A spirochaete () or spirochete is a member of the phylum Spirochaetota (), (synonym Spirochaetes) which contains distinctive diderm (double-membrane)

gram-negative bacteria Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...

, most of which have long, helically coiled (corkscrew-shaped or spiraled, hence the name) cells. Spirochaetes are

chemoheterotroph A Chemotroph is an organism that obtains energy by the oxidation of electron donors in their environments. These molecules can be organic (chemoorganotrophs) or inorganic ( chemolithotrophs). The chemotroph designation is in contrast to phototro ...

ic in nature, with lengths between 3 and 500 μm and diameters around 0.09 to at least 3 μm. Spirochaetes are distinguished from other bacterial phyla by the location of their flagella, called endoflagella which are sometimes called ''axial filaments''. Endoflagella are anchored at each end (pole) of the bacterium within the

periplasmic space The periplasm is a concentrated gel-like matrix in the space between the inner cytoplasmic membrane and the bacterial outer membrane called the ''periplasmic space'' in gram-negative bacteria. Using cryo-electron microscopy it has been found tha ...

(between the inner and outer membranes) where they project backwards to extend the length of the cell. 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 Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to: * Anaerobic adhesive, a bonding a ...

, but there are numerous exceptions. Spirochaete bacteria are diverse in their pathogenic capacity and the ecological niches that they inhabit, as well as molecular characteristics including

guanine-cytosine content In molecular biology and genetics, GC-content (or guanine-cytosine content) is the percentage of nitrogenous bases in a DNA or RNA molecule that are either guanine (G) or cytosine (C). This measure indicates the proportion of G and C bases out ...

and genome size.Paster BJ (2011) Phylum XV. Spirochaetes 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.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.

Pathogenicity

Many organisms within the Spirochaetota phylum cause prevalent diseases. Pathogenic members of this phylum include the following: * ''

Leptospira ''Leptospira'' ( grc, leptos, italics=yes, 'fine, thin' and la, spira, links=no, 'coil') is a genus of spirochaete bacteria, including a small number of pathogenic and saprophytic species. ''Leptospira'' was first observed in 1907 in kidney ti ...

'' species, which causes leptospirosis * ''

Borrelia burgdorferi ''Borrelia burgdorferi'' is a bacterial species of the spirochete class in the genus '' Borrelia'', and is one of the causative agents of Lyme disease in humans. Along with a few similar genospecies, some of which also cause Lyme disease, it mak ...

'', '' B. mayonii'', '' B. bissettiae'', '' B. garinii'', '' B. afzelii'', '' B. spielmanii'', '' B. lusitaniae'', which cause Lyme disease. * ''

Borrelia recurrentis ''Borrelia recurrentis'' is a species of ''Borrelia'', a spirochaete bacterium associated with relapsing fever. ''B. recurrentis'' is usually transmitted from person to person by the human body louse The body louse (''Pediculus humanus humanu ...

'', which causes

relapsing fever Relapsing fever is a vector-borne disease caused by infection with certain bacteria in the genus '' Borrelia'', which is transmitted through the bites of lice or soft-bodied ticks (genus ''Ornithodoros''). Signs and symptoms Most people who ar ...

* ''

Treponema pallidum ''Treponema pallidum'', formerly known as ''Spirochaeta pallida'', is a spirochaete bacterium with various subspecies that cause the diseases syphilis, bejel (also known as endemic syphilis), and yaws. It is transmitted only among humans. It is ...

'' subspecies which cause

treponematoses Treponematosis is a term used to individually describe any of the diseases caused by four members of the bacterial genus '' Treponema''. The four diseases are collectively referred to as treponematoses: * Syphilis (''Treponema pallidum pallidum'') ...

such as syphilis and

yaws Yaws is a tropical infection of the skin, bones, and joints caused by the spirochete bacterium ''Treponema pallidum pertenue''. The disease begins with a round, hard swelling of the skin, in diameter. The center may break open and form an ulce ...

. * '' Brachyspira pilosicoli'' and '' Brachyspira aalborgi'', which cause intestinal spirochaetosis

Salvarsan Arsphenamine, also known as Salvarsan or compound 606, is a drug that was introduced at the beginning of the 1910s as the first effective treatment for syphilis, relapsing fever, and African trypanosomiasis. This organoarsenic compound was the fi ...

, the first partially organic synthetic antimicrobial drug in medical history, was effective against spirochaetes and primarily used to cure syphilis. Additionally, oral spirochaetes are known to play a significant role in the

pathogenesis Pathogenesis is the process by which a disease or disorder develops. It can include factors which contribute not only to the onset of the disease or disorder, but also to its progression and maintenance. The word comes from Greek πάθος ''pat ...

of human

periodontal disease Periodontal disease, also known as gum disease, is a set of inflammatory conditions affecting the tissues surrounding the teeth. In its early stage, called gingivitis, the gums become swollen and red and may bleed. It is considered the main caus ...

