Glycyl Radical Enzymes and Sulfonate Metabolism in the Microbiome.

Sulfonates include diverse natural products and anthropogenic chemicals and are widespread in the environment. Many bacteria can degrade sulfonates and obtain sulfur, carbon, and energy for growth, playing important roles in the biogeochemical sulfur cycle. Cleavage of the inert sulfonate C-S bond involves a variety of enzymes, cofactors, and oxygen-dependent and oxygen-independent catalytic mechanisms. Sulfonate degradation by strictly anaerobic bacteria was recently found to involve C-S bond cleavage through O2-sensitive free radical chemistry, catalyzed by glycyl radical enzymes (GREs). The associated discoveries of new enzymes and metabolic pathways for sulfonate metabolism in diverse anaerobic bacteria have enriched our understanding of sulfonate chemistry in the anaerobic biosphere. An anaerobic environment of particular interest is the human gut microbiome, where sulfonate degradation by sulfate- and sulfite-reducing bacteria (SSRB) produces H2S, a process linked to certain chronic diseases and conditions.

Isethionate is an intermediate in the degradation of sulfoacetate by the human gut pathobiont Bilophila wadsworthia.

The obligately anaerobic sulfite-reducing bacterium Bilophila wadsworthia is a common human pathobiont inhabiting the distal intestinal tract. It has a unique ability to utilize a diverse range of food- and host-derived sulfonates to generate sulfite as a terminal electron acceptor (TEA) for anaerobic respiration, converting the sulfonate sulfur to H2S, implicated in inflammatory conditions and colon cancer. The biochemical pathways involved in the metabolism of the C2 sulfonates isethionate and taurine by B. wadsworthia were recently reported. However, its mechanism for metabolizing sulfoacetate, another prevalent C2 sulfonate, remained unknown. Here, we report bioinformatics investigations and in vitro biochemical assays that uncover the molecular basis for the utilization of sulfoacetate as a source of TEA (STEA) for B. wadsworthia, involving conversion to sulfoacetyl-CoA by an ADP-forming sulfoacetate-CoA ligase (SauCD), and stepwise reduction to isethionate by NAD(P)H-dependent enzymes sulfoacetaldehyde dehydrogenase (SauS) and sulfoacetaldehyde reductase (TauF). Isethionate is then cleaved by the O2-sensitive isethionate sulfolyase (IseG), releasing sulfite for dissimilatory reduction to H2S. Sulfoacetate in different environments originates from anthropogenic sources such as detergents, and natural sources such as bacterial metabolism of the highly abundant organosulfonates sulfoquinovose and taurine. Identification of enzymes for anaerobic degradation of this relatively inert and electron-deficient C2 sulfonate provides further insights into sulfur recycling in the anaerobic biosphere, including the human gut microbiome.

Impact of Gestational Exposure to Individual and Combined Per- and Polyfluoroalkyl Substances on a Placental Structure and Efficiency: Findings from the Ma'anshan Birth Cohort.

Prenatal exposure to perfluoroalkyl and polyfluoroalkyl substances (PFASs) is inevitable among pregnant women. Nevertheless, there is a scarcity of research investigating the connections between prenatal PFAS exposure and the placental structure and efficiency. Based on 712 maternal-fetal dyads in the Ma'anshan Birth Cohort, we analyzed associations between individual and mixed PFAS exposure and placental measures. We repeatedly measured 12 PFAS in the maternal serum during pregnancy. Placental weight, scaling exponent, chorionic disc area, and disc eccentricity were used as the outcome variables. Upon adjusting for confounders and implementing corrections for multiple comparisons, we identified positive associations between branched perfluorohexane sulfonate (br-PFHxS) and 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) with placental weight. Additionally, a positive association was observed between br-PFHxS and the scaling exponent, where a higher scaling exponent signified reduced placental efficiency. Based on neonatal sex stratification, female infants were found to be more susceptible to the adverse effects of PFAS exposure. Mixed exposure modeling revealed that mixed PFAS exposure was positively associated with placental weight and scaling exponent, particularly during the second and third trimesters. Furthermore, br-PFHxS and 6:2 Cl-PFESA played major roles in the placental measures. This study provides the first epidemiological evidence of the relationship between prenatal PFAS exposure and placental measures.

