Heterogeneous UV disinfection aided by ZnO/Al2O3 composites for inhibiting antibiotic resistant bacteria photoreactivation and gene recovery

Photoreactivation has limited antibiotic resistant bacteria (ARB) and gene (ARG) reduction by ultraviolet (UV) heterogeneous disinfection. ZnO/Al2O3 particles where ZnO length ranged around 400 nm was synthesized by template-hydrothermal method. Subsequently particle aided UV system was built to investigate the inhibitions on ARB (Escherichia coli carrying RP4 plasmid) photoreactivation and gene (three ARGs and two mobile genetic elements) recoveries after disinfection. All bacterial inactivation and 5 log gene reduction could be achieved within 5 min and 4 h respectively, and significant inhibitions on bacteria and gene recoveries after photoreactivation were observed, compared with individual UV. Hydroxyl radicals which were responsible for photoreactivation inhibition were detected during ZnO photocatalysis. The pathway of intracellular gene inactivation by extracellular OH was identified as a carpet model. Briefly, OH could destroy membrane, thus intracellular ARGs had accesses to OH and were inactivated. Subsequently the broken areas with negative charge were reclosed via electrostatic attraction due to the limited Zn2+ from zinc oxide, but the function of membrane cannot be restored. Our work further provided profound theoretical supports for practical application of antibiotic resistance removal by UV with ZnO aided method in wastewater treatment.

Automated summary

This study investigated the inhibitory effect of photoreactivation on antibiotic resistant bacteria and genes using UV with ZnO assistance. The results showed that all bacteria could be inactivated within 5 minutes and a 5 log gene reduction could be achieved within 4 hours after disinfection. Compared to individual UV treatment, significant inhibitions on bacteria and gene recoveries were observed after photoreactivation. Hydroxyl radicals generated during ZnO photocatalysis were found to be responsible for the inhibitory effect on photoreactivation, and the inactivation of intracellular genes followed a carpet model.