Reduction pathway of graphene oxide affects conjugation-mediated horizontal gene transfer under environmental conditions

Antimicrobial resistance in the environment has become a critical issue and its dissemination mediated by nanomaterials is receiving increasing attention. However, current studies overlook the contribution of the environmental transformation of nanomaterials to the horizontal transfer of antibiotic resistance genes (ARGs). Herein, graphene oxide (GO) was transformed by simulated illumination or ferrous iron (Fe2+) to mimic the naturally occurring GO reduction, and for the first time, the distinct effects of reduced GO (rGO) on ARGs horizontal transfer were observed. Compared with pristine GO, the transfer of plasmid-borne ARGs was dramatically enhanced by light-reduced GO. The remarkable production of stabilized graphene radical excited by ultraviolet irradiation triggered bacterial oxidative stress and contributed to membrane permeability. However, when reduced by Fe2+, the facilitation of ARGs transfer mediated by GO was attenuated, which was attributed to the physical wrapping of large rGO aggregates that hindered plasmid transfer between bacteria. Furthermore, the generated transconjugant strain via GO-mediated conjunction showed stronger macrophage infection than the original Escherichia coli under antibiotic treatment. These findings emphasize that nanomaterial-mediated ARGs transfer depends on its transformation pathways in a realistic environment, which is helpful for the under-standing of the dissemination of antimicrobial resistance.

Automated summary

Antimicrobial resistance in the environment has become a critical issue, and nanomaterial-mediated dissemination of antibiotic resistance genes (ARGs) is receiving increasing attention. This study investigates the impact of graphene oxide (GO) transformation on ARGs horizontal transfer. It is found that light-reduced GO significantly enhances the transfer of plasmid-borne ARGs, while GO reduced by ferrous iron attenuates this facilitation. Additionally, the transconjugant strain formed through GO-mediated conjugation exhibits higher macrophage infection under antibiotic treatment.