Occurrence of Major Perfluorinated Alkylate Substances in Human Blood and Target Organs.

Human exposure to perfluorinated alkylate substances (PFASs) is usually assessed from the concentrations in serum or plasma, assuming one-compartment toxicokinetics. To characterize body distributions of major PFASs, we obtained and extracted tissue samples from 19 forensic autopsies of healthy adult subjects who had died suddenly and were not known to have elevated levels of PFAS exposure. As target organs of toxicological importance, we selected the liver, kidneys, lungs, spleen, and brain, as well as whole blood. Samples weighing about 0.1 g were analyzed by liquid chromatography coupled to triple mass spectrometers. Minor variations in PFAS concentrations were found between the kidney cortex and medulla and between lung lobes. Organ concentrations of perfluorooctanoic sulfonate (PFOS) and perfluorononanoate (PFNA) correlated well with blood concentrations, while perfluorooctanoate (PFOA) and perfluorohexanoic sulfonate (PFHxS) showed more variable associations. Likewise, the liver concentrations correlated well with those of other organs. Calculations of relative distributions were carried out to assess the interdependence of organ retentions. Equilibrium model predictions largely explained the observed PFAS distributions, except for the brain. Although the samples were small and affected by a possible lack of homogeneity, these findings support the use of blood-PFAS concentrations as a measure of PFAS exposure, with the liver possibly acting as the main organ of retention.

Oxidative Transformation of Nafion-Related Fluorinated Ether Sulfonates: Comparison with Legacy PFAS Structures and Opportunities of Acidic Persulfate Digestion for PFAS Precursor Analysis.

The total oxidizable precursor (TOP) assay has been extensively used for detecting PFAS pollutants that do not have analytical standards. It uses hydroxyl radicals (HO•) from the heat activation of persulfate under alkaline pH to convert H-containing precursors to perfluoroalkyl carboxylates (PFCAs) for target analysis. However, the current TOP assay oxidation method does not apply to emerging PFAS because (i) many structures do not contain C-H bonds for HO• attack and (ii) the transformation products are not necessarily PFCAs. In this study, we explored the use of classic acidic persulfate digestion, which generates sulfate radicals (SO4-•), to extend the capability of the TOP assay. We examined the oxidation of Nafion-related ether sulfonates that contain C-H or -COO-, characterized the oxidation products, and quantified the F atom balance. The SO4-• oxidation greatly expanded the scope of oxidizable precursors. The transformation was initiated by decarboxylation, followed by various spontaneous steps, such as HF elimination and ester hydrolysis. We further compared the oxidation of legacy fluorotelomers using SO4-• versus HO•. The results suggest novel product distribution patterns, depending on the functional group and oxidant dose. The general trends and strategies were also validated by analyzing a mixture of 100000- or 10000-fold diluted aqueous film-forming foam (containing various fluorotelomer surfactants and organics) and a spiked Nafion precursor. Therefore, (1) the combined use of SO4-• and HO• oxidation, (2) the expanded list of standard chemicals, and (3) further elucidation of SO4-• oxidation mechanisms will provide more critical information to probe emerging PFAS pollutants.

Suspect, Nontarget Screening, and Toxicity Prediction of Per- and Polyfluoroalkyl Substances in the Landfill Leachate.

