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Cited by 63Per- and polyfluoroalkyl substances researchMicrobial bioremediation and biosurfactantsMicrobial Fuel Cells and Bioremediation

The DOI matches its Crossref record; 75 of the 75 references it cites were found in a registry or an index; none of the 57 sources its claims cite is checked for support yet.

Electron bifurcation and fluoride efflux systems implicated in defluorination of perfluorinated unsaturated carboxylic acids by Acetobacterium spp

Open access
Yu, Yaochun, Xu, Fengjun, Zhao, Weiyang, Thoma, Calvin, Che, Shun, Richman, Jack E., Jin, Bosen, Zhu, Yiwen, Xing, Yue, Wackett, Lawrence, Men, Yujie·2024·Science Advances
DOI 10.1126/sciadv.ado2957PMC PMC466959
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Abstract

Enzymatic cleavage of C─F bonds in per- and polyfluoroalkyl substances (PFAS) is largely unknown but avidly sought to promote systems biology for PFAS bioremediation. Here, we report the reductive defluorination of α, β-unsaturated per- and polyfluorocarboxylic acids by Acetobacterium spp. The microbial defluorination products were structurally confirmed and showed regiospecificity and stereospecificity, consistent with their formation by enzymatic reactions. A comparison of defluorination activities among several Acetobacterium species indicated that a functional fluoride exporter was required for the detoxification of the released fluoride. Results from both in vivo inhibition tests and in silico enzyme modeling suggested the involvement of enzymes of the flavin-based electron-bifurcating caffeate reduction pathway [caffeoyl-CoA reductase (CarABCDE)] in the reductive defluorination. This is a report on specific microorganisms carrying out enzymatic reductive defluorination of PFAS, which could be linked to electron-bifurcating reductases that are environmentally widespread.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

Acetobacterium spp. reductively defluorinate α,β-unsaturated per- and polyfluorocarboxylic acids, producing regiospecific and stereospecific products. A functional Fluc fluoride exporter and the flavin-based electron-bifurcating caffeate reduction complex CarABCDE are implicated in sustaining and catalyzing defluorination.

Key findings

  • A. bakii completely biotransformed ~90 μM PFMeUPA within 3 weeks when grown on fructose, releasing fluoride at near 1:1 molar ratio; M. barkeri showed only minor defluorination (5 μM fluoride from 55 μM PFMeUPA after 50 days).
  • Products included TP256 [(CF3)2CFCF═CHCOO−], TP259 [(CF3)2CFCHFCH2COO−], and TP276 [(CF3)2CF(CHF)2COO−]; ~82% of PFMeUPA was transformed via reductive defluorination, with α-C defluorination and stereospecific biohydrogenation.
  • A. bakii also transformed PFUPA and 6:2 FTUCA via reductive defluorination/hydrogenation, but only hydrogenated FTMeUPA without F− formation.
  • A functional fluoride exporter was required: crcB1/crcB2 were up-regulated ~2-fold with PFMeUPA; A. fimetarium had a truncated crcB2 and no defluorination; E. coli ΔcrcB was rescued by crcB genes except truncated crcB2 from A. fimetarium.
  • Caffeate (5 mM) completely inhibited PFMeUPA defluorination during the first week, with activity restored after caffeate depletion; CarC modeling and HMM searches identified 723 WWTP metagenomes with CarC homologs, 499 with sufficient location metadata.

Methods

  • Pure cultures of five Acetobacterium species, C. homopropionicum, and M. barkeri were grown under DSMZ-recommended conditions and spiked with 50 to 90 μM individual fluorinated compounds; fluoride was measured by ion-selective electrode, and products were analyzed by UHPLC-HRMS/MS and 19F-NMR.
  • A. bakii gene regulation was examined by transcriptomics and proteomics with and without 300 μM PFMeUPA; E. coli K-12 MG1655 ΔcrcB rescue tests used crcB genes from Acetobacterium spp. in LB with 250 μM NaF; caffeate competition used 5 mM caffeate.
  • CarC active-site models were built by docking caffeoyl-CoA and C5F9CO-CoA using PDB 6FAH aligned to PDB 1JQI; HMMs from BLAST sequences at ≥55% identity were used to search MGnify WWTP metagenomes.

