Мікроспоридії: відмінності між версіями

Матеріал з Вікіпедії — вільної енциклопедії.
Перейти до навігації Перейти до пошуку
Наступне редагування →
Вилучено вміст Додано вміст
ВізуальнийВікірозмітка
Створена сторінка: {{Automatic taxobox | image = Fibrillanosema_spore.jpg | image_width = 250px | image_caption = Sporoblast of<br />''Fibrillanosema crangonycis'' | subdivisi...
(Немає відмінностей)

Версія за 12:12, 29 березня 2013

Мікроспоридії
Sporoblast of
Fibrillanosema crangonycis
Біологічна класифікація редагувати
Бракує шаблону таксономії (створити): Мікроспоридії
Вікісховище: Microsporidia

The microsporidia constitute a phylum (Microspora) of spore-forming unicellular parasites. They were once thought to be protists but are now known to be fungi. Loosely 1500 of the probably more than one million[джерело?] species are named now. Microsporidia are restricted to animal hosts, and all major groups of animals host microsporidia. Most infect insects, but they are also responsible for common diseases of crustaceans and fish. The distinguished species of microsporidia usually infect one specific host or a related group of hosts. Several species, most of which are opportunistic, also infect humans.

Approximately 10 percent of the species are parasites of vertebrates, including humans.

After infection they influence their hosts in various ways and all organs and tissues are invaded, though generally by different species of microsporidia. Some species are lethal, and a few are used in biological control of insect pests. Parasitic castration, gigantism, or change of host sex are all potential effects of microsporidian parasitism (in insects). In the most advanced cases of parasitism the microsporidium rules the host cell completely and controls its metabolism and reproduction, forming a xenoma. .[1]

Replication takes place within the host's cells, which are infected by means of unicellular spores. These vary from 1-40 μm, making them some of the smallest eukaryotes.[джерело?] Microsporidia that infect mammals are 1.0-4.0 μm.[2] They also have the smallest eukaryotic genomes.

Microsporidium was once the vernacular name for a member of the class Microsporidea in the protozoan subphylum Cnidospora.[3]

Xenoma on flatfish caused by Glugea stephani

Morphology

Microsporidia lack mitochondria and possess, instead, mitosomes. They also lack motile structures such as flagella.
Microsporidia produce highly resistant spores to survive outside the host for up to several years. Spore morphology is useful in distinguishing between different species. Spores of most species are oval or pyriform, but rod-shaped or spherical spores are not unusual. A few genera produce spores of unique shape for the genus.

The spore is protected by a wall, consisting of three layers:

  • an outer electron-dense exospore
  • a median, wide and seemingly structureless endospore, containing chitin
  • a thin internal plasma membrane

In most cases there are two closely associated nuclei, forming a diplokaryon, but sometimes there is only one.
The anterior half of the spore contains a harpoon-like apparatus with a long thread-like polar filament, which is coiled up in the posterior half of the spore. The anterior part of the polar filament is surrounded by a polaroplast, a lamella of membranes. Behind the polar filament there is a posterior vacuole.[1]

Infection

In the gut of the host the spore germinates, it builds up osmotic pressure until its rigid wall ruptures at its thinnest point at the apex. The posterior vacuole swells, forcing the polar filament to rapidly eject the infectious content into the cytoplasm of the potential host. Simultaneously the material of the filament is rearranged to form a tube which functions as a hypodermic needle and penetrates the gut epithelium.

Once inside the host cell, a sporoplasm grows, dividing or forming a multinucleate plasmodium, before producing new spores. The life cycle varies considerably. Some have a simple asexual life cycle,[4] while others have a complex life cycle involving multiple hosts and both asexual and sexual reproduction. Different types of spores may be produced at different stages, probably with different functions including autoinfection (transmission within a single host).

