Where can ancient viruses be found?
Experts say that thousand-year-old viruses are in an eternal
Continent where there is no permafrostcompletely, - this is Australia, in Africa, its presence is possible only in the highlands. Much of today's permafrost is inherited from the last ice age and is now slowly melting. The ice content in frozen rocks varies from a few percent to 90%.
Permafrost soils are also observed underthe bottom of the oceans and seas, the determination of the permafrost-geological structure of the section and the cryogenic processes of which are a complex research task.
From 60% to 65% of the territory of Russia are permafrost areas. It is most widespread in Eastern Siberia and Transbaikalia.
The deepest limit of permafrost is observed in the upper reaches of the Vilyui River in Yakutia. The record depth of permafrost occurrence - 1370 meters - was recorded in February 1982.
How dangerous are viruses in permafrost
In the article “Re-emerging infectious diseasesfrom the past: Hysteria or real risk?” (“Resurrecting Infectious Diseases of the Past: Hysteria or Real Risk”), scientists recalled the anthrax outbreak that occurred in 2016 in Chukotka after hundred-year-old cattle burial grounds thawed.
According to the authors of the work, a revived microbe canto be even more dangerous for us, since we have never contacted him. However, people are not in danger of catching a giant virus from the permafrost, scientists say, since it affects only amoebas.
What viruses have already thawed
- Giant viruses
In 2014, two families of giant virusesfound in soil samples from permafrost obtained in the northeast of Yakutia. They are 30 thousand years old. These creatures were called pithoviruses (Pithovirus sibericum) and molliviruses.
Under a microscope, Pithovirus looks like an oval withthick walls and a hole at one end. This hole has a “plug” with a honeycomb structure. The virus reproduces by creating replication “factories” in the cytoplasm of its host, and only one-third of its proteins are similar to those of other viruses.
Scientists were also surprised that the huge particle is practically empty: in its structure, Pithovirus is 150 times less dense than any bacteriophage.
The contents of the virus are wrapped in a kind of folded envelope 60 nanometers thick, lined with lipids on the inside. To penetrate the amoeba, the pithovirus mimics the bacterium.
When he is inside the cage, in hisa hole opens in the membrane, the lipid membrane ruptures, forming a channel through which the contents of the virus are squeezed into the cytoplasm of the victim. As a result, something like a factory for replicating copies of full-fledged viruses appears in the amoeba.
Ordinary viruses have a very small, reducedto a minimum genome containing several hundred thousand base pairs. After all, they take everything they need for life and reproduction from the host organism.
The genome of the giant virus is quite large.For example, Pandoravirus has 2,770 kilobase pairs and 2,556 protein-coding genes. Moreover, the functions of 2155 of them are unknown. For comparison, ordinary viruses have no proteins at all.
Because of this, scientists at one time considered giants to be something closer to the cell. However, their main difference is undeniable: they do not have ribosomes and RNA, they do not synthesize ATP and do not multiply by division.
- 28 unknown viruses in Tibet
In addition, in ice samples 15 thousand years olddiscovered 28 viruses previously unknown to science. Scientists had to develop a special research method to exclude erroneous contamination of samples with bacteria.
Samples of one of the oldest ice was taken back in 2015 by scientists from the United States and China. To do this, they had to drill 50 meters of a glacier in Tibet.
Since the sample surface was contaminated with bacteriawhile drilling and transporting ice, the researchers examined the interior of the samples. To do this, they placed them in a cold room with a temperature of -5 degrees Celsius and used a sterile band saw to cut half a centimeter off the outer layer of the samples.
After that, the remaining ice was washed with ethanol andmelted it another 0.5 centimeters on each side. The final samples were rinsed with sterile water. Thus, scientists made sure that they were examining layers of ice that were not contaminated by other bacteria and viruses.
How millennial viruses appeared
Genome-rich giant viruses puzzled scientistsand sparked a debate about their origins. According to one hypothesis, viruses did not have a common ancestor, they descended from some protocellular forms that more than three billion years ago competed with the last universal common ancestor (LUCA), from which all living things originated. These protocells lost out to LUCA, but did not disappear from the scene, but adapted to parasitize on his descendants.
Giant viruses have survived to this day. Scientists describe more and more of their modern representatives not only in acanthamoebas, but also in other protists.
Conclusion
The threat of new viruses emerging due to melting glaciers exists, but it is not new: glaciers have been melting for centuries, so the potential danger has been present for many years.
In addition, the danger comes not only from viruses in honest permafrost: scientists have found that every year there is a 2% chance that a new pandemic will begin.
The deadliest pandemic in modern history was the Spanish Flu, which killed more than 30 million people between 1918 and 1920.
The likelihood of a recurrence of such a pandemic fluctuatesfrom 0.3% to 1.9% per year for the studied period of time. On the other hand, this means that a pandemic of this magnitude should occur within the next 400 years.
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