Signaling role of 6-benzylaminopurine in enhanced biotreatment of saline wastewater: performance and mechanisms.

This study introduced the phytohormone 6-benzylaminopurine (6-BA) as a novel, economical, and eco-friendly bacterial signal molecule (SM), which overcame the cost and instability limitations of acyl-homoserine lactones (AHLs) in high-salinity wastewater treatment. 6-BA bound to histidine kinases in two-component systems (TCS) through hydrogen bonding, triggering downstream signal transduction and metabolic regulation. Under high-salinity stress, 6-BA promoted cellular integrity and ionic homeostasis, increasing live-cell counts by 113.7%. To mitigate phenol toxicity, 6-BA enhanced extracellular polymeric substance (EPS) functions and antioxidant systems, reducing reactive oxygen species (ROS) by 19.8%. 6-BA upregulated genes related to DNA replication, the TCA cycle, and fatty acid synthesis, thereby repairing membrane integrity. 6-BA also enriched degrading enzymes and improved phenol degradation, leading to approximately 20% increases in COD, TN, and TP removal. Crucially, 6-BA restructured the microbial community, reducing antibiotic resistance gene (ARG) host abundance by 27.9% and ARG-encoding plasmids by 32.8, which curtailed horizontal gene transfer risks. Additionally, 6-BA exhibited no observable ecotoxicity. This work proposed 6-BA signaling as a novel bioaugmentation strategy for enhanced remediation of high-salinity wastewater.