Candidatus　Accumulibacter　has　been　identified　as　dominant　polyphosphate-accumulating　organisms　(PAOs)　in　enhanced　biological　phosphorus　(P)　removal　(EBPR)　sludges.　This　study　investigated　the　clade-level　community　structures　and　population　dynamics　of　Accumulibacter　using　polyphosphate　kinase　1　gene　(ppk1)　genes　in　12　sludge　samples　from　nine　full-scale　wastewater　treatment　plants　(WWTPs).　Results　of　Quantitative　PCR　indicate　that　six　clades　(IA,　IIA,　IIB,　IIC,　IID　and　IIF)　of　Accumulibacter　were　found　in　the　12　sludge　samples.　Abundances　of　Accumulibacter　in　the　anaerobic-anoxic-oxic　(A2O)　and　improved　processes　were　the　highest,　up　to　22.77%　of　total　bacteria.　Abundance　of　IIC　and　IID　reached　108　cells·g-1　MLSS,　accounting　for　75.34%　and　14.87%　of　total　Accumulibacter,　respectively.　They　were　the　dominant　species　of　Accumulibacter.　Clade　IA　abundance　was　the　lowest,　with　an　average　0.32%　of　total　Accumulibacter.　Clades　IIA,　IIC　and　IID　were　found　in　all　sludge　samples,　indicating　the　clades　diversity　in　the　sludge　samples.　Quantitative　PCR　and　phylogenetic　analysis　confirmed　EBPR　performance　was　closely　related　to　the　clade-level　community　structures　of　Accumulibacter.　Poor　EBPR　performance　was　possibly　related　to　a　high　proportion　of　IID　to　total　Accumulibacter.　©　2016,　Science　Press.　All　right　reserved.