Limitations

  • The paper states that a full demonstration requires future carC-knockout mutants in vivo and purified CarCDE complex in vitro under appropriate conditions; no differential expression of carABCDE was observed, possibly because the maximum nontoxic PFMeUPA concentration was about 10-fold lower than typical caffeate concentrations.
  • The paper states that the enzyme-assisted defluorination mechanism is proposed from in silico modeling and inhibition experiments, not yet from direct structural or biochemical demonstration with PFMeUPA-bound CarC.
  • Evident from the text: defluorination was shown only for α,β-unsaturated per- and polyfluorinated carboxylic acids, not saturated PFAS; C. homopropionicum did not transform PFMeUPA and only slowly defluorinated PFUPA; metagenomic prevalence is sequence-based and limited to WWTP databases.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1126/sciadv.ado2957

Cites

75 of 75 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

0 of 57 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    Reductive defluorination of α,β-unsaturated per- and polyfluorocarboxylic acids by Acetobacterium spp. was observed.

    “Here, we report the reductive defluorination of α, β-unsaturated per- and polyfluorocarboxylic acids by Acetobacterium spp.”
    Quote in the paperSubstantial claim
  • Findingown data

    Differential expression of carABCDE in A. bakii by PFMeUPA was not observed.

    “We were not able to observe differential expression of carABCDE in A. bakii by PFMeUPA (fig. S7 and tables S1 to S3).”
    Quote in the paperSubstantial claim
  • Findingown data

    C. homopropionicum achieved slow defluorination (20 μM of F− formation from 100 μM of parent compound over 15 days) for PFUPA.

    “However, it did achieve slow defluorination (20 μM of F− formation from 100 μM of parent compound over 15 days) for PFUPA (CF3CF2CF═CFCOOH) that is one carbon shorter than PFMeUPA (fig. S12).”
    Quote in the paperSubstantial claim
  • Findingown data

    M. barkeri exhibited very minor defluorination (5 μM fluoride ion from 55 μM PFMeUPA after 50 days of incubation).

    “While M. barkeri exhibited very minor defluorination (5 μM fluoride ion from 55 μM PFMeUPA after 50 days of incubation) (fig. S1)”
    Quote in the paperNot a substantial claim
  • Findingcitation

    The total defluorination of PFUPA and 6:2 FTUCA by A. bakii was similar to what was previously observed in an anaerobic microbial community.

    “The total defluorination was similar to what we previously observed in an anaerobic microbial community (13).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [13] Y. Yu, S. Che, C. Ren, B. Jin, Z. Tian, J. Liu, Y. Men, Microbial defluorination of unsaturated per- and polyfluorinated carboxylic acids under anaerobic and aerobic conditions: A structure specificity study. Environ. Sci. Technol. 56, 4894– 4904 (2022). 35373561 PMC9465985 source
  • It may state two separate claims as one. 26
  • Probably not a substantial claim. 17

  • It may state two separate claims as one.

    Findingown data

    The microbial defluorination products were structurally confirmed and showed regiospecificity and stereospecificity, consistent with formation by enzymatic reactions.

    “The microbial defluorination products were structurally confirmed and showed regiospecificity and stereospecificity, consistent with their formation by enzymatic reactions.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    A. bakii also transformed PFUPA and 6:2 FTUCA via reductive defluorination and hydrogenation.

    “A. bakii also transformed two other unsaturated PFAS with structures similar to PFMeUPA, PFUPA (CF3CF2CF═CFCOOH) and 6:2 FTUCA (CF3(CF2)4CF═CHCOOH) (Fig. 1D), via reductive defluorination and hydrogenation (fig. S5, A to D).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. It may state two separate claims as one.

    Findingown data

    A search of the MGnify database retrieved 723 WWTP metagenomes, of which 499 had sufficient location metadata.

    “A search of the MGnify database retrieved 723 WWTP metagenomes of which 499 had sufficient location metadata.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The MGnify WWTP metagenomes with location metadata are representative of global wastewater environments.

  • It may state two separate claims as one.

    Findingown data

    A. bakii transformed PFMeUPA into the same intermediates and end products as the community with the same stoichiometry of fluoride release at a near 1:1 molar ratio to the transformed PFMeUPA.

    “A. bakii transformed PFMeUPA into the same intermediates and end products as the community with the same stoichiometry of fluoride release at a near 1:1 molar ratio to the transformed PFMeUPA (Fig. 1A).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    PFMeUPA defluorination activity was detected in aqueous film forming foam-impacted soil and groundwater communities, suggesting that other environments may contain electron-bifurcating, defluorinating reductases of the type characterized in this study.

