Pithovirus

Pithovirus sibericum is a giant virus that was isolated in 2014 from 30,000 -year-old Siberian permafrost. It is to date the oldest eukaryotes infecting DNA virus that could be brought back to an infection. This suggests that from the thawing due to global warming permafrost other infectious viruses or microorganisms could still be released.

Discovery

To search in the permafrost for even infectious virus, a sample was taken from sterile late - Pleistocene sediments of the Kolyma lowland and those incubated with a culture of Acanthamoeba castellanii as a possible host for viruses. After the multiplication in Acanthamoeba virus particles were purified and analyzed by transmission electron microscopy and genome sequencing.

Properties

Pithovirus sibericum is already light microscopy to detect as egg-shaped particles. They have a length of about 1.5 microns and a width of about 500 nm by electron microscopy can be seen, having parallel upright strip having a thickness of about 60 nm viral envelope. The opening at the tip of the viral envelope is closed by an approximately 160 nm wide and 80 nm thick structure of 15 nm wide rods having a hexagonal lattice pattern in plan view, and seems to be connected with a coiled membrane inside. Inside the virus envelope is an membranumschlossenes compartment, having no internal structures except for a visible occasionally 50 nm measured by electron-dense ball and a tube- like structure along the longitudinal axis of the virus.

The genome consists of double-stranded DNA that may be present as a closed ring or as a linear molecule with redundant ends. 610,033 base pairs, which have a GC content of 36% and 467 encode for proteins.

Pithovirus sibericum thus differs from the externally similar Pandora viruses by the cork -like structure at the sheath tip and the much smaller, the AT -rich genome with fewer genes.

Life cycle

The life cycle is known from cultures Acanthamoeba and starts phagocytosis of virus particles by the host. After losing the cork -like structure, the viral membrane with the vacuolar membrane of the host fused so that a channel-like connection of the viral compartment together with the Wirtscytoplasma. Four to six hours after infection, a clear zone in the Wirtscytoplasma is visible in the accumulate numerous vesicles. The viral envelope and the inner compartment are formed together by first rectangular, closed particles, already with the characteristic cork -like structure, are obtained, the outer wall thickens later and then take the their ovoid shape. The striped, outermost layer is built up at the end and in individual pieces. At the end of the host cell is dissolved and hundreds of virus particles are released.