Mimiviridae
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''Mimiviridae'' is a family of
viruses A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's ...
.
Amoeba An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudop ...
and other protists serve as natural hosts. The family is divided in up to 4 subfamilies., UCPMS ID: 1889607
PDF
/ref> Fig. 4 and §Discussion: "Considering that tupanviruses comprise a sister group to amoebal mimiviruses…" Viruses in this family belong to the
nucleocytoplasmic large DNA virus ''Nucleocytoviricota'' is a phylum of viruses. Members of the phylum are also known as the nucleocytoplasmic large DNA viruses (NCLDV), which serves as the basis of the name of the phylum with the suffix - for virus phylum. These viruses are refe ...
clade (NCLDV), also referred to as
giant viruses A giant virus, sometimes referred to as a girus, is a very large virus, some of which are larger than typical bacteria. All known giant viruses belong to the phylum ''Nucleocytoviricota''. Description While the exact criteria as defined in the s ...
. ''Mimiviridae'' is the sole recognized member of order ''Imitervirales''. ''
Phycodnaviridae ''Phycodnaviridae'' is a family of large (100–560 kb) double-stranded DNA viruses that infect marine or freshwater eukaryotic algae. Viruses within this family have a similar morphology, with an icosahedral capsid (polyhedron with 20 f ...
'' and ''
Pandoraviridae ''Pandoraviridae'' is a family of DNA virus#Group I: dsDNA viruses, double-stranded DNA viruses that infect amoebae. There is only one genus in this family: ''Pandoravirus''. Several species in this genus have been described, including ''Pandora ...
'' of ''
Algavirales ''Phycodnaviridae'' is a family of large (100–560 kb) double-stranded DNA viruses that infect marine or freshwater eukaryotic algae. Viruses within this family have a similar morphology, with an icosahedral capsid (polyhedron with 20 fa ...
'' are sister groups of ''Mimiviridae'' in many phylogenetic analyses.PDF
/ref>


History

The first member of this family, Mimivirus, was discovered in 2003, and the first complete genome sequence was published in 2004. However, the mimivirus Cafeteria roenbergensis virus was isolated and partially characterized in 1995, although the host was misidentified at the time, and the virus was designated BV-PW1.


