CeO2 Nanoparticles Regulate the Propagation of Antibiotic Resistance Genes by Altering Cellular Contact and Plasmid Transfer

The dissemination and propagation of antibiotic resistance genes (ARGs) via plasmid-mediated conjugation pose a major threat to global public health. The potential effects of nanomaterials on ARGs fates have drawn much attention recently. In this study, CeO2 nanoparticles (NPs), one of the typical nanomaterials proposed for increasing crop production, were applied at the concentration range of 1-50 mg/L to investigate their effects on ARGs transfer between Escherichia coli. Our results revealed that the conjugative transfer of RP4 plasmid was enhanced by 118-123% at relatively high concentrations (25 and 50 mg/L) of CeO2 NPs, however, CeO2 NPs at low concentrations (1 and 5 mg/L) inhibited the transfer by 22-26%. The opposite effect at low concentrations is mainly attributed to (i) the reduced ROS level, (ii) the weakened intercellular contact via inhibiting the synthesis of polysaccharides in extracellular polymeric substances, and (iii) the down-regulated expression of plasmid transfer genes due to the shortage of ATP supply. Our findings highlight the distinct dose-dependent responses of ARGs conjugative transfer, providing evidence for selecting appropriate NPs dose to reduce the spread of ARGs while applying nanoagrotechnology.