    “We have detected PFMeUPA defluorination activity in aqueous film forming foam-impacted soil and groundwater communities (fig. S14), suggesting that other environments may contain electron-bifurcating, defluorinating reductases of the type characterized in this study.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    Similar defluorination activities were observed for A. bakii, A. woodii, and A. paludosum, while A. malicum exhibited partial defluorination and parent compound biotransformation.

    “Similar defluorination activities were observed for A. bakii, A. woodii, and A. paludosum, while A. malicum exhibited partial defluorination and parent compound biotransformation (Fig. 2B and fig. S10A).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    No defluorination activity was observed in the cell-free spent medium, suggesting that defluorination occurred within the outer membrane of the bacterium.

    “We did not observe defluorination activity in the cell-free spent medium (fig. S6), suggesting that the defluorination occurred within the outer membrane of the bacterium.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    A. bakii only hydrogenated FTMeUPA without any F− formation.

    “A. bakii only hydrogenated this structure without any F− formation (Fig. 1D and fig. S5, E and F).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    E. coli K-12 MG1655 ΔcrcB mutant is sensitive to F− and exhibited limited growth in the presence of 250 μM F−.

    “That strain is sensitive to F− and exhibited limited growth in the presence of 250 μM F−.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    The addition of 5 mM caffeate in A. bakii completely inhibited the defluorination of PFMeUPA during the first week without substantial inhibition on cell growth.

    “First, the addition of 5 mM caffeate in A. bakii completely inhibited the defluorination of PFMeUPA during the first week (Fig. 3A) without substantial inhibition on cell growth (fig. S9A).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    Although A. malicum has a complete caffeate reduction operon, its caffeate reduction activity was significantly lower than the other Acetobacterium species.

    “Although A. malicum has a complete caffeate reduction operon, its caffeate reduction activity was significantly lower than the other Acetobacterium species (t test, P < 0.05, fig. S10, B and C).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    PFMeUPA defluorination was inhibited by caffeate and restored after caffeate was depleted.

    “PFMeUPA defluorination was inhibited by caffeate and restored after caffeate was depleted”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim.

    Findingown data

    The multiple sequence alignments were used to create HMMs to search 499 metagenome sites containing genes with sequence signatures encoding putative electron-bifurcating reductases having the potential to catalyze defluorination.

    “The multiple sequence alignments in part A were used to create HMMs to search 499 metagenome sites containing genes with sequence signatures encoding putative electron-bifurcating reductases having the potential to catalyze defluorination.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The MGnify WWTP metagenomes with location metadata are representative of global wastewater environments.

  • It may state two separate claims as one.

    Findingown data

    In the genome of A. fimetarium, crcB1 is intact and homologous to that of A. bakii, while crcB2 is truncated by 64 bp from the 3′ tail.

    “In the genome of A. fimetarium, while crcB1 is intact and homologous to that of A. bakii, crcB2 was found to be truncated by 64 bp from the 3′ tail (Fig. 2A).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    Sites were identified as having Acetobacterium-like patterns, Clostridium-like patterns, or both.

    “Sites were identified as having Acetobacterium-like patterns, Clostridium-like patterns, or both, represented as red, blue, or green circles, respectively.”
    Quote in the paperNot a substantial claim

  • It may state two separate claims as one.

    Findingown data

    The region around E362 shows complete conservation in Acetobacterium spp. and high conservation with Clostridium.

    “The region around E362 shows complete conservation in Acetobacterium spp. and high conservation with Clostridium.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Findingown data

    A. fimetarium, which has an intact Car operon but a nonfunctional CrcB, was able to reduce caffeate but not able to defluorinate PFMeUPA at all.

    “A. fimetarium, which has an intact Car operon (Fig. 2A and fig. S10) but a nonfunctional CrcB (Fig. 2C and fig. S8), was able to reduce caffeate (fig. S10A) but not able to defluorinate PFMeUPA at all (Fig. 2B).”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Premisecitation

    The high energy required, fluoride toxicity, and short evolutionary time span of PFAS exposure to microbes likely constrain PFAS biodefluorination.

