Biotransformation of polyfluoroalkyl substances by microbial consortia from constructed wetlands under aerobic and anoxic conditions

The wide application of 6:2 fluorotelomer sulfonate (6:2 FTS) and its precursors results in their ubiquitous occurrence in the environment. This study investigated the biotransformation of 6:2 FTS using fresh slurries collected from constructed wetland under aerobic and anoxic conditions. Biotransformation rates of 6:2 FTS was extremely slow under both aerobic and anoxic conditions. The analysis of transformation products showed that less than 0.7 mol% of initial concentration of 6:2 FTS was biotransformed under anoxic conditions. Effects of 6:2 FTS on the shifts in microbial community in wetland slurry during aerobic and anoxic transformation were evaluated using 16S rRNA gene amplicon sequencing. Under aerobic conditions, 6:2 FTS altered the microbial community structure, in which Methylocaldum (Gamma-proteobacteria) became the predominant genus after being exposed to 6:2 FTS. This means that Methylocaldum appears to have higher tolerance to 6:2 FTS and seems to be potential 6:2 FTS-degrading bacteria. Under anoxic transformation, only the genus Methanomethylovorans (Euryarchaeota) was increased remarkably in wetland slurry exposed to 6:2 FTS.