CeO 2 Nanoparticles-Regulated Plasmid Uptake and Bioavailability for Reducing Transformation of Extracellular Antibiotic Resistance Genes.

The direct uptake of extracellular DNA (eDNA) via transformation facilitates the dissemination of antibiotic resistance genes (ARGs) in the environment. CeO nanoparticles (NPs) have potential in the regulation of conjugation-dominated ARGs propagation, whereas their effects on ARGs transformation remain largely unknown. Here, CeO NPs at concentrations lower than 50 mg L have been applied to regulate the transformation of plasmid-borne ARGs to competent () cells. Three types of exposure systems were established to optimize the regulation efficiency. Pre-incubation of competent cells with CeO NPs at 0.5 mg L 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 (, , and , 0.7-0.8 folds). Importantly, CeO 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 (, , and , 0.6-0.7 folds). Altogether, pre-exposure of plasmids with CeO NPs (10 and 25 mg L) 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.