''Medusavirus'' is a genus of

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 ...

es that is the sole representative of ''Mamonoviridae'' (from ''mamono'' (), the Japanese word for "monster" in reference to '' Megaviricetes'' + -viridae). It was first isolated from a

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

ese

hot spring A hot spring, hydrothermal spring, or geothermal spring is a Spring (hydrology), spring produced by the emergence of Geothermal activity, geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow ...

in 2019. It notably encodes all five types of

histone In biology, histones are highly basic proteins abundant in lysine and arginine residues that are found in eukaryotic cell nuclei and in most Archaeal phyla. They act as spools around which DNA winds to create structural units called nucleosomes ...

s — H1, H2A, H2B, H3, and H4 — which are involved in DNA packaging in

eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

s, raising the possibility that they may have been involved in the origin of eukaryotes. The virus can harden

amoeba An amoeba (; less commonly spelled ameba or amœba; : amoebas (less commonly, amebas) or amoebae (amebae) ), often called an amoeboid, is a type of Cell (biology), cell or unicellular organism with the ability to alter its shape, primarily by ...

s of the species '' Acanthamoeba castellanii'' into stone-like

cyst A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubb ...

s, but infection usually causes infected amoebas to burst open. The virus was named after

Medusa In Greek mythology, Medusa (; ), also called Gorgo () or the Gorgon, was one of the three Gorgons. Medusa is generally described as a woman with living snakes in place of hair; her appearance was so hideous that anyone who looked upon her wa ...

, the monster in

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

whose gaze turned people to stone.

Taxonomy

''Medusavirus'' is a part of a phylum called ''Nucleocytoviricota,'' which is referred as nucleocytoplasmic large DNA virus (NCLDV). These viruses have a large double-stranded DNA genome and the length of the genome could be more than 100kb. NCLDV infects various eukaryotic hosts such as amoebas. The genus contains two species: * '' Medusavirus medusae'' * '' Medusavirus sthenus''

Morphology

Viral particle is composed of icosahedral capsid which is 260 nm in diameter. This 8 nm single layered capsid is covered with 14 nm spherical-headed spikes. Viral double-stranded DNA is backed inside the 6 nm thick internal membrane.

Maturation

Medusaviruses have a unique viral particle maturation process compared to several other viruses. Virus does not form viral factory in the host cytoplasm to replicate the viral genome. The proposed maturation process starts by generating the pseudo-Empty viral particles with the help of scaffold proteins. Then these pseudo-Empty particles release the scaffold proteins and Empty particles are formed. After the release of proteins the Empty particle uptakes the viral DNA near the host nucleus and via semi-Full stages the Full particles are eventually formed.

References

{{Taxonbar, from=Q62003410, from2=Q62003418 DNA viruses Virus genera