Zamilon virus

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Zamilon virus
Zamilon and abnormal Mont1 (Gaia et al. Fig 3a) .jpg

Electron microscope image of a virus factory in an amoeba that
is co -infected with the Zamilon virus (small particles) and " Mont1 virus ".
Arrows show abnormal " Mont1 " virus particles (scale: 0.1  μm )

Systematics
Classification : Viruses
Area : Varidnaviria
Empire : Bamfordvirae
Phylum : Preplasmiviricota
Class : Maveriviricetes
Order : Priklausovirales
Family : Lavidaviridae
Genre : Sputnik virus
Type : Zamilon virus
Taxonomic characteristics
Genome : dsDNA circular
Baltimore : Group 1
Symmetry : spherical
Scientific name
Mimivirus-dependent virus Zamilon
Left
NCBI  Taxonomy: 1932926
NCBI  Reference: NC_022990
ICTV Taxon History: 201853750

The Zamilon virus (also Zamilon-Virophage scientifically Mimivirus-dependent virus Zamilon ) is a small DNA - virus , the protists infected and for their own replication a helper virus needed. The Zamilon discovered in Tunisia in 2013 is therefore a type of satellite virus , often classified as a virophage . Zamilon infects the amoeba of the genus Acanthamoeba polyphaga . It is very similar to the first virophage discovered, the related Sputnik virus (same virus genus).

The name Zamilon comes from Arabic ( Arabic  زميل zamil , German 'colleague, neighbor' , English colleague, coworker ).

All known virophages are associated with helper viruses of the giant virus family of the Mimiviridae . Zamilon is restricted in its choice of auxiliary viruses: It is within the mimiviridae the Mimivirus -like lines IB and IC instructed viruses line IA are for Zamilon no avail. This seems to be due to a rudimentary immune system (called MIMIVIRE, English mimivirus virophage resistance element ) of the designated helper viruses of line IA, which is similar to the CRISPR-Cas system. Unlike the Sputnik -Virophagen seems Zamilon not to compromise his helper virus replication.

Discovery and Related Virophages

Electron microscope image of a virus factory in an amoeba co-infected with Zamilon and " Mont1 " (scale bar : 0.1  μm )

Zamilon was discovered in 2013 in the amoeba Acanthamoeba polyphaga , which was co- infected with the giant virus " Mont1 " (genus Mimivirus , line C) isolated from a Tunisian soil sample .

As of 2015, Zamilon is one of three virophage species that have been physically isolated (the other two are Sputnik virus from the same genus and Mavirus , a sister genus within the Lavidaviridae family ).

Several other virophage DNAs have been found using metagenomic analysis but have not been physically isolated to date. A related strain within the Zamilon species named Zamilon 2 was discovered in 2015 through metagenomic analysis of a North American poplar wood chip bioreactor . Another virophage, Rio Negro , is also closely related to Sputnik .

Systematics

The Zamilon -Virophage was from the International Committee on Taxonomy of Viruses (ICTV) in the species Mimivirus-dependent virus Zamilon the genus Sputnik virus in the family Lavidaviridae divided.

construction

The Zamilon -Viruspartikel ( virions ) are spherical (spherical) having a diameter of 50-60  nm and are similar in appearance to those of Sputnik and Mavirus . The circular double-stranded DNA genome is 17,276  bp long.

Virophages typically have virions with a diameter in the range of 40-80 nm and a genome size in the range of 17-30 kbp. The with Zamilon related most closely Virophage is Sputnik , with which it shares 76% of the genome sequence, although part of the Zamilon sequence compared to Sputnik reversed (reverse) is. Zamilon's DNA is rich in the bases adenine and thymine , the GC share is only 29.7%.

The analyzes indicated that the Zamilon genome (20 open reading frame English open reading frames , ORFs) should contain a length between 222 bases and 2,337 bases; So 20 polypeptides should be encoded . Of the 20 predicted gene products, 15 are similar to those of Sputnik , three are similar to those of the Acanthamoeba polyphaga Mimivirus (APMV alias Mimivirus sensu stricto : genus Mimivirus line A), two are the “ Megavirus chilensis ” (genus Mimivirus line C) and one is the transpoviron (a mobile one genetic element in giant viruses) of " Moumouvirus Monve " (alias " Monve virus" , genus Mimivirus line B).

A Zamilon -ORf also shows some resemblance to " Mavirus " and another with " Organic Lake -Virophagen " and a " Phaeocystis globosa -Virophagen ", both are likely to be associated with algae than amoebae. The remaining two predicted gene products show limited similarity to other known proteins. Possible functions of the products include transposase , helicase , integrase , cysteine protease , primase / DNA polymerase and DNA-packaging ATPase enzymes, major and minor capsid proteins , a structural protein and a collagen-like protein.

ORF amino acids possible function Protein homologs Similarity
(%)
1 111 ? none -
2 73 ? none -
3 135 ? Megavirus chilensis mg3 gene product 67
4th 221 Transposase Sputnik virophage 2 putative IS3 family transposase A protein 40
5 376 Virion protein Sputnik virophage 2 virion protein 66
6th 609 Capsid protein Sputnik virophage capsid protein V20 86
7th 442 ? Sputnik virophage V21 70
8th 81 ? Moumouvirus Monve Suspected Protein tv_L8 72
9 778 Helicase Sputnik virophage V13 67
10 168 ? Sputnik virophage V11 53
11 247 Integrase Sputnik virophage V10 58
12 175 ? Sputnik virophage V9 77
13 184 Structural protein Sputnik virophage V8 71
14th 241 ? Sputnik virophage V7 80
15th 305 collagen-like protein Sputnik virophage V6 75
16 121 ? Sputnik virophage V5 59
17th 133 ? Sputnik virophage V4 55
18th 245 DNA-packaging ATPase Sputnik virophage V3 81
19th 147 ? Megavirus chilensis gene product mg664 50
20th 147 ? Sputnik virophage V1 60

Interestingly, a gene homologue of Sputnik and Zamilon with the " orpheovirus " was found in 2018 .

