Mummy virus

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"Mamavirus"
Systematics
Classification : Viruses
Area : Varidnaviria
Empire : Bamfordvirae
Phylum : Nucleocytoviricota
Class : Megaviricetes
Order : Impersonal
Family : Mimiviridae
Subfamily : "Mimivirinae" / "Megavirinae" / "Megamimivirinae"
Genre : Mimivirus
without rank: "Mimivirus Line A "
Type : "Acanthamoeba castellanii mamavirus"
Taxonomic characteristics
Genome : dsDNA linear, unsegmented
Baltimore : Group 1
Symmetry : icosahedral
Cover : available
Scientific name
"Acanthamoeba castellanii mamavirus"
Short name
ACMV
Left
NCBI  Taxonomy: 554168

" Acanthamoeba castellanii mama virus " ( ACMV even " Acanthamoeba castellanii Mimivirus " Amav or ACMaV shortly Mama virus is a species of large and complex dsDNA viruses from the family of mimiviridae . The virus is exceptionally large, even larger than many bacteria. " Mamavirus “belongs like the other Mimiviridae to the Phylum Nucleocytoviricota (outdated Nucleocytoplasmic large DNA viruses , NCLDV ).

" Mamavirus " was originally isolated from Acanthamoeba polyphaga , but subsequent work looked at Acanthamoeba castellanii as the host, hence the name " Acanthamoeba castellanii mamavirus " (ACMV). As "Mama viruses" viruses are informally referred to (with one of them produced in the host cell virus factory , English virus factory ) of one Virophagen be parasitized (s. U.).

discovery

It was first published on " Mamavirus " in September 2008. Like Mimivirus ApMV, " Mamavirus " was isolated from an amoeba in a cooling tower . The mimivirus was not isolated until 1992; because of their size, the Mimiviridae are retained by bacterial filters along with the bacteria. Therefore, the mimivirus was initially mistaken for a bacterium as " Bradfordcoccus ". Only electron microscopy later showed that it was an icosahedral virus, similar to the iridovirus (also an NCLDV). This then paved the way for the discovery of " Mamavirus ", since one now knew where and how to look for such giant viruses.

Structure and genome

Like other Mimiviridae, “ Mamavirus ” is icosahedral with a core capsid and a peripheral fiber layer. It contains a linear double-stranded DNA genome with a very high coding density characteristic of NCLDVs . The Mimiviridae show gene duplication and a larger part of the genome is associated with functions never before found in a virus. The genome has a total length of 1,191,693 base pairs (bp) and codes for a predicted 997 proteins , the GC content is 23%.

Propagation cycle

" Mamavirus " has its own transcription machinery and packages transcription proteins in its virus particles (virions). It is believed that transcription takes place in the cell nuclei of the host cell . The nucleus releases viral DNA and forms a cytoplasmic replication factory ( English virus factory ), in which DNA replication begins and other subsequent genes are transcribed. The replication factory expands until it takes up a large part of the amoeba volume. Later stages of the replication cycle include partially assembled procapsids that are subjected to DNA packaging ( English DNA packaging ).

Systematics

The International Committee on Taxonomy of Viruses (ICTV) has been with stand April 2020 only the two genera Cafeteria virus and Mimivirus (with species Acanthamoeba polyphaga Mimivirus , ApMV) as members of the family mimiviridae officially confirmed. The list of proposed genera and species is all the more extensive. Within the Mimiviridae family, a distinction is usually made between the following kinship groups (by suggestion also subfamilies):

  • Mimiviridae group I - as subfamily " Megamimivirinae " (or " Mimivirinae ")
  • Cafeteriavirus group alias Mimiviridae group II
  • Klosneuvirus group - as a subfamily " Klosneuvirinae "

In the Mimiviridae group I, all representatives of the genus Mimivirus were assigned to the discovery of " Tupan virus " . Within this group I the following lines ( English lineages ) are distinguished:

The exact relationships are still under discussion, according to Schulz et al. stands z. B. the line A basal in group I, not the Tupan viruses.

In addition to AcMV, the National Center for Biotechnology Information (NCBI) knows the other species " Mamavirus AC-2012 ".

Sputnik virus phages

If the Mimiviridae themselves were a surprise, " Mamavirus " came up with an even bigger surprise. Under the electron microscope, while looking at the " Mamavirus ", discovered a second small virus that is closely associated with it and bears the name Sputnik virophage , a satellite virus . Sputnik contains 21 genes and is tiny compared to the " Mamavirus ", but its presence has a very large impact on the " Mamavirus ". Sputnik cannot replicate itself in the acanthamoeba cells if these are not infected with " Mamavirus " (or Mimivirus ) at the same time . It infects and hijacks the virus factory created by these Mimiviridae in order to replicate its own genome. As a result, the Mimiviridae virus produces fewer of its virions, which are also often deformed and less effective. There is also evidence of partial capsid thickening. These effects suggest that it is a viral parasite, so that Sputnik was identified as the first representative of the so-called virophages . A virophage is like a bacterial virus ( bacteriophage ) that infects bacteria and makes them sick, virophages infect viruses instead. Sputnik contains a circular double-stranded DNA with a size of 18,343  bp and also has an icosahedral shape. Of the 21 genes it contains, eight encode proteins that have homologues : of these eight genes, three are believed to come from " Mamavirus " or Mimivirus . This indicates that Sputnik can participate in gene transfer processes and is therefore able to mediate lateral gene transfer (LGT) between giant viruses.

