This discovery practically erases the line between living things and the viruses that parasitize them.
Molecular biologists from the United States have discovered many viruses that can not only multiply inside algal cells, but also manipulate their metabolism. This erases the next line between living organisms and non-living viruses, the researchers write in the scientific journal Nature Communications.
“In the past, we thought there was little in common between the genes of viruses and living cells. We have now reached the point where we can name only a small number of unique genes that are only found in cells or viruses. They turned out to be much more similar than we expected, - said one of the authors of the study, associate professor at the Polytechnic University of Virginia (USA) Frank Aylward.
In recent years, biologists have discovered many viruses that are unusually large. As a rule, their particles are orders of magnitude larger than those of most other viruses, and the genome in terms of length and degree of complexity is almost as good as the DNA of living organisms on which they parasitize.
The most interesting feature of these viruses is that such giant viruses (NCLDVs), as scientists call them, greatly blur the line between full-fledged living things and viruses.
The fact is that in the genome of the latter there are not only “instructions” on how to bypass the protection of cells and multiply inside them, but also genes that are associated with the production of various proteins that are not directly related to the reproduction of the virus. Scientists previously considered the latter feature to be characteristic exclusively for living things, but not for viruses.
Researchers led by Aylward have found another example of how the line between living organisms and viruses is blurring. They studied the genetic diversity of giant viruses that infect algae.
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Conducting viruses
To do this, scientists collected the genomes of all members of the NCLDV group that parasitize algae, compared them with each other and identified the most interesting regions that have no analogues in the genomes of other types of viruses.
The analysis showed that a significant proportion of the 500 viruses that Aylward and his colleagues studied had not only the classic set of genes needed to reproduce them, but also large segments of DNA designed to control the metabolism of algae. Moreover, in the genomes of some viruses, scientists have found almost complete chains of genes that are responsible for the breakdown of glucose or other important parts of the metabolism of living organisms.
Most interestingly, these DNA fragments did not get into viruses by accident. As the researchers found, they have existed in the genome of viruses for many millions of years. During this time, they did not become unusable due to the accumulation of mutations. This, Aylward explains, means that genes like these play an important role in the survival and spread of giant viruses.
This fact, in turn, suggests that many NCLDV representatives are able to directly control the metabolism of their victims. The virus does not just use algae as a factory for the production of new copies of itself, but takes full control of it.
“When such a virus enters a cell, we can no longer consider it as an autonomous being. The fundamental aspects of her life are changed as a result of infection. In other words, although we cannot call viruses living things, they play an important role in the balance of nutrients and the functioning of all aquatic ecosystems in the world,”concluded Aylward.