Segmented filamentous bacteria

Segmented filamentous bacteria or Candidatus Savagella are members of the gut microbiota of rodents, fish and chickens, and have been shown to potently induce immune responses in mice.[2] They form a distinct lineage within the Clostridiaceae and the name Candidatus Savagella has been proposed for this lineage.[1]

Segmented filamentous bacteria
Scientific classification
Domain: Bacteria
Phylum: Firmicutes
Class: Clostridia
Order: Clostridiales
Family: Clostridiaceae
Genus: Candidatus Savagella
Thompson et al. 2012[1]

They were previously named Candidatus Arthromitus because of their morphological resemblance to bacterial filaments previously observed in the guts of insects by Joseph Leidy.[3]

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 or even if segmented filamentous bacteria are actually several different bacterial species. In mice, 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.[4]

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.[5] This goes hand in hand with an earlier study demonstrating the ability of monocolonization with Segmented Filamentous Bacteria to dramatically increase mucosal IgA levels.[6] Segmented Filamentous Bacteria are species specific, and may be important to immune development.

References
  1. Thompson, C. L.; Vier, R.; Mikaelyan, A.; Wienemann, T.; Brune, A. (2012). "'Candidatus Arthromitus' revised: Segmented filamentous bacteria in arthropod guts are members of Lachnospiraceae". Environmental Microbiology. 14 (6): 1454–65. doi:10.1111/j.1462-2920.2012.02731.x. PMID 22436008.
  2. Ivanov, I. I.; Littman, D. R. (2010). "Segmented filamentous bacteria take the stage". Mucosal Immunology. 3 (3): 209–212. doi:10.1038/mi.2010.3. PMC 3010405. PMID 20147894.
  3. Leidy, J. 1849. On the existence of entophyta in healthy animals, as a natural condition. Proc. National Academy of Science. USA 4:225–233
  4. Ivanov, I.; Atarashi, K.; Manel, N.; Brodie, E.; Shima, T.; Karaoz, U.; Wei, D.; Goldfarb, K.; Santee, C.; Lynch, S. V.; Tanoue, T.; Imaoka, A.; Itoh, K.; Takeda, K.; Umesaki, Y.; Honda, K.; Littman, D. R. (2009). "Induction of intestinal Th17 cells by segmented filamentous bacteria". Cell. 139 (3): 485–498. doi:10.1016/j.cell.2009.09.033. PMC 2796826. PMID 19836068.
  5. Suzuki, K.; Meek, B.; Doi, Y.; Muramatsu, M.; Chiba, T.; Honjo, T.; Fagarasan, S. (2004). "Aberrant expansion of segmented filamentous bacteria in IgA-deficient gut". Proceedings of the National Academy of Sciences of the United States of America. 101 (7): 1981–1986. Bibcode:2004PNAS..101.1981S. doi:10.1073/pnas.0307317101. PMC 357038. PMID 14766966.
  6. Klaasen, H. L.; Van Der Heijden, P. J.; Stok, W.; Poelma, F. G.; Koopman, J. P.; Van Den Brink, M. E.; Bakker, M. H.; Eling, W. M.; Beynen, A. C. (1993). "Apathogenic, intestinal, segmented, filamentous bacteria stimulate the mucosal immune system of mice". Infection and Immunity. 61 (1): 303–306. PMC 302719. PMID 8418051.
  • Gut Immune Maturation Depends on Colonization with a Host-Specific Microbiota (Cell Volume 149, Issue 7 2012 1578 – 1593)

Further reading

Two review articles

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