Interaction Mechanisms between 6:2 Fluorotelomer Sulfonic Acid (6:2 FTSA) and Soil-Soybean System: Insight from Biodegradation, Phytotoxicity, and Microbial Shifts

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.