Bilateral transmission of plasmid-mediated antibiotic resistance genes under polycyclic aromatic hydrocarbons...

The global dissemination of antibiotic resistance genes (ARGs) via plasmid-mediated conjugation poses a critical threat to public health. Polycyclic aromatic hydrocarbons (PAHs) are persistent environmental contaminants, but their impacts on ARGs transmission remain unclear. This study investigated how PAHs types and concentrations modulate ARGs conjugation in Escherichia coli. Results demonstrate concentration-dependent dual effects: environmental concentrations of parent PAHs (naphthalene, fluorene) and fluorene derivatives (dibenzothiophene, dibenzofuran, carbazole, nitrofluorene) significantly enhanced conjugation frequencies, whereas phenanthrene inhibited conjugation and pyrene exhibited no effect. Naphthalene, fluorene and fluorene derivatives promoted generation of intracellular reactive oxygen species, increased outer membrane permeability via reduced lipopolysaccharides synthesis, and decreased hydrophobic chain interactions. These PAHs increased proteins synthesis and secretion among extracellular polymeric substances and intercellular adhesion, positively correlated with conjugation frequency. We firstly found that these PAHs promoted energetic activation through tricarboxylic acid cycle upregulation, which enhances electron transfer chain activity to boost proton motive force and elevate intracellular ATP levels. Furthermore, downregulation of global regulatory genes (korA, korB) coupled with upregulation of mating pair formation genes (trbB, trbC, trbJ), facilitating plasmid transfer/replication and mating bridge assembly. This work reveals PAHs-triggered mechanisms associated with plasmid conjugation and underscores the risk posed by PAHs pollution in ARGs dissemination.