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Glacier virus provides insight into evolution's arms race between viruses and organisms

An international research team has looked at life on the surfaces of glaciers. Their work may turn out to challenge our previous understanding about the evolutionary arms race between viruses and their host organisms. The study has just been published in Nature Communications.

2020.09.03 | Rasmus Rørbæk

Cryoconite holes houses a plethora of life forms. Viruses included. (Photo: Alexandre Anesio)

Viruses are often perceived as a nightmare that haunts humans in particular. Especially during these coronavirus times, it may seem as if nature has chosen us humans as the victims having always to look over our shoulders when a new virus crops up. If life could be compared with a comic, the virus would be our archenemy in an eternal struggle between life and death. But the reality is that viruses are the most widespread biological form of life on the planet.

There are millions of different kinds of viruses in something as banal as a teaspoon of water from a lake, and where other forms of life can also be found. Of course, the vast majority are harmless to humans, and they live in various microscopic animals, plants and bacteria. On the other hand, they are anything but harmless for these hosts, because they often shanghai their involuntary host’s organism and reprogram it to produce new viruses, often destroying itself in the process.

Every day, viruses are capable of destroying vast amounts of microorganisms in nature, and this changes the flow of nutrients that would otherwise permeate food chains and energy flows globally. The scope is not yet fully known, but if it were, it would be easier to predict their role and impact in the environment, and how they 'move in' and interact with their host organisms.

An international team of researchers, with participation from the Department of Environmental Science at Aarhus University, has now sought out some of the more unusual habitats for viruses, namely the Alps, Greenland and Svalbard, to analyse and register the genome of the viruses found in cryoconite holes on the surface of glaciers and ice in these areas. The small holes in the surface contain melt water, and this provides optimal conditions for testing how the viruses develop, because they are directly comparable miniature worlds with very similar life and climate conditions for microbes and viruses across the geographical boundaries.

They have discovered that, although viruses may change very rapidly to be effective in a given area, virus types found at distances of several thousand kilometres are surprisingly similar. This gives us new insight into the DNA of our "archenemy".

 

So far. So near.

In brief, this means that viruses found in the Alps, Greenland and Svalbard are highly comparable at DNA level, and thus that their life strategies can also be compared. What’s new?

"We had expected to find micro-communities with widely different types of viruses in the different areas. But this is not the case. We discovered that there were very large similarities between the DNA in the viruses we found thousands of kilometres apart from each other. The similarities were found in the genetic sections that give the virus its ability to overcome the defence mechanisms of the host organism," explains Senior Researcher Alexandre Anesio from the Department of Environmental Science, who has participated in the study and is one of the main authors of the scientific article, which has just been published in Nature Communications.

The similarities are in the process called recombination. This is a process by which the virus can replace genes in the DNA strand with others in order to form new genetic properties, thereby allowing a virus to survive and to link to foreign organisms and infect them.

"This challenges the previous perception of viral evolution. Until now, we have believed that if you sequence viruses from two very different places on the planet, you should never find the same virus genome in both. But we have. This can mean that, in a natural environment, the gene replacements, which enable the virus to quickly adapt to new surroundings, can be compared," says Alexandre Anesio.

This discovery is no "Enigma" moment like the discovery of the German code during the Second World War. The researchers have not neutralised the virus's ability to invade and disable the genetic defences of the organisms being attacked. But the researchers themselves have been surprised to find the similarities.

 

........why?

Because it is well-known in research circles from laboratory experiments with viruses that they are capable of developing very quickly and efficiently to keep up with the developments taking place in the genetic defences of other organisms. It is like an arms race, where the virus and the host organisms each have to develop new ways of attacking and defending themselves in a struggle that is as old as life itself.

We are talking about a so-called "Red Queen" effect; terminology borrowed from Alice in Wonderland, where the Red Queen says that "it takes all the running you can do, to keep in the same place". Translated into genome research, this means that the evolution of the attack and the defence follow each other, and simultaneously develop to withstand each other.

But if the researchers have found what may resemble a mechanism in the evolutionary arms development of the virus, it may be possible to give the Mad Hatter new means to fight the Queen in the long term – to stay with Lewis Carroll's characters.

The scientific article is called "Flexible genes establish widespread bacteriophage pan-genomes in cryoconite hole ecosystems", and can be found via this link. It was published on September 2.

Contact:
Professor Alexandre Anesio,
Institute Environmental Sciences,
Email: ama@envs.au.dk
Telephone: 22568980

Department of Environmental Science