This article is about the bacterial phylum. For spiral-shaped bacteria in general, see spiral bacteria.
Spirochaetes.  Numbered ticks are 10 µm apart.  Gram-stained.
Treponema pallidum spirochaetes.
Scientific classification
Domain: Bacteria
Phylum: Spirochaetes Garrity & Holt 2001
Class: Spirochaetia Paster 2011
Orders & Families
  • Spirochaetae Cavalier-Smith 2002
  • Spirochaetaeota Oren et al. 2015
Cross section of a spirochaete cell

A spirochaete (/ˈsprˌkt/)[1] or spirochete is a member of the phylum Spirochaetes (/ˌsprˈktiz/),[2] which contains distinctive diderm (double-membrane) bacteria, most of which have long, helically coiled (corkscrew-shaped or spiraled, hence the name) cells.[3] Spirochaetes stain gram-negative and are chemoheterotrophic in nature, with lengths between 3 and 500 µm and diameters around 0.09 to at least 3 µm.[4]

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. Spirochaetes bacteria are diverse in their pathogenic capacity, the ecological niches that they inhabit, as well as molecular characteristics including GC content and genome size.[5][6]


Many organisms within the Spirochaetes phylum are causative agents of prevalent diseases. Disease-causing members of this phylum include the following:

Spirochetes may also cause dementia and may be involved in the pathogenesis of Alzheimer's disease.[10] Salvarsan, the first partially organic synthetic antimicrobial drug in medical history, was effective against spirochaetes only and was primarily used to cure syphilis.

Taxonomy and molecular signatures

The class currently consists of 14 validly named genera across 4 orders and 5 families.[11][12][13] The orders Brachyspirales, Brevinematales and Leptospirales each contain a single family, Brachyspiraceae, Brevinemataceae and Leptospiraceae, respectively. The Spirochaetales order harbours two families, Spirochaetaceae and Borreliaceae. Molecular markers in the form of conserved signature indels (CSIs) and CSPs have been found specific for each of the orders, with the exception of Brevinimetales, that provide a reliable means to demarcate these clades from one another within the diverse phylum.[12] Additional CSIs have been found exclusively shared by each family within the Spirochaetales. These molecular markers are in agreement with the observed phylogenetic tree branching of two monophyletic clades within the Spirochaetales order.[12] CSIs have also been found that further differentiate taxonomic groups within the Borreliaceae family that further delineate evolutionary relationships that are in accordance with physical characteristics such as pathogenicity (viz. Borrelia emend. Borreliella gen. nov.).[14]

A conserved signature indel has also been found exclusively shared by all Spirochaetes species.[12] This CSI is a 3 amino acid insert in the flagellar basal body rod protein FlgC which is an important part of the unique endoflagellar structure shared by Spirochaetes species.[15] Given that the CSI is exclusively shared by members within this phylum, it has been postulated that it may be related to the characteristic flagellar properties observed among Spirochaetes species.[12][15]

Historically, the all families belonging to the Spirochaetes phylum were assigned to a single order, the Spirochaetales.[5][6] However, the current taxonomic view is more connotative of accurate evolutionary relationships, where the distribution of conserved signature indels are indicative of shared ancestry within each respective clade for which they are specific. These synapomorphic characteristics justify the phylogenetic divisions and are a means to identify each order/family within the phylum.[12]


The phylogeny is based on 16S rRNA-based LTP release 123 by 'The All-Species Living Tree' Project.[16]


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


Spirochaeta Ehrenberg 1835 emend. Pikuta et al. 2009

Treponema Schaudinn 1905 emend Abt et al. 2013

Spirochaeta clade 2

Spirochaeta aurantia (ex Vinzent 1926) Canale-Parola 1980


Borreliella Adeolu & Gupta 2015 (Lyme disease Borrelia)

Borrelia Swellengrebel 1907 emend. Adeolu & Gupta 2014 (relapsing fever Borrelia)


The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[17] and National Center for Biotechnology Information (NCBI).[18]

