- Oral Microbiome Library
- Gums
- F. animalis
Fusobacterium animalis
Also called the Fusobacterium cousin
- Evidence
- Emerging evidenceEmerging · The lineage found in colorectal tumours
- Class
- Bacterium · Gum pocket · panel code Fa
- Sources
- 4 peer-reviewed sources
Key takeaway
F. animalis was a subspecies of F. nucleatum until genome analysis showed it deserved its own name [1][2]. In 2024 it stepped into the spotlight: a specific clade of F. animalis, not F. nucleatum broadly, turned out to dominate colorectal cancer tissue [3].
| What it is | A close relative of F. nucleatum, recently elevated from subspecies to species. |
|---|---|
| Where it lives | Plaque biofilms, especially in inflamed gum sites. |
| Role in the mouth | Biofilm bridging and inflammation, like its cousin [4]. |
| Beyond the mouth | One lineage dominates the colorectal tumour niche in human samples [3]. |
| Evidence strength | Emerging evidence. Promising human data, but causation is not established. |
| How we measure it | Quantitative PCR (qPCR) on your saliva sample, reported as genomic copies per mL against a reference range. Ranges are for context, not diagnostic cut-offs. |
What is Fusobacterium animalis?
First described in 1992 as Fusobacterium nucleatum subspecies animalis, it was reclassified as a species in 2017 after whole-genome comparisons showed it was as distinct from F. nucleatum as many separate species are from each other [1][2].
That matters for test panels: older assays that counted “F. nucleatum” were often counting both. Measuring them separately gives a clearer picture.
How does F. animalis work?
It shares the Fusobacterium toolkit: adhesins for co-aggregation, tolerance for the gum pocket and a knack for travelling. The 2024 work found that the tumour-associated clade carries extra genes for surviving stomach acid and for metabolising nutrients found in the gut, hinting at how it makes the trip from mouth to colon [3].
What does the research show?
Across a large set of colorectal tumours, researchers found that a single F. animalis clade, called Fna C2, accounted for the great majority of Fusobacterium in the cancer niche and was enriched in stool from colorectal cancer patients compared with healthy controls [3].
In the mouth, it behaves like F. nucleatum and is tied to inflamed sites. Because the species-level literature is only a few years old, we grade the evidence emerging.
What does a result mean?
A detected level is information for your dentist, not a diagnosis of gum disease. Periodontitis is diagnosed by probing, bleeding and bone loss on an exam, and this result is read alongside that.
Read with F. nucleatum. A high level of either signals an active, mature biofilm; it is not a cancer test, and no saliva marker is.
Frequently asked questions
Is F. animalis the same as F. nucleatum?
Not any more. It was a subspecies until 2017, when genome data showed it was distinct enough to be its own species [2].
Should I be worried about the cancer link?
It is an association found in tumour tissue, not a cause-and-effect finding, and oral levels are not a cancer screen. Keep up colorectal screening as your doctor advises [3].
Sources
- Gharbia SE, Shah HN. Fusobacterium nucleatum subsp. fusiforme subsp. nov. and Fusobacterium nucleatum subsp. animalis subsp. nov. as additional subspecies within Fusobacterium nucleatum. Int J Syst Bacteriol 1992. DOI: 10.1099/00207713-42-2-296PMID 1581188
- Kook JK, Park SN, Lim YK, et al.. Genome-Based Reclassification of Fusobacterium nucleatum Subspecies at the Species Level. Curr Microbiol 2017. DOI: 10.1007/s00284-017-1296-9PMID 28687946
- Zepeda-Rivera M, Minot SS, Bouzek H, et al.. A distinct Fusobacterium nucleatum clade dominates the colorectal cancer niche. Nature 2024. DOI: 10.1038/s41586-024-07182-wPMID 38509359
- Kolenbrander PE, Palmer RJ Jr, Periasamy S, et al.. Oral multispecies biofilm development and the key role of cell-cell distance. Nat Rev Microbiol 2010. DOI: 10.1038/nrmicro2381PMID 20514044
This page is educational and does not constitute medical or dental advice, a diagnosis, or a health claim. The OneOral Bio Test reports the organisms and measurements present in a saliva sample; reference ranges are for context only and are not diagnostic thresholds. A licensed dentist reviews results in the context of your examination and history. Content reviewed by the OneOral Clinical Team; research summaries reflect the cited sources as of Oct 27, 2026.