Taxonomy and molecular signatures

The class currently consists of 14 validly named genera across 4 orders and 5 families. The orders ''

Brachyspirales Brachyspiraceae is a family of Spirochaetota. Spirochetosis of the appendix, caused by '' Brachyspira aalborgi'' or '' Brachyspira pilosicoli'', is not associated with appendicitis Appendicitis is inflammation of the appendix. Symptoms comm ...

'', ''

Brevinematales ''Brevinema andersonii'' (Brev. i. ne' ma. L. adj. brevis, short; Gr. n. nema, thread; N.L. neut. n. Brevinema, a short thread.) (an.derso'ni.i. N.L. gen. n. andersonii, of Anderson), named for John F. Anderson, who first described the organism. ...

'' and ''

Leptospirales The Leptospiraceae are a family of spirochete bacteria. It includes the genus '' Leptospira'' which contains some pathogenic species. Systematic These genera belong to the family Leptospiraceae: * '' Leptonema'' (with species ''Leptonema illi ...

'' each contain a single family, '' Brachyspiraceae'', '' Brevinemataceae'' and '' Leptospiraceae'', respectively. The ''

Spirochaetales The Spirochaetales are an order of spirochete bacteria. Some species within this order are known to causes syphilis, Lyme disease, relapsing fever Relapsing fever is a vector-borne disease caused by infection with certain bacteria in the genus ...

'' order harbours two families, ''

Spirochaetaceae The Spirochaetaceae are a family of spirochete bacteria. Some species within this family are known to causes syphilis, Lyme disease, relapsing fever Relapsing fever is a vector-borne disease caused by infection with certain bacteria in the genus ...

'' and ''

Borreliaceae The Borreliaceae are a family of spirochete bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. ...

''. Molecular markers in the form of

conserved signature indels Conserved signature inserts and deletions (CSIs) in protein sequences provide an important category of molecular markers for understanding phylogenetic relationships. CSIs, brought about by rare genetic changes, provide useful phylogenetic markers ...

(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. Additional CSIs have been found exclusively shared by each family within the ''

''. These molecular markers are in agreement with the observed phylogenetic tree branching of two monophyletic clades within the ''

'' order. CSIs have also been found that further differentiate taxonomic groups within the ''

'' family that further delineate evolutionary relationships that are in accordance with physical characteristics such as pathogenicity (viz. ''

Borrelia ''Borrelia'' is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of ''Borrelia'' cause relapsing fever, and are t ...

'' emend. '' Borreliella'' gen. nov.). However, this study has been criticized, and other studies using different approaches do not support the proposed split. The new naming system for the Lyme and relapsing fever ''Borrelia'' has not been adopted by the scientific literature. A CSI has also been found exclusively shared by all Spirochaetota species. This CSI is a 3 amino acid insert in the flagellar

basal body A basal body (synonymous with basal granule, kinetosome, and in older cytological literature with blepharoplast) is a protein structure found at the base of a eukaryotic undulipodium (cilium or flagellum). The basal body was named by Theodor Wi ...

rod protein FlgC which is an important part of the unique endoflagellar structure shared by Spirochaetota species. 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 Spirochaetota species. Historically, all families belonging to the Spirochaetota phylum were assigned to a single order, the ''

''. However, the current taxonomic view is more connotative of accurate evolutionary relationships. The distribution of a CSI is indicative of shared ancestry within the clade for which it is specific. It thus functions as a synapomorphic characteristic, so that the distributions of different CSIs provide the means to identify different orders and families within the phylum and so justify the phylogenetic divisions.

Phylogeny

Taxonomy

The currently accepted taxonomy is based on the

List of Prokaryotic names with Standing in Nomenclature List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the nomenclature, naming and Taxonomy (biology), taxonomy of prokaryotes, following the taxonomy requirements and rulings of the In ...

(LPSN) and

National Center for Biotechnology Information The National Center for Biotechnology Information (NCBI) is part of the United States National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The ...

