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.