Landfills are the final stage of urban wastes containing perfluoroalkyl and polyfluoroalkyl substances (PFASs). PFASs in the landfill leachate may contaminate the surrounding groundwater. As major environmental pollutants, emerging PFASs have raised global concern. Besides the widely reported legacy PFASs, the distribution and potential toxic effects of numerous emerging PFASs remain unclear, and unknown PFASs still need discovery and characterization. This study proposed a comprehensive method for PFAS screening in leachate samples using suspect and nontarget analysis. A total of 48 PFASs from 10 classes were identified; nine novel PFASs including eight chloroperfluoropolyether carboxylates (Cl-PFPECAs) and bistriflimide (HNTf2) were reported for the first time in the leachate, where Cl-PFPECA-3,1 and Cl-PFPECA-2,2 were first reported in environmental media. Optimized molecular docking models were established for prioritizing the PFASs with potential activity against peroxisome proliferator-activated receptor α and estrogen receptor α. Our results indicated that several emerging PFASs of N-methyl perfluoroalkyl sulfonamido acetic acids (N-MeFASAAs), n:3 fluorotelomer carboxylic acid (n:3 FTCA), and n:2 fluorotelomer sulfonate (n:2 FTSA) have potential health risks that cannot be ignored.

Sulfonated Polyimide Membranes Constructed by Main-Chain and Molecular-Network Engineering Strategy for Direct Methanol Fuel Cell.

Excessive swelling is one important factor that leads to high fuel permeability and limited operating concentration of methanol for proton exchange membranes. Herein, a collaborative strategy of main-chain and molecular-network engineering is applied to lower swelling ratio and improve methanol resistance for highly sulfonated polyimide. Two m-phenylenediamine monomers (4-(2,3,5,6-tetrafluoro-4-vinylphenoxy)benzene-1,3-diamine and 4,6-bis(2,3,5,6-tetrafluoro-4-vinylphenoxy)benzene-1,3-diamine) with tetrafluorostyrol groups are designed and synthesized. Two series of cross-linked sulfonated polyimides (CSPI-Ts, CSPI-Bs) are prepared from the two diamines, 4,4'-diaminostilbene-2,2'-disulfonic acid and 1,4,5,8-naphthalenetetracarboxylicdianhydride. The rigid main-chain structure is cornerstone for wet CSPI-Ts and CSPI-Bs remaining stable at elevated temperatures. The introduction of hydrophobic cross-linked network further improves their dimensional stability and methanol resistance. CSPI-Ts and CSPI-Bs show obviously improved performances containing high proton conductivity (121 ± 0.27-158 ± 0.35 S cm-1 ), low swelling ratio (9.6 ± 0.40%-16.1 ± 0.01%) and methanol permeability (4.14-7.69 × 10-7 cm2 s-1 ) at 80 °C. The direct methanol fuel cell (DMFC) is assembled from CSPI-T-10 with balanced properties, and it exhibits high maximum power density (PDmax ) of 82.3 and 72.6 mW cm-2 in 2 and 10 m methanol solution, respectively. The ratio of PDmax in 10 m methanol solution to the value in 2 m methanol solution is as high as 88%. The CSPI-T-10 is promising proton exchange membrane candidate for DMFC application.

Sulfonate-Containing Polyelectrolytes for Perovskite Modification: Chemical Configuration, Property, and Performance.

Three sulfonate-containing polyelectrolytes are elaborately designed and used to passivate perovskite film with the anti-solvent method. Under the influence of the secondary monomer, three copolymers present various chemical configurations and deliver different modification effects. Fluorene-thiophene copolymer STF has linear and highly-conjugated chain. STF-perovskite film presents large crystal grains. Fluorene-carbazole copolymer SCF has flexible chain and easily enters into grain boundary areas. SCF-perovskite film is homogenous and continuous. Fluorene-fluorene copolymer SPF agglomerates on the surface and is not applicable to the anti-solvent method. The full investigation demonstrates that STF and SCF not only conduct surface defect passivation, but also improve the film quality by being involved in the perovskite's crystallization process. Compared with the control device, the devices with STF and SCF deliver high efficiency and excellent stability. The unencapsulated devices with STF and SCT maintain ≈80% of the initial power conversion efficiency (PCE) after 40 days of storage under 30-40% relative humidity. SCF performs better and the device maintains 60% of the initial PCE after 20 days of storage under 60-80% relative humidity.

Genomic, Physiological, Biochemical, and Phenotypic Evidences Reveal a New Species, Halomicroarcula salaria sp. nov.