Taxonomy

Group: dsDNA Family ''Mimiviridae'' is currently divided into three subfamilies. * One subfamily (genus ''
Mimivirus ''Mimivirus'' is a genus of giant viruses, in the family '' Mimiviridae''. Amoeba serve as their natural hosts. This genus contains a single identified species named ''Acanthamoeba polyphaga mimivirus'' (APMV). It also refers to a group of phyl ...
'', proposed names: ''Megavirinae'' or ''Megamimivirinae'') is divided into three "lineages": ** A — Mimivirus group: includes ''Acanthamoeba polyphaga Mimivirus'', Hirudovirus,
Mamavirus Mamavirus is a large and complex virus in the Group I family ''Mimiviridae''. The virus is exceptionally large, and larger than many bacteria. Mamavirus and other mimiviridae belong to nucleocytoplasmic large DNA virus (NCLDVs) family. Mamavirus ...
, Kroon virus, Lentille virus, Terra2, Niemeyer virus, Samba virus.See also ** B — Moumouvirus group: includes Moumouvirus, Saudi moumouvirus, Moumouvirus goulette, Monve virus (aka Moumouvirus monve), and Ochan virus. ** C — Courdo11 virus group: includes Mont1, Courdo7, Courdo11, Megavirus chilensis, LBA111, Powai lake megavirus and Terra1. : The majority of ''Mimiviridae'' appear to belong to this subfamily (Mimiviruses). : It is sometimes also referred to as Mimiviridae group I. * The second subfamily ( Cafeteriavirus or Mimiviridae group II) includes the '' Cafeteria roenbergensis virus'' (CroV). * The '' Klosneuvirinae'' have been proposed as a third subfamily and are divided into four "lineages":
Klosneuvirus ''Klosneuvirus'' (KNV, also KloV) is a new type of giant virus found by the analysis of low-complexity metagenomes from a wastewater treatment plant in Klosterneuburg, Austria. It has a 1.57-Mb genome coding unusually high number of genes typic ...
, Indivirus, Catovirus and Hokovirus. They seem to be closely related to the Mimivirus subfamily rather than the Cafeteriavirus subfamily (and so might be summarized in Mimivirus group I as well). The first isolate from this group is
Bodo saltans virus The Bodo saltans virus is a giant virus of the ''Mimiviridae'' family that infects the protozoa ''Bodo saltans''. It has a genome of 1.39 megabases A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleo ...
infecting the kinetoplastid ''
Bodo saltans ''Bodo saltans'' (alternatively known as ''Pleuromonas jaculans'') is a free-living nonparasitic species of kinetoplastid flagellated phagotrophic protozoa that feed on bacteria. ''Bodo saltans'' cells have been reported in freshwater and marine e ...
''. *
Tupanvirus Tupanvirus is a genus of viruses first described in 2018. The genus is composed of two species of virus that are in the giant virus group. Researchers discovered the first isolate in 2012 from deep water sediment samples taken at 3000m depth o ...
strains have been discussed to comprise a sister group of mimiviruses. Furthermore, it has been proposed either to extend ''Mimiviridae'' by an additional tentative group III (subfamily ''Mesomimivirinae'') or to classify this group as a sister family ''Mesomimiviridae'' instead,Jonathan Filée
Giant viruses and their mobile genetic elements: the molecular symbiosis hypothesis
in: Current Opinion in Virology, Volue 33, December 2018, pp. 81–88;
comprising legacy OLPG (Organic Lake Phycodna Group). This extension (or sister family) may consist of the following: * Phaeocystis globosa virus (PgV, represented by PgV-16T strain) and Phaeocystis pouchetii virus (PpV, e. g. PpV 01) * "Organic Lake Phycodnavirus" 1 and 2 (OLV1, OLV2, hosts of
Organic Lake virophage Organic Lake virophage (OLV) is a double-stranded DNA virophage (a virus that requires the presence of another virus to replicate itself and in so doing limits the ability of the other virus to replicate). It was detected metagenomically in sampl ...
) * "Yellowstone Lake Mimivirus" aka "Yellowstone Lake Phycodnavirus" 4 ( YSLGV4) * Chrysochromulina ericina virus (CeV, e. g. CeV 01) * Aureococcus anophagefferens virus ( AaV) * Pyramimonas orientalis virus (PoV) * Tetraselmis virus (TetV-1) This group seems to be closely related to ''Mimiviridae'' rather than to ''
Phycodnaviridae ''Phycodnaviridae'' is a family of large (100–560 kb) double-stranded DNA viruses that infect marine or freshwater eukaryotic algae. Viruses within this family have a similar morphology, with an icosahedral capsid (polyhedron with 20 f ...
'' and therefore is sometimes referred to as a further subfamily candidate '' Mesomimivirinae''. Sometimes the extended family Mimiviridae is referred to as ''
Megaviridae ''Mimiviridae'' is a family of viruses. Amoeba and other protists serve as natural hosts. The family is divided in up to 4 subfamilies., UCPMS ID: 1889607PDF/ref> Fig. 4 and §Discussion: "Considering that tupanviruses comprise a sister gr ...
'' although this has not been recognized by ICTV; alternatively the extended group may be referred to just as ''Mimiviridae''. With recognition of new order ''Imitervirales'' by the ICTV im march 2020 there is no longer need to extend the ''Mimiviridae'' family to comprise a group of viruses of the observed high diversity. Instead, the extension (or at least its main
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
) may be referred to as a sister family ''Mesomimiviridae''. Although only a couple of members of this order have been described in detail it seems likely there are many more awaiting description and assignment Unassigned members include ''Aureococcus anophagefferens'' virus (AaV), CpV-BQ2 and Terra2.


Structure

Viruses in Mimiviridae have icosahedral and round geometries, with between T=972 and T=1141, or T=1200 symmetry. The diameter is around 400 nm, with a length of 125 nm. Genomes are linear and non-segmented, around 1200kb in length. The genome has 911 open reading frames.


Life cycle

Replication follows the DNA strand displacement model. DNA-templated transcription is the method of transcription. Amoeba serve as the natural host.


Molecular biology

Within the genome of Lentille virus integrated genome of a
virophage Virophages are small, double-stranded DNA viral phages that require the Coinfection, co-infection of another virus. The co-infecting viruses are typically giant viruses. Virophages rely on the viral replication factory of the co-infecting giant ...
(Sputnik 2) and a transpoviron—a mobile genetic element—have been reported. Transpovirons are linear DNA elements of about 7 kilobases that encompass six to eight protein coding genes, two of which are homologous to virophage genes. Broad spectrum of mimiviridae
virophage Virophages are small, double-stranded DNA viral phages that require the Coinfection, co-infection of another virus. The co-infecting viruses are typically giant viruses. Virophages rely on the viral replication factory of the co-infecting giant ...
allows its isolation using a mimivirus reporter.


Clinical

Mimiviruses have been associated with pneumonia but their significance is currently unknown. The only virus of this family isolated from a human to date is LBA 111. At the Pasteur Institute of Iran (Tehran), researchers identified mimivirus DNA in bronchoalveolar lavage (BAL) and sputum samples of a child patient, utilizing real-time PCR (2018).  Analysis reported 99% homology of LBA111, lineage C of the ''Megavirus chilensis''. With only a few reported cases previous to this finding, the legitimacy of the mimivirus as an emerging infectious disease in humans remains controversial. ''Mimivirus'' has also been implicated in
rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are invol ...
.


See also

*
Virophage Virophages are small, double-stranded DNA viral phages that require the Coinfection, co-infection of another virus. The co-infecting viruses are typically giant viruses. Virophages rely on the viral replication factory of the co-infecting giant ...


References


External links


Viralzone: Mimiviridae

ICTV
{{Use dmy dates, date=April 2017 Virus families