PFAS triggers a SpoT-associated metabolic switch that promotes persister-like phenotype in Salmonella Typhi

Per- and polyfluoroalkyl substances (PFAS) are new pollutants in the environment whose effects on bacteria’s physiology is not well understood. In this study, we show that exposure to PFAS causes membrane depolarization in Salmonella enterica serovar Typhi. This works as a metabolic uncoupler that breaks down proton motive force without immediately killing the cells. This disturbance results in a significant elevation of intracellular NADH and NAD⁺ levels while preserving redox equilibrium, signifying an augmented metabolic flux. At the same time, we see that β-oxidation pathways are turned on, which suggests that the cells are shifting toward breaking down fats to make up for the lack of energy.

Even though there are more reducing equivalents, ATP levels go down, which is what happens when respiration is uncoupled. This puts the cells in a state of “pseudo-starvation.” This metabolic stress triggers the SpoT-dependent stringent response, leading to the accumulation of (p)ppGpp. Genetic analysis employing Δ relA and Δ relA Δ spoT mutants confirm that SpoT is necessary for this adaptive response. Functionally, PFAS-treated populations show an enhanced proportion of persister-like cells, which connects exposure to environmental pollutant in the environment to antibiotic tolerance.

Our findings reveal a previously unidentified mechanism by which PFAS alters bacterial metabolism and stress responses, facilitating persistence through membrane depolarization, metabolic reconfiguration, and stringent response activation. This study underscores the potential influence of environmental pollutants on bacterial survival mechanisms and antibiotic resistance.