An extremely halophilic archaeon strain named FL173T was isolated from a salt mine (Anhui Province, China). Colonies on agar plate are orange-red, moist, and opaque. Cells are motile, Gram-stain-negative, polymorphic, and lyse in distilled water. Cells are able to grow at temperatures, NaCl concentrations, and pH ranging from 20 to 50 °C (optimum 42 °C), 2.6 to 5.1 M NaCl concentration (optimum 3.4 M), and 5.5 to 9.5 pH (optimum 7.0), respectively. Mg2+ is not necessary for growth. The major polar lipids of strain FL173T were phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me), phosphatidylglycerol sulfonate (PGS), sulfonated mannosyl glycolipid (S-DGD-1). It has two copies of the 16S rRNA gene, which share the highest sequence similarity (93.04-99.02% sequence similarity) to the 16S rRNA genes of Halomicroarcula salinisoli F24AT, respectively. The rpoB' gene of strain FL173T showed the highest sequence similarity (93.76%) to that of H. salinisoli F24AT. The genome-based analysis showed that the average amino-acid identity (AAI), orthologous average nucleotide identity (ANI) and in silico DNA-DNA hybridization values between strains FL173T and H. salinisoli F24AT were 84.80%, 85.29%, and 29.70%, respectively, which are far below the threshold for the delineation of a prokaryotic new species. The DNA G+C content of strain FL173T is 64.9%. Genomic, physiological, biochemical, and phenotypic evidences showed that strain FL173T (CGMCC 1.18851=NBRC 114260) represents a new species of the genus Halomicroarcula, for which the name Halomicroarcula salaria sp. nov. is proposed.

Per- and polyfluoroalkyl substances in waterbird feathers around Poyang Lake, China: Compound and species-specific bioaccumulation.

As a nondestructive means of environmental monitoring, bird feathers have been used to analyze levels of per- and polyfluoroalkyl substances (PFASs) in specific environments. In this study, feather samples from 10 waterbird species around Poyang Lake were collected, and a pretreatment method for PFASs in feathers was optimized. The results showed that a combined cleaning method using ultrapure water and n-hexane effectively removed external PFASs. Twenty-three legacy and emerging PFASs were identified in the feathers of waterbirds, of which hexafluoropropylene oxides (HFPOs), chlorinated polyfluoroalkyl ether sulfonates (Cl-PFESAs), and sodium p-perfluorinated noneoxybenzene sulfonate (OBS) were reported for the first time, with their concentrations ranging from 0.060-2.4 ng·g-1 dw, 0.046-30 ng·g-1 dw, and lower than the method detection limit to 30 ng·g-1 dw, respectively. Compound- and species-specific bioaccumulation of PFASs was observed in the feathers of different waterbird species, suggesting that different PFAS types can be monitored through the selection of different species. Moreover, the concentrations of most PFCAs (except perfluorobutyric acid), perfluorooctane sulfonate (PFOS), and perfluorooctane sulfonamide (FOSA) were significantly positively correlated with δ15N (p < 0.05), while the concentrations of HFPOs, Cl-PFESAs, and OBS had significant positive correlations with δ13C. This indicates that the bioaccumulation of legacy and emerging PFASs in waterbird feathers is affected by their trophic level, feeding habits, and foraging area.

F-53B mediated ROS affects uterine development in rats during puberty by inducing apoptosis.

Perfluoroalkyl and polyfluoroalkyl substances (PFASs), as pollutants, can cause palpable environmental and health impacts around the world, as endocrine disruptors, can disrupt endocrine homeostasis and increase the risk of diseases. Chlorinated polyfluoroalkyl ether sulfonate (F-53B), as a substitute for PFAS, was determined to have potential toxicity. Puberty is the stage when sexual organs develop and hormones change dramatically, and abnormal uterine development can increase the risk of uterine lesions and lead to infertility. This study was designed to explore the impact of F-53B on uterine development during puberty. Four-week-old female SD rats were exposed to 0.125 and 6.25 mg/L F-53B during puberty. The results showed that F-53B interfered with growth and sex hormone levels and bound to oestrogen-related receptors, which affected their function, contributed to the accumulation of reactive oxygen species, promoted cell apoptosis and inhibited cell proliferation, ultimately causing uterine dysplasia.