(NCBI). * Phylum Spirochaetota Garrity and Holt 2021 ** Class Spirochaetia Paster 2020 *** Genus ?'' Exilispira'' Imachi et al. 2008 *** Genus ?"'' Spirosymplokos''" Guerrero et al. 1993 *** Order

Gupta et al. 2014 **** Family Leptospiraceae Hovind-Hougen 1979 ***** Genus '' Leptonema'' Hovind-Hougen 1983 ***** Genus ''

'' Noguchi 1917 ***** Genus '' Turneriella'' Levett et al. 2005 *** Order

corrig. Gupta et al. 2014 **** Family Brachyspiraceae Paster 2012 ***** Genus '' Brachyspira'' Hovind-Hougen et al. 1982 ***** Genus ?"''Ca.'' Maribrachyspira" Matsuyama et al. 2017 *** Order

Gupta et al. 2014 **** Family Brevinemataceae Paster 2012 ***** Genus '' Brevinema'' Defosse et al. 1995 **** Family " Longinemaceae" Karnachuk et al. 2021 ***** Genus ?"'' Longinema''" Karnachuk et al. 2021 *** Order

Buchanan 1917 **** Family

Gupta et al. 2014 ***** Genus ''

'' Swellengrebel 1907 (relapsing fever Borrelia, Lreptile-associated Borrelia and Echidna-associated Borrelia) ***** Genus '' Borreliella'' Adeolu & Gupta 2015 (yme borreliosis Borrelia) ***** Genus ?'' Cristispira'' Gross 1910 **** Family " Pillotinaceae" Margulis & Hinkle 1992 ***** Genus ?'' Pillotina'' Hollande and Gharagozlou 1967 ex Bermudes et al. 1988 **** Family Sphaerochaetaceae Hördt et al. 2020 ***** Genus '' Bullifex'' Wylensek et al. 2021 ***** Genus '' Marispirochaeta'' Shivani et al. 2017 ***** Genus "''Ca.'' Ornithospirochaeta" Gilroy et al. 2021 ***** Genus '' Parasphaerochaeta'' Bidzhieva et al. 2020 ***** Genus '' Pleomorphochaeta'' Arroua et al. 2016 ***** Genus '' Sediminispirochaeta'' Shivani et al. 2016 ***** Genus '' Sphaerochaeta'' Ritalahti et al. 2012 **** Family

Swellengrebel 1907 ***** Genus ?"'' Canaleparolina''" Wier, Ashen & Margulis 2000 ***** Genus ?'' Clevelandina'' Bermudes et al. 1988 ***** Genus ?'' Diplocalyx'' Gharagozlou 1968 ex Bermudes et al. 1988 non Richard 1850 non Presl 1845 ***** Genus ?'' Hollandina'' To et al. 1978 ex Bermudes et al. 1988 non Haynes 1956 ***** Genus ?"'' Mobilifilum''" Margulis et al. 1990 ***** Genus '' Alkalispirochaeta'' Sravanthi et al. 2016 ***** Genus "'' Entomospira''" Grana-Miraglia et al. 2020 non Enderlein 1917 ***** Genus '' Oceanispirochaeta'' Subhash & Lee 2017b ***** Genus '' Salinispira'' Ben Hania et al. 2015 ***** Genus ''

Spirochaeta ''Spirochaeta'' is a genus of bacteria classified within the phylum Spirochaetota.See the List of Prokaryotic names with Standing in Nomenclature. Data extracted from See the NCBIbr>webpage on SpirochaetesData extracted from Phylogeny Taxono ...

'' Ehrenberg 1835 em. Pikuta et al. 2009 non Turczaninow 1851 ***** Genus '' Thiospirochaeta'' Dubinina et al. 2020 *** Order " Treponematales" Song et al. 2021 **** Family " Rectinemataceae" Song et al. 2021 ***** Genus '' Rectinema'' Koelschbach et al. 2017 **** Family Breznakiellaceae Brune et al. 2022 ***** Genus '' Breznakiella'' Song et al. 2022 ***** Genus '' Gracilinema'' Brune et al. 2022 ***** Genus '' Helmutkoenigia'' Brune et al. 2022 ***** Genus '' Leadbettera'' Brune et al. 2022 ***** Genus ?'' Zuelzera'' Brune et al. 2022 **** Family

Treponemataceae The Treponemataceae are a family of spirochete bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganism ...

Robinson 1948 ***** Genus ?"'' Brucepastera''" Song et al. 2022 ***** Genus "''Ca.'' Avitreponema" Gilroy et al. 2021 ***** Genus "''Ca.'' Gallitreponema" Gilroy et al. 2021 ***** Genus ?"'' Teretinema''" Song et al. 2022 ***** Genus ''

Treponema ''Treponema'' is a genus of spiral-shaped bacteria. The major treponeme species of human pathogens is ''Treponema pallidum'', whose subspecies are responsible for diseases such as syphilis, bejel, and yaws. '' Treponema carateum'' is the cause ...

'' Schaudinn 1905 em. Abt et al. 2013

References

External links