Transformation and Defluorination of Fluorotelomer Carboxylic Acids by Pseudomonas sp. strain 273

Per- and polyfluoroalkyl substances (PFASs) are persistent contaminants with potential risks to environmental and human health. While perfluorinated compounds are highly recalcitrant, polyfluoroalkyl substances (aka precursors) can undergo biotransformation with fluorotelomer carboxylic acids (FTCAs) commonly observed as intermediates. We evaluated how FTCA structural features impact biotransformation and demonstrate that the soil bacterium Pseudomonas sp. strain 273 defluorinates FTCAs with even numbers of nonfluorinated carbons (n:2 and n:4 FTCAs), but not those with uneven numbers (n:3 and n:5 FTCAs). Growth and transformation occurred with 1:5 FTCA but defluorination of FTCAs containing <5 nonfluorinated carbons was cometabolic and required a primary carbon substrate (e.g., sebacate). Fluoride release started with the onset of growth, increased throughout the exponential growth phase, and extended into the stationary phase. Transformation of n:2 FTCAs yielded inorganic fluoride, the corresponding (n-1):3 FTCAs, perfluorocarboxylic acids (PFCAs) with one less perfluorinated carbon atom (i.e., [n-1] PFCAs), and trace amounts of shorter-chain ([n-2], [n-3]) PFCAs. The detection of 2:2 fluorotelomer unsaturated carboxylic acid, 3-OH-1:3 FTCA, 3-keto-1:3 FTCA, 1:3 FTCA, and trifluoroacetic acid, a maximum defluorination degree of ∼35.9%, and a total fluorine recovery of ∼96.8% support that 2:2 FTCA cometabolism involves β-oxidation pathway enzymes. These findings advance our understanding of bacterial FTCA transformation and defluorination, providing insights into the environmental fate of precursors.