Candidatus MicrothrixDid we forget anything? Let us know

Genus nameCandidatus Microthrix
Alternative names
NCBI taxonomy ID41949

Taxonomy (MiDAS 2.0)


16S gene copy number1

 In situOther
Hydrophobic cell surface6

Gram positive Microthrix parvicella sampled at a conventional activated sludge plant. Bar = 10 microns. - Source:4

Aerobic heterotroph

POSNEGVariableNot assessed


Microthrix are filamentous organisms which are probably the most problematic bulking and foaming organisms in nutrient removal plants 4. They can sometimes be controlled with the addition of poly-aluminium compounds 5. They are aerobic heterotrophs that can also reduce nitrate 4. They consume long chain fatty acids and can accumulate and store lipids under both aerobic and anaerobic conditions. They also appear to excrete lipases in situ 6. Long chain fatty acids, anaerobic/aerobic alternation and low temperature are advantageous conditions for the competitive growth of *Microthrix" 452. Although polyphosphate is accumulated it is not cycled with aerobic and anerobic conditions, as it is for the PAO 7 8 3.

Show full entry


"Ca. M. parvicella" - most common; "Ca. M. calida" (thinner, rare);

FISH probes

MPAmix(MPA60 + MPA223 + MPA645) targets "Ca. M. parvicella" and "Ca. M. calida" 14 13; Mpa-T1-1260 specific for "Ca. M. calida" 15 13.


 In situOther
Aerobic Heterotroph8710
Nitrite Reduction8931011
Sulfate Reduction3
Short-chain Fatty Acids123
Proteins/Amino Acids1210

Abundance Information

 10 % percentileMedian90 % percentile
Activated Sludge0.52.57.2

Predominant InActivated sludge


[1] - NCBI genome database, NCBI id 41949 -

[2] Muller, Pinel, Gillece, Schupp, Price, Engelthaler, et al. (2012): Genome sequence of "Candidatus Microthrix parvicella" Bio17-1, a long-chain-fatty-acid-accumulating filamentous actinobacterium from a biological wastewater treatment plant. J. Bacteriol. 194 (23): 6670-1. doi:10.1128/JB.01765-12

[3] McIlroy, Kristiansen, Albertsen, Karst, Rossetti, Nielsen, et al. (2013): Metabolic model for the filamentous 'Candidatus Microthrix parvicella' based on genomic and metagenomic analyses. ISME J 7 (6): 1161-72. doi:10.1038/ismej.2013.6

[4] Rossetti, Tomei, Nielsen, Tandoi (2005): "Microthrix parvicella", a filamentous bacterium causing bulking and foaming in activated sludge systems: a review of current knowledge. FEMS Microbiol. Rev. 29 (1): 49-64. doi:10.1016/j.femsre.2004.09.005

[5] Roels, Dauwe, Van Damme, De Wilde, Roelandt (2002): The influence of PAX-14 on activated sludge systems and in particular on Microthrix parvicella. Water Sci. Technol. 46 (1-2): 487-90.

[6] Nielsen, Roslev, Dueholm, Nielsen (2002): Microthrix parvicella, a specialized lipid consumer in anaerobic-aerobic activated sludge plants. Water Sci. Technol. 46 (1-2): 73-80.

[7] Blackall, Stratton, Bradford, Dot, Sjörup, Seviour, et al. (1996): "Candidatus Microthrix parvicella", a filamentous bacterium from activated sludge sewage treatment plants. Int. J. Syst. Bacteriol. 46 (1): 344-6. doi:10.1099/00207713-46-1-344

[8] Andreasen K, Nielsen PH (2000) Growth of Microthrix parvicella in nutrient removal activated sludge plants: studies of in situ physiology. Water Res. 34(5): 1559-1569 - Andreasen And Nielsen -

[9] Hesselsoe, Nielsen, Roslev, Nielsen (2005): Isotope labeling and microautoradiography of active heterotrophic bacteria on the basis of assimilation of 14CO(2). Appl. Environ. Microbiol. 71 (2): 646-55. doi:10.1128/AEM.71.2.646-655.2005

[10] Tandoi V, Rossetti S, Blackall LL, Majone M (1998) Some physiological properties of an italian isolate of "Microthrix parvicella". Water Sci Technol 37: (4-5) 1-8 - Tandoi Et Al -

[11] Rossetti, Tomei, Levantesi, Ramadori, Tandol (2002): "Microthrix parvicella": a new approach for kinetic and physiological characterization. Water Sci. Technol. 46 (1-2): 65-72.

[12] Andreasen, Nielsen (1997): Application of microautoradiography to the study of substrate uptake by filamentous microorganisms in activated sludge. Appl. Environ. Microbiol. 63 (9): 3662-8.

[13] Nielsen PH, Daims H, and Lemmer, H (2009) FISH Handbook for Biological Wastewater Treatment: Identification and quantification of microorganisms in activated sludge and biofilms by FISH. IWA Publishing Company - Nielsen Et Al 2009 -

[14] Erhart, R., Bradford, D., Seviour, R.J., Amman, R., and Blackall, L.L. (1997) Development and Use of Fluorescent In Situ Hybridization Probes for the Detection and Identification of "Microthrix parvicella" in Activated Sludge. System Appl. Microbiol. 20 (310-318). - Erhart Et Al 1997docx -

[15] Levantesi, Rossetti, Thelen, Kragelund, Krooneman, Eikelboom, et al. (2006): Phylogeny, physiology and distribution of 'Candidatus Microthrix calida', a new Microthrix species isolated from industrial activated sludge wastewater treatment plants. Environ. Microbiol. 8 (9): 1552-63. doi:10.1111/j.1462-2920.2006.01046.x

[16] Fan, Qi, Rossetti, Tandoi, Gao, Yang, et al. (2017): Factors affecting the growth of Microthrix parvicella: Batch tests using bulking sludge as seed sludge. Sci. Total Environ. 609 (): 1192-1199. doi:10.1016/j.scitotenv.2017.07.261

Hide details

Contact us at