Kinetoplastida

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Kinetoplastida
Trypanosoma cruzi crithidia.jpeg
Trypanosoma cruzi parasites
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Phylum: Euglenozoa
Subphylum: Glycomonada
Class: Kinetoplastea
Honigberg, 1963 emend. Cavalier-Smith, 1981 [1] [2]
Subdivisions
Synonyms
  • Kinetoplastida Honigberg 1963 emend. Margulis 1974

Kinetoplastida (or Kinetoplastea, as a class) is a group of flagellated protists belonging to the phylum Euglenozoa, [3] [4] and characterised by the presence of a distinctive organelle called the kinetoplast (hence the name), a granule containing a large mass of DNA. The group includes a number of parasites responsible for serious diseases in humans and other animals, as well as various forms found in soil and aquatic environments. The organisms are commonly referred to as "kinetoplastids" or "kinetoplasts". [5]

Contents

The kinetoplastids were first defined by Bronislaw M. Honigberg in 1963 as the members of the flagellated protozoans. [1] They are traditionally divided into the biflagellate Bodonidae and uniflagellate Trypanosomatidae; the former appears to be paraphyletic to the latter. One family of kinetoplastids, the trypanosomatids, is notable as it includes several genera which are exclusively parasitic. Bodo is a typical genus within kinetoplastida, which also includes various common free-living species which feed on bacteria. Others include Cryptobia and the parasitic Leishmania .

Taxonomy

History

Honigberg created the taxonomic names Kinetoplastida and Kinetoplastea in 1963. [1] Since then there is no consensus on the use of either of the two as a definite taxon. Kinetoplastea is more widely used as the class, [6] [7] [8] [9] [10] while Kinetoplastida is mostly used to designate the order, [4] [11] [12] [13] but is also used as a class. [3] [14] Lynn Margulis, who initially accepted Kinetoplastida as an order in 1974, later placed it as a class. [15] Use of Kinetoplastida as an order also creates confusion as there is already an older name Trypanosomatida Kent, 1880, under which the kinetoplastids are most often placed. [16]

Classification

Kinetoplastida is divided into two subclasses - Metakinetoplastina and Prokinetoplastina. [17] [18]

Morphology

Kinetoplastids are eukaryotic and possess normal eukaryotic organelles, for example the nucleus, mitochondrion, golgi apparatus and flagellum. Along with these universal structures, kinetoplastids have several distinguishing morphological features such as the kinetoplast, sub-pellicular microtubule array and paraflagellar rod.[ citation needed ]

Mitochondrion and kinetoplast DNA

The kinetoplast, after which the class is named, is a dense DNA-containing granule within the cell's single mitochondrion, containing many copies of the mitochondrial genome. The structure is made up of a network of concatenated circular DNA molecules and their related structural proteins along with DNA and RNA polymerases. The kinetoplast is found at the base of a cell's flagella and is associated to the flagellum basal body by a cytoskeletal structure.[ citation needed ]

Cytoskeleton

The cytoskeleton of kinetoplastids is primarily made up of microtubules. These make a highly regular array, the sub-pellicular array, which runs parallel just under the cell surface along the long axis of the cell. Other microtubules with more specialised roles, such as the rootlet microtubules, are also present. Kinetoplastids are capable of forming actin microfilaments but their role in the cytoskeleton is not clear. Other cytoskeletal structures include the specialised attachment between the flagellum and the kinetoplast.[ citation needed ]

Flagella

All kinetoplastids possess at least one flagellum; species in the order trypanosomatida have one and bodonida have two. In kinetoplastids with two flagella most forms have a leading and trailing flagellum, the latter of which may be attached to the side of the cell. The flagella are used for locomotion and attachment to surfaces. The bases of the flagella are found in a specialised pocket structure which is also the location of the cytostome.[ citation needed ]

Life cycle

Kinetoplastids may be free-living or parasitic. The order trypanosomatida is notable as it includes many genera which are exclusively parasitic. Trypanosomatids may have simple life cycles in a single host or more complex ones which progress through multiple differentiation stages in two hosts. Dramatic morphological changes are possible between lifecycle stages. Diseases caused by members of the order trypanosomatida include sleeping sickness and Chagas disease, caused by species of Trypanosoma , and leishmaniasis, caused by species of Leishmania . Trypanosoma brucei can undergo meiosis as a likely part of a sexual cycle. [19] [20] Leishmania major is also capable of a meiotic process that is likely part of a sexual cycle. [21]

Related Research Articles

<span class="mw-page-title-main">Euglenozoa</span> Phylum of protozoans

Euglenozoa are a large group of flagellate Discoba. They include a variety of common free-living species, as well as a few important parasites, some of which infect humans. Euglenozoa are represented by four major groups, i.e., Kinetoplastea, Diplonemea, Euglenida, and Symbiontida. Euglenozoa are unicellular, mostly around 15–40 μm (0.00059–0.00157 in) in size, although some euglenids get up to 500 μm (0.020 in) long.

