Potential role of N-acyl homoserine lactone-mediated quorum sensing in the adaptation of anammox granular sludge system to salinity stress

Anammox granular sludge (AnGS) systems efficiently remove nitrogen from saline wastewater, but their adaptation mechanisms to salt stress are unclear. This study explores the adaptability of the AnGS system when exposed to salinity (0-30 g NaCl/L), focusing on the role of N-acyl homoserine lactone-mediated quorum sensing (AHL-QS) in microbial responses and community symbiosis under stress. Based on Hill model assessments, AnGS tolerates salt stress up to 15.73 g/L. Within this range, AnGS maintains cellular stability by enhancing extracellular polymeric substances (EPS) release, regulating oxidative stress; and drives nitrogen metabolism by increasing cytochrome c-activity to maintain electron transfer. With the mantel test and validation experiments, salt stimulates QS, leading to increased AHL (C6-HSL and C8-HSL) secretion associated with EPS release, extracellular electron transfer, and oxidative stress. Stabilization of AHL-QS genera supports AHL secretion and microbial symbiosis, promoting AnGS adaptation to salt stress. These insights facilitate optimizing AnGS for saline wastewater treatment.