    “the high energy (i.e., low reduction potential) required, together with fluoride toxicity and the short evolutionary time span of PFAS exposure to microbes, likely constrains PFAS biodefluorination (4).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [4] L. P. Wackett, Nothing lasts forever: Understanding microbial biodegradation of polyfluorinated compounds and perfluorinated alkyl substances. Microb. Biotechnol. 15, 773– 792 (2022). 34570953 PMC8913905

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    C─F bond reduction is thermodynamically favorable overall.

    “Although C─F bond reduction is thermodynamically favorable overall (5)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [5] J. R. Parsons, M. Sáez, J. Dolfing, P. de Voogt, in Rev. Environ. Contam. Toxicol., D. M. Whitacre, Ed. (Springer US, New York, NY, 2008), vol. 196, pp. 53–71. 19025092

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • It may state two separate claims as one.

    Interpretationown data

    Specific microorganisms carry out enzymatic reductive defluorination of PFAS, which could be linked to electron-bifurcating reductases that are environmentally widespread.

    “This is a report on specific microorganisms carrying out enzymatic reductive defluorination of PFAS, which could be linked to electron-bifurcating reductases that are environmentally widespread.”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Interpretationreasoning

    A. bakii carried out reduction of a number of α,β-unsaturated per- and polyfluorinated carboxylic acids, but only specifically cleaved C─F bonds on the unsaturated carbons.

    “This indicated that while A. bakii carried out the reduction of a number of α, β-unsaturated per- and polyfluorinated carboxylic acids, it only specifically cleaved C─F bonds on the unsaturated carbons.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim.

    Premisecitation

    Some acetogens have been reported to be involved in cometabolic dechlorination and debromination.

    “Some acetogens have been reported to be involved in cometabolic dechlorination and debromination (20, 21).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [20] D. P. Terzenbach, M. Blaut, Transformation of tetrachloroethylene to trichloroethylene by homoacetogenic bacteria. FEMS Microbiol. Lett. 123, 213– 218 (1994). 7988892 source
    • cites [21] C. Ding, W. L. Chow, J. He, Isolation of Acetobacterium sp. strain AG, which reductively debrominates octa- and pentabrominated diphenyl ether technical mixtures. Appl. Environ. Microbiol. 79, 1110– 1117 (2013). 23204415 PMC3568622 source

  • It may state two separate claims as one.

    Interpretationown data

    The enzyme-assisted defluorination explains the regiospecific fluoride elimination observed for the microbiological defluorination, whereas chemical reductions eliminate fluorine from either C-3 or C-2, or both.

    “This enzyme-assisted defluorination explains the regiospecific fluoride elimination observed for the microbiological defluorination, whereas we see the elimination of fluorine from either C-3 or C-2, or both, in chemical reductions (figs. S2 and S4).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim.

    Interpretationreasoning

    The consistency between the biochemical reactions observed for PFMeUPA and the pathways was inferred based on the function of each gene in the car operon.

    “the consistency between the biochemical reactions observed for PFMeUPA and the pathways was inferred based on the function of each gene in the car operon”
    Quote in the paperSubstantial claim

  • It may state two separate claims as one.

    Interpretationnone given

    Defluorination occurring intracellularly accumulates toxic F−, thereby requiring functional F− transporters.

    “Defluorination occurring intracellularly accumulates toxic F−, thereby requiring functional F− transporters.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    C. homopropionicum utilizes electron bifurcation in a fermentation pathway yielding propionic acid.

    “We further tested Clostridium homopropionicum (DSM5847), a species that utilizes electron bifurcation in a fermentation pathway yielding propionic acid (33).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [33] W. Buckel, R. K. Thauer, Flavin-based electron bifurcation, a new mechanism of biological energy coupling. Chem. Rev. 118, 3862– 3886 (2018). 29561602 source

  • It may state two separate claims as one.

    Premisecitation

    Defluorination of perfluorinated acids by Acidimicrobium sp. A6 has been reported, but no enzymes responsible have been identified.

