Segmented filamentous bacteria or ''

Candidatus In prokaryote nomenclature, ''Candidatus'' (abbreviated ''Ca.''; Latin for "candidate of Roman office") is used to name prokaryotic taxa that are well characterized but yet- uncultured. Contemporary sequencing approaches, such as 16S ribosomal R ...

'' Savagella are members of the

gut microbiota Gut microbiota, gut microbiome, or gut flora are the microorganisms, including bacteria, archaea, fungi, and viruses, that live in the digestive tracts of animals. The gastrointestinal metagenome is the aggregate of all the genomes of the g ...

of rodents, fish and chickens, and have been shown to potently induce

immune response An immune response is a physiological reaction which occurs within an organism in the context of inflammation for the purpose of defending against exogenous factors. These include a wide variety of different toxins, viruses, intra- and extracellula ...

s in mice. They form a distinct lineage within the

Clostridiaceae The Clostridiaceae are a family of the bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryo ...

and the name ''Candidatus'' Savagella has been proposed for this lineage. They were previously named ''Candidatus'' Arthromitus because of their morphological resemblance to bacterial filaments previously observed in the guts of insects by

Joseph Leidy Joseph Mellick Leidy (September 9, 1823 – April 30, 1891) was an American paleontologist, parasitologist and anatomist. Leidy was professor of anatomy at the University of Pennsylvania, later becoming a professor of natural history at Swarth ...

. Despite the fact that they have been widely referred to as segmented filamentous bacteria, this term is somewhat problematic as it does not allow one to distinguish between bacteria that colonize various

hosts A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County * Host Island, in the Wilhelm Archipelago, Antarctica People * ...

or even if segmented

filamentous The word filament, which is descended from Latin ''filum'' meaning "Thread (yarn), thread", is used in English for a variety of thread-like structures, including: Astronomy * Galaxy filament, the largest known cosmic structures in the universe * ...

bacteria are actually several different bacterial species. In mice, these bacteria grow primarily in the

terminal ileum The ileum () is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine ma ...

in close proximity to the

intestinal epithelium The intestinal epithelium is the single cell layer that forms the luminal surface (lining) of both the small and large intestine (colon) of the gastrointestinal tract. Composed of simple columnar epithelium its main functions are absorptio ...

where they are thought to help induce

T helper 17 cell T helper 17 cells (Th17) are a subset of pro-inflammatory T helper cells defined by their production of interleukin 17 (IL-17). They are related to T regulatory cells and the signals that cause Th17s to actually inhibit Treg differentiation. Howe ...

responses. Intriguingly, Segmented Filamentous Bacteria were found to expand in

AID In international relations, aid (also known as international aid, overseas aid, foreign aid, economic aid or foreign assistance) is – from the perspective of governments – a voluntary transfer of resources from one country to another. Th ...

-deficient mice, which lack the ability to mount an appropriate

humoral immune response Humoral immunity is the aspect of immunity that is mediated by macromolecules – including secreted antibodies, complement proteins, and certain antimicrobial peptides – located in extracellular fluids. Humoral immunity is named so because ...

because of impaired

somatic hypermutation Somatic hypermutation (or SHM) is a cellular mechanism by which the immune system adapts to the new foreign elements that confront it (e.g. microbes). A major component of the process of affinity maturation, SHM diversifies B cell receptors used t ...

; parabiotic experiments revealed the importance of IgA in eliminating Segmented Filamentous Bacteria. This goes hand in hand with an earlier study demonstrating the ability of monocolonization with Segmented Filamentous Bacteria to dramatically increase

mucosal A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

IgA IGA or IgA may refer to: Businesses and organizations * IGA (supermarkets) (initially Independent Grocers Alliance), a name used by many independent supermarkets throughout the world ** IGA (Australian supermarket group), the local Australian v ...

levels. Segmented Filamentous Bacteria are species specific, and may be important to immune development.

References

*Gut Immune Maturation Depends on Colonization with a Host-Specific Microbiota (Cell Volume 149, Issue 7 2012 1578 – 1593)

See also

References

Further reading