Giant virus explained

A giant virus, sometimes referred to as a girus, is a very large virus, some of which are larger than typical bacteria.[1] [2] All known giant viruses belong to the phylum Nucleocytoviricota.[3]

Description

While the exact criteria as defined in the scientific literature vary, giant viruses are generally described as viruses having large, pseudo-icosahedral capsids (200 to 400 nanometers in diameter)[4] that may be surrounded by a thick (approximately 100 nm) layer of filamentous protein fibers. The viruses have large, double-stranded DNA genomes (300 to >1000 kilobasepairs) that encode a large contingent of genes (of the order of 1000 genes).[3] The best characterized giant viruses are the phylogenetically related mimivirus and megavirus, which belong to the family Mimiviridae (aka Megaviridae), and are distinguished by their large capsid diameters.[3] [5] Giant viruses from the deep ocean, terrestrial sources, and human patients contain genes encoding cytochrome P450 (CYP; P450) enzymes. The origin of these P450 genes in giant viruses remains unknown but may have been acquired from an ancient host.[6]

The genomes of many giant viruses encode many unusual genes that are not found in other viruses, including genes involved in glycolysis and the TCA cycle,[7] fermentation,[8] and the cytoskeleton.[9] [10] [11]

History

The first giant viruses to be described were chloroviruses of the family Phycodnaviridae. These were discovered in 1981 by Russel H. Meints, James L. Van Etten, Daniel Kuczmarski, Kit Lee, and Barbara Ang. The first chlorovirus was initially called HVCV (Hydra viridis Chlorella virus) since it was first found to infect Chlorella-like algae.[12] [13]

Other giant viruses that infected marine flagellates were described later. The first mimivirus (BV-PW1) was described in 1995,[14] but was not recognized as such until its sequenced genome was released as Cafeteria roenbergensis virus (CroV) in 2010.[15] Subsequently, the Giant Virus Acanthamoeba polyphaga Mimivirus was characterized[16] (which had been mistaken as a bacterium in 1993),[17] and then sequenced.[18] The term "girus" was coined to refer to the group in 2006.[19]

Genetics and evolution

The genomes of giant viruses are the largest known for viruses, and contain genes that encode for important elements of translation machinery, a characteristic that had previously been believed to be indicative of cellular organisms. These genes include multiple genes encoding a number of aminoacyl tRNA synthetases, enzymes that catalyze the esterification of specific amino acids or their precursors to their corresponding cognate tRNAs to form an aminoacyl tRNA that is then used during translation.[5] The presence of four aminoacyl tRNA synthetase encoding genes in mimivirus and mamavirus genomes, both species within the Mimiviridae family, as well as the discovery of seven aminoacyl tRNA synthetase genes in the megavirus genome (including those in Mimiviridae) provide evidence that these large DNA viruses may have evolved from a shared cellular genome ancestor by means of genome reduction.[5]

The discovery and subsequent characterization of giant viruses has triggered debate on their evolutionary origins. The two main hypotheses are that they evolved from small viruses by picking up DNA from host organisms; or that they evolved from very complicated organisms via genome reduction, losing various functions including self-reproduction.[20] The possible complicated ancestral organism is also a topic of debate: by one proposal, it might represent a fourth domain of life,[5] but this has been largely discounted.[21] [22] [23]

Comparison of largest known giant viruses

Largest giant viruses with complete sequenced genomes !Giant virus name!!Genome Length!!Genes!!Capsid diameter (nm)!!Hair cover!!Genbank #
Bodo saltans virus[24] 1,385,8691227 proteins (predicted)~300yes (~40 nm)MF782455
Megavirus chilensis[25] 1,259,1971120 proteins (predicted)440yes (75 nm)JN258408
Mamavirus[26] 1,191,6931023 proteins (predicted)500yes (120 nm)JF801956
Mimivirus[27] [28] 1,181,549979 proteins 39 non-coding500yes (120 nm)NC_014649
M4[29] (Mimivirus "bald" variant)981,813756 proteins (predicted)390NoJN036606
Tupanvirus[30] 1,500,000 1276–1425 proteins ≥450+550[31] KY523104
MF405918[32]
Cafeteria roenbergensis virus[33] 617,453 (730 kb)544 proteins (predicted)300NoNC_014637

The whole list is in the Giant Virus Toplist created by the Giant Virus Finder software.[34] As of June 11, 2018, there were 183 listed.[35]

