Shuyan Zhao

Perfluorobutane sulfonamide (FBSA), an emerging short-chain perfluorooctanesulfonate (PFOS) alternative used in semiconductor manufacturing and fire suppression, has been detected in environmental matrices and poses environmental risks via industrial emissions and product leaching. However, the microbial degradation characteristics of FBSA are still unclear. In this study, two FBSA-transforming bacterial strains (designated LH-1 and BO-1) were isolated from the contaminated sediments of the Liaohe Estuary and the Bohai Sea, northeastern China. Based on 16S rDNA gene sequence analysis, strain LH-1 showed 99.66% sequence similarity with Neobacillus cucumis C7-N-8-8, while strain BO-1 showed 100% similarity with Glutamicibacter nicotianae OTC-16. Genomic analysis identified key degradation-related genes, including oxidoreductases, hydrolases, and genes involved in chloroalkane (LH-1) or fluorobenzoate (BO-1) degradation pathways, providing genetic evidence that supported their FBSA biotransformation potential. After 5 days of incubation with 133.8 nmol/mL FBSA, LH-1 and BO-1 removed 8.78% and 11.37% of FBSA, respectively. Perfluorobutanesulfonic acid (PFBS), perfluorobutanoic acid (PFBA), and perfluoropropionic acid (PFPrA) were detected as biodegradation products, with PFBS and PFPrA as the main products in strains LH-1 and BO-1, respectively. Genome annotation revealed candidate genes associated with deamination, oxidation, desulfonation, decarboxylation, and defluorination, as well as strain-specific enrichment of chloroalkane degradation genes in LH-1 and fluorobenzoate degradation genes in BO-1. Neither strain showed detectable degradation of perfluorooctanoic acid (PFOA) or PFOS, suggesting an apparent preference for the sulfonamide precursor FBSA over terminal perfluoroalkyl acids (PFAAs). This study provides the first genomic and metabolic insights into FBSA biotransformation by coastal sediment bacteria and improves our understanding of the environmental fate of sulfonamide-based PFAS precursors.

As an important perfluorooctanesulfonate (PFOS) substitute, 6:2 fluorotelomer sulfonic acid (6:2 FTSA) has been widely detected in soil. However, the interaction mechanisms between 6:2 FTSA and the soil-plant system are still unknown. Here, we explored the biodegradation, phytotoxicity, and microbial impact of 6:2 FTSA in a soil-soybean system. The biodegradation of 6:2 FTSA in plants was mediated by both enzymes and coexisting microorganisms. 6:2 FTSA (2.97 nmol/g) inhibited soybean growth and caused oxidative damage, while soybeans enhanced their stress tolerance and metabolism of 6:2 FTSA by modulating genes involved in fatty acid metabolism, hormone signaling, oxidative stress, xenobiotic detoxification, and transmembrane transport. 6:2 FTSA affected rhizospheric and root endophytic microbial communities, with symbiotic fungi being more sensitive to 6:2 FTSA stress than bacteria. Five 6:2 FTSA-degrading rhizospheric and endophytic bacterial strains belonging to genera Acinetobacter, Rhodococcus, and Klebsiella were isolated and identified, with the rhizosphere bacteria exhibiting more effective degradation. Our findings reveal the ecological risks and detoxification mechanisms of emerging PFOS alternatives in soil-crop systems.

As a novel perfluorooctane sulfonate (PFOS) alternative, 6:2 fluorotelomer sulfonamide alkylbetaine (6: 2 FTAB) has been detected in the environment and biotas. However, its behaviors and toxicity in earthworms remain unclear. Here, earthworms (Eisenia fetida) were exposed to 6:2 FTAB to investigate its bioaccumulation, biotransformation and toxicity. Results indicated that 6:2 FTAB could be biodegraded in soil into perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), perfluorobutanoic acid (PFBA) and perfluoropropionic acid (PFPrA). The uptake rate constant (k_u) and the bioaccumulation factor (BAF) of 6:2 FTAB in earthworms were 0.0504 g_oc g_ww⁻¹ d and 1.65 g_oc g_ww⁻¹, respectively. 6:2 FTAB was biotransformed to form PFHxA, PFPeA, PFBA and PFPrA in earthworms after in vivo and in vitro exposure. The aerobic bacteria isolated from worm gut could degrade 6:2 FTAB to form PFPeA and PFHxA, while the anaerobic bacteria did not contribute to 6:2 FTAB biodegradation in worms. Peroxidase (POD) and superoxide dismutase (SOD) activities were significantly increased, while no significant changes were observed for catalase (CAT) activities, demonstrating activation of the primary antioxidant defense system against oxidative stress in earthworms after exposure to 6:2 FTAB. The significant increase of glutathione-S-transferase (GST) activities suggested indirect evidence on the conjugation of 6:2 FTAB or its metabolites in phase II of detoxication. This study provides important information on the fate of 6:2 FTAB in earthworms.