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[[File:Endoflagella Components.pdf|thumb|Endoflagella Components. Legend:
Fig. 1: A cross-section of a typical spirochete cell showing endoflagella located in the periplasm between the inner cytoplasmic membrane and the outer membrane. Periplasm, consisting of a gel-like matrix, provides a semi-stable medium to secure endoflagella during rotation. The axial filament, indicated in red, is composed of bundles of endoflagella.
Fig. 2: A side-view of a spirochete cell which shows two axial filaments in opposing motion. One axial filament rotates in a clockwise orientation; an adjacent axial filament rotates in a counter-clockwise orientation. Rotation of the endoflagella creates torsion and drives the corkscrew rotation of the cell.
Fig. 3: An expanded view of the cellular membranes that surround endoflagellum. Both the inner and outer membrane contain a phospholipid bi-layer, with non-polar fatty acid chains in-ward of polar phosphorus heads. Peptidoglycan, the cell wall, provides structure in bacterial microorganisms. Axial filaments are superior to the peptidoglycan.
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A spirochaete () or spirochete is a member of the phylum Spirochaetota (also called Spirochaetes ), which contains distinctive diderm bacteria (double-membrane) Gram-negative bacteria, most of which have long, spiral bacteria (corkscrew-shaped or spiraled, hence the name) cells. (2025). 9780838585290, McGraw Hill. ISBN 9780838585290 Spirochaetes are 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 flagellum, called endoflagella, or periplasmic flagella, 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. (2025). 9781292235103, Pearson. ISBN 9781292235103 These cause a twisting motion which allows the spirochaete to move. When reproducing, a spirochaete will undergo asexual Binary fission. Most spirochaetes are free-living and anaerobic, but there are numerous exceptions. Spirochaete bacteria are diverse in their pathogenic capacity and the that they inhabit, as well as molecular characteristics including GC content and genome size.
Salvarsan, 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 of human periodontal disease.
A CSI has also been found exclusively shared by all Spirochaetota species. This CSI is a three-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 synapomorphy 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).
See also
External links
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