Kinetoplastida (or Kinetoplastea, as a class) is a group of
flagellated
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 fro ...
protists
A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the excl ...
belonging to the phylum
Euglenozoa
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 three major clades, i.e., Kinetoplastea, Di ...
,
and characterised by the presence of an organelle with a large massed DNA called
kinetoplast
A kinetoplast is a network of circular DNA (called kDNA) inside a large 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. Kinet ...
(hence the name). The organisms are commonly referred to as "kinetoplastids" or "kinetoplasts"
The group includes a number of
parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
s responsible for serious diseases in humans and other animals, as well as various forms found in soil and aquatic environments. Their distinguishing feature, the presence of a kinetoplast, is an unusual
DNA-containing granule located within the single
mitochondrion
A mitochondrion (; ) is an organelle found in the cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...
associated with the base of the cell's flagellum (the
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 W ...
). The kinetoplast contains many copies of the mitochondrial genome.
The kinetoplastids were first defined by
Bronislaw M. Honigberg
Bronisław M. Honigberg (14 May 1920 – 1 May 1992) was a Polish-born American zoologist. Born in Warsaw, he settled in the United States as a refugee during World War II. He was Professor of parasitology at the University of Massachusetts Amhers ...
in 1963 as the members of the flagellated protozoans.
They are traditionally divided into the biflagellate
Bodonidae and uniflagellate
Trypanosomatidae; the former appears to be
paraphyletic
In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...
to the latter. One family of kinetoplastids, the
trypanosomatid
Trypanosomatida is a group of kinetoplastid excavates 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 ...
s, is notable as it includes several genera which are exclusively parasitic. ''
Bodo Bodo may refer to:
Ethnicity
* Boro people, an ethno-linguistic group mainly from Northwest Assam, India
* Bodo-Kachari people, an umbrella group from Nepal, India and Bangladesh that includes the Bodo people
Culture and language
* Boro cu ...
'' is a typical genus within kinetoplastida and including various common free-living species which feed on
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
. Others include ''
Cryptobia
''Cryptobia'' is a genus of kinetoplastids. Several species are known for being fish pathogens. They can be found in other animals, as well. The name ''Trypanoplasma'' is occasionally used for some of these.Woo, P. T. K. (2003)''Cryptobia'' (''Tr ...
'' and the parasitic ''
Leishmania
''Leishmania'' is a parasitic protozoan, a single-celled organism of the genus '' Leishmania'' that are responsible for the disease leishmaniasis. They are spread by sandflies of the genus ''Phlebotomus'' in the Old World, and of the genus '' ...
''.
Taxonomy
History
Bronislaw M. Honigberg created the taxonomic names Kinetoplastida and Kinetoplastea in 1963.
[ 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. While Kinetoplastida is mostly used to designate the order,][ but is also used as a class.][ ]Lynn Margulis
Lynn Margulis (born Lynn Petra Alexander; March 5, 1938 – November 22, 2011) was an American evolutionary biologist, and was the primary modern proponent for the significance of symbiosis in evolution. Historian Jan Sapp has said that "Lynn Ma ...
, who initially accepted Kinetoplastida as an order in 1974, later placed it as a class. Use of Kinetoplastida as an order also creates confusion as there is already an older name Trypanosomatida
Trypanosomatida is a group of kinetoplastid excavates 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. ...
Kent, 1880, under which the kinetoplastids are most often placed.
Classification
Kinetoplastida is divided into two subclasses - Metakinetoplastina and Prokinetoplastina.
* Family ? Bordnamonadidae Cavalier-Smith 2013
* Family ? Trypanophididae Poche 1911
* Subclass Prokinetoplastina Vickerman 2004
** Order Prokinetoplastida Vickerman 2004
*** Family Ichthyobodonidae Isaksen et al. 2007
* Subclass Metakinetoplastina Vickerman 2004
** Order Neobodonida Vickerman 2004
*** Family Rhynchomonadidae Cavalier-Smith 2016
*** Family Neobodonidae Cavalier-Smith 2016
** Order Parabodonida Vickerman 2004
*** Family Parabodonidae Cavalier-Smith 2016 Poche 1911; Cryptobiidae Vickerman 1976; Trypanoplasmatidae Hartmann & Chagas 1910">ryptobiaceae Poche 1911; Cryptobiidae Vickerman 1976; Trypanoplasmatidae Hartmann & Chagas 1910
** Order Bodonida Hollande 1952 emend. Vickerman 1976
*** Family Bodonidae Bütschli 1883
** Order Trypanosomatida
Trypanosomatida is a group of kinetoplastid excavates 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. ...
Kent 1880 stat. n. Hollande 1952 emend. Vickerman 2004
*** Family Trypanosomatidae Doflein 1901 Woodcock 1906">rypanomorphidae Woodcock 1906
Morphology
Kinetoplastids are eukaryotic
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
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 the paraflagellar rod.