<span class="mw-page-title-main">Flagellate</span> Group of protists with at least one whip-like appendage

A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word flagellate also describes a particular construction characteristic of many prokaryotes and eukaryotes and their means of motion. The term presently does not imply any specific relationship or classification of the organisms that possess flagella. However, the term "flagellate" is included in other terms which are more formally characterized.

<span class="mw-page-title-main">Flagellum</span> Cellular appendage functioning as locomotive or sensory organelle

A flagellum is a hairlike appendage that protrudes from certain plant and animal sperm cells, from fungal spores (zoospores), and from a wide range of microorganisms to provide motility. Many protists with flagella are known as flagellates.

<i>Leishmania</i> Genus of parasitic flagellate protist

Leishmania is a parasitic protozoan, a single-celled organism of the genus Leishmania that is responsible for the disease leishmaniasis. They are spread by sandflies of the genus Phlebotomus in the Old World, and of the genus Lutzomyia in the New World. At least 93 sandfly species are proven or probable vectors worldwide. Their primary hosts are vertebrates; Leishmania commonly infects hyraxes, canids, rodents, and humans.

<span class="mw-page-title-main">Trypanosomatida</span> Flagellate kinetoplastid excavate order

Trypanosomatida is a group of kinetoplastid unicellular organisms distinguished by having only a single flagellum. The name is derived from the Greek trypano (borer) and soma (body) because of the corkscrew-like motion of some trypanosomatid species. All members are exclusively parasitic, found primarily in insects. A few genera have life-cycles involving a secondary host, which may be a vertebrate, invertebrate or plant. These include several species that cause major diseases in humans. Some trypanosomatida are intracellular parasites, with the important exception of Trypanosoma brucei.

<i>Trypanosoma</i> Genus of parasitic flagellate protist in the Kinetoplastea class

Trypanosoma is a genus of kinetoplastids, a monophyletic group of unicellular parasitic flagellate protozoa. Trypanosoma is part of the phylum Euglenozoa. The name is derived from the Greek trypano- (borer) and soma (body) because of their corkscrew-like motion. Most trypanosomes are heteroxenous and most are transmitted via a vector. The majority of species are transmitted by blood-feeding invertebrates, but there are different mechanisms among the varying species. Trypanosoma equiperdum is spread between horses and other equine species by sexual contact. They are generally found in the intestine of their invertebrate host, but normally occupy the bloodstream or an intracellular environment in the vertebrate host.

<span class="mw-page-title-main">Trypanothione</span> Chemical compound

Trypanothione is an unusual form of glutathione containing two molecules of glutathione joined by a spermidine (polyamine) linker. It is found in parasitic protozoa such as leishmania and trypanosomes. These protozoal parasites are the cause of leishmaniasis, sleeping sickness and Chagas' disease. Trypanothione was discovered by Alan Fairlamb. Its structure was proven by chemical synthesis. It is present mainly in the Kinetoplastida but can be found in other parasitic protozoa such as Entamoeba histolytica. Since this thiol is absent from humans and is essential for the survival of the parasites, the enzymes that make and use this molecule are targets for the development of new drugs to treat these diseases.

<span class="mw-page-title-main">Cytostome</span>

A cytostome or cell mouth is a part of a cell specialized for phagocytosis, usually in the form of a microtubule-supported funnel or groove. Food is directed into the cytostome, and sealed into vacuoles. Only certain groups of protozoa, such as the Ciliophora and Excavata, have cytostomes. An example is Balantidium coli, a ciliate. In other protozoa, and in cells from multicellular organisms, phagocytosis takes place at any point on the cell or feeding takes place by absorption.

<i>Bodo</i> (excavate) Genus of micro-organisms

Bodo is a genus of microscopic kinetoplastids, flagellate excavates first described in 1831 by Christian Gottfried Ehrenberg. The genus is small, as it has recently been redefined to include only four species. Bodo includes free-living, phagotrophic organisms that can be found in many marine and freshwater environments as well as some terrestrial environments. Being phagotrophic, Bodo feeds on bacteria and other microorganisms that it finds while swimming through its water-based habitats. The swimming-like movement is facilitated by the two unequal flagella that Bodo possesses which arise from an anteriorly located flagellar pocket. Bodo is roughly bean-shaped and is often missed in samples from water or terrestrial environments due to its small size.

<i>Bodo saltans</i>

Bodo saltans is a free-living nonparasitic species of kinetoplastid flagellated phagotrophic protozoa that feed on bacteria. Bodo saltans cells have been reported in freshwater and marine environments.

