Hunan Province Key Laboratory of Rare Metal Minerals Exploitation and Geological Disposal of Wastes, School of Resources Environment and Safety Engineering, University of South China, Hengyang 421001, China.
Hunan Province Key Laboratory of Pollution Control and Resources Reuse Technology, School of Civil Engineering, University of South China, Hengyang 421001, China.
J Hazard Mater. 2024 Nov 5;479:135624. doi: 10.1016/j.jhazmat.2024.135624. Epub 2024 Aug 26.
Transformation represents one of the most important pathways for the horizontal transfer of antibiotic resistance genes (ARGs), which enables competent bacteria to acquire extracellular ARGs from the surrounding environment. Both heavy metals and irradiation have been demonstrated to influence the bacterial transformation process. However, the impact of ubiquitously occurring radioactive heavy metals on the transformation of ARGs remains largely unknown. Here, we showed that a representative radioactive nuclide, uranium (U), at environmental concentrations (0.005-5 mg/L), improved the transformation frequency of resistant plasmid pUC19 into Escherichia coli by 0.10-0.85-fold in a concentration-dependent manner. The enhanced ARGs transformation ability under U stress was demonstrated to be associated with reactive oxygen species (ROS) overproduction, membrane damage, and up-regulation of genes related to DNA uptake and recombination. Membrane permeability and ROS production were the predominant direct and indirect factors affecting transformation ability, respectively. Our findings provide valuable insight into the underlying mechanisms of the impacts of U on the ARGs transformation process and highlight concerns about the exacerbated spread of ARGs in radioactive heavy metal-contaminated ecosystems, especially in areas with nuclear activity or accidents.
转化是水平转移抗生素抗性基因（ARGs）的最重要途径之一，使有能力的细菌能够从周围环境中获得细胞外的 ARGs。已经证明重金属和辐射会影响细菌转化过程。然而，普遍存在的放射性重金属对 ARGs 转化的影响在很大程度上仍然未知。在这里，我们表明，在环境浓度（0.005-5mg/L）下，一种代表性的放射性核素铀（U）以浓度依赖的方式将抗性质粒 pUC19 转化为大肠杆菌的转化频率提高了 0.10-0.85 倍。在 U 胁迫下增强的 ARGs 转化能力与活性氧（ROS）的过度产生、膜损伤以及与 DNA 摄取和重组相关的基因的上调有关。膜通透性和 ROS 产生分别是影响转化能力的主要直接和间接因素。我们的研究结果为 U 对 ARGs 转化过程的影响的潜在机制提供了有价值的见解，并强调了在放射性重金属污染的生态系统中，特别是在核活动或事故地区，ARGs 传播加剧的问题。
