Pseudomonas sp. Strain 273 Degrades Fluorinated Alkanes

Abstract

Fluorinated organic compounds have emerged as environmental constituents of concern. We demonstrate that the alkane degrader Pseudomonas sp. strain 273 utilizes terminally monofluorinated C7–C10 alkanes and 1,10-difluorodecane (DFD) as the sole carbon and energy sources in the presence of oxygen. Strain 273 degraded 1-fluorodecane (FD) (5.97 ± 0.22 mM, nominal) and DFD (5.62 ± 0.13 mM, nominal) within 7 days of incubation, and 92.7 ± 3.8 and 90.1 ± 1.9% of the theoretical maximum amounts of fluorine were recovered as inorganic fluoride, respectively. With n-decane, strain 273 attained (3.24 ± 0.14) × 107 cells per μmol of carbon consumed, while lower biomass yields of (2.48 ± 0.15) × 107 and (1.62 ± 0.23) × 107 cells were measured with FD or DFD as electron donors, respectively. The organism coupled decanol and decanoate oxidation to denitrification, but the utilization of (fluoro)­alkanes was strictly oxygen-dependent, presumably because the initial attack on the terminal carbon requires oxygen. Fluorohexanoate was detected as an intermediate in cultures grown with FD or DFD, suggesting that the initial attack on the fluoroalkanes can occur on the terminal methyl or fluoromethyl groups. The findings indicate that specialized bacteria such as Pseudomonas sp. strain 273 can break carbon–fluorine bonds most likely with oxygenolytic enzyme systems and that terminally monofluorinated alkanes are susceptible to microbial degradation. The findings have implications for the fate of components associated with aqueous film-forming foam (AFFF) mixtures.

Pseudomonas: versatile biocatalysts for PFAS

“…Pseudomonas strains have already been shown to grow on fluorinated aliphatic and aromatic compounds as the sole source of carbon or other nutrients (Goldman, 1965; Goldman et al ., 1967; Harper and Blakley, 1971; Engesser et al ., 1980; Key et al ., 1997; Misiak et al ., 2011; Xie et al ., 2020). Most examples are with monofluorinated, a few with difluorinated, compounds.…”

“…Many details on the interactions of Pseudomonas with polyfluorinated alkyl, alkenyl and aryl compounds (as we have defined PFAS) have yet to be revealed. Currently, several dozen fluorinated compounds have been shown to undergo defluorination in direct experiments with different Pseudomonas strains (Goldman, 1965;Renganathan, 1989;Li and Wackett, 1993;Kim et al, 2012;Butt et al, 2014;Xie et al, 2020;Bygd et al, 2021;Bygd et al, 2022). This author expects many more to come.…”

“…Fluoroacetate dehalogenase has been extensively studied and is now the paradigm for understanding hydrolytic defluorinating enzymes (Kawasaki et al ., 1981; Au and Walsh, 1984; Meyer et al ., 1990; Hefferman et al ., 2009; Chan et al ., 2011). Other alkyl compounds containing multiple fluorine substituents have since been reported to undergo biodegradation by Pseudomonas strains (Hur et al ., 1994; Xie et al ., 2020). Most recently, there have been numerous reports on the biodegradation of commercially relevant fluorotelomer compounds by different Pseudomonas strains (Liu et al ., 2007; Kim et al ., 2012; Butt et al ., 2014; Kim et al ., 2014; Presentato et al ., 2020).…”

Nothing lasts forever: understanding microbial biodegradation of polyfluorinated compounds and perfluorinated alkyl substances

“…The mechanisms of monodefluorination have been studied with cytochrome P450 monooxygenases (Harkey et al ., 2012 ), dioxygenases (Li et al., 2020 ; Renganathan, 1989 ) and oxidases (Li et al ., 2020 ). Recently, bacterial degradation of monofluorinated alkyl chains via oxygenase‐initiated reactions was reported (Xie et al ., 2020 ). This type of reaction is best represented by the second mechanism from the top depicted in Fig.…”

Unexpected Mechanism of Biodegradation and Defluorination of 2,2-Difluoro-1,3-Benzodioxole by Pseudomonas putida F1

“…As such, it is completely oxidized and unlikely to undergo oxidative defluorination directly. Defluorination by oxidizing enzymes such as oxygenases is known ( 14 , 15 ), typically with a carbon atom bonded to a single fluorine atom, unlike in DFBD ( 16 – 19 ). Perfluoroethylene is biodegraded to defluorinated products by soluble methane monooxygenase from Methylosinus trichosporium Ob3B ( 20 ).…”