Shorter Alkanesulfonate Carbon Chains Destabilize the Active Site Architecture of SsuD for Desulfonation.

Bacteria have evolved to utilize alternative organosulfur sources when sulfur is limiting. The SsuE/SsuD and MsuE/MsuD enzymes expressed when sulfur sources are restricted, are responsible for providing specific bacteria with sulfur in the form of alkanesulfonates. In this study, we evaluated why two structurally and functionally similar FMNH2-dependent monooxygenase enzymes (MsuD and SsuD) are needed for the acquisition of alkanesulfonates in some bacteria. In desulfonation assays, MsuD was able to utilize the entire range of alkanesulfonates (C1-C10). However, SsuD was not able to utilize smaller alkanesulfonate substrates. Interestingly, SsuD had a similar binding affinity for methanesulfonate (MES) (15 ± 1 µM) as MsuD (12 ± 1 µM) even though SsuD was not able to catalyze the desulfonation of the MES substrate. SsuD and MsuD showed decreased proteolytic susceptibility in the presence of FMNH2 with MES and octanesulfonate (OCS). Tighter loop closure was observed for the MsuD/FMNH2 complex with MES and OCS compared to SsuD under comparable conditions. Analysis of the SsuD/FMNH2/MES structure using accelerated molecular dynamics simulations found three different conformations for MES, demonstrating the instability of the bound structure. Even when MES was bound in a similar fashion to OCS within the active site, the smaller alkane chain resulted in a shift of FMNH2 so that it was no longer in a position to catalyze the desulfonation of MES. The active site of SsuD requires a longer alkane chain to maintain the appropriate architecture for desulfonation.

A Variant of the Sulfoglycolytic Transketolase Pathway for the Degradation of Sulfoquinovose into Sulfoacetate.

Sulfoquinovose (SQ, 6-deoxy-6-sulfo-glucose) constitutes the polar head group of plant sulfolipids and is one of the most abundantly produced organosulfur compounds in nature. Degradation of SQ by bacterial communities contributes to sulfur recycling in many environments. Bacteria have evolved at least four mechanisms for glycolytic degradation of SQ, termed sulfoglycolysis, producing C3 sulfonate (dihydroxypropanesulfonate and sulfolactate) and C2 sulfonate (isethionate) by-products. These sulfonates are further degraded by other bacteria, leading to the mineralization of the sulfonate sulfur. The C2 sulfonate sulfoacetate is widespread in the environment and is also thought to be a product of sulfoglycolysis, although the mechanistic details are yet unknown. Here, we describe a gene cluster in an Acholeplasma sp., from a metagenome derived from deeply circulating subsurface aquifer fluids (GenBank accession no. QZKD01000037), encoding a variant of the recently discovered sulfoglycolytic transketolase (sulfo-TK) pathway that produces sulfoacetate instead of isethionate as a by-product. We report the biochemical characterization of a coenzyme A (CoA)-acylating sulfoacetaldehyde dehydrogenase (SqwD) and an ADP-forming sulfoacetate-CoA ligase (SqwKL), which collectively catalyze the oxidation of the transketolase product sulfoacetaldehyde into sulfoacetate, coupled with ATP formation. A bioinformatics study revealed the presence of this sulfo-TK variant in phylogenetically diverse bacteria, adding to the variety of mechanisms by which bacteria metabolize this ubiquitous sulfo-sugar. IMPORTANCE Many bacteria utilize environmentally widespread C2 sulfonate sulfoacetate as a sulfur source, and the disease-linked human gut sulfate- and sulfite-reducing bacteria can use it as a terminal electron receptor for anaerobic respiration generating toxic H2S. However, the mechanism of sulfoacetate formation is unknown, although it has been proposed that sulfoacetate originates from bacterial degradation of sulfoquinovose (SQ), the polar head group of sulfolipids present in all green plants. Here, we describe a variant of the recently discovered sulfoglycolytic transketolase (sulfo-TK) pathway. Unlike the regular sulfo-TK pathway that produces isethionate, our biochemical assays with recombinant proteins demonstrated that a CoA-acylating sulfoacetaldehyde dehydrogenase (SqwD) and an ADP-forming sulfoacetate-CoA ligase (SqwKL) in this variant pathway collectively catalyze the oxidation of the transketolase product sulfoacetaldehyde into sulfoacetate, coupled with ATP formation. A bioinformatics study revealed the presence of this sulfo-TK variant in phylogenetically diverse bacteria and interpreted the widespread existence of sulfoacetate.