Multiplication cycle and helper viruses

Like all other virophages, Zamilon replicates in the cytoplasm within the virus factory of its helper, who acts as a host. Zamilon was first isolated in association with the Mont1 virus , a Mimivirus -like member of the Mimiviridae that was classified in the Mimiviridae line IC by its polymerase B gene sequence . It was then shown that the Virophage is also able to replicate in connection with Moumouvirus Monve ( Monve virus ) and Acanthamoeba polyphaga Moumouvirus (APMoV) from the Mimiviridae line IB, as well as with Terra1 and Courdo11 from line IC. However, it cannot be replicated in conjunction with mimivirus or mamavirus (both line IA). This is where Zamilon differs from Sputnik , which can replicate in connection with a Mimivirus -like member of the Mimiviridae .

Zamilon does not seem to significantly inhibit the replication ability of its helper virus, nor to impair the lysis of the amoebic cell hosts finally brought about by the helper virus . Although the helper virus produced a high proportion of abnormal virions in the presence of zamilon, these were also observed at a comparable level in the absence of the virophage. This is also a difference from Sputnik , which noticeably reduces the infectivity of its helper virus, inhibits its lysis of the amoeba and which is associated with the production of an increased proportion of abnormal Mimiviridae virions. Bernard La Scola and colleagues, who isolated both Sputnik and Zamilon , stated that if confirmed, this "would question the concept of the virophage", as this unlike other satellite viruses is believed to have a harmful effect on the Underlying helper virus.

Web links

Individual evidence

  1. ↑ a b c d e ICTV: ICTV Master Species List 2019.v1 , New MSL including all taxa updates since the 2018b release, March 2020 (MSL # 35)
  2. ↑ a b c d e f g h i Krupovic M, Kuhn JH, Fischer MG: A classification system for virophages and satellite viruses . In: Archives of Virology . 161, 2016, pp. 233-47. doi : 10.1007 / s00705-015-2622-9 . PMID 26446887 .
  3. ↑ a b c d e f g h i j k l m n Gaia M, Benamar S, Boughalmi M, Pagnier I, Croce O, Colson P, Raoult D, La Scola B: Zamilon, a Novel Virophage with Mimiviridae Host Specificity . In: PLOS ONE . 9, 2014, p. E94923. doi : 10.1371 / journal.pone.0094923 . PMID 24747414 . PMC 3991649 (free full text).
  4. ↑ Anthony Levasseur, Meriem Bekliz, Eric Chabrière, Pierre Pontarotti, Bernard La Scola, Didier Raoult: MIMIVIRE is a defense system in Mimivirus did confers resistance to virophage . In: Nature . 531, 2016, pp. 249-252. doi : 10.1038 / nature17146 .
  5. ↑ Ewen Callaway: CRISPR-like 'immune' system discovered in giant virus , in: Nature : News, June 29, 2016
  6. ↑ Boughalmi M, Saadi H, Pagnier I, Colson P, Fournous G, Raoult D, La Scola B: High-throughput isolation of giant viruses of the Mimiviridae and Marseilleviridae families in the Tunisian environment . In: Environmental Microbiology . 15, 2013, pp. 2000-2007. doi : 10.1111 / 1462-2920.12068 . PMID 23298151 .
  7. ↑ Yutin N, Kapitonov VV, Koonin EV: A new family of hybrid virophages from metagenome of animal well . In: Biology Direct . 10, 2015, p. 19. doi : 10.1186 / s13062-015-0054-9 .
  8. ↑ Bekliz M, Verneau J, Benamar S, Raoult D, La Scola B, Colson P: A New Zamilon-like Virophage Partial Genome Assembled from a Bioreactor Metagenome . In: Frontiers in Microbiology . 6, 2015, p. 1308. doi : 10.3389 / fmicb.2015.01308 . PMID 26640459 . PMC 4661282 (free full text).
  9. ↑ NCBI: Moumouvirus Monve
  10. ↑ Zhang X, Sun S, Xiang Y, Wong J, Klose T, Raoult D, Rossmann MG: Structure of Sputnik, a virophage, at 3.5-Å resolution . In: Proceedings of the National Academy of Sciences of the United States of America . 109, 2012, pp. 18431-36. doi : 10.1073 / pnas.1211702109 . PMID 23091035 . PMC 3494952 (free full text).
  11. ↑ All data from Gaia et al .
  12. ↑ Julien Andreani, Jacques YB Khalil, Emeline Baptiste, Issam Hasni, Caroline Michelle, Didier Raoult, Anthony Levasseur, Bernard La Scola: Orpheovirus IHUMI-LCC2: A New Virus among the Giant Viruses , in: Front. Microbiol., January 22, 2018, doi: 10.3389 / fmicb.2017.02643
  13. ^ Virus host DB: Acanthamoeba polyphaga moumouvirus
  14. ↑ NCBI: Acanthamoeba polyphaga moumouvirus
  15. ↑ Aherfia S, La Scola B, Pagniera I, Raoult D, Colson P: The expanding family Marseilleviridae . In: Virology . 466-467, 2014, pp. 27-37. doi : 10.1016 / j.virol.2014.07.014 . PMID 25104553 .