Sputnik virus

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Sputnik virus
Sputnik virofago.jpg

Sputnik virus phages

Systematics
Classification : Viruses
Area : Varidnaviria
Empire : Bamfordvirae
Phylum : Preplasmiviricota
Class : Maveriviricetes
Order : Priklausovirales
Family : Lavidaviridae
Genre : Sputnik virus
Type : Sputnik virus
Taxonomic characteristics
Genome : dsDNA circular
Baltimore : Group 1
Symmetry : icosahedral
Cover : no
Scientific name
Mimivirus-dependent virus Sputnik
Left
NCBI  Taxonomy: 1932924
ViralZone ( ExPASy , SIB): 670
ICTV Taxon History: 201853749

The Sputnik virus (also Sputnik-Virophage , scientifically Mimivirus-dependent virus Sputnik ) is a species of virus of the family Lavidaviridae , which can only reproduce in the amoeba Acanthamoeba castellanii in the presence of another virus from the genus Mimivirus . It was discovered as an accompanying virus in 2008 and the name " virophage " was proposed for it as a possible representative of a presumably new group of pathogens . In fact, the Sputnik virus does not multiply in the virion (virus particle) of the mimivirus , but uses the protein synthesis apparatus of the cell ( viroplasm ) that has been remodeled by the mimivirus and is dependent on the replication enzymes of the mimivirus . It is therefore very similar in its reproduction behavior to the hepatitis D virus ( virusoid ) and the adeno-associated viruses (genus Dependovirus ) in animal viruses and the satellite viruses in some plant viruses . A related Virophage called Zamilon (scientifically Mimivirus-dependent virus Zamilon , same virus genus) invades another Mama virus baptized representatives of mimiviridae .

Genome

The genome of the Sputnik virus consists of a double-stranded DNA that is closed in a ring. It is 18,343  kb in size and, like the mimiviruses, is characterized by a very low GC content of 27%. The genome contains 21 possible open reading frames (ORFs), some of which overlap. By comparing the protein sequences that can be derived from them with known proteins , a probable, homologous secondary structure and thus a possible function could be deduced for some gene products . In the virus particle (virion) of the Sputnik virus , three proteins are identified as structural proteins by polyacrylamide gel electrophoresis , which could be assigned to ORFs 8, 19 and 20 according to MALDI-TOF data. The protein sequences from ORF 6 and 12 are somewhat similar to proteins of the Acanthamoeba polyphaga mimivirus APMV (MIMI R196 and MIMI R546). The gene sequences of the Sputnik virus thus consist of the next previously unknown viral sequences of two additional shares, on the one hand similar to the Mimivirus genome and the other known sequences from viruses that archaea or bacteria to the host have. During the replication of the Sputnik virus DNA, genes can be exchanged with the APMV.

ORF amino acids possible function Protein homologs
ORF 1 144 unknown unknown
ORF 2 114 unknown unknown
ORF 3 245 DNA packaging RecA superfamily ATPases (54%)
ORF 4 139 Transcription regulation? Zinc finger proteins
ORF 5 119 unknown unknown
ORF 6 310 Protein-protein interaction in the viroplasm? Triple helix proteins, MIMI R196 (53%)
ORF 7 236 Protein-protein interaction in the viroplasm? Triple helix proteins, TNF -associated protein 5 (27%)
ORF 8 184 Structural protein, capsid unknown
ORF 9 175 unknown unknown
ORF 10 226 DNA integrase Integrase family in bacteriophage (27%), Tyr recombinase
ORF 11 162 unknown unknown
ORF 12 152 unknown MIMI R546 (64%)
ORF 13 779 DNA replication (viral DNA polymerase ) DNA primase , helicase
ORF 14 114 Transcription regulation? Zinc finger proteins
ORF 15 109 Membrane protein? no
ORF 16 130 unknown unknown
ORF 17 88 DNA binding protein IS3 superfamily transposases
ORF 18 167 unknown unknown
ORF 19 218 Structural proteins, capsid unknown
ORF 20 595 Structural proteins, main capsid protein unknown
ORF 21 438 unknown unknown

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

morphology

A virus particle ( virion ) of the mimivirus with two smaller virions of the Sputnik virophage (arrows).

The virions of the Sputnik virus are around 50 nm in diameter and consist of an unenveloped , icosahedral capsid . The capsid is probably formed exclusively from a 595 amino acid capsid protein (ORF 20); two further structural proteins (ORF 8 and 19) are only found once in the virion. In infected amoeba, densely packed aggregates of Sputnik capsids can be found in the area of ​​the viroplasm. Since the virus affects the packaging and morphogenesis of the APMV, packaged Sputnik viruses can be found inside deformed, defective APMV virions.