Specific common features among giant viruses!Giant virus name!!Aminoacyl-tRNA synthetase!!Octocoral-like 1MutS!!2Stargate[36] !!Known virophage[37] !!Cytoplasmic virion factory!!Host
Megavirus chilensis7 (Tyr, Arg, Met, Cys, Trp, Asn, Ile)yesyesnoyesAcanthamoeba (Unikonta, Amoebozoa)
Mamavirus4 (Tyr, Arg, Met, Cys)yesyesyesyesAcanthamoeba (Unikonta, Amoebozoa)
Mimivirus4 (Tyr, Arg, Met, Cys)yesyesyesyesAcanthamoeba (Unikonta, Amoebozoa)
M4 (Mimivirus "bald" variant)3 (Met, Cys, Arg)yesyesResistantyesAcanthamoeba (Unikonta, Amoebozoa)
Cafeteria roenbergensis virus1 (Ile)yesnoyesyesPhagotrophic protozoan (Heterokonta, Stramenopiles)
1Mutator S (MutS) and its homologs are a family of DNA mismatch repair proteins involved in the mismatch repair system that acts to correct point mutations or small insertion/deletion loops produced during DNA replication, increasing the fidelity of replication.2A stargate is a five-pronged star structure present on the viral capsid forming the portal through which the internal core of the particle is delivered to the host's cytoplasm.

