Segmented filamentous bacteria
Encyclopedia
Segmented filamentous bacteria are members of the gut flora
that potently induce immune responses. Although not taxonomically classified, they have been given a candidate name "Candidatus
Arthromitus". Referring to these bacteria
by their morphology
has been somewhat problematic as this terminology does not allow one to distinguish between bacteria that colonize various eukaryotic species or even if segmented filamentous bacteria are actually several groups of bacteria. These bacteria grow primarily in the terminal ileum
in close proximity to the intestinal epithelium
where they are thought to help induce T helper 17 cell
responses. Described over 100 years ago by Joseph Leidy
, to date there have been no techniques described to facilitate their growth outside of the mammalian intestinal tract, and recognition of their importance in immunity
has seen a slow but steady rise over the past decade. Intriguingly, Segmented Filamentous Bacteria were found to expand in AID
-deficient mice, which lack the ability to mount an appropriate humoral immune response because of impaired somatic hypermutation
; parabiotic experiments revealed the importance of IgA in eliminating Segmented Filamentous Bacteria. This goes hand and hand with an earlier study demonstrating the ability of monocolonization with Segmented Filametnous Bacteria to dramatically increase mucosal IgA
levels. Segmented Filamentous Bacteria are species specific, and may be important to immune development.
Two review articles
Gut flora
Gut flora consists of microorganisms that live in the digestive tracts of animals and is the largest reservoir of human flora. In this context, gut is synonymous with intestinal, and flora with microbiota and microflora....
that potently induce immune responses. Although not taxonomically classified, they have been given a candidate name "Candidatus
Candidatus
Candidatus is in scientific classification a component of the taxonomic name for a bacterium that cannot be maintained in a Bacteriology Culture Collection. It is an interim taxonomic status for noncultivable organisms. An example would be "Candidatus Phytoplasma allocasuarinae"...
Arthromitus". Referring to these bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
by their morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
has been somewhat problematic as this terminology does not allow one to distinguish between bacteria that colonize various eukaryotic species or even if segmented filamentous bacteria are actually several groups of bacteria. These bacteria grow primarily in the terminal ileum
Terminal ileum
The terminal ileum is the most distal part of the small intestine. It connects to the cecum, the pouch between the small and the large intestine, via the ileocecal valve.-Pathology of the terminal ileum:...
in close proximity to the intestinal epithelium
Intestinal epithelium
The intestinal epithelium is the epithelium that covers the small and large intestine. It is simple columnar and nonciliated.They primarily take part in the digestive system. However, they also express TLR 4 receptors, and are thus a part of the immune system, both as a barrier and as a first-line...
where they are thought to help induce T helper 17 cell
T helper 17 cell
T helper 17 cells are a subset of T helper cells producing interleukin 17 discovered in 2007. They are considered developmentally distinct from Th1 and Th2 cells and excessive amounts of the cell are thought to play a key role in autoimmune disease such as multiple sclerosis , but also...
responses. Described over 100 years ago by Joseph Leidy
Joseph Leidy
Joseph Leidy was an American paleontologist.Leidy was professor of anatomy at the University of Pennsylvania, and later was a professor of natural history at Swarthmore College. His book Extinct Fauna of Dakota and Nebraska contained many species not previously described and many previously...
, to date there have been no techniques described to facilitate their growth outside of the mammalian intestinal tract, and recognition of their importance in immunity
Immunity (medical)
Immunity is a biological term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. Immunity involves both specific and non-specific components. The non-specific components act either as barriers or as eliminators of wide...
has seen a slow but steady rise over the past decade. Intriguingly, Segmented Filamentous Bacteria were found to expand in AID
Activation-Induced (Cytidine) Deaminase
Activation-induced deaminase is a 24 kDa enzyme that creates deliberate mutations in DNA.AID removes the amino group from a cytidine base, turning it into a uridine...
-deficient mice, which lack the ability to mount an appropriate humoral immune response because of impaired somatic hypermutation
Somatic hypermutation
Somatic hypermutation is a mechanism inside cells that is part of the way the immune system adapts to the new foreign elements that confront it . SHM diversifies the receptors used by the immune system to recognize foreign elements and allows the immune system to adapt its response to new threats...
; parabiotic experiments revealed the importance of IgA in eliminating Segmented Filamentous Bacteria. This goes hand and hand with an earlier study demonstrating the ability of monocolonization with Segmented Filametnous Bacteria to dramatically increase mucosal IgA
IGA
Iga or IGA may stand for:-Given name:* a female given name of Polish origin. The name originates from the female given name Jadwiga and stands for gia,or gina in the USA....
levels. Segmented Filamentous Bacteria are species specific, and may be important to immune development.
Further reading
- At least 50 scholarly articles on the subject at Google scholarGoogle ScholarGoogle Scholar is a freely accessible web search engine that indexes the full text of scholarly literature across an array of publishing formats and disciplines. Released in beta in November 2004, the Google Scholar index includes most peer-reviewed online journals of Europe and America's largest...
.
Two review articles