Conclusions

Mamavirus prompted scientists to review the criteria of life. In doing so, they stimulate the debate about the origin of DNA viruses and their possible role in the formation of the eukaryotic cell nucleus.

Individual evidence

  1. ↑ a b c d e f ICTV: ICTV Taxonomy history: Acanthamoeba polyphaga mimivirus , EC 51, Berlin, Germany, July 2019; Email ratification March 2020 (MSL # 35)
  2. ↑ Christoph M. Deeg, Cheryl-Emiliane T. Chow, Curtis A. Suttle: The kinetoplastid-infecting Bodo saltans virus (BsV), a window into the most abundant giant viruses in the sea ... , in: eLife Sciences 7, March 2018 , doi: 10.7554 / eLife.33014
  3. ↑ Center national de la recherche scientifique: List of the main “giant” viruses known as of today (March 2019) , Université Aix Marseille, March 2019.
  4. ↑ a b c Frederik Schulz, Lauren Alteio, Danielle Goudeau, Elizabeth M. Ryan, Feiqiao B. Yu, Rex R. Malmstrom, Jeffrey Blanchard, Tanja Woyke: Hidden diversity of soil giant viruses , in: Nature Communicationsvolume 9, Article number: 4881 (2018) of November 19, 2018, doi : 10.1038 / s41467-018-07335-2
  5. ↑ Tan Yeh Fong, Chai Ying Lim, Chun Wie Chong, Patricia Kim Chooi Lim, Ivan KS Yap, Pooi Pooi Leong, Kenny Voon: Isolation and Quantification of Mimivirus-Like and Marseillevirus-Like Viruses from Soil Samples in An Aboriginal (Orang asli ) Village in Peninsular Malaysia , in: Intervirology 61 (2), pp. 1-4, August 2018, doi: 10.1159 / 000491602 , Medscape , PDF , Fig. 2
  6. ↑ Sharon Clouthier, Eric Anderson, Gael Kurath, Rachel B. Breyta: Molecular systematics of sturgeon nucleocytoplasmic large DNA viruses , in: MOL PHYLOGENET EVOL 128, July 2018, doi: 10.1016 / j.ympev.2018.07.019
  7. ↑ NCBI: Acanthamoeba castellanii mamavirus (species)
  8. ↑ a b c James L. Van Etten, Leslie C. Lane, David D. Dunigan: DNA Viruses: The Really Big Ones (Giruses) . In: Annual Review of Microbiology (Ed.): Annual Review of Microbiology . 64, October 13, 2010, pp. 83-99. doi : 10.1146 / annurev.micro.112408.134338 . PMID 20690825 . PMC 2936810 (free full text).
  9. ^ A b Jean-Michel Claverie, Chantal Abergel: Mimivirus and its Virophage . Annual Review of Genetics. Pp. 49-66. 2009.
  10. ↑ Colson P, Yutin N, Shabalina SA, etal: Viruses with more than 1000 genes: Mamavirus, a new Acanthamoeba castellanii mimivirus strain, and reannotation of mimivirus genes . In: Genome Biol Evol . 3, June 2011, pp. 737-42. doi : 10.1093 / gbe / evr048 . PMID 21705471 . PMC 3163472 (free full text).
  11. ↑ Rachel Ehrenberg: Enter the Virosphere: As evidence of the influence of viruses escalates, appreciation of these master manipulators grows . In: Science News (ed.): Science News . 176, No. 8, October 10, 2009, pp. 22-25. doi : 10.1002 / scin.5591760820 .
  12. ↑ David M. Needham, Alexandra Z. Worden et al .: A distinct lineage of giant viruses brings a rhodopsin photosystem to unicellular marine predators , in: PNAS, 23 September 2019, doi: 10.1073 / pnas.1907517116 , ISSN 0027-8424 , here: Supplement 1 (xlsx)
  13. ↑ ICTV : Master Species List 2018b.v2 . Retrieved August 6, 2019. MSL # 34v
  14. ↑ NCBI: Mamavirus AC-2012 (species)
  15. ↑ a b Helen Pearson: 'Virophage' suggests viruses are alive . Nature. August 7, 2008. Archived from the original on March 22, 2012. Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved April 11, 2011. @1@ 2Template: Webachiv / IABot / www.igs.cnrs-mrs.fr
  16. ↑ Bernard La Scola, Christelle Desnues, Isabelle Pagnier, Catherine Robert, Lina Barrassi, Ghislain Fournous, Michele Merchat, Marie Suzan-Monti, Patrick Forterre, Eugene Koonin, Didier Raoult: The virophage as a unique parasite of the giant mimivirus . Nature . Pp. 100-105. September 4, 2008., PDF , doi: 10.1038 / nature07218
  17. ↑ Christelle Desnues, D. Raoult: Inside the Lifestyle of the Virophage . Intervirology. Pp. 293-303. June 15, 2010.
  18. ^ Siyang Sun, Bernard La Scola, Valorie D. Bowman, Christopher M. Ryan, Julian P. Whitelegge, Didier Raoult, Michael G. Rossmann: Structural Studies of the Sputnik Virophage . In: Journal of Virology (Ed.): Journal of Virology . 84, No. 2, January 2010, pp. 894-897. doi : 10.1128 / JVI.01957-09 . PMID 19889775 . PMC 2798384 (free full text).
  19. ↑ Rachel Small Ridge: Virology: A virus gets a virus . Nature Reviews. October 1, 2008.

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