Perfluorooctane sulfonate (PFOS) promotes transformational transfer of antibiotic resistance genes and cross-resistance between antibiotics and PFOS.

Both per- and polyfluoroalkyl substances (PFASs) pollution and antibiotic resistance genes (ARGs) dissemination pose significant threats to global public health. PFASs and ARGs coexist in the environment, but little research was done on associations between PFASs and ARGs dissemination. This study demonstrated that perfluorooctane sulfonate (PFOS) increased ARGs transformation by 1.5-1.7-fold in Escherichia coli DH5α carrying pBR322 plasmid as a model. Moreover, pre-exposure of DH5α to PFOS increased ARGs transformation up to 7-fold. PFOS triggered up-regulation of the gene of outer membrane protein A (OmpA), enhancing cell membrane permeability and thus increasing ARGs transformation. Interestingly, the presence of ARGs decreased ompA gene expression and consequently lowered the accumulation and toxicity response of transformants to PFOS, which established cross-resistance between antibiotics and PFOS. This cross-resistance is attributed to the multifunctional role of the OmpA that acted as a major channel for ARGs entry into cells and facilitated cellular accumulation of PFOS. The OmpA-mediated cellular accumulation was also observed in structurally analogous PFASs (perfluorohexylsulfonic acid and pentadecafluorooctanoic acid), indicating a potential universality in the cross-resistance between antibiotics and PFASs. The United States, Canada and China are likely being confronted with high risks of PFOS-induced ARGs dissemination based on the global risk assessments. These findings demonstrate the overlooked eco-environmental risks associated with the interactions among PFASs, ARGs, and microorganisms, highlighting adaptability of organisms to chemical stress.