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Pandoravirus

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Pandoravirus
Pandoravirus virion
Virus classification Edit this classification
(unranked): Virus
Realm: Varidnaviria
Kingdom: Bamfordvirae
Phylum: Nucleocytoviricota
Class: Megaviricetes
Order: Algavirales (?)
Family: Pandoraviridae
Genus: Pandoravirus
Species

Pandoravirus is a proposed genus of giant virus, first discovered in 2013.[5] It is the third largest in physical size of any known viral genus, behind Pithovirus and Megaklothovirus.[6] Pandoraviruses have double stranded DNA genomes, with the largest genome size (2.5 million base pairs) of any known viral genus.[7]

Discovery

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The discovery of Pandoraviruses by a team of French scientists, led by husband and wife Jean-Michel Claverie and Chantal Abergel, was announced in a report in the journal Science in July 2013.[5] Other scientists had previously observed the pandoravirus particles, but owing to their enormous size they were not expected to be viruses.[5] Patrick Scheid, a parasitologist from the Central Institute of the Bundeswehr Medical Service in Koblenz, Germany, found one in 2008, in an amoeba living in the contact lens of a woman with keratitis. Its development within the amoebal host was documented extensively. Unlike in other cases with such giant viruses, the large particles within Acanthamoeba were not mistaken for bacteria. The authors initially termed them "endocytobionts".[8]

Mimivirus, a nucleocytoplasmic large DNA virus with a genome size of about 1.1 megabases, was described in 1992 but not recognized as a virus until 2003.[9] Megavirus, discovered in seawater off the coast of Chile in 2011, has a genome size of approximately 1.2 megabases.[10]

The prior discovery of these viruses prompted a search for other types of large amoeba-infecting viruses, which led to the finding of two species; Pandoravirus salinus, found in seawater taken from the coast of Chile, with a genome size of ~2.5 megabases, and Pandoravirus dulcis, found in a shallow freshwater pond in La Trobe University, Melbourne, Australia, with a 1.9 megabase genome.[5][11]

Description

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Pandoraviruses are oval in shape and are about 1 micrometer (1000 nanometers) in length. Other viruses range from 25 to 100 nanometers. In addition to being large physically, Pandoraviruses have a large genome made up of 2,500 genes, compared to only 10 genes on average in other viruses. For example, the Influenza A virus contains 7 genes and HIV contains only 9 genes. Gene content varies among species of Pandoravirus, with Pandoravirus salinus containing 2,500 genes and Pandoravirus dulcis containing about 1,500 genes. Pandoraviruses were originally mistaken for bacteria; however, they lack some of the characteristics of bacteria, such as the ability to make their own proteins. The dissimilarity of the remaining genes to any cellular genes led researchers to speculate that this virus represents a previously unknown branch of the tree of life. However, other experts have called this proposal premature because there is very little evidence supporting the idea.[12]

Replication

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Pandoraviruses have double stranded DNA. Like most giant viruses, Pandoraviruses have a viral replication cycle. They lack the ability to make their own proteins, rely on the host cells for ATP (energy) and replication, and also do not contain ribosomes or produce energy to divide. Under the microscope, scientists observed the virus enter the amoeba through fusion with membrane vacuoles, and integrate their DNA into the host cells. The host cell replicates the viral particles and eventually splits open, releasing the viral particles. The process of replication lasts 10–15 hours.[13] Viral replication and assembly happens simultaneously. In other words, viral DNA is replicated within the cytoplasm of the host cell and assembled into new viral particles followed by lysis of the host cell.[14]

Prevalence in the environment

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Pandoraviruses do not seem to be harmful to humans. They are mostly found in marine environments, infecting amoebae. One reason for their only relatively recent discovery is because they exist in environments that are not well studied. Pandoraviruses, like other marine viruses, infect plankton, which are organisms that live in the water column and form the basis of the food chain for other marine species. More study and research needs to be done in order to confirm the prevalence of Pandoraviruses in different environments. Currently, not much is known about their role in marine ecosystems. however, viruses are not mere pathogens for their host, but are also key players in aquatic ecosystems and the biosphere. Almost all genomes of cellular organisms contain viral sequences, elements of which are also essential in gene regulation. Viral infection and lysis can influence community structure, as well as the transfer of matter and energy in aquatic ecosystems. They can also dramatically alter host physiology through viral gene expression and drive evolutionary innovation through virus-mediated horizontal gene transfer.[15]

Phylogenetic affinities

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Approximately 93% of Pandoravirus genes are not known from any other microbes,[16] suggesting that they belong to an as of yet undescribed "fourth domain" aside from Bacteria, Archaea, and Eukaryotes.[16] Viruses are not widely considered to belong within these three domains, although they have been proposed as one in the past by some biologists.[17]

Comparison with other giant viruses

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Other giant viruses such as the Mimivirus, Pithovirus, and Megavirus have much smaller genomes. For example, Mimivirus, considered one of the largest giant viruses, has a genome size of 1.1 million base pairs compared to 2.5 million base pairs for Pandoraviruses. Another feature that is different in Pandoraviruses compared to other giant viruses is the replication cycle. Pandoraviruses infect amoebas, which are single celled eukaryotes.[18] Pandoravirus enters amoebas through phagocytic vacuoles, then fuses with the membrane vacuole of the amoeba. This leads to viral particles to be released into the cytoplasm of the amoeba.[19]

