Diisobutyl phthalate at environmental concentration promotes the conjugative transfer of antibiotic resistance genes: Mechanistic insights and ecological implications

The synergistic effects between antibiotic resistance genes (ARGs) and horizontal gene transfer involving non-antibiotic pollutants such as microplastics represent an emerging frontier in ecological and public health research. Diisobutyl phthalate (DIBP), a prevalent phthalate (PAE) plasticizer, volatilizes into aquatic environments, posing significant risks to aquatic ecosystems. This study systematically investigated the regulatory mechanisms by which DIBP promotes conjugative transfer of ARGs at environmentally relevant concentrations (0.01–100 μg/L), showing increases of 1.02–1.67-fold and 1.02–1.36-fold compared to controls. By establishing both intra- and inter-genus systems, we elucidated the synergistic interactions among oxidative stress, membrane permeability, and energy metabolism that collectively drive ARG dissemination. Moving beyond previous studies, the present work establishes a more comprehensive mechanistic evaluation framework through with DIBP induced ARG conjugation, namely “oxidative stress-membrane permeability-energy metabolism” coupling model. Related results extend the specificity of PAEs in facilitating ARG transfer from straight-chain to branched-chain isomers, representing a deep attempt to move from observational phenomena to systematic mechanistic analysis within this field. These findings reveal potential aquatic ecological and public health risks, ultimately providing novel theoretical support for mitigating PAE-induced antibiotic resistance transmission.