Mimivirus
Mimivirus | |
---|---|
Mimivirus with two satellite Sputnik virophages (arrows) [1] | |
Virus classification | |
(unranked): | Virus |
Realm: | Varidnaviria |
Kingdom: | Bamfordvirae |
Phylum: | Nucleocytoviricota |
Class: | Megaviricetes |
Order: | Imitervirales |
Family: | Mimiviridae |
Genus: | Mimivirus |
Species[citation needed] | |
|
Mimivirus is a genus of giant viruses, in the family Mimiviridae. Amoeba serve as their natural hosts.[2][3] This genus contains a single identified species named Acanthamoeba polyphaga mimivirus (APMV). It also refers to a group of phylogenetically related large viruses.[4]
In colloquial speech, APMV is more commonly referred to as just "mimivirus". Mimivirus, short for "mimicking microbe", is so called to reflect its large size and apparent
Mimivirus has a large and complex genome compared with most other viruses. Until 2013, when a larger virus Pandoravirus was described, it had the largest capsid diameter of all known viruses.[6]
History
APMV was discovered accidentally in 1992 within the
The same team that discovered the mimivirus later discovered a slightly larger virus, dubbed the mamavirus, and the Sputnik virophage that infects it.[9]
Classification
Mimivirus has been placed into a viral family by the International Committee on Taxonomy of Viruses as a member of the Mimiviridae,[10] and has been placed into Group I of the Baltimore classification system.[11]
Although not strictly a method of classification, mimivirus joins a group of large viruses known as
Structure
The mimivirus is the fourth-largest virus, after the
Its capsid appears hexagonal under an electron microscope, therefore the capsid symmetry is icosahedral.[12] It does not appear to possess an outer viral envelope, suggesting that the virus does not exit the host cell by exocytosis.[13] Mimivirus shares several morphological characteristics with all members of the NCLDV group of viruses. The condensed central core of the virion appears as a dark region under the electron microscope. The large genome of the virus resides within this area. An internal lipid layer surrounding the central core is present in all other NCLDV viruses, so this features may also be present in mimivirus.[12]
Several
Genus | Structure | Symmetry | Capsid | Genomic arrangement | Genomic segmentation |
---|---|---|---|---|---|
Mimivirus | Icosahedral | T = 972–1141 or T = 1200 (h = 19 ± 1, k = 19 ± 1) | Linear | Monopartite |
Genome
The mimivirus genome is a linear, double-stranded molecule of DNA with 1,181,404 base pairs in length.[14] This makes it one of the largest viral genomes known, outstripping the next-largest virus genome of the Cafeteria roenbergensis virus by about 450,000 base pairs. In addition, it is larger than at least 30 cellular clades.[15]
In addition to the large size of the genome, mimivirus possesses an estimated 979 protein-coding
Replication
The stages of mimivirus replication are not well known, but as a minimum it is known that mimivirus attaches to a chemical receptor on the surface of an amoeba cell and is taken into the cell. Once inside, an eclipse phase begins, in which the virus disappears and all appears normal within the cell. After about 4 hours small accumulations can be seen in areas of the cell. 8 hours after infection many mimivirus virions are clearly visible within the cell. The cell cytoplasm continues to fill with newly synthesised virions, and about 24 hours after initial infection the cell likely bursts open to release the new mimivirus virions.[13]
Little is known[
Genus | Host details | Tissue tropism | Entry details | Release details | Replication site | Assembly site | Transmission |
---|---|---|---|---|---|---|---|
Mimivirus | Zooplankton | None | Unknown | Unknown | Cytoplasm | Nucleus | Passive diffusion |
Pathogenicity
Mimivirus may be a causative agent of some forms of
Implications for defining "life"
Mimivirus shows many characteristics which place it at the boundary between living and non-living. It is as large as several bacterial species, such as
Because its lineage is very old and could have emerged prior to cellular organisms,
Nevertheless, mimivirus does not exhibit the following characteristics, all of which are part of many conventional definitions of life:[citation needed]
- homeostasis
- energy metabolism
- response to stimuli
- autopoiesis
- growth via cellular division (instead of replication via self-assembly of individual components)
See also
- Cafeteria roenbergensis virus a giant marine virus
- Marseillevirus—another giant virus
- Megavirus—another giant virus
- Mycoplasma genitalium—one of the smallest bacteria
- Nanoarchaeum equitans—smallest known independent cell
- Nanobacterium
- Nanobe
- Non-cellular life
- Pandoravirus
- Pithovirus—the largest known virus
- Parvovirus—smallest known viruses
- Pelagibacter ubique—possesses one of the smallest bacterial genomes
- Virophage—a virus that requires the host cell to be co-infected with a giant virus
- The Giant Virus Finder is a software tool that identifies giant viruses in environmental Metagenomes.
