Genus nameActinomyces
Alternative names
NCBI taxonomy ID1654



16S gene copy number3

 In situOther
Hydrophobic cell surface910

CLSM images of in situ biofilm on glass surfaces (x-y sections). Biofilms were stained simultaneously with all-bacterium-specific EUB338 probe, Streptococcus-specific STR405 probe and Actinomyces-specific ACT476 probe. Green (yellow), blue (purple) and red represent streptococci, A. naeslundii and the remaining bacteria, respectively. Images of the microbial colonization pattern after 6 h (d, e) in four different individuals, showing solitary bacteria and bacteria in clusters. A. naeslundii was observed in mixed clusters with other bacteria. Panels (d) and (e) are maximum projection images. Scale bar for all images, 10 microns. - Source:6

Aerobic heterotroph

POSNEGVariableNot assessed


The genus Actinomyces, contains a group of organisms which do not conform to a single criterion or definition. Species in the genus demonstrate considerable variation in their physiology 7. Generally, they are chemoorganotrophs, with a fermentative metabolism 7. Carbohydrates are preferred sources of carbon for energy and growth 7. A wide range of carbohydrates are utilized, but species may vary in their carbohydrate utilizing ability 7. Acetate, lactate, succinate and formate are end products of glucose fermentation 7. Oxygen requirements vary considerably between species 7. Growth occurs under anaerobic conditions, however Actinomyces can be facultatively anaerobic in the presence of 5% CO2 atmosphere or aerotolerant 7. Considerable variability also occurs with respect to cell morphology, between species and between strains within the same species 7. Cells of the type species of the genus A. bovis, appear as straight to slightly curved rods 7. In some spp. rods may show branching and in others they may develop into filamentous branching forms 7. Coccoid or coccobacillary forms can also occur in some species 7. Microcolonies may also occur 7. No in situ information has been determined for the genus in activated sludge, however certain members of the genus have been implicated in biofilm formation in the oral cavity and as initial colonizers of tooth surfaces 6.

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FISH probes

Probe JF201 (A. naeslundii species-specific probe) 8; ACT476 (species-specific probe for A. naeslundii- A. viscosus- A. bowdeni- A. denticolens) 6


 In situOther
Aerobic Heterotroph7
Nitrite Reduction
Sulphate Reduction
Fatty Acids
Proteins/Amino Acids

Abundance Information

 10 % percentileMedian90 % percentile
Activated Sludge00.10.2

Predominant InInfluent


[1] - NCBI genome database, NCBI id 1654 -

[2] McLean, Liu, Bor, Bedree, Cen, Watling, et al. - Draft Genome Sequence of Actinomyces odontolyticus subsp. actinosynbacter Strain XH001, the Basibiont of an Oral TM7 Epibiont. - Genome Announc 4(1): . doi:10.1128/genomeA.01685-15

[3] Roux, Robert, Gimenez, Gharbi, Raoult - Draft genome sequence of Actinomyces massiliensis strain 4401292T. - J. Bacteriol. 194(18): 5121. doi:10.1128/JB.01039-12

[4] Henssge, Do, Radford, Gilbert, Clark, Beighton, et al. - Emended description of Actinomyces naeslundii and descriptions of Actinomyces oris sp. nov. and Actinomyces johnsonii sp. nov., previously identified as Actinomyces naeslundii genospecies 1, 2 and WVA 963. - Int. J. Syst. Evol. Microbiol. 59(Pt 3): 509-16. doi:10.1099/ijs.0.000950-0

[5] Gorlas, Gimenez, Raoult, Roux - Draft genome sequences of Actinomyces timonensis strain 7400942T and its prophage. - J. Bacteriol. 194(23): 6613-4. doi:10.1128/JB.01730-12

[6] Dige, Raarup, Nyengaard, Kilian, Nyvad - Actinomyces naeslundii in initial dental biofilm formation. - Microbiology (Reading, Engl.) 155(Pt 7): 2116-26. doi:10.1099/mic.0.027706-0

[7] - -

[8] Foster, Kolenbrander - Development of a multispecies oral bacterial community in a saliva-conditioned flow cell. - Appl. Environ. Microbiol. 70(7): 4340-8. doi:10.1128/AEM.70.7.4340-4348.2004

[9] - -

[10] Schlafer, Meyer, Sutherland, Städler - Effect of osteopontin on the initial adhesion of dental bacteria. - J. Nat. Prod. 75(12): 2108-12. doi:10.1021/np300514z

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The online MiDAS field guide is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.


The MiDAS taxonomy is a manual curation of the Silva database and is redistributed for non-commercial use only.


Citing MiDAS: McIlroy S.J., Saunders A.M., Albertsen M., Nierychlo M., McIlroy B., Hansen A.A., Karst S.M., Nielsen J.L., Nielsen P.H. (2015) MiDAS: the field guide to the microbes of activated sludge. Database, Vol. 2015

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