Metatranscriptomic Insights into Aerobic Biotransformation of 6:2 Fluorotelomer Sulfonate by an Enrichment Culture under Sulfur-Limiting Conditions

6:2 Fluorotelomer sulfonate (6:2 FTS), an alternative for PFOS, has become an environmental concern due to its toxicity. This study investigated the aerobic biotransformation of 6:2 FTS under sulfur-limiting conditions using an enrichment culture, SXC01. The enriched culture achieved ≥99.5% degradation of 6:2 FTS at initial concentrations of 0.5, 2.5, and 5 mg/L within 14 days, with notable corresponding defluorination ratios of 77.2%, 28%, and 16.8%, respectively. Eleven transformation products were identified and quantified over time, and the accumulation of intermediate product 6:2 FTUCA suggested that its further degradation may represent a rate-limiting step. Furthermore, the production of PFHxA is more significant than that of PFBA, suggesting the transformation of 6:2 FTUCA via 5:2 sFTOH pathway is more dominant than the other proposed alternative pathway. Metatranscriptomic analysis revealed the upregulation of key genes associated with desulfonation (e.g., ssuEADCB cluster, cysI, sbp, iscS) and defluorination (e.g., ladA, dehH, crcB, dhaA), indicating a synergistic metabolic network driving 6:2 FTS biotransformation. Active genera identified included Brucella, Rhodococcus, and Pseudoclavibacter. Moreover, the predominant Brucella anthropi SX009 was successfully isolated and shown to completely degrade 6:2 FTS within 14 days. This study provides novel insights into the mechanisms of 6:2 FTS biotransformation.6:2氟调聚磺酸盐（6:2 Fluorotelomer sulfonate, 6:2 FTS）作为全氟辛烷磺酸（Perfluorooctane Sulfonate, PFOS）的替代品，因其毒性已成为环境关切的对象。本研究采用富集培养物SXC01，探究了硫限制条件下6:2 FTS的好氧生物转化过程。该富集培养物在初始浓度分别为0.5、2.5和5 mg/L时，可在14天内实现≥99.5%的6:2 FTS降解率，对应的脱氟率分别达77.2%、28%和16.8%，脱氟效果显著。研究期间共鉴定并定量了11种转化产物，中间产物6:2氟调聚羧酸（6:2 Fluorotelomer carboxylic acid, 6:2 FTUCA）的积累表明，其后续降解步骤可能是整个生物转化过程的限速环节。此外，全氟己酸（Perfluorohexanoic acid, PFHxA）的生成量显著高于全氟丁酸（Perfluorobutanoic acid, PFBA），这提示6:2 FTUCA通过5:2短链氟调聚醇（5:2 short-chain fluorotelomer alcohol, 5:2 sFTOH）途径的转化路径，相较于其他已提出的替代途径更为占优。宏转录组分析结果显示，与脱磺化作用相关的关键基因（如ssuEADCB基因簇、cysI、sbp、iscS）以及脱氟作用相关的关键基因（如ladA、dehH、crcB、dhaA）均出现表达上调，表明存在协同代谢网络驱动6:2 FTS的生物转化过程。本次研究鉴定出的活性菌属包括布鲁氏菌属（Brucella）、红球菌属（Rhodococcus）与假棒杆菌属（Pseudoclavibacter）。此外，优势菌株食酸布鲁氏菌SX009（Brucella anthropi SX009）已成功分离，并被证实可在14天内完全降解6:2 FTS。本研究为6:2 FTS的生物转化机制研究提供了全新的认知。