Synergistic Regulation by Long- and Short-Chain Quorum Sensing Signaling Molecules Enhances Sulfamethoxazole Metabolism in Electroactive Biofilms within a Microbial Electrolysis Cell Coupled Anaerobic Digestion System

• • Combined C6-HSL and C12-HSL (T3) achieved the highest SMX removal increase of 10.67% and methane yield improvement of 23.1% relative to control, demonstrating synergistic enhancement of MEC-AD performance. • • Single C6-HSL (T1) increased SMX removal by 9.26% and methane yield by 20.4%, while C12-HSL (T2) showed lower gains (7.44% and 16.9%), indicating chain-length-dependent efficacy. • • AHLs promoted electroactive biofilm formation via enhanced EPS production, with Georgenia abundance increasing by 16.77% (T1) and 36.47% (T3) but decreasing by 15.99% (T2), highlighting species-specific responses to signaling molecules. • • Combined AHLs (T3) reduced sul2 gene abundance by 4.92% compared to control, whereas single AHLs increased intI1, sul1, and sul2 abundances, suggesting that synergistic signaling mitigates ARG amplification risk.