Abstract

Nitrate + C4-HSL mitigated As(III) mobilization and GHG emissions. • Nitrate + PA exacerbated As(III) leaching and GHG emissions. • C4-HSL acts as a QS promoter for fostering consortia and biofilm/EPS production. • The quencher PA disrupts QS and impair microbial synergy. • Nitrate + C4-HSL offers a novel signal-based co-management strategy. The concurrent mitigation of arsenic (As) pollution and greenhouse gas (GHG) emissions in constructed wetlands represents a significant challenge, largely due to the complex interactions within microbial-driven elemental cycles. This study investigated the regulatory roles of distinct quorum-sensing (QS) signals, i.e., C4-homoserine lactone (C4-HSL, a promoter) and penicillic acid (PA, a quencher), in concert with nitrate on the microbial-mediated transformation of As and GHGs (CH 4 and N 2 O) in flooded paddy soil microcosms. The results revealed that the nitrate + C4-HSL treatment concurrently enhanced As(III) immobilization (increased by 8%) while suppressing CH 4 and N 2 O emissions (by 7% and 56%) over a 24-day incubation period, compared to nitrate alone. Conversely, the nitrate + PA treatment inhibited As(III) oxidation (∼17.6 µM residual As(III) leaching) and promoted the accumulation of GHGs (increasing CH 4 and N 2 O emissions by 8% and 77%). Mechanistically, C4-HSL activated the complete QS signaling network under nitrate amendment. This activation led to the enrichment of key functional microbial consortia (e.g., Pseudogulbenkiania , Streptomyces and Alicyclobacillus ), an increase in relative abundance of critical metabolic genes (e.g., aox , pmo , nosZ , cpaF , tadA and cco ), stimulated the secretion of protein-rich extracellular polymeric substances, and enhanced overall electron transfer system activity. These coordinated changes fostered coupled biogeochemical processes such as Fe(II)/Mn(II)-coupled denitrification and denitrifying AOM. In contrast, PA disrupted native QS communication, suppress