Biotransformation of Perfluorooctane Sulfonamide (FOSA) and Microbial Community Dynamics in Aerobic Soils

Despite widespread detection of perfluorooctane sulfonamide (FOSA) in the environment, its potential for biotransformation by native soil microorganisms and the resulting impacts on microbial communities remain poorly understood. This study examined the biotransformation of FOSA over 308 days in microcosms prepared with two soils, a historically per- and polyfluoroalkyl substances (PFAS)-contaminated soil and a PFAS-free agricultural soil. Indigenous microorganisms in both soils were able to biotransform FOSA with half-lives ranging from 203.0 to 335.1 days. Perfluorooctanesulfonate (PFOS) was the primary biotransformation product, with a molar yield of 21.6 ± 5.2 mol% in the historically PFAS-contaminated soil and 29.5 ± 3.8 mol% in the initially PFAS-free soil. Microbial community analysis revealed that members of the phyla Cyanobacteria and Bacteroidota, as well as the genus Afipia, exhibited greater tolerance to elevated concentrations of FOSA and/or its biotransformation products. Metagenomic predictions using Tax4Fun2 identified functional genes related to amino acid metabolism, sulfur metabolism, and the two-component system, which may be linked to FOSA exposure and/or its biotransformation. These findings highlight the role of biotransformation processes in shaping the environmental fate of FOSA and PFOS, and offer insights into the capacity of native soil microbial communities to transform FOSA and related perfluorooctane sulfonamide derivatives.