A Commonly Used Tire Rubber Antioxidant and its Quinone Derivative Facilitate the Conjugative Transfer of Plasmid-Mediated Antibiotic Resistance Genes in <i>Escherichia coli</i>

The conjugative transfer of plasmid-mediated antibiotic resistance genes (ARGs) plays a key role in the spread of antibiotic resistance, posing a major global public health threat. The tire rubber antioxidant <i>N</i>-(1,3-dimethylbutyl)-<i>N</i>'-phenyl-<i>p</i>-phenylenediamine (6PPD) and its quinone derivative (6PPD-Q) are emerging pollutants that are widely present in the environment and pose significant ecological risks. However, their potential impact on plasmid transfer remains poorly understood. Here, we established in vitro conjugation models under simulated aquatic conditions to evaluate the effects of environmentally relevant concentrations of 6PPD and 6PPD-Q on RP4 plasmid transfer in <i>Escherichia coli</i>(<i>E. coli</i>). Our results demonstrate that both compounds significantly enhance plasmid transfer, with 6PPD-Q exhibiting a markedly greater impact. The primary mechanisms underlying this enhancement include increased reactive oxygen species (ROS) production, enhanced membrane permeability, improved cell adhesion, and promoted adenosine triphosphate (ATP) synthesis. Transcriptomic analysis, nontargeted metabolomics profiling, and molecular docking simulations corroborate these findings. Notably, 6PPD-Q significantly upregulated ATP synthesis-related genes in donor bacteria and altered metabolic processes in the conjugation system. This study provides novel insights into how 6PPD and 6PPD-Q facilitate the conjugative transfer of ARGs and highlights the potential environmental impact of 6PPD-Q in promoting the spread of ARGs.