Biological importance

The Sputnik virus is a first example of dependent reproduction and genetic exchange between two marine virus species. So far, this has only been described for plant viruses, bacteriophages and animal viruses (virusoids). Although it is known that viruses (especially bacteriophages) as femto - or virioplankton represent the largest biomass and probably the most species-rich group in the oceans and other bodies of water , little research has been done into their ecological and genetic connection. The newly discovered mimivirus and genetic elements similar to it are regularly detectable in marine ecosystems. Since the taxonomic and phylogenetic position of the mimivirus itself is still unclear, this also applies to the relationship between mimivirus and Sputnik virus . Large gene segments of the mimivirus are very similar to bacterial genes ( plasmid- like) and eukaryotic genes of the parasitized alga, which could be based on a horizontal gene transfer between virus and host as well as on a possible bacterial origin of the evolution of the mimivirus . Based on this, it can be postulated that the Sputnik virus would represent an original bacteriophage of the original bacterium from which the mimivirus developed through the loss of its own synthesis apparatus .

swell

  • B. La Scola et al. : The virophage as a unique parasite of the giant mimivirus . Nature (2008) 455 (7209): pp. 100-104 PMID 18690211
  • H. Ogata H, JM Claverie: Microbiology. How to infect a Mimivirus . Science (2008) Sep 5; 321 (5894): pp. 1305-1306 PMID 18772426

Systematics

In addition to Sputnik 1 other (proposed) representatives of this genus were found. In order to:

  • Genus Sputnik virus
  • Species Sputnik virus 1 (officially Mimivirus-dependent virus Sputtnik ) - infects " Mamavirus " from the Mimivirus group A.
  • Species " Sputnik virus 2 " - found in 2012, infected " Lentille virus ", also from the Mimivirus group A.
  • Species “ Sputnik virus 3 ” - found in 2013, can infect the mimivirus (type APMV), which is not the natural host.
  • Species Zamilon virus (officially Mimivirus-dependent virus Zamilon ) with Zamilon 1 (2013, Tunisia) and Zamilon 2 (2015, North America)

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 Morgan Gaia et al. : Zamilon, a Novel Virophage with Mimiviridae Host Specificity . In: PLoS One. 2014; 9 (4), p. E94923. Published online 2014 Apr 18. doi: 10.1371 / journal.pone.0094923 , PMC 3991649 (free full text)
  3. ↑ 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
  4. ^ S. Duponchel, M. G. Fischer: "Viva lavidaviruses! Five features of virophages that parasitize giant DNA viruses". PLoS pathogens , 15 (3), 2019. doi: 10.1371 / journal.ppat.1007592 . CC-BY icon.svgThe material is copied from this source, which is available under a Creative Commons Attribution 4.0 International License .
  5. ↑ KE Wommack, RR Colwell: Virioplankton: viruses in aquatic ecosystems . Microbiology and Molecular Biology Reviews (2000) 64.1: pp. 69-114 PMID 10704475 , PMC 98987 (free full text)
  6. ↑ A. Monier, JM Claverie, H. Ogata: Taxonomic distribution of large DNA viruses in the sea . Genome Biol. (2008) 9 (7): R106 PMID 18598358
  7. ↑ D. Moreira, C. Brochier-Armanet: Giant viruses, giant chimeras: the multiple evolutionary histories of Mimivirus genes . BMC Evol Biol. (2008) 8: p. 12 PMID 18205905
  8. ↑ Ed Yong: A Parasite's Parasites , in: The Scientist, October 15, 2012
  9. ↑ Gaia M, Pagnier I, Campocasso A, Fournous G, Raoult D, et al: Broad spectrum of mimiviridae virophage allows its isolation using a mimivirus reporter . PLoS One 8: e61912 (2013) doi: 10.1371 / journal.pone.0061912
  10. ↑ Clara Rolland, Julien Andreani, Amina Cherif Louazani, Sarah Aherfi, Rania Francis, Rodrigo Rodrigues, Ludmila Santos Silva, Dehia Sahmi, Said Mougari, Nisrine Chelkha, Meriem Bekliz, Lorena Silva, Felipe Assis, Fábio Dornas, Jacques Yaacoub Bou Khalil, Isabelle Pagnier, Christelle Desnues, Anthony Levasseur, Philippe Colson, Jônatas Abrahão, Bernard La Scola: Discovery and Further Studies on Giant Viruses at the IHU Mediterranee Infection That Modified the Perception of the Virosphere , in: Viruses 11 (4), March / April 2019, pii: E312, doi: 10.3390 / v11040312 , PMC 6520786 (free full text), PMID 30935049

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