains unclear whether and how Hg influences the conjugative transfer of ARGs mediated by mobilizable plasmids. In the present study, we found that Hg2+ at the environmentally relevant concentrations (0.001–0.5 mg L−1) facilitated the conjugative transfer of ARGs through the mobilizable plasmid RP4 from the donor Escherichia coli HB101 to the recipient E. coli K12. Exposure to Hg2+ significantly increases the formation of reactive oxygen species, malondialdehyde production, antioxidant enzyme activities, and cell membrane permeability, while decreasing the concentration of glutathione. Scanning electron microscopy and transmission electron microscopy showed that the cell membrane suffered from oxidative damage, which is beneficial for conjugative transfer. The expression of global regulatory genes (korA, korB, and trbA) negatively regulating conjugative transfer was restrained by Hg2+, while promoting the expression of positive regulatory genes involved in the mating pair formation system (trbBp and traF) and the DNA transfer and replication systems (trfAp and traJ). Although a high Hg2+ concentration (1.0 mg L−1) suppressed ARGs conjugative transfer, our results suggest that Hg2+ facilitates the dissemination of ARGs in aquatic environments at environmentally relevant concentrations. This study improves our understanding of ARGs dissemination in Hg-contaminated aquatic environments.

https://www.sciencedirect.com/science/article/abs/pii/S0048969722053712