    “The defluorination of perfluorinated acids by Acidimicrobium sp. A6 has been reported, but no enzymes responsible for these processes have been identified (14–16).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [14] S. Huang, P. R. Jaffé, Defluorination of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) by Acidimicrobium sp. strain A6. Environ. Sci. Technol. 53, 11410– 11419 (2019). 31529965 source
    • cites [15] J. Liu, E. Edwards, J. Van Hamme, M. Manefield, C. P. Higgins, J. Blotevogel, J. Liu, L. S. Lee, Correspondence on “Defluorination of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) by Acidimicrobium sp. strain A6”. Environ. Sci. Technol. 57, 20440– 20442 (2023). 37948637 source
    • cites [16] P. R. Jaffé, S. Huang, Rebuttal to correspondence on “Defluorination of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) by Acidimicrobium sp. strain A6”. Environ. Sci. Technol. 57, 20443– 20447 (2023). 37913821 source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Nature has evolved effective proteins to protect against fluoride leaking into cells from mineral fluoride.

    “Thus, nature has evolved effective proteins to protect against fluoride leaking into cells from mineral fluoride (24, 49).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [24] J. L. Baker, N. Sudarsan, Z. Weinberg, A. Roth, R. B. Stockbridge, R. R. Breaker, Widespread genetic switches and toxicity resistance proteins for fluoride. Science 335, 233– 235 (2012). 22194412 PMC4140402 source
    • cites [49] R. B. Stockbridge, H. H. Lim, R. Otten, C. Williams, T. Shane, Z. Weinberg, C. Miller, Fluoride resistance and transport by riboswitch-controlled CLC antiporters. Proc. Natl. Acad. Sci. U.S.A. 109, 15289– 15294 (2012). 22949689 PMC3458365 source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Fluoride is abundant in Earth's crust.

    “Fluoride is abundant in Earth’s crust (47, 48).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [47] C. J. Allègre, J.-P. Poirier, E. Humler, A. W. Hofmann, The chemical composition of the Earth. Earth Planet. Sci. Lett. 134, 515– 526 (1995). source
    • cites [48] M. Amini, K. Mueller, K. C. Abbaspour, T. Rosenberg, M. Afyuni, K. N. Møller, M. Sarr, C. A. Johnson, Statistical modeling of global geogenic fluoride contamination in groundwaters. Environ. Sci. Technol. 42, 3662– 3668 (2008). 18546705 source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    Unstable intermediates such as gem-fluoroalcohols may be formed, leading to spontaneous C─F bond cleavage.

    “Unstable intermediates such as gem-fluoroalcohols may be formed, leading to spontaneous C─F bond cleavage (6, 7, 13).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [6] S. Che, B. Jin, Z. Liu, Y. Yu, J. Liu, Y. Men, Structure-specific aerobic defluorination of short-chain fluorinated carboxylic acids by activated sludge communities. Environ. Sci. Technol. Lett. 8, 668– 674 (2021). 35316934 PMC8936751 source
    • cites [7] B. Jin, H. Liu, S. Che, J. Gao, Y. Yu, J. Liu, Y. Men, Substantial defluorination of polychlorofluorocarboxylic acids triggered by anaerobic microbial hydrolytic dechlorination. Nat. Water 1, 451– 461 (2023). 38405335 PMC10888525 source
    • cites [13] Y. Yu, S. Che, C. Ren, B. Jin, Z. Tian, J. Liu, Y. Men, Microbial defluorination of unsaturated per- and polyfluorinated carboxylic acids under anaerobic and aerobic conditions: A structure specificity study. Environ. Sci. Technol. 56, 4894– 4904 (2022). 35373561 PMC9465985 source

  • Probably not a substantial claim.

    Premisecitation

    Direct enzymatic cleavage of C─F bonds in perfluorinated structures is rare.

    “In contrast, direct enzymatic cleavage of C─F bonds in perfluorinated structures is rare (5).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [5] J. R. Parsons, M. Sáez, J. Dolfing, P. de Voogt, in Rev. Environ. Contam. Toxicol., D. M. Whitacre, Ed. (Springer US, New York, NY, 2008), vol. 196, pp. 53–71. 19025092

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.

    Premisecitation

    Other key members of the community included heterotrophic fermenters, autotrophic methanogens, and homoacetogens capable of utilizing H2 and CO2.

    “Other key members of the community included a variety of heterotrophic fermenters, along with autotrophic methanogens and homoacetogens capable of utilizing H2 and CO2 (18, 19).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [18] L. A. Hug, R. G. Beiko, A. R. Rowe, R. E. Richardson, E. A. Edwards, Comparative metagenomics of three Dehalococcoides-containing enrichment cultures: The role of the non-dechlorinating community. BMC Genomics 13, 327 (2012). 22823523 PMC3475024 source
    • cites [19] M. Duhamel, E. A. Edwards, Growth and yields of dechlorinators, acetogens, and methanogens during reductive dechlorination of chlorinated ethenes and dihaloelimination of 1,2-dichloroethane. Environ. Sci. Technol. 41, 2303– 2310 (2007). 17438779 source

  • It may state two separate claims as one.

