Anammox　technology,　known　for　its　environmental　benefits,　is　predominantly　characterized　by　sludge　in　the　form　of　biofilms　or　granules　in　both　industrial　applications　and　laboratory　settings.　The　start-up　period,　a　critical　phase　for　sludge　transformation,　necessitates　the　reconstruction　of　microbe-matter　interactions.　Understanding　the　adaptive　mechanisms　that　enable　anammox　microorganisms　to　thrive　in　these　environments　is　essential　for　optimizing　treatment　performance　and　advancing　practical　applications.　This　study　analyzed　the　nitrogen　removal　efficiency　of　various　anammox　sludges　during　the　start-up　phase,　focusing　on　changes　in　extracellular　polymeric　substances　(EPS),　quorum　sensing　capabilities　(11　types　of　AHLs　and　c-di-GMP),　sludge　aggregation　capacity,　and　the　directional　evolution　of　microbial　communities.　Results　demonstrated　that　granular　sludge　exhibited　higher　overall　nitrogen　removal　efficiency　during　start-up,　attributed　to　significant　differences　in　EPS　composition　compared　to　biofilm　and　flocculent　seed　sludge.　Quorum　sensing　systems　played　a　crucial　role,　with　biofilms　secreting　higher　levels　of　signaling　molecules,　promoting　closer　cell-to-cell　communication　within　microbial　communities.　Additionally,　the　microbial　community　evolved　in　a　fixed　direction　to　adapt　to　external　environmental　conditions,　with　anammox　bacteria　showing　high　adaptability　within　biofilms.　Understanding　the　differences　in　adaptation　mechanisms　between　biofilms　and　granular　sludge　can　optimize　anammox　treatment　systems,　enhance　their　reliability,　and　promote　widespread　application　in　sustainable　wastewater　management.　©　2024　Elsevier　Ltd