摘要

       重金属对抗生素抗性基因 (ARGs) 的共同选择可能会促进 ARGs 在环境中的传播。镉污染无处不在，而镉 (Cd2+) 对水生细菌群落中质粒介导的 ARG 转移的影响程度仍然未知。在本研究中，我们发现亚抑制浓度的 Cd2+ 修正剂通过液体交配法显着增加了来自恶臭假单胞菌 KT2442 的 RP4 质粒与淡水微生物群落的结合频率。 Cd2+ 处理（1-100 mg/L）显着增加了结合混合物的细胞膜通透性和抗氧化活性。由于调节基因（korA、korB 和 trbA）的抑制，10 和 100 mg/L Cd2+ 的修正显着提高了交配对形成基因 (trbBp) 和 DNA 转移和复制基因 (trfAp) 的 mRNA 表达水平。转接合子的系统发育分析表明变形菌是主要受体，高浓度的 Cd2+ 处理导致受体分类群扩大。该研究表明，亚抑制性 Cd2+ 污染将促进质粒结合并有助于质粒相关 ARG 的维持和传播，并强调迫切需要有效修复水生环境中的 Cd2+。

       Co-selection of antibiotic resistance genes (ARGs) by heavy metals might facilitate the spread of ARGs in the environments. Cadmium contamination is ubiquitous, while, it remains unknown the extent to which cadmium (Cd2+) impact plasmid-mediated transfer of ARGs in aquatic bacterial communities. In the present study, we found that Cd2+ amendment at sub-inhibitory concentration significantly increased conjugation frequency of RP4 plasmid from Pseudomonas putida KT2442 to a fresh water microbial community by liquid mating method. Cd2+ treatment (1–100 mg/L) significantly increased the cell membrane permeability and antioxidant activities of conjugation mixtures. Amendments of 10 and 100 mg/L Cd2+ significantly enhanced the mRNA expression levels of mating pair formation gene (trbBp) and the DNA transfer and replication gene (trfAp) due to the repression of regulatory genes (korA, korB and trbA). Phylogenetic analysis of transconjugants indicated that Proteobacteria was the dominant recipients and high concentration of Cd2+ treatment resulted in expanded recipient taxa. This study suggested that sub-inhibitory Cd2+ contamination would facilitate plasmid conjugation and contributed to the maintenance and spread of plasmid associated ARGs, and highlighted the urgent need for effective remediation of Cd2+ in aquatic environments.
https://www.sciencedirect.com/science/article/abs/pii/S0269749120365921