摘要
      通过转化直接摄取细胞外DNA（eDNA）促进了抗生素抗性基因（ARGs）在环境中的传播。CeO2纳米颗粒（NP）在调节共轭主导的ARGs传播方面具有潜力，而它们对ARGs转化的影响在很大程度上仍然未知。在这里，浓度低于50 mg L−1的CeO2 NP已被用于调节质粒携带的ARGs向主管大肠杆菌（E.coli）细胞的转化。为了优化监管效率，建立了三种类型的暴露系统。用0.5 mg L−1的CeO2 NP预孵育感受态大肠杆菌细胞，通过降低ROS含量（0.9倍）和细胞膜通透性（0.9倍，从而下调与DNA摄取和加工相关的基因的表达（bhsA、ybaV和nfsB，0.7–0.8倍），抑制了转化（35.4%）。重要的是，CeO2 NP与质粒表现出优异的结合能力，减少了可用于细胞摄取的质粒数量，并下调了DNA摄取的基因表达（bhsA、ybaV和recJ，0.6–0.7倍）。总之，用CeO2 NP（10和25 mg L−1）预暴露质粒抑制转化的效率为44.5–51.6%。本研究为控制ARGs的转化提供了一种纳米策略，提高了我们对纳米材料介导的ARGs传播机制的理解。
Abstract
The direct uptake of extracellular DNA (eDNA) via transformation facilitates the dissemination of antibiotic resistance genes (ARGs) in the environment. CeO2 nanoparticles (NPs) have potential in the regulation of conjugation-dominated ARGs propagation, whereas their effects on ARGs transformation remain largely unknown. Here, CeO2 NPs at concentrations lower than 50 mg L−1 have been applied to regulate the transformation of plasmid-borne ARGs to competent Escherichia coli (E. coli) cells. Three types of exposure systems were established to optimize the regulation efficiency. Pre-incubation of competent E. coli cells with CeO2 NPs at 0.5 mg L−1 inhibited the transformation (35.4%) by reducing the ROS content (0.9-fold) and cell membrane permeability (0.9-fold), thereby down-regulating the expression of genes related to DNA uptake and processing (bhsA, ybaV, and nfsB, 0.7–0.8 folds). Importantly, CeO2 NPs exhibited an excellent binding capacity with the plasmids, decreasing the amounts of plasmids available for cellular uptake and down-regulating the gene expression of DNA uptake (bhsA, ybaV, and recJ, 0.6–0.7 folds). Altogether, pre-exposure of plasmids with CeO2 NPs (10 and 25 mg L−1) suppressed the transformation with an efficiency of 44.5–51.6%. This study provides a nano-strategy for controlling the transformation of ARGs, improving our understanding on the mechanisms of nanomaterial-mediated ARGs propagation.

https://www.mdpi.com/2079-4991/13/6/969