Trypanosomatida is a group of kinetoplastid unicellular organisms distinguished by having only a single flagellum. The name is derived from the Greek language trypano (borer) and soma (body) because of the corkscrew-like motion of some trypanosomatid species. All members are exclusively parasite, found primarily in .
Medical importance
The three major
human diseases caused by trypanosomatids are; African
trypanosomiasis (sleeping sickness, caused by
Trypanosoma brucei and transmitted by
Tsetse fly), South American trypanosomiasis (
Chagas disease, caused by
T. cruzi and transmitted by
Triatominae bugs), and
leishmaniasis (a set of trypanosomal diseases caused by various species of
Leishmania transmitted by
Phlebotominae[
]
- This review cites this research.
).
Evolution
The family is known from fossils of the extinct genus
Paleoleishmania preserved in Burmese
amber dating to the
Albian (100 mya) and
Dominican amber from the
Burdigalian (20–15 mya) of
Hispaniola.
The genus
Trypanosoma is also represented in Dominican amber in the extinct species
T. antiquus.
Taxonomy
Three genera are
heteroxenous (two hosts in the life cycle) –
Leishmania,
Phytomonas and
Trypanosoma, while The remainder are monoxenous (one host in the life cycle).
Paratrypanosoma appears to be the first evolving branch in this order. Fifteen genera are recognised in the
Trypanosomatidae and there are three subfamilies –
Blechomonadinae,
Leishmaniinae and
Strigomonadinae. The genera in the subfamily
Strigomonadinae are characterised by the presence of obligatory intracellular bacteria of the Kinetoplastibacterium genus.
-
Family Trypanosomatidae Calkins 1926 Trypanomorphidae
- :* Genus Trypanosoma Gruby 1843
- * Subfamily Blechomonadinae Votypka & Suková 2013
- :* Genus Blechomonas Votypka & Suková 2013
- * Subfamily Leishmaniinae sensu Maslov & Lukeš 2012
- :* Clade Crithidiatae Maslov & Lukeš 2012
- ::* Genus Crithidia Léger 1902
- ::* Genus Leptomonas Kent 1880
- ::* Genus Lotmaria Schwarz 2015
- :* Clade Leishmaniatae Maslov & Lukeš 2012
- ::* Genus Borovskyia Kostygov & Yurchenko 2017
- ::* Genus Endotrypanum Mesnil & Brimont 1908
- ::* Genus Leishmania Ross 1903
- ::* Genus Novymonas Votýpka et al. 2015
- ::* Genus Paraleishmania Cupolillo et al. 2000
- ::* Genus Zelonia Shaw, Camargo et Teixeira 2016
- * Subfamily Phytomonadinae Kostygov & Yurchenko 2015
- :* Genus Herpetomonas Kent 1880 non Donovan 1909
- :* Genus Lafontella Kostygov & Yurchenko 2015
- :* Genus Phytomonas Donovan 1909
- * Subfamily Strigomonadinae Votypka et al. 2014
- :* Genus Angomonas Souza & Corte-Real 1991
- :* Genus Kentomonas Votypka et al. 2014
- :* Genus Strigomonas Lwoff & Lwoff 1931
Life cycle
Some trypanosomatids only occupy a single host, while many others are
heteroxenous: they live in more than one host species over their life cycle. This heteroxenous life cycle typically includes the
intestine of a bloodsucking
insect and the blood and/or tissues of a
vertebrate. Rarer hosts include other bloodsucking invertebrates, such as
,
and other organisms such as
. Different species go through a range of different morphologies at different stages of the life cycle, with most having at least two different morphologies. Typically the promastigote and epimastigote forms are found in insect hosts, trypomastigote forms in the mammalian
bloodstream and amastigotes in
intracellular environments.
Among commonly studied examples, T. brucei, T. congolense, and T. vivax are extracellular, while T. cruzi and Leishmania spp. are intracellular.[
]
Sexual reproduction
Trypanosomatids that cause globally known diseases such
leishmaniasis (
Leishmania species), African trypanosomiasis referred to as sleeping sickness (
Trypanosoma brucei), and
Chagas disease (
Trypanosoma cruzi) were found to be capable of
meiosis and genetic exchange.
These findings indicate the capability for sexual reproduction in the Trypanosomatida.
[
]
Morphologies
A variety of different morphological forms appear in the life cycles of trypanosomatids, distinguished mainly by the position, length and the cell body attachment of the flagellum. The kinetoplast is found closely associated with the basal body at the base of the flagellum and all species of trypanosomatid have a single nucleus. Most of these morphologies can be found as a life cycle stage in all trypanosomatid genera however certain morphologies are particularly common in a particular genus. The various morphologies were originally named from the genus where the morphology was commonly found, although this terminology is now rarely used because of potential confusion between morphologies and genus. Modern terminology is derived from the Greek; "mastig", meaning whip (referring to the flagellum), and a prefix which indicates the location of the flagellum on the cell. For example, the amastigote (prefix "a-", meaning no flagellum) form is also known as the leishmanial form as all Leishmania have an amastigote life cycle stage.
-
Amastigote (leishmanial).
-
(leptomonad).
-
(crithidial).
-
(trypanosomal).
-
(herpetomonad).
-
.
Image:LeishmaniaMexicana Amastigote SEM.jpg| Amastigote: False colour SEM micrograph of amastigote form Leishmania mexicana. The cell body is shown in orange and the flagellum is in red. 219 pixels/μm.
Image:LeishmaniaMexicana Promastigote SEM.jpg| Promastigote: False colour SEM micrograph of promastigote form Leishmania mexicana. The cell body is shown in orange and the flagellum is in red. 119 pixels/μm.
Image:TrypanosomaBrucei_ProcyclicTrypomastigote_SEM.jpg| Trypomastigote: False colour SEM micrograph of procyclic form Trypanosoma brucei. The cell body is shown in orange and the flagellum is in red. 84 pixels/μm.
Other features
Notable characteristics of trypanosomatids are the ability to perform trans-splicing of RNA and possession of , where much of their glycolysis is confined to. The acidocalcisome, another organelle, was first identified in trypanosomes.
Bacterial endosymbiont
Six species of trypanosomatids are known to carry an additional proteobacterial endosymbiont, termed TPE (trypanosomatid proteobacterial endosymbionts). These trypansomatids ( Strigomonas oncopelti, S. culicis, S. galati, Angomonas desouzai, and Angomonas deanei) are in turn known as SHTs, for symbiont-harboring trypanosomatids. All such symbionts have a shared evolutionary origin and are classified in the Candidatus genus " Kinetoplastibacterium".
As with many symbionts, the bacteria have a much reduced genome compared to their free-living relatives of genera Taylorella and Achromobacter. (GTDB finds the genus sister to Proftella, a symbiont of Diaphorina citri.)
-
( online). A comprehensive survey of the organisms' natural history.
External links