    Interpretationown data

    The enzyme-assisted defluorination pathway is supported by the TP formation trend, with TP256 first increasing then decreasing while both TP276 and TP259 increase over time.

    “This enzyme-assisted defluorination pathway (fig. S11) is also supported by the TP formation trend (Fig. 1A), with TP256 first increasing then decreasing while both TP276 and TP259 increase over time.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. It may be too vague to check against evidence. The paper’s conclusions may not depend on it.

    Interpretationreasoning

    Given the occurrence of unsaturated PFAS in the environment, the findings could help with a better understanding of their environmental fate.

    “given the occurrence of unsaturated PFAS in the environment, the findings could help with a better understanding of their environmental fate.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim.

    Premisecitation

    Proteins with 50% identity and higher have been reported to have less than 1-Å difference between their backbones.

    “Proteins with 50% identity and higher have been reported to have less than 1-Å difference between their backbones (60).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [60] P. Koehl, M. Levitt, Sequence variations within protein families are linearly related to structural variations. J. Mol. Biol. 323, 551– 562 (2002). 12381308 PMC2692051 source

  • It may state two separate claims as one.

    Interpretationown data

    Caffeate competition experiments implicate PFMeUPA as a possible electron acceptor alternative to caffeate and undergoing enzyme-assisted α-defluorination within the electron-bifurcating enzyme complex.

    “This is also consistent with caffeate competition experiments implicating PFMeUPA as a possible electron acceptor alternative to caffeate and undergoing enzyme-assisted α-defluorination within the electron-bifurcating enzyme complex.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    CarCDE is naturally evolved to reduce plant aromatic enoic acids such as caffeic acid, coupled with formation of reducing power for autotrophic growth or sodium transport to generate incremental ATP in energy-marginalized environments.

    “CarCDE is naturally evolved to reduce plant aromatic enoic acids such as caffeic acid, coupled with formation of reducing power for autotrophic growth or sodium transport to generate incremental ATP in energy-marginalized environments (30).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [30] V. Hess, J. M. González, A. Parthasarathy, W. Buckel, V. Müller, Caffeate respiration in the acetogenic bacterium Acetobacterium woodii: A coenzyme A loop saves energy for caffeate activation. Appl. Environ. Microbiol. 79, 1942– 1947 (2013). 23315745 PMC3592220 source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    The published crystal structure of A. woodii CarC (PDB 6FAH) does not include caffeoyl-CoA in complex with the enzyme.

    “The published crystal structure of A. woodii CarC [Protein Data Bank (PDB) 6FAH] does not include caffeoyl-CoA in complex with the enzyme.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites PDB 6FAH

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Study design and conductcitation

    The accuracy of fluoride ion measurement by ion-selective electrode was cross-validated using ion chromatography.

    “The accuracy of the fluoride measurement by ISE was cross-validated using ion chromatography as described in our previous study (17).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [17] Y. Yu, K. Zhang, Z. Li, C. Ren, J. Chen, Y. H. Lin, J. Liu, Y. Men, Microbial cleavage of C-F bonds in two C6 per- and polyfluorinated compounds via reductive defluorination. Environ. Sci. Technol. 54, 14393– 14402 (2020). 33121241 source

  • Probably not a substantial claim. The paper’s conclusions may not depend on it.

    Premisecitation

    Four fluorinated carboxylic acids have previously reported biodefluorination feasibilities in an anaerobic enrichment community.

    “Four fluorinated carboxylic acids were investigated based on their previously reported biodefluorination feasibilities in an anaerobic enrichment community (13).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [13] Y. Yu, S. Che, C. Ren, B. Jin, Z. Tian, J. Liu, Y. Men, Microbial defluorination of unsaturated per- and polyfluorinated carboxylic acids under anaerobic and aerobic conditions: A structure specificity study. Environ. Sci. Technol. 56, 4894– 4904 (2022). 35373561 PMC9465985 source
40 of 40

  • The paper relies on this without support.

    If fluoride is formed in the periplasm, it spontaneously enters cells as hydrogen fluoride (HF).