Mitochondrion and kinetoplast DNA
The kinetoplast, after which the class is named, contains the mitochondrial genome and is a dense DNA-containing granule within the cell's single mitochondrion. The structure is made up of a network of concatenated circular DNA molecules and their related structural proteins along with DNA and RNA polymerase
In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that synthesizes RNA from a DNA template.
Using the enzyme helicase, RNAP locally opens the ...
s. The kinetoplast is found at the base of a cell's flagella and is associated to the flagellum basal body by a cytoskeletal structure.
Cytoskeleton
The cytoskeleton of kinetoplastids is primarily made up of microtubules
Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 an ...
. 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
Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of over ...
microfilaments
Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin, but are modified by and interact with numerous other pr ...
but their role in the cytoskeleton is not clear. Other cytoskeletal structures include the specialised attachment between the flagellum and the kinetoplast.
Flagella
All kinetoplastids possess at least one flagellum, species in the order trypanosomatida
Trypanosomatida is a group of kinetoplastid excavates 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. ...
have one and bodonina have two. In kinetoplastids with two flagella most forms have a leading and trailing flagellum
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 ...
, 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
A cytostome (from ''cyto-'', cell and ''stome-'', mouth) 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 vacuole ...
.
Life cycle
Kinetoplastids may be free-living or parasitic. The order trypanosomatida
Trypanosomatida is a group of kinetoplastid excavates 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. ...
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
Trypanosomatida is a group of kinetoplastid excavates 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. ...
include sleeping sickness
African trypanosomiasis, also known as African sleeping sickness or simply sleeping sickness, is an insect-borne parasitic infection of humans and other animals. It is caused by the species ''Trypanosoma brucei''. Humans are infected by two typ ...
and Chagas disease
Chagas disease, also known as American trypanosomiasis, is a tropical parasitic disease caused by ''Trypanosoma cruzi''. It is spread mostly by insects in the subfamily ''Triatominae'', known as "kissing bugs". The symptoms change over the cou ...
, caused by species of ''Trypanosoma
''Trypanosoma'' is a genus of kinetoplastids (class Trypanosomatidae), a monophyletic group of unicellular parasitic flagellate protozoa. Trypanosoma is part of the phylum Sarcomastigophora. The name is derived from the Greek ''trypano-'' (bore ...
'', and leishmaniasis
Leishmaniasis is a wide array of clinical manifestations caused by parasites of the trypanosome genus ''Leishmania''. It is generally spread through the bite of phlebotomine sandflies, ''Phlebotomus'' and ''Lutzomyia'', and occurs most freq ...
, caused by species of ''Leishmania
''Leishmania'' is a parasitic protozoan, a single-celled organism of the genus '' Leishmania'' that are responsible for the disease leishmaniasis. They are spread by sandflies of the genus ''Phlebotomus'' in the Old World, and of the genus '' ...
''.
''Trypanosoma brucei
''Trypanosoma brucei'' is a species of parasitic Kinetoplastida, kinetoplastid belonging to the genus ''Trypanosoma'' that is present in sub-Saharan Africa. Unlike other protozoan parasites that normally infect blood and tissue cells, it is exclus ...
'' can undergo meiosis
Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately resu ...
as a likely part of a sexual cycle. ''Leishmania major
''Leishmania major'' is a species of parasite found in the genus '' Leishmania'', and is associated with the disease zoonotic cutaneous leishmaniasis (also known as Aleppo boil, Baghdad boil, Bay sore, Biskra button, Chiclero ulcer, Delhi boil, K ...
'' is also capable of a meiotic process that is likely part of a sexual cycle.
Gallery
Cryptobia helicis x15,000 Scanning EM.jpg, ''Cryptobia
''Cryptobia'' is a genus of kinetoplastids. Several species are known for being fish pathogens. They can be found in other animals, as well. The name ''Trypanoplasma'' is occasionally used for some of these.Woo, P. T. K. (2003)''Cryptobia'' (''Tr ...
'' sp.
File:Bodo saltans - 400x (13895749563).jpg, ''Bodo Bodo may refer to:
Ethnicity
* Boro people, an ethno-linguistic group mainly from Northwest Assam, India
* Bodo-Kachari people, an umbrella group from Nepal, India and Bangladesh that includes the Bodo people
Culture and language
* Boro cu ...
'' sp.
File:Trypanosoma sp. PHIL 613 lores.jpg, ''Trypanosoma
''Trypanosoma'' is a genus of kinetoplastids (class Trypanosomatidae), a monophyletic group of unicellular parasitic flagellate protozoa. Trypanosoma is part of the phylum Sarcomastigophora. The name is derived from the Greek ''trypano-'' (bore ...
'' sp.
References
Bibliography
*Lumsden, W.H.R. & D.A. Evans (eds.). 1976-1979. ''Biology of the Kinetoplastida'', 2 vols. London: Academic Press.
External links
Tree of Life: Kinetoplastida
KBD -- Kinetoplastid Biology and Disease
{{Taxonbar, from1=Q131630, from2=Q21446856
Excavata classes