<span class="mw-page-title-main">Kinetoplast</span>

A kinetoplast is a network of circular DNA inside a mitochondrion that contains many copies of the mitochondrial genome. The most common kinetoplast structure is a disk, but they have been observed in other arrangements. Kinetoplasts are only found in Excavata of the class Kinetoplastida. The variation in the structures of kinetoplasts may reflect phylogenic relationships between kinetoplastids. A kinetoplast is usually adjacent to the organism's flagellar basal body, suggesting that it is bound to some components of the cytoskeleton. In Trypanosoma brucei this cytoskeletal connection is called the tripartite attachment complex and includes the protein p166.

Crithidia fasciculata is a species of parasitic excavates. C. fasciculata, like other species of Crithidia have a single host life cycle with insect host, in the case of C. fasciculata this is the mosquito. C. fasciculata have low host species specificity and can infect many species of mosquito.

<i>Trypanosoma antiquus</i> Extinct species in the kinetoplast class

Trypanosoma antiquus is an extinct species of kinetoplastid, a monophyletic group of unicellular parasitic flagellate protozoa.

Trypanosome may refer to:

<i>Paleoleishmania</i> Extinct genus of parasitic flagellate protist in the Kinetoplastea class

Paleoleishmania is an extinct genus of kinetoplastids, a monophyletic group of unicellular parasitic flagellate protozoa. At present it is placed in the family Trypanosomatidae. The genus contains two species, the type species Paleoleishmania proterus and the later described Paleoleishmania neotropicum.

<i>Crithidia luciliae</i> Species of parasitic flagellate protist in the Kinetoplastea class

Crithidia luciliae is a flagellate parasite that uses the housefly, Musca domestica, as a host. As part of the family of Trypanosomatidae, it is characterised by the presence of a kinetoplast, a complex network of interlocking circular double-stranded DNA (dsDNA) molecules. The presence of the kinetoplast makes this organism important in the diagnosis of systemic lupus erythamatosus (SLE). By using C. luciliae as a substrate for immunofluorescence, the organelle can be used to detect anti-dsDNA antibodies, a common feature of the disease.

<span class="mw-page-title-main">Diplonemidae</span> Family of protozoans

Diplonemidae is a family of biflagellated unicellular protists that may be among the more diverse and common groups of planktonic organisms in the ocean. Although this family is currently made up of three named genera; Diplonema, Rhynchopus, and Hemistasia, there likely exist thousands of still unnamed genera. Organisms are generally colourless and oblong in shape, with two flagella emerging from a subapical pocket. They possess a large mitochondrial genome composed of fragmented linear DNA. These non-coding sequences must be massively trans-spliced, making it one of the most complicated post-transcriptional editing process known to eukaryotes.

Phytomonas is a genus of trypanosomatids that infect plant species. Initially described using existing genera in the family Trypanosomatidae, such as Trypanosoma or Leishmania, the nomenclature of Phytomonas was proposed in 1909 in light of their distinct hosts and morphology. When the term was originally coined, no strict criterion was followed, and the term was adopted by the scientific community to describe flagellate protozoa in plants as a matter of convenience. Members of the taxon are globally distributed and have been discovered in members of over 24 plant families. Of these 24, the two main families that are infected by Phytomonas are Euphorbiaceae and Asclepiadiacae. These protists have been found in hosts between 50° latitude North and South, and thus they can be found on all continents save for Antarctica.

<i>Neobodo</i> Genus of protists

Neobodo are diverse protists belonging to the eukaryotic supergroup Excavata. They are Kinetoplastids in the subclass Bodonidae. They are small, free-living, heterotrophic flagellates with two flagella of unequal length used to create a propulsive current for feeding. As members of Kinetoplastids, they have an evident kinetoplast There was much confusion and debate within the class Kinetoplastid and subclass Bodonidae regarding the classification of the organism, but finally the new genera Neobodo was proposed by Keith Vickerman. Although they are one of the most common flagellates found in freshwater, they are also able to tolerate saltwater Their ability to alternate between both marine and freshwater environments in many parts of the world give them a “cosmopolitan” character. Due to their relatively microscopic size ranging between 4–12 microns, they are further distinguished as heterotrophic nanoflagellates. This small size ratio limits them as bacterivores that swim around feeding on bacteria attached to surfaces or in aggregates.

Postgaardia is a proposed basal clade of flagellate Euglenozoa, following Thomas Cavalier-Smith. As of April 2023, the Interim Register of Marine and Nonmarine Genera treats the group as a subphylum. A 2021 review of Euglenozoa places Cavalier-Smith's proposed members of Postgaardia in the class Symbiontida. As Euglenozoans may be basal eukaryotes, the Postgaardia may be key to studying the evolution of Eukaryotes, including the incorporation of eukaryotic traits such as the incorporation of alphaproteobacterial mitochondrial endosymbionts.