♦ 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)

See also


  1. spirochaete - Oxford Dictionaries
  2. Elsevier, Dorland's Illustrated Medical Dictionary, Elsevier.
  3. Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0-8385-8529-9.
  4. Margulis, L.; Ashen, J. B.; Solé, M.; Guerrero, R. (1993-08-01). "Composite, large spirochetes from microbial mats: spirochete structure review" (PDF). Proceedings of the National Academy of Sciences. 90 (15): 6966–6970. doi:10.1073/pnas.90.15.6966. ISSN 0027-8424. PMC 47056Freely accessible. PMID 8346204.
  5. 1 2 Paster BJ (2011) Phylum XV. Sprochaetes Garrity and Holt. In: Bergey’s Manual of Systematic Bacteriology, pp. 471. Eds D.J. Brenner, N.R.Krieg, G.M.Garrity, and J.T. Staley Springer-: New York.
  6. 1 2 Paster BJ (2011) Family I. Sprochaetes Swellengrebel 1907, 581AL. In: Bergey’s Manual of Systematic Bacteriology, pp. 473-531. Eds D.J. Brenner, N.R.Krieg, G.M.Garrity, and J.T. Staley Springer-: New York.
  7. McBride A, Athanazio D, Reis M, Ko A (2005). "Leptospirosis". Current Opinion in Infectious Diseases. 18 (5): 376–86. doi:10.1097/01.qco.0000178824.05715.2c. PMID 16148523.
  8. Schwan T (1996). "Ticks and Borrelia: model systems for investigating pathogen-arthropod interactions". Infect Agents Dis. 5 (3): 167–81. PMID 8805079.
  9. 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. PMID 14718105.
  10. Miklossy, Judith (2011-08-04). "Alzheimer's disease - a neurospirochetosis. Analysis of the evidence following Koch's and Hill's criteria". Journal of Neuroinflammation. 8: 90. doi:10.1186/1742-2094-8-90. ISSN 1742-2094. PMC 3171359Freely accessible. PMID 21816039.
  11. Sayers; et al. "TherSpirochaetia". National Center for Biotechnology Information (NCBI) taxonomy database. Retrieved 2016-10-25.
  12. 1 2 3 4 5 6 Gupta RS, Mahmood S, Adeolu M (2013). "A phylogenomic and molecular signature based approach for characterization of the phylum Spirochaetes and its major clades: proposal for a taxonomic revision of the phylum". Front Microbiol. 4 (217). doi:10.3389/fmicb.2013.00217. PMID 23908650.
  13. Oren A, Garrity GM (2014). "List of new names and new combinations previously effectively, but not validly, published" (PDF). Int. J. Syst. Evol. Microbiol. 64: 693–696. doi:10.1099/ijs.0.062521-0.
  14. Adeolu M, Gupta RS (2014). "A phylogenomic and molecular marker based proposal for the division of the genus Borrelia into two genera: the emended genus Borrelia containing only the members of the relapsing fever Borrelia, and the genus Borreliella gen. nov. containing the members of the Lyme disease Borrelia (Borrelia burgdorferi sensu lato complex)". Antonie Van Leeuwenhoek. 105 (6): 1049–1072. doi:10.1007/s10482-014-0164-x. PMID 24744012.
  15. 1 2 Macnab RM (2003). "How bacteria assemble flagella". Annu Rev Microbiol. 57: 77–100. doi:10.1146/annurev.micro.57.030502.090832. PMID 12730325.
  16. 'The All-Species Living Tree' Project."16S rRNA-based LTP release 123 (full tree)" (PDF). Silva Comprehensive Ribosomal RNA Database. Retrieved 2013-03-20.
  17. J.P. Euzéby. "Spirochaetes". List of Prokaryotic names with Standing in Nomenclature (LPSN). Retrieved 2013-03-20.
  18. Sayers; et al. "Spirochaetes". National Center for Biotechnology Information (NCBI) taxonomy database. Retrieved 2013-03-20.
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