Generation of Sulfonated Lignin-Starch Polymer and Its Use As a Flocculant.

This paper reports the polymerization of tall oil lignin (TOL), starch, and 2-methyl-2-propene-1-sulfonic acid sodium salt (MPSA), a sulfonate-containing monomer, in a three-component system to generate flocculants for colloidal systems. By utilizing the advanced 1H, COSY, HSQC, HSQC-TOCSY, and HMBC NMR techniques, it was confirmed that the phenolic substructures of TOL and the anhydroglucose unit of starch were covalently polymerized by the monomer to generate the three-block copolymer. The molecular weight, radius of gyration, and shape factor of the copolymers were fundamentally correlated to the structure of lignin and starch, as well as the polymerization outcomes. The deposition behavior of the copolymer, studied by a quartz crystal microbalance with dissipation (QCM-D) analysis, revealed that the copolymer with a larger molecular weight (ALS-5) deposited more and generated more compact adlayer than the copolymer with a smaller molecular weight on a solid surface. Owing to its higher charge density, molecular weight, and extended coil-like structure, ALS-5 produced larger flocs with faster sedimentation in the colloidal systems, regardless of the extent of agitation and gravitational force. The results of this work provide a new approach to preparing a lignin-starch polymer, i.e., a sustainable biomacromolecule with excellent flocculation performance in colloidal systems.

Hydrogel Based on Polyhydroxyalkanoate Sulfonate: Control of the Swelling Rate by the Ionic Group Content.

Hydrogels based on poly(3-hydroxyalkanoate) (PHA) sulfonate and poly(ethylene glycol) diacrylate, PEGDA, are prepared. First, PHA sulfonate is synthesized from unsaturated PHA by a thiol-ene reaction in the presence of sodium-3-mercapto-1-ethanesulfonate. The hydrophilicity of PHAs is considerably increased by adding sulfonate functions, and three amphiphilic PHAs are synthesized, containing 10, 22, or 29% sulfonate functions. Then, hydrogels are formed in the presence of PEGDA having different molar masses, that is, 575 or 2000 g mol-1. The hydrogels show fibrillar and porous structures observed in cryo-MEB with pore sizes that vary according to the content of sulfonated groups (10 to 29 mol %) ranging from 50 to more than 150 nm. Furthermore, depending on the proportions of the two polymers, a variable rigidity is observed from 2 to 40 Pa. In fact, the evaluation of the dynamic mechanical properties of the hydrogel determined by DMA reveals that the less rigid hydrogels hinder the adhesion of Pseudomonas aeruginosa PaO1 bacteria. Finally, these hydrogels swelling up to 5000% are noncytotoxic, allowing the adhesion and amplification of immortalized C2C12 cells, and they are therefore seen as promising materials both for repelling PaO1 bacteria and for amplifying myogenic cells.

Improving the production of the micafungin precursor FR901379 in an industrial production strain.