References
- doi:10.1371/journal.ppat.1007592. Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.
- ^ "Viral Zone". ExPASy. Retrieved 15 June 2015.
- ^ ICTV. "Virus Taxonomy: 2014 Release". Retrieved 15 June 2015.
- PMID 16105173.
- ^ Wessner, D. R. (2010). "Discovery of the Giant Mimivirus". Nature Education. 3 (9): 61. Retrieved 7 January 2012.
- ^ "World's biggest virus found in sea off Chile". London: Telegraph UK. 11 October 2011. Archived from the original on 11 October 2011. Retrieved 11 November 2011.
- S2CID 5382736.
- ^ S2CID 39606235.
- PMID 18685665.
- ^ Claverie J-M (2010). Mahy W.J. and Van Regenmortel M. H. V. (ed.). Desk Encyclopedia of General Virology (1 ed.). Oxford: Academic Press. p. 189.
- ISBN 9781405136457.
- ^ PMID 19402750.
- ^ PMID 16181700.
- ^ "Acanthamoeba polyphaga mimivirus, complete genome". NCBI.
- S2CID 8791457.
- ISBN 0-697-01372-3.[page needed]
- PMID 15757563. Archived from the originalon 24 April 2009. Retrieved 10 September 2017.
- PMID 2772465.
- PMID 23709652.
- PMID 18551172.
- ^ a b c Garry Hamilton (23 January 2016). "How giant viruses could rewrite the story of life on Earth". New Scientist.
- ^ a b Siebert, Charles (15 March 2006). "Unintelligent Design". Discover Magazine.
- ^ PMID 16505372.
Further reading
- Raoult, D.; et al. (2004). "The 1.2-megabase genome sequence of Mimivirus". S2CID 84298461.
- Ghedin, Elodie; Claverie, J. M. (2005). "Mimivirus relatives in the Sargasso sea". Virology Journal. 2: 62. PMID 16105173.
- Peplow, Mark, 2004, "Giant virus qualifies as 'living organism'," News@Nature.
- "Mimivirus: discovery of a giant virus". Press Release. Paris: Centre national de la recherche scientifique. 28 March 2003. Archived from the original on 3 June 2004.
- New Scientist, Issue 2544, 25 March 2006.
- Highfield, Roger (15 October 2004). "The Bradford bug that may be a new life form". The Daily Telegraph. London. Archived from the original on 13 March 2007.
- "Scientists investigate structural details of the largest known virus". Science News. 28 April 2009. Archived from the original on 7 January 2012. Retrieved 29 April 2009.
- Keim, Brandon (5 May 2009). "Viral Missing Link Caught on Film". Wired. Wired Science.
External links
- Viralzone: Mimiviridae
- International Committee on Taxonomy of Viruses (ICTV) picture gallery—images of mimivirus.
- Van Etten, James L. (2011). "Giant Viruses: The recent discovery of really, really big viruses is changing views about the nature of viruses and the history of life". doi:10.1511/2011.91.304. Archived from the originalon 10 June 2016. Retrieved 8 July 2011.
- The webpage for Mimivirus
- Radiolab.org Shrink on the discovery of Mimivirus Thursday, July 30, 2015 - 08:54 PM.