Candidatus CompetibacterDid we forget anything? Let us know

Genus nameCandidatus Competibacter
Alternative namesGB1
NCBI taxonomy ID221279

Taxonomy (MiDAS 2.0)


16S gene copy number2

 In situOther
Hydrophobic cell surface

Composite FISH image of activated sludge. Yellow = "Competibacteraceae"; Blue = "Ca. Accumulibacter"; Green = other cells. Scale bar = 10 microns. - Source:1

Aerobic heterotroph
Short-chain fatty acids

POSNEGVariableNot assessed


The originally defined "Ca. Competibacter" genus has been split. What was originally known as sub-group GB1 has essentially been redefined to represent the genus "Ca. Competibacter" 2. In situ behaviour is consistent with the GAO phenotype and they are thought to compete with the PAO for resources with their proliferation at the theoretical expense of EBPR efficiency 3 4. Members from the genus have not been demonstrated to denitrify in situ, utilizing nitrate, but not nitrite as an electron acceptor 3. It is suggested to supply nitrite in anoxic conditions to PAO for P-uptake in a partly syntrophic relationship 8. However, genomic analysis of the species “Ca. C. denitrificans” indicates the potential for full denitrification to nitrogen 2. Members also appear to vary in their ability to assimilate thymidine and to ferment glucose, with single cell in situ analysis 3 2. Genome analysis of “Ca. C. denitrificans” reveals the potential for fermentation of glucose, and glycolysis via the Entner-Doudoroff (ED) and Embden-Mayerhof-Parnas (EMP) pathways.

Show full entry

FISH probes

CPB_838 5


 In situOther
Aerobic Heterotroph32
Nitrite Reduction32
Sulfate Reduction
Short-chain Fatty Acids32
Proteins/Amino Acids3

Abundance Information

 10 % percentileMedian90 % percentile
Activated Sludge000.8

Predominant InActivated sludge


[1] McIlroy SJ (2010) Phylogenetic Diversity and Ecophysiology of Alphaproteobacterial Glycogen Accumulating Organisms in Enhanced Biological Phosphorus Removal Activated Sludge Systems. PhD Thesis La Trobe University. - Mcilroy -

[2] McIlroy, Albertsen, Andresen, Saunders, Kristiansen, Stokholm-Bjerregaard, et al. (2014): 'Candidatus Competibacter'-lineage genomes retrieved from metagenomes reveal functional metabolic diversity. ISME J 8 (3): 613-24. doi:10.1038/ismej.2013.162

[3] Kong, Xia, Nielsen, Nielsen (2006): Ecophysiology of a group of uncultured Gammaproteobacterial glycogen-accumulating organisms in full-scale enhanced biological phosphorus removal wastewater treatment plants. Environ. Microbiol. 8 (3): 479-89. doi:10.1111/j.1462-2920.2005.00914.x

[4] Blackall, Crocetti, Saunders, Bond (2002): A review and update of the microbiology of enhanced biological phosphorus removal in wastewater treatment plants. Antonie Van Leeuwenhoek 81 (1-4): 681-91.

[5] McIlroy, Nittami, Kanai, Fukuda, Saunders, Nielsen, et al. (2015): Re-appraisal of the phylogeny and fluorescence in situ hybridization probes for the analysis of the Competibacteraceae in wastewater treatment systems. Environ Microbiol Rep 7 (2): 166-74. doi:10.1111/1758-2229.12215

[6] Kong, Ong, Ng, Liu (2002): Diversity and distribution of a deeply branched novel proteobacterial group found in anaerobic-aerobic activated sludge processes. Environ. Microbiol. 4 (11): 753-7.

[7] Brand, Crosby, Criddle (2019): Niche Differentiation among Three Closely Related Clades at a Full-Scale Activated Sludge Wastewater Treatment Plant and Putative Linkages to Process Performance. Appl. Environ. Microbiol. 85 (5): . doi:10.1128/AEM.02301-18

[8] Rubio-Rincón, Lopez-Vazquez, Welles, van Loosdrecht, Brdjanovic (2017): Cooperation between Candidatus Competibacter and Candidatus Accumulibacter clade I, in denitrification and phosphate removal processes. Water Res. 120 (): 156-164. doi:10.1016/j.watres.2017.05.001

Hide details

Contact us at