See also

Notes and References

  1. Reynolds . Kelly A. . vanc . Mysterious Microbe in Water Challenges the Very Definition of a Virus . Water Conditioning & Purification . 2010 . dead . https://web.archive.org/web/20140319025858/http://www.wcponline.com/pdf/June_OnTap.pdf . 2014-03-19 .
  2. Ogata H, Toyoda K, Tomaru Y, Nakayama N, Shirai Y, Claverie JM, Nagasaki K . Remarkable sequence similarity between the dinoflagellate-infecting marine girus and the terrestrial pathogen African swine fever virus . Virology Journal . 6 . 178 . 178 . October 2009 . 19860921 . 2777158 . 10.1186/1743-422X-6-178 . free .
  3. American Scientist . Giant Viruses . James L. . Van Etten . vanc . July–August 2011 . 99 . 4 . 304–311 . 10.1511/2011.91.304 . https://web.archive.org/web/20110621223431/http://www.americanscientist.org/issues/feature/2011/4/giant-viruses. 2011-06-21.
  4. Xiao C, Fischer MG, Bolotaulo DM, Ulloa-Rondeau N, Avila GA, Suttle CA . Cryo-EM reconstruction of the Cafeteria roenbergensis virus capsid suggests novel assembly pathway for giant viruses . Scientific Reports . 7 . 5484 . 14 July 2017 . 5484 . 28710447 . 5511168 . 10.1038/s41598-017-05824-w . 2017NatSR...7.5484X .
  5. Legendre M, Arslan D, Abergel C, Claverie JM . Genomics of Megavirus and the elusive fourth domain of Life . Communicative & Integrative Biology . 5 . 1 . 102–6 . January 2012 . 22482024 . 3291303 . 10.4161/cib.18624 .
  6. 6. Lamb DC, Follmer AH, Goldstone JV, Nelson DR, Warrilow AG, Price CL, True MY, Kelly SL, Poulos TL, Stegeman JJ. June 2019. On the occurrence of cytochrome P450 in viruses. Proceedings of the National Academy of Sciences of the United States of America. 116. 25. 12343–12352. 10.1073/pnas.1901080116. 6589655. 31167942. 2019PNAS..11612343L . free.
  7. Moniruzzaman M, Martinez-Gutierrez CA, Weinheimer AR, Aylward FO . Dynamic genome evolution and complex virocell metabolism of globally-distributed giant viruses . Nature Communications . 11 . 1710 . 2020 . 1710 . 10.1038/s41467-020-15507-2 . 32249765 . 7136201 . 2020NatCo..11.1710M .
  8. Schvarcz CR, Steward GF . A giant virus infecting green algae encodes key fermentation genes . Virology . 2018 . 518 . 423–433 . 10.1016/j.virol.2018.03.010 . 29649682 . free .
  9. Da Cunha V, Gaia M, Ogata H, Jaillon O, Delmont TO, Patrick Forterre P . Giant viruses encode novel types of actins possibly related to the origin of eukaryotic actin: the viractins . bioRxiv . 2020 . 10.1101/2020.06.16.150565 . 219947620 .
  10. Ha AD, Moniruzzaman M, Aylward FO . High Transcriptional Activity and Diverse Functional Repertoires of Hundreds of Giant Viruses in a Coastal Marine System . mSystems . 6 . 4 . 2021 . e0029321 . 10.1128/mSystems.00293-21 . 34254826. 8407384 .
  11. Kijima S, Delmont TO, Miyazaki U, Gaia M, Endo H, Ogata H . Discovery of Viral Myosin Genes With Complex Evolutionary History Within Plankton . Frontiers in Microbiology . 7 June 2021 . 12 . 683294 . 10.3389/fmicb.2021.683294. 34163457 . 8215601 . free .
  12. Meints. Russel H.. Van Etten. James L.. Kuczmarski. Daniel. Lee. Kit. Ang. Barbara. Viral infection of the symbiotic chlorella-like alga present in Hydra viridis. Virology. September 1981. 113. 2. 698–703. 10.1016/0042-6822(81)90198-7. 18635088.
  13. Hoshina. Ryo. Shimizu. Mayumi. Makino. Yoichi. Haruyama. Yoshihiro. Ueda. Shin-ichiro. Kato. Yutaka. Kasahara. Masahiro. Ono. Bun-ichiro. Imamura. Nobutaka. Isolation and characterization of a virus (CvV-BW1) that infects symbiotic algae of Paramecium bursaria in Lake Biwa, Japan. Virology Journal. 13 September 2010. 7. 222. 10.1186/1743-422X-7-222. 20831832. 2949830. en. 1743-422X . free .
  14. Garza. D. Randy. Suttle. Curtis A.. 1995-12-31. Large double-stranded DNA viruses which cause the lysis of a marine heterotrophic nanoflagellate (Bodo sp) occur in natural marine viral communities . Aquatic Microbial Ecology . 9 . 3 . 133–144 . 10.3354/ame009203 . free.
  15. 19508–13 . 10.1073/pnas.1007615107 . 2984142 . Giant virus with a remarkable complement of genes infects marine zooplankton . 2010 . Fischer . M. G. . Allen . M. J. . Wilson . W. H. . Suttle . C. A. . Proceedings of the National Academy of Sciences . 107 . 45 . 20974979. 2010PNAS..10719508F . free .
  16. La Scola B, Audic S, Robert C, Jungang L, de Lamballerie X, Drancourt M, Birtles R, Claverie JM, Raoult D . A giant virus in amoebae . Science . 299 . 5615 . 2033. 2003. 12663918. 10.1126/science.1081867. 39606235.
  17. Web site: 2017-02-06. Giant Viruses. 2021-09-02. American Scientist. en.
  18. Raoult D, Audic S, Robert C, Abergel C, Renesto P, Ogata H, La Scola B, Suzan M, Claverie JM . The 1.2-megabase genome sequence of Mimivirus . Science . 306 . 5700 . 1344–50 . November 2004 . 15486256 . 10.1126/science.1101485 . 2004Sci...306.1344R . 84298461 .