BACKGROUND: Micafungin is an echinocandin-type antifungal agent used for the clinical treatment of invasive fungal infections. It is semisynthesized from the sulfonated lipohexapeptide FR901379, a nonribosomal peptide produced by the filamentous fungus Coleophoma empetri. However, the low fermentation efficiency of FR901379 increases the cost of micafungin production and hinders its widespread clinical application. RESULTS: Here, a highly efficient FR901379-producing strain was constructed via systems metabolic engineering in C. empetri MEFC09. First, the biosynthesis pathway of FR901379 was optimized by overexpressing the rate-limiting enzymes cytochrome P450 McfF and McfH, which successfully eliminated the accumulation of unwanted byproducts and increased the production of FR901379. Then, the functions of putative self-resistance genes encoding ß-1,3-glucan synthase were evaluated in vivo. The deletion of CEfks1 affected growth and resulted in more spherical cells. Additionally, the transcriptional activator McfJ for the regulation of FR901379 biosynthesis was identified and applied in metabolic engineering. Overexpressing mcfJ markedly increased the production of FR901379 from 0.3 g/L to 1.3 g/L. Finally, the engineered strain coexpressing mcfJ, mcfF, and mcfH was constructed for additive effects, and the FR901379 titer reached 4.0 g/L under fed-batch conditions in a 5 L bioreactor. CONCLUSIONS: This study represents a significant improvement for the production of FR901379 and provides guidance for the establishment of efficient fungal cell factories for other echinocandins.

Perfluoroalkyl Substances in Seabird Eggs from Canada's Pacific Coast: Temporal Trends (1973-2019) and Interspecific Patterns.

Whether perfluoroalkyl sulfonates (PFSAs) and perfluoroalkyl carboxylates (PFCAs) are responding to legislative restrictions and showing decreasing trends in top marine predators that range across the eastern North Pacific Ocean is unclear. Here, we examined longer-term temporal trends (1973-2019) of 4 PFSAs and 13 PFCAs, as well stable isotopes of δ13C and δ15N, in the eggs of 4 seabird species sampled along a nearshore-offshore gradient; double-crested cormorants (Nannopterum auritum), pelagic cormorants (Urile pelagicus), rhinoceros auklets (Cerorhinca monocerata), and Leach's storm-petrels (Hydrobates leucorhous) from the Pacific coast of British Columbia, Canada. PFOS was the most abundant PFSA (79-94%) detected in all eggs regardless of colony and year, with the highest concentrations, on average, measured in auklet eggs (mean = 58 ng g-1, range = 11-286 ng g-1 ww). Perfluoroundecanoic acid (PFUdA) and perfluorotridecanoic acid (PFTriDA) were the dominant long-chain PFCAs (≥30% combined). The majority of PFSAs (including PFOS) are statistically declining (p < 0.001) in the eggs of all 4 species with PFOS half-lives ranging from 2.6 to 7.8 years. Concentrations of long-chain PFCAs exhibited a trajectory comprised of linear increases and second-order declines, suggesting that the rate of uptake of PFCAs is slowing or leveling off. These trends are consistent with the voluntarily ceased production of PFSAs by 3M circa 2000-2003 and are among the first from the northeast Pacific to indicate a positive response to several regulations and restrictions on PFCAs from facility emissions and product content.

Penetration of Perfluorooctanesulfonate Isomers and Their Alternatives from Maternal Blood to Milk and Its Associations with Chemical Properties and Milk Primary Components.

Perfluorooctanesulfonate (PFOS) and its alternatives, including chlorinated polyfluorinated ether sulfonates (Cl-PFESAs), are mainly detected per- and polyfluoroalkyl substances (PFAS) in human samples such as milk. However, the mechanism of their blood to milk transfer was not well studied. Here, 145 paired maternal serum and human milk samples were analyzed for six PFOS isomers and Cl-PFESAs to evaluate the transfer efficiency from maternal serum to human milk (TEHM/MS). Besides physicochemical properties, this study for the first time evaluated the influencing effects of the primary components in human milk (carbohydrate, lipid, and protein) on TEHM/MS of PFAS. No significant association was observed between TEHM/MS and the albumin binding affinity of the compounds (p = 0.601), but TEHM/MS was significantly negatively correlated with the logarithmic octanol-water partition coefficients (r2 = 0.853, p = 0.001), the logarithmic membrane-water partition coefficients (r2 = 0.679, p = 0.012), and the carbohydrate contents in human milk. The effect of carbohydrate was further confirmed using in vitro tests. The negative associations between TEHM/MS and hydrophobicity, membrane passive permeability, and the carbohydrate content in human milk consistently indicated that passive diffusion through the paracellular route might be the main transfer pathway for PFOS and Cl-PFESAs from blood to milk in humans.