    “If formed in the periplasm, fluoride is known to spontaneously enter cells as hydrogen fluoride (HF).”

  • The paper relies on this without support.

    The MGnify WWTP metagenomes with location metadata are representative of global wastewater environments.

    “A search of the MGnify database retrieved 723 WWTP metagenomes of which 499 had sufficient location metadata.”

  • The paper relies on this without support.

    The E. coli ΔcrcB mutant growth rescue assay is a valid proxy for fluoride export function in Acetobacterium species.

    “Except for E. coli ΔcrcB with crcB1 and truncated crcB2 from A. fimetarium, all other strains were rescued from F− toxicity (Fig. 2C).”

  • The paper relies on this without support.

    The CarC active site model based on the A. woodii CarCDE x-ray structure is representative of CarC in A. bakii and other Acetobacterium species.

    “Using the x-ray structure coordinates of the CarCDE enzyme complex (28), we modeled the caffeoyl-CoA binding site of CarC”

  • The paper relies on this without support.

    The E. coli K-12 MG1655 ΔcrcB mutant strain is sensitive to high fluoride concentration.

    “The mutant strain E. coli K-12 MG1655 ΔcrcB was constructed using the λ-red homologous recombination system and is sensitive to high fluoride concentration.”

  • The paper relies on this without support.

    The CarC homolog from a Rat protein complexed with acetoacetyl-CoA (PDB 1JQI) is highly similar to A. woodii CarC.

    “a highly similar CarC homolog from a Rat protein complexed with acetoacetyl-CoA (PDB 1JQI) was aligned to the A. woodii structure.”
6 of 6

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Reported Clostridium test concentration falls outside the stated dosing range

    Minor

    The results describe a PFUPA test starting at 100 μM, but the methods state that the biotransformation groups were spiked with 50 to 90 μM of the individual compounds.

  • NMR instrument frequency differs by a factor of one million

    Minor

    The chemical-hydrogenation methods specify a 400-MHz NMR spectrometer, while the later NMR methods section describes the instrument for the same products as 400 Hz.

2 of 2

Citations

Cites

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Metadata

Authors
Yu, Y., Xu, F., Zhao, W., Thoma, C., Che, S., Richman, J. E., Jin, B., Zhu, Y., Xing, Y., Wackett, L., & Men, Y.
Affiliations
  • University of California, Riverside (US)
  • University of Minnesota (US)
Corresponding author
Men, Yujie
ORCID
Venue
Science Advances
Publisher
American Association for the Advancement of Science (AAAS)
Published
2024-07-19
Volume
10
Issue
29
Pages
eado2957-eado2957
ISSN
2375-2548 (ISSN-L)
DOI
10.1126/sciadv.ado2957
PMC
PMC466959
OpenAlex
W4400726249
Cited by
63
References
75
Citations by year
2026: 26 · 2025: 29 · 2024: 8
FWCI
7.19
Type
journal article
Language
en
Open access
Licence
Locations
  • Science Advances (publishedVersion, cc-by-nc)
  • bioRxiv (Cold Spring Harbor Laboratory) (submittedVersion)
  • PubMed Central (publishedVersion, cc-by-nc)
  • PubMed (publishedVersion)
  • DORA Eawag (Swiss Federal Institute of Aquatic Science and Technology (Eawag)) (submittedVersion, cc-by-nc)
  • eScholarship (California Digital Library) (submittedVersion, cc-by-nc)
  • PubMed Central (submittedVersion)
Funders
  • National Science Foundation (1931941)
  • Strategic Environmental Research and Development Program (ER20-1541)
  • National Institute of Environmental Health Sciences (R01ES032668)
Topics
  • Physical Sciences › Environmental Science › Environmental Chemistry › Per- and polyfluoroalkyl substances research
  • Physical Sciences › Environmental Science › Pollution › Microbial bioremediation and biosurfactants
  • Physical Sciences › Environmental Science › Environmental Engineering › Microbial Fuel Cells and Bioremediation
Keywords
electron bifurcation, reductive defluorination, perfluorinated carboxylic acids, polyfluoroalkyl substances, Acetobacterium, C–F bond cleavage

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

A language model drew the claims from the paper on 2026-11-10, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).

A second model labelled each claim on 2026-11-10 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).

Statistics and arithmetic are recomputed, not judged.

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