New "Pithovirus" Found in Siberia
Mayank Mali
researchers from the Information Génomique et Structurale laboratory have recently discovered a new type of virus named "Pithovirus" or binomial Pithovirus sibericum in the frozen ground of the autonomous region of Chukotka in north-eastern Siberia. The Pithovirus has been buried for over 30,000 years, and is harmless to human and animals. This virus is part of the group of giant viruses, including Pandovirus and Mimivirus, which typically have diameters exceeding 0.5 microns and infect amoeba including Acanthamoeba. These giant viruses also have large genomes usually the same as or more than those of bacteria, compared to more common viruses such as AIDS and influenza with smaller genomes.
Initially, Pithovirus has been thought to be part of the Pandovirus family due to similar size and amphora-like shape. However genome and protein analysis has confirmed that the Pithovirus genome has only about 500 genes compared to Pandovirus' 2,500 genes, and only one or two proteins comprising the Pithovirus is common to the Pandovirus. Also, in order to replicate, the Pithovirus replication process takes place in the cytoplasm of an host amoeba and is less dependent on the amoeba's cellular mechanisms, while the Pandovirus replication process takes place inside the nucleus of the host amoeba and uses the amoeba's mechanisms more intricately.
In final, the Pithovirus has been deemed its own group of virus of giant viruses, and thus there are now three distinct groups of giant viruses known to date. The discovery of Pithovirus also indicates that amphora-shaped viruses are as diverse as the most-widespead-to-date icosahedral-shaped viruses. This study has additionally proved that viruses can 'survive' in permafrost over large geological times, which legitimizes the possible re-appearance of other viruses thought to be eradicated.
Relevance:
The study of the Pithovirus relates to the unit about microbes. Just as in the curricula, this article refers to the way a virus reproduces inside of a living host cell, using the host mechanisms to create new duplications of the viral DNA by DNA polymerase. In the case of the Pithovirus, it replicates inside an amoeba. This study also refers to the 'life cycle' of viruses through the lytic and lysogenic cycles. The study so far has established that Pithovirus in particular uses the lytic cycle in amoebas, but for a virus to reproduce by the lysogentic cycle in a eukaryote is not rare.
Author: Le Centre national de la recherche scientifique (CNRS)
Published: March 4, 2014
URL: http://www.sciencedaily.com/releases/2014/03/140304071433.htm
How were the researchers able to replicate the virus if it had been frozen? How did the extremely cold temperatures not kill it?
ReplyDeleteThe Siberian researchers did not necessarily have to replicate the virus to understand how it worked, they just took a DNA sample, analyzed it, and compared it to previous data collected about similar giant viruses. The fact that it was frozen doesn't imply that it cannot be "thawed" and collected.
DeleteExtreme cold is known to preserve even eukaryotic cells (this is a common practice by researchers via cryopreservation, especially known by humans for preserving a freshly fertilized egg: http://www.reprotech.com/embryo-storage.html) since no cell parts are actually damaged (only the structure of large tissues are i.e. by frostbite). That would make viruses easier to preserve keeping in mind their simple structure. I would also like to point out that it is not fully appropriate to say "a virus was killed" since they aren't really alive in the first place: they are just nucleotide strands bound by a protein coat or a plasma membrane, containing information for other host cells to replicate with their own machinery: the virus doesn't reproduce by itself.
Are there any properties of the virus that enabled its survival within the freezing temperatures? Or are other cells such as eukaryotic cells even able to survive in the cold? If so, have they found any old frozen eukaryotic cells that were not destroyed?
ReplyDeleteThere is no "special property" of viruses that allow them to be preserved in freezing temperatures, but their simplicity in structure and lack of complex cellular organelles and other "cellular machinery" help with their versatility in surviving long periods of inactivity. Your second question is basically answered in the comment above yours: single to few eukaryotic cells are purposely frozen for preservation and "thawed" later for use by researchers, otherwise if a whole tissue dependent on inter-cellular structures and processes is frozen with ice crystals penetrating and rupturing cell layers while withering cells away by inaction, then there may be a problem.
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