(514i) Perfluoroalkyl Substances (PFAS) Affect the Membrane Fluidity of Alcanivorax Borkumensis but Do Not Delay Growth

Poly- and perfluoroalkyl substances (PFAS) are known to accumulate in fatty tissues and partition into cellular membranes. Each of these processes has implications for bioaccumulation and pharmacokinetic modeling. In this work, we examined the interaction of a range of PFASs with the cellular membrane of a marine bacterium, Alcanivorax Borkumensis. This organism is typically found in alkane-rich environments and is one of the most abundant bacteria known to participate in the bioremediation of oil spills. Although it can readily uptake and degrade hydrocarbons, octanoic acid has been shown to be toxic by disrupting the cell membrane.

We monitored the fluorescence anisotropy of diphenylhexatriene (DPH), a common fluorophore used to investigate fluidity of model liposomes, soon after addition of individual PFASs and mixtures of PFASs to Alcanivorax Borkumensis. Multiple PFAS carbon chain lengths (C₆-C₁₀ for carboxylates and C₄, C₆, and C₈ for sulfonates) were examined, as industry shifts toward shorter chain compounds. Further, we tested perfluoro(2-methyl-3-oxahexanoic) acid (Gen X) and an aqueous firefighting foam (AFFF) mixture to determine how they compare with the “legacy” PFAS in terms of interaction with Alcanivorax Borkumensis. In this bacterium, we observed a previously unexpected decrease in membrane fluidity, contrary to the increase in fluidity reported upon addition of PFAS to liposomes.

In addition to fast-acting cellular membrane response to PFAS, we investigated how PFASs affect the growth of Alcanivorax Borkumensis. The same range of PFASs as well as strategic mixtures were added to the growth medium of the bacteria at three different concentrations that include current drinking water guidelines to a representation of a highly-exposed population. By looking into both fast-acting cell membrane responses as well as longer term growth effects, this work systematically elucidates the effect of different types of individual PFASs and mixtures on a marine bacterium.