Cellular mechanism of perfluoroalkyl substances with different chain lengths influence conjugative transfer of antibiotic resistance genes

Per- and polyfluoroalkyl substances (PFAS) are emerging persistent environmental pollutants with potential risks to microbial ecosystems. However, the influence of PFAS with different chain lengths on horizontal gene transfer, particularly plasmid-mediated antibiotic resistance genes (ARGs) conjugation, remains poorly understood. This study investigated the impacts of short-chain (PFBA, PFHxA) and long-chain (PFNA) PFAS exhibited dual effects on the conjugative transfer of ARGs: PFAS with lower concentration (<0.05 mg/L) enhanced ARGs transfer by increasing the permeability of the cell membrane and ROS content, while higher concentration (>0.05 mg/L) of PFAS led to stronger inhibition through suppressing adenosine triphosphate (ATP) production. The scarcity of ATP caused cells to rebuild their energy allocation strategies, diverting more energy towards maintaining vital life activities rather than for gene transmission. Notably, short-chain PFAS (e.g. PFBA) of smaller molecular possessed greater facility for entering cells and caused stronger dual effects on cells. However, long-chain PFAS with high hydrophobicity prefers to embed in the phospholipid bilayer, causing weaker dual effects on cells and less frequency of conjugative transfer. These findings revealed the distinct effects of PFAS with different chain lengths on the conjugative transfer of ARGs, and highlighted the critical role of the cell membrane in this phenomenon. This research provides critical insights into the ecological risks posed by PFAS.