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16S rRNA RefSeq: V15.23    Genomic RefSeq: V10.1
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Actinomyces viscosus (HMT-688)
Taxon Description:
Actinomyces naeslundii II sequences are essentially identical to A. viscosus. The reference strain for this taxon is that for the type strain of A. viscosus which is a hamster isolate. Strains from animals are often different than those from humans however in this case there appear to be a human taxon with high sequence similarity to the hamster strain. The Oral phylotypes 169 170 171 175 176 and 688 cluster together and all are probably members of the species Actinomyces naeslundii (a fuzzy group). At this time the Dewhirst laboratory has not examined whether strains classified as A. naeslundii genospecies 1 or 2 fall consistently into particular phylotypes in this cluster. The taxonomy of this group is is discussed in the references [1-3]. Over the next year we will be sequencing a number of actinomyces strains from the Moores' collection and should be able to clarify these issues.There is a vast literature o­n Actinomyces naeslundii which we will not attempt to review here.

Disease Associations:
Appears to contribute to periodontal disease. Can be invasive and cause actinomycotic infections throughout the body.

Prevalence and Source:
Common member of dental plaque
species/ActinoYellow_CoryneMagenta_FromMW2016FigS3.jpg Actinomyces (yellow) intermingled with Corynebacterium (magenta) in human dental plaque. From Mark Welch et al. 2016

Class: Actinomycetia
Order: Actinomycetales
Genus: Actinomyces
Species:Actinomyces viscosus
Status: Named - Cultured
Type/Reference Strain:
[Check LPSN.dsmz.de]
[Check Global Catalogue of Microorganisms]
Former Names or Synonyms:
Phylum: Actinobacteria
16S rRNA Reference Sequences:    view in
RefSeq tree
RefSeq ID: 688_2453

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Genotypic Description:
Phenotypic Characteristics: Gram positive non-motile bacillusFacultative anaerobe
Easily cultivatedMoores' Collection included 34 isolates
(Anvi`o-server hosted on VAMPS)
Microbial Ecology
[Open Abundance/Prevalence Page for ]
NCBI Taxon ID: 1656 [Link to NCBI]
PubMed Searches:
[NCBI PubMed Link]
[NCBI (Entrez) Nucleotide Link]
[NCBI (Entrez) Protein Link]
Number of
Genome Sequences:
3 See List
Phylogenetic Trees:
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View in ribosome protein tree
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[1] Ramos CP, Foster G, Collins MD. Phylogenetic analysis of the genus Actinomyces based on 16S rRNA gene sequences: description of Arcanobacterium phocae sp. nov., Arcanobacterium bernardiae comb. nov., and Arcanobacterium pyogenes com Int J Syst Bacteriol. 1997 Jan;47(1):46-53
[2] Putnins EE, Bowden GH. Antigenic relationships among oral Actinomyces isolates, Actinomyces naeslundii genospecies 1 and 2, Actinomyces howellii, Actinomyces denticolens, and Actinomyces slackii. J Dent Res. 1993 Oct;72(10):1374-85
[3] Johnson JL, Moore LV, Kaneko B, Moore WE. Actinomyces georgiae sp. nov., Actinomyces gerencseriae sp. nov., designation of two genospecies of Actinomyces naeslundii, and inclusion of A. naeslundii serotypes II and III and Actinomyces viscosus Int J Syst Bacteriol. 1990 Jul;40(3):273-86