Spirochaetes.  Numbered ticks are 10 µm apart.  Gram-stained.
Treponema pallidum spirochaetes.
Scientific classification
Domain: Bacteria
Phylum: Spirochaetae Cavalier-Smith 2002
Class: Spirochaetes Cavalier-Smith 2002
Order: Spirochaetales Buchanan 1917
Families & Genera
Cross section of a spirochaete cell

Spirochaetes (also spelled spirochetes) belong to a phylum of distinctive diderm (double-membrane) bacteria, most of which have long, helically coiled (corkscrew-shaped) cells.[1] Spirochaetes are chemoheterotrophic in nature, with lengths between 5 and 250 µm and diameters around 0.1–0.6 µm.

Spirochaetes are distinguished from other bacterial phyla by the location of their flagella, sometimes called axial filaments, which run lengthwise between the bacterial inner membrane and outer membrane in periplasmic space. These cause a twisting motion which allows the spirochaete to move about. When reproducing, a spirochaete will undergo asexual transverse binary fission.

Most spirochaetes are free-living and anaerobic, but there are numerous exceptions.


  • Classification 1
  • Phylogeny 2
  • Historical 3
  • See also 4
  • References 5
  • External links 6


The spirochaetes are divided into three families (Brachyspiraceae, Leptospiraceae, and Spirochaetaceae), all placed within a single order (Spirochaetales). Disease-causing members of this phylum include the following:

Cavalier-Smith has postulated that the Spirochaetes belong in a larger clade called Gracilicutes.[5]


The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[6] and National Center for Biotechnology Information (NCBI)[7] and the phylogeny is based on 16S rRNA-based LTP release 111 by 'The All-Species Living Tree' Project.[8]


Turneriella parva (Hovind-Hougen et al. 1982) Levett et al. 2005

Leptonema illini Hovind-Hougen 1983

Leptospira Noguchi 1917 emend. Faine and Stallman 1982

Brevinema andersonii Defosse et al. 1995

Brachyspira Hovind-Hougen et al. 1982

Exilispira thermophila Imachi et al. 2008


?Clevelandina reticulitermitidisBermudes et al. 1988

?Cristispira pectinisGross 1910

?Diplocalyx calotermitidis(ex Gharagozlou 1968) Bermudes et al. 1988

?Hollandina pterotermitidis(ex To et al. 1978) Bermudes et al. 1988

?Pillotina calotermitidis(ex Hollande and Gharagozlou 1967) Bermudes et al. 1988

Spironema culicisTurk et al. 1999

Spirochaeta [paraphyletic incl. Borrelia, Sphaerochaeta and Treponema]

♦ Type strain lost or not available
♪ Prokaryotes where no pure (axenic) cultures are isolated or available, i. e. not cultivated or can not be sustained in culture for more than a few serial passages
♠ Strains found at the National Center for Biotechnology Information (NCBI) but not listed in the List of Prokaryotic names with Standing in Nomenclature (LSPN)


antimicrobial drug in medical history, was effective against spirochaetes only and was primarily used to cure syphilis.

See also


  1. ^ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill.  
  2. ^ McBride A, Athanazio D, Reis M, Ko A (2005). "Leptospirosis". Current Opinion in Infectious Diseases 18 (5): 376–86.  
  3. ^ Schwan T (1996). "Ticks and Borrelia: model systems for investigating pathogen-arthropod interactions". Infect Agents Dis 5 (3): 167–81.  
  4. ^ Amat Villegas I, Borobio Aguilar E, Beloqui Perez R, de Llano Varela P, Oquiñena Legaz S, Martínez-Peñuela Virseda JM (January 2004). "[Colonic spirochetes: an infrequent cause of adult diarrhea]". Gastroenterol Hepatol (in Spanish) 27 (1): 21–3.  
  5. ^ Cavalier-Smith, T. (2006). "Rooting the tree of life by transition analyses". Biology Direct 1 (19): 19.  
  6. ^ J.P. Euzéby. "Spirochaetes".  
  7. ^ Sayers; et al. "Spirochaetes".  
  8. ^  

External links

  • Introduction to the Spirochetes University of California Museum of Paleontology (UCMP)