<i>N</i> -Ethyl Perfluorooctane Sulfonamide ( <i>N</i> -EtFOSA) Exposure Alters Microbiome Composition and Causes Microbiome-Dependent Behavior Effects in Larval Zebrafish

High Resolution Image Download MS PowerPoint Slide We hypothesized that host-associated microorganisms can alter host behavior by modifying perfluorooctane sulfonamides to produce perfluorooctanesulfonic acid (PFOS) or other potentially neuroactive metabolites. Zebrafish larvae ( Danio rerio ) were exposed to PFOS (0.28–5 μM), N -ethyl perfluorooctane sulfonamide ( N -EtFOSA, 0.07–1.25 μM), or perfluorooctane sulfonamido ammonium iodide (PFOSAmS, 0.83–15 μM) from 5 to 6 days post fertilization (dpf). This resulted in altered dark-phase swimming behavior at 8 dpf. Exposure to PFOS, or N -EtFOSA, but not PFOSAmS caused a similar shift in community structure. We exposed microbiome-depleted (axenic, AX), conventionally colonized (CC), or axenic conventionalized on day 1 (AC1) zebrafish larvae to N -EtFOSA (0.22–0.7 μM) from 5 to 6 dpf. In comparison to CC and AC1 larvae, AX-larvae did not exhibit concentration-dependent hypoactivity at 8 dpf. Chemical analysis at 7 dpf revealed a significant increase in N -EtFOSA levels in AX-larvae and AX-water samples, relative to colonized cohorts. The main metabolite detected was perfluorooctane sulfonamide (FOSA), which was not microbiome-dependent. Perfluorooctane sulfonamidoacetic acid (FOSAA) was detected at lower levels in AX-larvae, relative to colonized groups. This study revealed that the presence of the microbiome enhanced N -EtFOSA-dependent behavior effects at the level of the host. This supports the concept that chemical–microbiome interactions can influence host phenotypic outcomes.