Defluorination of organofluorine sulfur compounds by Pseudomonas sp. strain D2

Little is known of the potential for biodegradation of fluorinated sulfonates. To evaluate this potential, the following model compounds were selected: difluoromethane sulfonate (DFMS), trifluoromethane sulfonate (TFMS), 2,2,2-trifluoroethane sulfonate (TES), perfluorooctane sulfonate (PFOS), and 1H,1H,2H,2H-perfluorooctane sulfonate (H-PFOS). A laboratory isolate designated Pseudomonas sp, strain D2 completely defluorinated DFMS under aerobic, sulfur-limiting conditions in a defined mineral medium. Strain D2 utilized DFMS as the sole source of sulfur, but not as a source of carbon or energy. DFMS utilization was inhibited by other forms of sulfur, and noncompetitive inhibition kinetics were observed, with K-i values of 3-4 mu M for sulfate, sulfite, methane sulfonate, and cystine. Strain D2 was subsequently used to evaluate degradation of other fluorinated sulfonates. Growth and defluorination were only observed for those compounds containing hydrogen (TES and H-PFOS). TFMS and PFOS were not degraded. TES was completely defluorinated, and H-PFOS was partially defluorinated. No volatile transformation products were detected for TES or DFMS, but six volatile products were detected for H-PFOS. All of the volatile products contained oxygen and fluorine, but not sulfur. This is the first report of defluorination of fluorinated sulfonates, a linkage between sulfur assimilation and defluorination, and generation of volatile fluorinated biotransformation products.