References

  1. 1 2 3 Honigberg, B. M. (1963). "A contribution to systematics of the non-pigmented flagellates.". In Ludvík, J.; Lom, J.; Vávra J. (eds.). Progress in Protozoology: proceedings of the first International Congress on protozoology held at Prague. Academic Press.
  2. ↑ Cavalier-Smith, T. (1981). Eukaryote kingdoms: seven or nine? Biosystems 14, 461–481.
  3. 1 2 Berman, Jules J. (2012). Taxonomic Guide to Infectious Diseases: Understanding the Biologic Classes of Pathogenic Organisms. London: Elsevier/Academic Press. p. 96. ISBN   978-0-12415-895-5.
  4. 1 2 "Kinetoplastida (kinetoplasts)". UniProt Consortium. Retrieved 22 January 2015.
  5. ↑ Lukes, Julius (2009). "Kinetoplastida". The Tree of Life Web Project. Retrieved 10 September 2013.
  6. ↑ "Kinetoplastea". EOL. Retrieved 22 January 2015.
  7. ↑ "Kinetoplastea". World Register of Marine Species. Retrieved 22 January 2015.
  8. ↑ "Kinetoplastea". ZipcodeZoo. Archived from the original on 22 January 2015. Retrieved 22 January 2015.
  9. ↑ "Taxon: Class Kinetoplastea". The Taxonomicon. Archived from the original on 22 January 2015. Retrieved 22 January 2015.
  10. ↑ Moreira, D. (2004). "An updated view of kinetoplastid phylogeny using environmental sequences and a closer outgroup: proposal for a new classification of the class Kinetoplastea". International Journal of Systematic and Evolutionary Microbiology. 54 (5): 1861–1875. doi: 10.1099/ijs.0.63081-0 . PMID   15388756.
  11. ↑ "Kinetoplastida". EOL. Retrieved 22 January 2015.
  12. ↑ "Kinetoplastida". Metalife. Archived from the original on 22 January 2015. Retrieved 22 January 2015.
  13. ↑ "Kinetoplastida". NCBI Taxonomy. Retrieved 22 January 2015.
  14. ↑ Gutierrez, Yezid (2000). Diagnostic Pathology of Parasitic Infections with Clinical Correlations (2 ed.). New York: Oxford University Press. p. 63. ISBN   978-0-1951214-38.
  15. ↑ Chapman, Lynn Margulis, Michael J. (2009). Kingdoms & Domains : An Illustrated Guide to the Phyla of Life on Earth (4 ed.). Amsterdam: Academic Press/Elsevier. p.  158. ISBN   978-0-12-373621-5.{{cite book}}: CS1 maint: multiple names: authors list (link)
  16. ↑ Deschamps, P.; Lara, E.; Marande, W.; Lopez-Garcia, P.; Ekelund, F.; Moreira, D. (2010). "Phylogenomic analysis of kinetoplastids supports that trypanosomatids arose from within bodonids". Molecular Biology and Evolution. 28 (1): 53–58. doi: 10.1093/molbev/msq289 . PMID   21030427.
  17. ↑ Moreira, D; López-García, P; Vickerman, K (2004). "An updated view of kinetoplastid phylogeny using environmental sequences and a closer outgroup: proposal for a new classification of the class Kinetoplastea". International Journal of Systematic and Evolutionary Microbiology. 54 (Pt 5): 1861–1875. doi: 10.1099/ijs.0.63081-0 . PMID   15388756.
  18. ↑ Stevens, JR (2008). "Kinetoplastid phylogenetics, with special reference to the evolution of parasitic trypanosomes". Parasite. 15 (3): 226–232. doi: 10.1051/parasite/2008153226 . PMID   18814685.
  19. ↑ Peacock L, Ferris V, Sharma R, Sunter J, Bailey M, Carrington M, Gibson W (2011). "Identification of the meiotic life cycle stage of Trypanosoma brucei in the tsetse fly" (PDF). Proc. Natl. Acad. Sci. U.S.A. 108 (9): 3671–6. Bibcode:2011PNAS..108.3671P. doi: 10.1073/pnas.1019423108 . PMC   3048101 . PMID   21321215.
  20. ↑ Gibson W (2015). "Liaisons dangereuses: sexual recombination among pathogenic trypanosomes". Res. Microbiol. 166 (6): 459–66. doi:10.1016/j.resmic.2015.05.005. hdl: 1983/1ecb5cba-da25-4e93-a3cb-b00a0477cb23 . PMID   26027775.
  21. ↑ Akopyants NS, Kimblin N, Secundino N, Patrick R, Peters N, Lawyer P, Dobson DE, Beverley SM, Sacks DL (2009). "Demonstration of genetic exchange during cyclical development of Leishmania in the sand fly vector". Science. 324 (5924): 265–8. Bibcode:2009Sci...324..265A. doi:10.1126/science.1169464. PMC   2729066 . PMID   19359589.

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