Candidatus AccumulibacterDid we forget anything? Let us know

Genus nameCandidatus Accumulibacter
Alternative namesRhodocyclus-related PAO; CAP
NCBI taxonomy ID327159

Taxonomy (MiDAS 2.0)


16S gene copy number2

 In situOther
Hydrophobic cell surface

Micrographs of methylene blue stained sludge from an Accumulibacter enrichment in a lab-scale SBR. Standard-arrowed purple clusters of cells are those containing polyphosphate, while diamond-ended-arrowed blue cells do not contain polyphosphate. The scale bar corresponds to 6 microns. - Source:5

Aerobic heterotroph
Nitrite reduction
Short-chain fatty acids
Proteins/Amino acids

POSNEGVariableNot assessed


They possess a PAO phenotype of anaerobic-aerobic cycling of carbon, and have long been thought to be the primary bacteria in treatment plants configured for biological phosphorus removal 6. Thought to specialise in short chain fatty acids which are stored as PHA under anaerobic conditions. Amino acids and alcohols may also be utilised anaerobically for some species 7 4. The hydrolysis and release of aerobically stored polyphosphate supplements anaerobic energy requirements 6. Under certain conditions they may switch to the GAO phenotype 8 and member species have been shown to vary in their reliance on P cycling 9. Sometimes P-uptake can be coupled with denitrification 10.

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Distribution plant/process configuration

Nutrient removal systems treating municipal wastewater. Relative higher abundance in EBPR plants 13.


Types I and II encompass several clades each (clades IA to E and IIA to I) 11 12 18.

FISH probes

The traditionally applied PAOmix set (PAO492 + PAO651 + PAO846) 5 also targets the Propionivibrio GAO and it is recommended that PAO651 be used alone 14; More specific probes also available but some of these also have specificity problems 15 16.


 In situOther
Aerobic Heterotroph517234
Nitrite Reduction10161723418
Sulfate Reduction
Short-chain Fatty Acids517
Proteins/Amino Acids17

Abundance Information

 10 % percentileMedian90 % percentile
Activated Sludge00.10.5

Predominant InActivated sludge


[1] - NCBI genome database, NCBI id 327159 -

[2] García Martín, Ivanova, Kunin, Warnecke, Barry, McHardy, et al. (2006): Metagenomic analysis of two enhanced biological phosphorus removal (EBPR) sludge communities. Nat. Biotechnol. 24 (10): 1263-9. doi:10.1038/nbt1247

[3] Flowers, He, Malfatti, del Rio, Tringe, Hugenholtz, et al. (2013): Comparative genomics of two 'Candidatus Accumulibacter' clades performing biological phosphorus removal. ISME J 7 (12): 2301-14. doi:10.1038/ismej.2013.117

[4] Skennerton, Barr, Slater, Bond, Tyson (2015): Expanding our view of genomic diversity in Candidatus Accumulibacter clades. Environ. Microbiol. 17 (5): 1574-85. doi:10.1111/1462-2920.12582

[5] Crocetti, Hugenholtz, Bond, Schuler, Keller, Jenkins, et al. (2000): Identification of polyphosphate-accumulating organisms and design of 16S rRNA-directed probes for their detection and quantitation. Appl. Environ. Microbiol. 66 (3): 1175-82.

[6] He, McMahon (2011): Microbiology of 'Candidatus Accumulibacter' in activated sludge. Microb Biotechnol 4 (5): 603-19. doi:10.1111/j.1751-7915.2011.00248.x

[7] Oyserman, Noguera, del Rio, Tringe, McMahon (2016): Metatranscriptomic insights on gene expression and regulatory controls in Candidatus Accumulibacter phosphatis. ISME J 10 (4): 810-22. doi:10.1038/ismej.2015.155

[8] Acevedo, Oehmen, Carvalho, Seco, Borrás, Barat, et al. (2012): Metabolic shift of polyphosphate-accumulating organisms with different levels of polyphosphate storage. Water Res. 46 (6): 1889-900. doi:10.1016/j.watres.2012.01.003

[9] Welles, Tian, Saad, Abbas, Lopez-Vazquez, Hooijmans, et al. (2015): Accumulibacter clades Type I and II performing kinetically different glycogen-accumulating organisms metabolisms for anaerobic substrate uptake. Water Res. 83 (): 354-66. doi:10.1016/j.watres.2015.06.045

[10] Flowers, He, Yilmaz, Noguera, McMahon (2009): Denitrification capabilities of two biological phosphorus removal sludges dominated by different "Candidatus Accumulibacter" clades. Environ Microbiol Rep 1 (6): 583-588. doi:10.1111/j.1758-2229.2009.00090.x

[11] Peterson, Warnecke, Madejska, McMahon, Hugenholtz (2008): Environmental distribution and population biology of Candidatus Accumulibacter, a primary agent of biological phosphorus removal. Environ. Microbiol. 10 (10): 2692-703. doi:10.1111/j.1462-2920.2008.01690.x

[12] He, Gall, McMahon (2007): "Candidatus Accumulibacter" population structure in enhanced biological phosphorus removal sludges as revealed by polyphosphate kinase genes. Appl. Environ. Microbiol. 73 (18): 5865-74. doi:10.1128/AEM.01207-07

[13] Mielczarek, Nguyen, Nielsen, Nielsen (2013): Population dynamics of bacteria involved in enhanced biological phosphorus removal in Danish wastewater treatment plants. Water Res. 47 (4): 1529-44. doi:10.1016/j.watres.2012.12.003

[14] Albertsen, McIlroy, Stokholm-Bjerregaard, Karst, Nielsen (2016): "Candidatus Propionivibrio aalborgensis": A Novel Glycogen Accumulating Organism Abundant in Full-Scale Enhanced Biological Phosphorus Removal Plants. Front Microbiol 7 (): 1033. doi:10.3389/fmicb.2016.01033

[15] Kim, Lee, Kim, Song, Park, Jeon, et al. (2010): Analysis of the fine-scale population structure of "Candidatus accumulibacter phosphatis" in enhanced biological phosphorus removal sludge, using fluorescence in situ hybridization and flow cytometric sorting. Appl. Environ. Microbiol. 76 (12): 3825-35. doi:10.1128/AEM.00260-10

[16] Kim, Lee, Lee, Jeon (2013): Characterization of the denitrification-associated phosphorus uptake properties of "Candidatus Accumulibacter phosphatis" clades in sludge subjected to enhanced biological phosphorus removal. Appl. Environ. Microbiol. 79 (6): 1969-79. doi:10.1128/AEM.03464-12

[17] Kong, Nielsen, Nielsen (2004): Microautoradiographic study of Rhodocyclus-related polyphosphate-accumulating bacteria in full-scale enhanced biological phosphorus removal plants. Appl. Environ. Microbiol. 70 (9): 5383-90. doi:10.1128/AEM.70.9.5383-5390.2004

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