  19. Claverie . Jean-Michel . Ogata . Hiroyuki . Audic . Stéphane . Abergel . Chantal . Suhre . Karsten . Fournier . Pierre-Edouard . Mimivirus and the emerging concept of "giant" virus . Virus Research . April 2006 . 117 . 1 . 133–144 . 10.1016/j.virusres.2006.01.008. 16469402 . q-bio/0506007 . 8791457 .
  20. News: Rae Ellen . Bichell . vanc . In Giant Virus Genes, Hints About Their Mysterious Origin . All Things Considered .
  21. Schulz F, Yutin N, Ivanova NN, Ortega DR, Lee TK, Vierheilig J, Daims H, Horn M, Wagner M, Jensen GJ, Kyrpides NC, Koonin EV, Woyke T . Giant viruses with an expanded complement of translation system components . Science . 356 . 6333 . 82–85 . April 2017 . 28386012 . 10.1126/science.aal4657 . 2017Sci...356...82S . 206655792 . free .
  22. Bäckström D, Yutin N, Jørgensen SL, Dharamshi J, Homa F, Zaremba-Niedwiedzka K, Spang A, Wolf YI, Koonin EV, Ettema TJ . Virus Genomes from Deep Sea Sediments Expand the Ocean Megavirome and Support Independent Origins of Viral Gigantism . mBio . 10 . 2 . e02497-02418 . March 2019 . 10.1128/mBio.02497-18 . 30837339 . 6401483 .
  23. Yutin N, Wolf Y, Koonin EV . Origin of giant viruses from smaller DNA viruses not from a fourth domain of cellular life . Virology . 466–467 . 2014 . 38–52 . 2014 . 10.1016/j.virol.2014.06.032 . 25042053 . 4325995 .
  24. Deeg CM, Chow CT, Suttle CA . The kinetoplastid-infecting Bodo saltans virus (BsV), a window into the most abundant giant viruses in the sea . eLife . 7 . e33014 . March 2018 . 29582753 . 5871332 . 10.7554/eLife.33014 . free .
  25. Arslan D, Legendre M, Seltzer V, Abergel C, Claverie JM . Distant Mimivirus relative with a larger genome highlights the fundamental features of Megaviridae . Proceedings of the National Academy of Sciences of the United States of America . 108 . 42 . 17486–91 . October 2011 . 21987820 . 3198346 . 10.1073/pnas.1110889108 . 2011PNAS..10817486A . free .
  26. Colson P, Yutin N, Shabalina SA, Robert C, Fournous G, La Scola B, Raoult D, Koonin EV . Viruses with more than 1,000 genes: Mamavirus, a new Acanthamoeba polyphaga mimivirus strain, and reannotation of Mimivirus genes . Genome Biology and Evolution . 3 . 737–42 . 2011 . 21705471 . 3163472 . 10.1093/gbe/evr048 .
  27. Raoult D, Audic S, Robert C, Abergel C, Renesto P, Ogata H, La Scola B, Suzan M, Claverie JM . The 1.2-megabase genome sequence of Mimivirus . Science . 306 . 5700 . 1344–50 . November 2004 . 15486256 . 10.1126/science.1101485 . 2004Sci...306.1344R . 84298461 .
  28. Legendre M, Santini S, Rico A, Abergel C, Claverie JM . Breaking the 1000-gene barrier for Mimivirus using ultra-deep genome and transcriptome sequencing . Virology Journal . 8 . 1 . 99 . March 2011 . 21375749 . 3058096 . 10.1186/1743-422X-8-99 . free .
  29. 10296–301 . 10.1073/pnas.1101118108 . 3121840 . Mimivirus shows dramatic genome reduction after intraamoebal culture . 2011 . Boyer . M. . Azza . S. . Barrassi . L. . Klose . T. . Campocasso . A. . Pagnier . I. . Fournous . G. . Borg . A. . Robert . C. . Zhang . X. . Desnues . C. . Henrissat . B. . Rossmann . M. G. . La Scola . B. . Raoult . D. . Proceedings of the National Academy of Sciences . 108 . 25 . 21646533. 2011PNAS..10810296B . 8 . free .
  30. Abrahão J, Silva L, Silva LS, Khalil JY, Rodrigues R, Arantes T, Assis F, Boratto P, Andrade M, Kroon EG, Ribeiro B, Bergier I, Seligmann H, Ghigo E, Colson P, Levasseur A, Kroemer G, Raoult D, La Scola B . Tailed giant Tupanvirus possesses the most complete translational apparatus of the known virosphere . Nature Communications . 9 . 1 . 749 . February 2018 . 29487281 . 5829246 . 10.1038/s41467-018-03168-1 . 2018NatCo...9..749A .
  31. head and tail, respectively
  32. soda lake and deep ocean species of Tupanvirues, respectively
  33. 19508–13 . 10.1073/pnas.1007615107 . 2984142 . Giant virus with a remarkable complement of genes infects marine zooplankton . 2010 . Fischer . M. G. . Allen . M. J. . Wilson . W. H. . Suttle . C. A. . Proceedings of the National Academy of Sciences . 107 . 45 . 20974979. 2010PNAS..10719508F . free .
  34. Web site: Giant Virus Toplist . PIT Bioinformatics Group, Department of Computer Science . Eötvös University . 2015-03-26 .
  35. Web site: Giant Virus Toplist . 26 March 2015 . PIT Bioinformatics Group . 10 May 2023.
  36. Zauberman N, Mutsafi Y, Halevy DB, Shimoni E, Klein E, Xiao C, Sun S, Minsky A . Distinct DNA exit and packaging portals in the virus Acanthamoeba polyphaga mimivirus . PLOS Biology . 6 . 5 . e114 . May 2008 . 18479185 . 2430901 . 10.1371/journal.pbio.0060114 . Sugden . Bill . free .
  37. Fischer MG, Suttle CA . A virophage at the origin of large DNA transposons . Science . 332 . 6026 . 231–4 . April 2011 . 21385722 . 10.1126/science.1199412 . 2011Sci...332..231F . 206530677 .

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