See also

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References

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  1. ^ "Pandoravirus dulcis". NCBI Taxonomy Browser. 1349409. Archived from the original on 31 August 2017. Retrieved 7 September 2017.
  2. ^ "Pandoravirus salinus". NCBI Taxonomy Browser. 1349410. Archived from the original on 20 June 2017. Retrieved 7 September 2017.
  3. ^ "Pandoravirus tropicalis". NCBI Taxonomy Browser. Archived from the original on 14 December 2022. Retrieved 14 December 2022.
  4. ^ "'Zombie' virus revived after 50,000 years trapped in Siberian permafrost – National | Globalnews.ca". Global News. Archived from the original on 26 November 2022. Retrieved 26 November 2022.
  5. ^ a b c d Philippe N, Legendre M, Doutre G, Couté Y, Poirot O, Lescot M, Arslan D, Seltzer V, Bertaux L, Bruley C, Garin J, Claverie JM, Abergel C (July 2013). "Pandoraviruses: Amoeba Viruses with Genomes Up to 2.5 Mb Reaching That of Parasitic Eukaryotes" (PDF). Science. 341 (6143): 281–286. Bibcode:2013Sci...341..281P. doi:10.1126/science.1239181. PMID 23869018. S2CID 16877147. Archived (PDF) from the original on 2 April 2020. Retrieved 5 March 2020.
  6. ^ Sirucek S (3 March 2014). "Ancient "Giant Virus" Revived From Siberian Permafrost". National Geographic. Archived from the original on 4 March 2014.
  7. ^ Yong E (3 March 2014). "Giant virus resurrected from 30,000-year-old ice : Nature News & Comment". Nature. doi:10.1038/nature.2014.14801. S2CID 87146458.
  8. ^ Scheid P, Hauröder B, Michel R (2010). "Investigations of an extraordinary endocytobiont in Acanthamoeba sp.: development and replication". Parasitol Res. 106 (6): 1371–7. doi:10.1007/s00436-010-1811-4. PMID 20393749. S2CID 20548450.
  9. ^ La Scola B, Audic S, Robert C, Jungang L, de Lamballerie X, Drancourt M, Birtles R, Claverie JM, Raoult D (2003). "A giant virus in amoebae". Science. 299 (5615): 2033. doi:10.1126/science.1081867. PMID 12663918. S2CID 39606235.
  10. ^ Arslan D, Legendre M, Seltzer V, Abergel C, Claverie JM (2011). "Distant Mimivirus relative with a larger genome highlights the fundamental features of Megaviridae". Proceedings of the National Academy of Sciences. 108 (42): 17486–91. Bibcode:2011PNAS..10817486A. doi:10.1073/pnas.1110889108. PMC 3198346. PMID 21987820.
  11. ^ Smith B (26 July 2013). "Pandoravirus discovered in La Trobe uni pond". The Age. Archived from the original on 20 August 2013. Retrieved 18 August 2013.
  12. ^ "Pandoraviruses Are Not Alive". www.virology.ws. 3 December 2020. Archived from the original on 12 September 2021. Retrieved 19 September 2021.
  13. ^ "Pandoravirus, bigger and unlike anything seen before". www.virology.ws. August 2013. Archived from the original on 18 November 2017. Retrieved 25 November 2017.
  14. ^ Pereira Andrade AC, Victor de Miranda Boratto P, Rodrigues RA, Bastos TM, Azevedo BL, Dornas FP, Oliveira DB, Drumond BP, Kroon EG, Abrahão JS (March 2019). Sandri-Goldin RM (ed.). "New Isolates of Pandoraviruses: Contribution to the Study of Replication Cycle Steps". Journal of Virology. 93 (5). doi:10.1128/JVI.01942-18. ISSN 0022-538X. PMC 6384056. PMID 30541841.
  15. ^ Zhang QY, Ke F, Gui L, Zhao Z (November 2022). "Recent insights into aquatic viruses: Emerging and reemerging pathogens, molecular features, biological effects, and novel investigative approaches". Water Biology and Security. 1 (4): 100062. Bibcode:2022WBSec...100062Z. doi:10.1016/j.watbs.2022.100062. ISSN 2772-7351.
  16. ^ a b Dell'Amore C (19 July 2013). "Biggest Virus Yet Found, May Be Fourth Domain of Life?". National Geographic. Archived from the original on 21 July 2013. Retrieved 20 March 2018.
  17. ^ Berezow AB (16 November 2014). "Simmer Down: Viruses Not 'Fourth Domain' of Life | RealClearScience". realclearscience. Archived from the original on 20 March 2018. Retrieved 20 March 2018.
  18. ^ "What Is an Amoeba?". Live Science. Archived from the original on 12 October 2017. Retrieved 10 November 2017.
  19. ^ "Pandoravirus, bigger and unlike anything seen before". www.virology.ws. August 2013. Archived from the original on 18 November 2017. Retrieved 10 November 2017.
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