In　this　study,　impacts　of　quorum　sensing　(QS)　on　the　performance　activated　sludge　and　microbial　community　structure　were　comprehensively　investigated　under　different　ratios　of　COD,　NH4+-N　and　PO43−　(300:15:3,　300:15:1.5,　and　300:15:0.27)　in　the　influent.　The　potential　role　of　QS　in　inducing　filamentous　sludge　bulking　was　examined.　Results　showed　that　under　a　COD/NH4+-N/PO43−　ratio　of　300:15:0.27,　concentrations　of　N-heptyl-L-homoserine　lactone　(C7-HSL)　and　3-oxo-N-decanoyl-L-homoserine　lactone　(3-oxo-C10-HSL)　in　SBR　significantly　increased.　Furthermore,　these　AHLs　were　significantly　correlated　with　the　particle　size,　zeta　potential,　and　hydrophobicity　of　sludge　flocs.　Additionally,　changes　in　the　concentration　of　C7-HSL　and　3-oxo-C10-HSL　showed　significant　negative　correlations　with　the　changes　in　extracellular　polymeric　substance　(EPS)　and　protein　(PN).　High-throughput　sequencing　revealed　significant　changes　in　the　microbial　community　structure　with　variations　in　the　COD/NH4+-N/PO43−　ratio　of　influent.　Metagenomic　analysis　further　revealed　the　expression　of　QS　genes　during　the　filamentous　sludge　bulking.　This　study　provides　new　information　on　the　microscopic　mechanism　of　filamentous　bacteria　bulking　for　QS.　©　2025