Medical implications

The microsporidia often cause chronic, debilitating diseases rather than lethal infections. Effects on the host include reduced longevity, fertility, weight, and general vigor. Vertical transmission of microsporidia is frequently reported. In the case of insect hosts, vertical transmission often occurs as transovarial transmission, where the microsporidian parasites pass from the ovaries of the female host into eggs and eventually multiply in the infected larvae. Amblyospora salinaria n. sp. which infects the mosquito Culex salinarius Coquillett, and Amblyospora californica which infects the mosquito Culex tarsalis Coquillett, provide typical examples of transovarial transmission of microsporidia.[5][6][7][8]

Microsporidia, specifically the mosquito-infecting Vavraia culicis, are being explored as a possible 'evolution-proof' malaria-control method.[9] Microsporidian infection of Anopheles gambiae (the principal vector of Plasmodium falciparum malaria) reduces malarial infection within the mosquito, and shortens the mosquito lifespan.[10] As the majority of malaria-infected mosquitoes naturally die before the malaria parasite is mature enough to transmit, any increase in mosquito mortality through microsporidian-infection may reduce malaria transmission to humans.

Clinical

A number of species may infect humans: these include Trachipleistophora hominis.[11]

Classification

For some time microsporidia were considered as very primitive eukaryotes, especially because of the lack of mitochondria, and placed along with the other Protozoa such as diplomonads, parabasalia and archamoebae in the protist-group Archezoa. More recent research has falsified this theory of early origin (for all of these). Yet microsporidia are proposed to be highly developed and specialized organisms, which just dispensed functions that are needed no longer, because they are supplied by the host.[12] Furthermore, spore-forming organisms in general do have a complex system of reproduction, both sexual and asexual, which look far from primitive.

Nowadays microsporidia are placed within the Fungi or as a sister-group of the Fungi with a common ancestor.[13][14][15][16]

Forming of clades is largely based on habitat and host. Three classes of Microsporidia are proposed by Vossbrinck and Debrunner-Vossbrinck, based on the habitat: Aquasporidia, Marinosporidia and Terresporidia.[17]

One classification could be:

  1. Subclass: Dihaplophasea
  2. Subclass Haplophasea

See also

References

  1. ↑ а б Ronny Larsson, Lund University (Department of Cell and Organism Biology) Cytology and taxonomy of the microsporidia 2004.
  2. ↑ Didier, ES. (Apr 2005). Microsporidiosis: an emerging and opportunistic infection in humans and animals. Acta Trop. 94 (1): 61—76. doi:10.1016/j.actatropica.2005.01.010. PMID 15777637.
  3. ↑ Corliss JO, Levine ND (1963). Establishment of the Microsporidia as a new class in the protozoan subphylum Cnidospora. The Journal of Protozoology. 10 (Suppl.): 26—27.
  4. ↑ Ironside JE (2007). Multiple losses of sex within a single genus of Microsporidia. BMC Evolutionary Biology. 7: 48. doi:10.1186/1471-2148-7-48. PMC 1853083. PMID 17394631.{{cite journal}}: Обслуговування CS1: Сторінки із непозначеним DOI з безкоштовним доступом (посилання)
  5. ↑ Andreadis TG, Hall DW (August 1979). Development, ultrastructure, and mode of transmission of Amblyospora sp. (Microspora) in the mosquito. The Journal of Protozoology. 26 (3): 444—52. PMID 536933.
  6. ↑ Andreadis TG, Hall DW (September 1979). Significance of transovarial infections of Amblyospora sp. (Microspora:Thelohaniidae) in relation to parasite maintenance in the mosquito Culex salinarius. Journal of Invertebrate Pathology. 34 (2): 152—7. doi:10.1016/0022-2011(79)90095-8. PMID 536610.
  7. ↑ Jahn GC, Hall DW, Zam SG (1986). A comparison of the life cycles of two Amblyospora (Microspora: Amblyosporidae) in the mosquitoes Culex salinarius and Culex tarsalis Coquillett. Journal of the Florida Anti-Mosquito Association. 57 (1): 24—27.
  8. ↑ Becnel JJ, Andreadis TG (May 1998). Amblyospora salinaria n. sp. (Microsporidia: amblyosporidae), parasite of Culex salinarius (Diptera: culicidae): its life cycle stages in an intermediate host. Journal of Invertebrate Pathology. 71 (3): 258—62. doi:10.1006/jipa.1998.4729. PMID 9538031.
  9. ↑ Jacob C. Koella, Lena Lorenz and Irka Bargielowski; Lorenz, L; Bargielowski, I (2009). Chapter 12 Microsporidians as Evolution-Proof Agents of Malaria Control?. Advances in Parasitology. Advances in Parasitology. 68: 315—327. doi:10.1016/S0065-308X(08)00612-X. ISBN 978-0-12-374787-7. PMID 19289199. Процитовано 10 грудня 2009. {{cite journal}}: Вказано більш, ніж один |author1= та |last= (довідка)
  10. ↑ Bargielowski I, Koella JC (2009). Baylis, Matthew (ред.). A Possible Mechanism for the Suppression of Plasmodium berghei Development in the Mosquito Anopheles gambiae by the Microsporidian Vavraia culicis. PLoS ONE. 4 (3): e4676. doi:10.1371/journal.pone.0004676. PMC 2651578. PMID 19277119.{{cite journal}}: Обслуговування CS1: Сторінки із непозначеним DOI з безкоштовним доступом (посилання)
  11. ↑ Heinz E, Williams TA, Nakjang S, Noël CJ, Swan DC, Goldberg AV, Harris SR, Weinmaier T, Markert S, Becher D, Bernhardt J, Dagan T, Hacker C, Lucocq JM, Schweder T, Rattei T, Hall N, Hirt RP, Embley TM (2012) The genome of the obligate intracellular parasite Trachipleistophora hominis: New insights into microsporidian genome dynamics and reductive evolution. PLoS Pathog. 2012 Oct;8(10):e1002979. doi: 10.1371/journal.ppat.1002979
  12. ↑ Keeling PJ, Slamovits CH (December 2004). Simplicity and Complexity of Microsporidian Genomes. Eukaryotic Cell. 3 (6): 1363—9. doi:10.1128/EC.3.6.1363-1369.2004. PMC 539024. PMID 15590811.
  13. ↑ Fischer WM, Palmer JD (September 2005). Evidence from small-subunit ribosomal RNA sequences for a fungal origin of Microsporidia. Molecular Phylogenetics and Evolution. 36 (3): 606—22. doi:10.1016/j.ympev.2005.03.031. PMID 15923129.
  14. ↑ Liu YJ, Hodson MC, Hall BD (2006). Loss of the flagellum happened only once in the fungal lineage: phylogenetic structure of Kingdom Fungi inferred from RNA polymerase II subunit genes. BMC Evolutionary Biology. 6: 74. doi:10.1186/1471-2148-6-74. PMC 1599754. PMID 17010206.{{cite journal}}: Обслуговування CS1: Сторінки із непозначеним DOI з безкоштовним доступом (посилання)
  15. ↑ Gill EE, Fast NM (June 2006). Assessing the microsporidia-fungi relationship: Combined phylogenetic analysis of eight genes. Gene. 375: 103—9. doi:10.1016/j.gene.2006.02.023. PMID 16626896.
  16. ↑ Lee SC, Corradi N, Byrnes EJ та ін. (November 2008). Microsporidia evolved from ancestral sexual fungi. Current Biology. 18 (21): 1675—9. doi:10.1016/j.cub.2008.09.030. PMC 2654606. PMID 18976912. {{cite journal}}: Явне використання «та ін.» у: |author= (довідка)
  17. ↑ Vossbrinck CR, Debrunner-Vossbrinck BA (May 2005). Molecular phylogeny of the Microsporidia: ecological, ultrastructural and taxonomic considerations. Folia Parasitologica. 52 (1–2): 131—42, discussion 130. PMID 16004372.
Проєкт Віківиди має дані за темою:
Вікісховище має мультимедійні дані за темою: Мікроспоридії

Шаблон:Eukaryota classification Шаблон:Fungi classification

Отримано з https://uk.wikipedia.org/w/index.php?title=Мікроспоридії&oldid=12326317