New insight into nanomaterial-mediated dissemination of phage-borne resistance genes: Roles of humic acid and illumination

Abstract

Bacteriophages are key reservoirs of antibiotic resistance genes (ARGs) and are pivotal for their acquisition, maintenance, and dissemination. As extensively distributed contaminants, nanomaterials can interfere with the horizontal transfer of phage-borne ARGs. However, the effects of environmental factors on this process remain unclear. Therefore, the effect of nanoscale titanium dioxide (nTiO2) on the dissemination of ARGs via bacteriophage transduction under humic acid (HA) and Ultraviolet A illumination was investigated in this study. In the dark, 20 mg/L nTiO2 did not promote the propagation of ARGs and attenuated the positive effect of HA on the transductive transfer of ARGs. Further evidence revealed that nTiO2 can absorb HA on its surface and decrease the free HA content, thereby mitigating the instability of the outer membrane and leading to diminished transductant formation. Conversely, coexposure to HA and nTiO2 synergistically promoted transduction under Ultraviolet A illumination. Massive superoxide radicals produced by photoexcitation of the HA-nTiO2 complex elevated the membrane permeability and boosted intracellular oxidative stress, resulting in the enhanced dissemination of ARGs through phage transduction. The results of this study provide insights into the roles of environmental factors in transductive ARGs dissemination mediated by nTiO2 and are beneficial for the risk assessment of nanomaterials.