Uptake of Per- and Polyfluoroalkyl Substances by Fish, Mussel, and Passive Samplers in Mobile-Laboratory Exposures Using Groundwater from a Contamination Plume at a Historical Fire Training Area, Cape Cod, Massachusetts.

Aqueous film-forming foams historically were used during fire training activities on Joint Base Cape Cod, Massachusetts, and created an extensive per- and polyfluoroalkyl substances (PFAS) groundwater contamination plume. The potential for PFAS bioconcentration from exposure to the contaminated groundwater, which discharges to surface water bodies, was assessed with mobile-laboratory experiments using groundwater from the contamination plume and a nearby reference location. The on-site continuous-flow 21-day exposures used male and female fathead minnows, freshwater mussels, polar organic chemical integrative samplers (POCIS), and polyethylene tube samplers (PETS) to evaluate biotic and abiotic uptake. The composition of the PFAS-contaminated groundwater was complex and 9 PFAS were detected in the reference groundwater and 17 PFAS were detected in the contaminated groundwater. The summed PFAS concentrations ranged from 120 to 140 ng L-1 in reference groundwater and 6100 to 15,000 ng L-1 in contaminated groundwater. Biotic concentration factors (CFb) for individual PFAS were species, sex, source, and compound-specific and ranged from 2.9 to 1000 L kg-1 in whole-body male fish exposed to contaminated groundwater for 21 days. The fish and mussel CFb generally increased with increasing fluorocarbon chain length and were greater for sulfonates than for carboxylates. The exception was perfluorohexane sulfonate, which deviated from the linear trend and had a 10-fold difference in CFb between sites, possibly because of biotransformation of precursors such as perfluorohexane sulfonamide. Uptake for most PFAS in male fish was linear over time, whereas female fish had bilinear uptake indicated by an initial increase in tissue concentrations followed by a decrease. Uptake of PFAS was less for mussels (maximum CFb = 200) than for fish, and mussel uptake of most PFAS also was bilinear. Although abiotic concentration factors were greater than CFb, and values for POCIS were greater than for PETS, passive samplers were useful for assessing PFAS that potentially bioconcentrate in fish but are present at concentrations below method quantitation limits in water. Passive samplers also accumulate short-chain PFAS that are not bioconcentrated.

Nitrifying Microorganisms Linked to Biotransformation of Perfluoroalkyl Sulfonamido Precursors from Legacy Aqueous Film-Forming Foams.

Drinking water supplies across the United States have been contaminated by firefighting and fire-training activities that use aqueous film-forming foams (AFFF) containing per- and polyfluoroalkyl substances (PFAS). Much of the AFFF is manufactured using electrochemical fluorination by 3M. Precursors with six perfluorinated carbons (C6) and non-fluorinated amine substituents make up approximately one-third of the PFAS in 3M AFFF. C6 precursors can be transformed through nitrification (microbial oxidation) of amine moieties into perfluorohexane sulfonate (PFHxS), a compound of regulatory concern. Here, we report biotransformation of the most abundant C6 sulfonamido precursors in 3M AFFF with available commercial standards (FHxSA, PFHxSAm, and PFHxSAmS) in microcosms representative of the groundwater/surface water boundary. Results show rapid (<1 day) biosorption to living cells by precursors but slow biotransformation into PFHxS (1-100 pM day-1). The transformation pathway includes one or two nitrification steps and is supported by the detection of key intermediates using high-resolution mass spectrometry. Increasing nitrate concentrations and total abundance of nitrifying taxa occur in parallel with precursor biotransformation. Together, these data provide multiple lines of evidence supporting microbially limited biotransformation of C6 sulfonamido precursors involving ammonia-oxidizing archaea (Nitrososphaeria) and nitrite-oxidizing bacteria (Nitrospina). Further elucidation of interrelationships between precursor biotransformation and nitrogen cycling in ecosystems would help inform site remediation efforts.