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.
Keywords: CeO2 nanoparticles; binding and uptake; plasmid-borne ARGs; regulation; transformation.