Hidden in the snow and frost of the Greenland ice sheet, mysterious giant viruses have been discovered. They share the ice with an abundance of algae, meaning this is the first time these viruses – about which we know relatively little – have been found in such a habitat. But it’s not all bad news (unless you’re algae): it’s thought that by infecting microalgae, giant viruses can act as a kind of secret weapon to minimize melting.
How giant are we talking? Viruses cannot be seen with the naked eye, but next to your average viruses (which measure 20-200 nanometers) they are relatively massive. Giant viruses can grow up to 2.5 micrometers – that’s 2,500 nanometers – making them up to 125 times larger than normal viruses and larger than most bacteria. They also have humongous genomes, containing about 2.5 million base pairs.
Previously, giant viruses have been found to reside in all kinds of environments, including the sea, land, and even humans. However, this latest discovery marks the first time they have been found in surface ice and snow that is filled with microalgae.
Here, the team behind the discovery believes, they may have an important role to play in regulating algal blooms and thus protecting the ice from accelerated melting.
When arctic algae bloom in the spring, they darken large parts of the ice sheet, limiting its ability to reflect sunlight, increasing melting. That’s bad news for the environment, which is why the newly discovered giant viruses would be such a boon to protecting the ice if they can act as a natural control of algae as the researchers suspect.
“We don’t know much about viruses, but I think they could be useful as a way to ease the melting of ice caused by algal blooms,” first author Laura Perini of the University’s Department of Environmental Science said in a statement. Aarhus. “How specific they are and how efficient it would be, we don’t know yet. But by exploring them further, we hope to answer some of these questions.”
The team collected samples from a variety of snow and ice habitats in the Greenland ice sheet, including dark ice, ice cores, red and green snow and melt holes (cryoconite), before analyzing them for DNA -in and to search for specific marker genes of the giant virus. . In almost all samples, they found sequences that matched known giant viruses.
This isn’t dirty water, it’s actually a sample full of microorganisms, including algae and giant viruses.
Image: Laura Perini
To make sure these had come from active viruses and not long-dead microbes, the researchers also extracted messenger RNA, or mRNA—a single-stranded molecule that contains the instructions from DNA that direct cells to created a protein – from the samples.
“In the total RNAi sequenced from the samples, we found the same markers as in the total DNA, so we know they are transcribed,” explained Perini. “That means the viruses are alive and active in the ice.”
Your standard bog viruses are not capable of transcribing double-stranded DNA into single-stranded mRNA. Instead, they have free-floating RNA strands in their cells that are activated when the virus infects its host and uses its machinery. But giant viruses are different. They are able to repair, reproduce, transcribe and translate DNA without the help of a host – although we are not sure why this is.
When it comes to giant viruses, there are many more unknowns. What do these mysterious microbes infect, for example?
“Some of them may be infecting protists, while others attack snow algae. We just can’t be sure yet,” added Perini.
But with further research, she hopes, we can better understand these pathogens and their potential role in protecting the ice from algae-accelerated melting.
The study is published in the journal Microbiome.
