Herein,　the　mutual　effect　between　azo　dye　and　the　performance　of　electrochemically　active　bacteria　(EAB)　is　investigated　in　detail,　which　is　crucial　to　understand　and　control　the　bio-electrochemical　systems　(BESs)　operation　for　azo　dye　containing　wastewater　treatment.　EAB　is　enriched　at　controlled　potential　of　-0.2　V　vs　Ag/AgCl　in　single-chamber　BESs.　Over　95%　azo　dye　(alizarin　yellow　R　(AYR))　was　decolorized　regardless　of　the　initial　AYR　concentration　ranging　from　30　to　120　mg/L　within　24　h.　The　fastest　decolorization　rate　was　obtained　at　AYR　initial　concentration　of　70　mg/L,　which　was　4.25　times　greater　in　the　closed　circuit　BESs　than　that　in　the　open　circuit　one.　16S　rRNA　gene　based　microbial　community　analysis　showed　that　Geobacter　was　dominant　in　EAB　with　relative　abundance　increased　from　77.98%　(0　mg/L　AYR)　to　92.22%　(70　mg/L　AYR),　indicating　that　azo　dye　selectively　boosts　the　growth　of　exoelectrogens　in　electrode　biofilm　communities.　Under　electricity　stimulation,　extracellular　process　can　be　mutually　conducted　by　azo　dye　compounds,　which　is　favorable　for　accelerating　reaction　rate　and　avoiding　of　significant　toxic　effect　on　EAB.　(C)　2019　Elsevier　Ltd.　All　rights　reserved.