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Giant virus

A giant virus is a very large virus. They are sometimes called a girus. Some of them are larger than typical bacteria.[1][2] All known giant viruses belong to the phylum Nucleocytoviricota.[3]

Megaviricetes
Electron microscopic image of a mimivirus - journal.ppat.1000087.g007 crop.png
Mimivirus
Virus classification e
Unrecognized taxon (fix): Megaviricetes

The genomes of many giant viruses code for unusual genes which are not found in other viruses. These include genes involved in glycolysis and the TCA cycle,[4] fermentation,[5] and the cytoskeleton.[6][7][8]

The first giant viruses to be described were discovered in 1981.[9]

Note, in the illustration from an electron microscope, the virus is surrounded by a thick (~100 nm) layer of filamentous protein fibres.

Origin

There are two main hypotheses. Either they evolved from small viruses by picking up DNA from host organisms; or they evolved from very complicated organisms by genome reduction.[10]

Giant Virus Media

  • Cryo-EM images of the giant viruses CroV and APMV. (A) Cryo-electron micrograph of four CroV particles. (B) Single CroV particle with concave core depression (white arrow). (C) Single APMV particle. Scale bars in (A–C) represent 2,000 Å.

  • Phylogeny of Nucleocytoviricota

References

  1. ↑ Reynolds KA (2010). "Mysterious microbe in water challenges the very definition of a virus" (PDF). Water Conditioning & Purification. Archived from the original (PDF) on 2014-03-19.
  2. ↑ Ogata H, Toyoda K, Tomaru Y, Nakayama N, Shirai Y, Claverie JM, Nagasaki K (October 2009). "Remarkable sequence similarity between the dinoflagellate-infecting marine girus and the terrestrial pathogen African swine fever virus". Virology Journal. 6 (178): 178. doi:10.1186/1743-422X-6-178. PMC 2777158. PMID 19860921.
  3. ↑ Van Etten JL (July–August 2011). "Giant Viruses". American Scientist. 99 (4): 304–311. doi:10.1511/2011.91.304. Archived from the original on 2011-06-11.
  4. ↑ Moniruzzaman M, Martinez-Gutierrez CA, Weinheimer AR, Aylward FO (2020). "Dynamic genome evolution and complex virocell metabolism of globally-distributed giant viruses". Nature Communications. 11 (1710): 1710. Bibcode:2020NatCo..11.1710M. doi:10.1038/s41467-020-15507-2. PMC 7136201. PMID 32249765.
  5. ↑ Schvarcz CR, Steward GF (2018). "A giant virus infecting green algae encodes key fermentation genes". Virology. 518: 423–433. doi:10.1016/j.virol.2018.03.010. PMID 29649682.
  6. ↑ Da Cunha V, Gaia M, Ogata H, Jaillon O, Delmont TO, Patrick Forterre P (2020). "Giant viruses encode novel types of actins possibly related to the origin of eukaryotic actin: the viractins". bioRxiv. doi:10.1101/2020.06.16.150565. S2CID 219947620.
  7. ↑ Ha AD, Moniruzzaman M, Aylward FO (2021). "High Transcriptional Activity and Diverse Functional Repertoires of Hundreds of Giant Viruses in a Coastal Marine System". mSystems. 6 (4): e0029321. doi:10.1128/mSystems.00293-21. PMC 8407384. PMID 34254826.
  8. ↑ Kijima S, Delmont TO, Miyazaki U, Gaia M, Endo H, Ogata H (7 June 2021). "Discovery of Viral Myosin Genes With Complex Evolutionary History Within Plankton". Frontiers in Microbiology. 12: 683294. doi:10.3389/fmicb.2021.683294. PMC 8215601. PMID 34163457.
  9. ↑ Meints, Russel H.; Van Etten, James L.; Kuczmarski, Daniel; Lee, Kit; Ang, Barbara (September 1981). "Viral infection of the symbiotic chlorella-like alga present in Hydra viridis". Virology. 113 (2): 698–703. doi:10.1016/0042-6822(81)90198-7. PMID 18635088.
  10. ↑ Bichell, Rae Ellen. "In giant virus genes, hints about their mysterious origin". All Things Considered. https://www.npr.org/sections/health-shots/2017/04/06/522478901/in-giant-virus-genes-hints-about-their-mysterious-origin. 


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