A spirochaete () or spirochete is a member of the

phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...

Spirochaetota (), (synonym Spirochaetes) which contains distinctive diderm (double-membrane) gram-negative bacteria, most of which have long, helically coiled (corkscrew-shaped or spiraled, hence the name) cells. Spirochaetes are chemoheterotrophic 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 A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

, called endoflagella which are sometimes called ''axial filaments''. Endoflagella are anchored at each end (pole) of the bacterium within the periplasmic space (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, 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 o ...

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'' species, which causes

leptospirosis Leptospirosis is a blood infection caused by the bacteria ''Leptospira''. Signs and symptoms can range from none to mild (headaches, muscle pains, and fevers) to severe ( bleeding in the lungs or meningitis). Weil's disease, the acute, severe ...

* '' Borrelia burgdorferi'', '' B. mayonii'', '' B. bissettiae'', '' B. garinii'', '' B. afzelii'', '' B. spielmanii'', '' B. lusitaniae'', which cause Lyme disease. * '' Borrelia recurrentis'', which causes relapsing fever * '' Treponema pallidum'' subspecies which cause treponematoses such as

syphilis Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, an ...

and yaws. * ''

Brachyspira pilosicoli ''Brachyspira pilosicoli'' is a gram-negative, anaerobic, host-associated spirochete that colonizes the intestinal tract of animals and humans. It appears as a characteristic "false brush border" due to its end-on attachment to enterocytes of th ...

'' and ''

Brachyspira aalborgi ''Brachyspira aalborgi'' is a species of bacteria, one of the causative agents of intestinal spirochetosis. Its cells are anaerobic, sigmoidal with tapered ends, 2 to 6 µm long. Four flagella are inserted at each end of the cells. The m ...

'', which cause intestinal spirochaetosis Salvarsan, the first partially organic synthetic

antimicrobial drug An antimicrobial is an agent that kills microorganisms or stops their growth. Antimicrobial medicines can be grouped according to the microorganisms they act primarily against. For example, antibiotics are used against bacteria, and antifungals ar ...

in medical history, was effective against spirochaetes and primarily used to cure

. Additionally, oral spirochaetes are known to play a significant role in the pathogenesis of human periodontal disease.

Taxonomy and molecular signatures

The class currently consists of 14 validly named genera across 4 orders and 5 families. The orders '' Brachyspirales'', '' Brevinematales'' and '' Leptospirales'' each contain a single family, ''

Brachyspiraceae 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 common ...

'', ''

Brevinemataceae ''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 ''

Leptospiraceae 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 ill ...

'', 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. 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. 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.). 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 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 '' Spirochaetales''. 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 In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

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 (LPSN) and National Center for Biotechnology Information (NCBI). * Phylum Spirochaetota Garrity and Holt 2021 ** Class Spirochaetia Paster 2020 *** Genus ?'' Exilispira'' Imachi et al. 2008 *** Genus ?"'' Spirosymplokos''" Guerrero et al. 1993 *** Order Leptospirales Gupta et al. 2014 **** Family

Hovind-Hougen 1979 ***** Genus ''

Leptonema ''Leptonema'' is a genus of flowering plant belonging to the family Phyllanthaceae first described in 1824. The entire genus is endemic to Madagascar. It is dioecious, with male and female flowers on separate plants. ;Species # '' Leptonema g ...

'' Hovind-Hougen 1983 ***** Genus '' Leptospira'' Noguchi 1917 ***** Genus '' Turneriella'' Levett et al. 2005 *** Order Brachyspirales corrig. Gupta et al. 2014 **** Family

Paster 2012 ***** Genus ''

Brachyspira ''Brachyspira'' 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 ''Brachyspira sp ...

'' Hovind-Hougen et al. 1982 ***** Genus ?"''Ca.'' Maribrachyspira" Matsuyama et al. 2017 *** Order Brevinematales Gupta et al. 2014 **** Family

Paster 2012 ***** Genus '' Brevinema'' Defosse et al. 1995 **** Family " Longinemaceae" Karnachuk et al. 2021 ***** Genus ?"'' Longinema''" Karnachuk et al. 2021 *** Order Spirochaetales Buchanan 1917 **** Family Borreliaceae Gupta et al. 2014 ***** Genus '' Borrelia'' Swellengrebel 1907 (relapsing fever Borrelia, Lreptile-associated Borrelia and Echidna-associated Borrelia) ***** Genus '' Borreliella'' Adeolu & Gupta 2015 (yme borreliosis Borrelia) ***** Genus ?''

Cristispira ''Cristispira'' is a genus of bacteria of the spirochete phylum. They are known as large spirochetes. They are characterized by the host species in which they reside. They are known as harmless parasites of freshwater and marine molluscs and gas ...

'' 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 Spirochaetaceae Swellengrebel 1907 ***** Genus ?"'' Canaleparolina''" Wier, Ashen & Margulis 2000 ***** Genus ?'' Clevelandina'' Bermudes et al. 1988 ***** Genus ?''

Diplocalyx ''Diplocalyx'' is a genus of bacteria of the spirochete phylum. The genus was originally established in 1968 on the basis of differential morphology when compared to other spirochete species. No species within it has been successfully grown in cu ...

'' 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'' 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 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'' Schaudinn 1905 em. Abt et al. 2013

References

External links