Glacier viruses in the Arctic and the Alps very similar | Polarjournal
The viruses found in the small meltwater pools on glaciers, so-called cryoconit holes, in Greenland, in Spitsbergen and in the Alps, have remarkably similar genomes. Photo: Christopher Bellas

An international team of scientists studied life in small meltwater pools on glaciers in Greenland, Spitsbergen and the Alps. In their study, published earlier this month in the journal Nature Communications, the researchers question the assumptions about virus evolution: They showed that the genomes of viruses between these isolated regions are surprisingly stable in the environment, contrary to expectations.

The results of the study, which was led by Christopher Bellas from the Institute for Ecology at the University of Innsbruck, are indeed remarkable. Until now, scientists assumed that viruses continuously mutate in order to stay one step ahead of their hosts’ defense mechanisms. As a result, Bellas and his team expected the viruses studied from the distant cryoconite holes – the meltwater pools – in the Arctic and the Alps would show large differences in the genome. Instead, they discovered an astonishing similarity between the bacteriophages studied, i.e. viruses that infect bacteria. “90 to 95 percent of their approximately 50,000 base pairs of long DNA were identical”, Bellas told the APAnews agency.

Cryoconite is the term used to describe the dark dust deposits on glaciers caused by forest fires or other emissions. The dark color accelerates the melting of the underlying ice or snow, creating small holes on the glacier surface, the cryoconite holes. Each of these cryoconite holes contains millions to billions of viruses. Photo: Joseph Dsilva/Flickr

The glaciers of the Arctic and the Alps are dotted with such cryoconite holes and in each of them are millions to billions of viruses, as in every other water body on earth. Where there is life, there are also viruses. Most of them are completely harmless to humans. They infect microscopic animals, plants and bacteria, which they reprogram to produce new virus particles, usually destroying their cells. Viruses therefore also play a crucial role in the global carbon and nutrient cycles – every day viruses destroy a huge number of microorganisms in the environment that are responsible for the flow of energy in the food webs. “Understanding how viruses evolve and function allows us to predict their role in the environment and how they interact with their hosts”, says Bellas.
These small meltwater pools on glaciers are ideal places to test how viruses develop, as they are tiny, replicated communities of microbes found on widely dispersed glaciers around the world.

A genetic fruit machine
The researchers initially assumed that the investigated bacteriophages are only distantly related to each other. In fact, they found that most of these viruses were almost identical between the Arctic and the Alps. However, when they took a closer look at their stable genomes, they discovered that there were many small sections in each genome in which the genomes of other, related viruses were repeatedly inserted and removed – a process called recombination.

Transmission electron microscope image of a Synechococcusphage from seawater – a virus that infects Synechococcusbacteria. Photo: Hans-Wolfgang Ackermann, The Third Age of Phage. Man NH, PLoS Biology Vol. 3/5/2005

At all three study sites, the viruses simply shuffled the existing genes like a kind of genetic fruit machine. “This means that in the natural environment, gene swapping between viruses by recombination creates much diversity in the virus population, specifically in genes which are involved in recognising and attaching to different hosts, this probably gives viruses the potential to quickly adapt to different hosts in the environment,” explains Bellas. By contrast, mutations are permanent changes in genetic information.

In addition to the almost identical viruses, the Arctic and the Alps also have other common inhabitants. For example, Mountain Sorrel (Oxyria digyna), Moss Campion (Silene acaulis) and White Dryas (Dryas octopetala) grow in Greenland and Spitsbergen as well as in the Alps. Rock ptarmigan (Lagopus muta) can also be found in the Arctic and in the Alps above the tree line.
With the melting of the ice after the last ice age, cold-loving plants and animals spread over a large area of the northern hemisphere. With further warming, however, they could only survive in alpine habitats or in the far north of the Arctic.

Julia Hager, PolarJournal

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