Every spring in the Arctic, life returns as the sun rises after months of darkness. Polar bears emerge from their winter dens, arctic terns return from their long migration south, and musk oxen migrate further north. However, along with the animals reawakening in the spring sun, dormant algae on the ice also start blooming, darkening large areas of the ice. This algae growth reduces the ice’s ability to reflect the sun, accelerating the melting process and contributing to global warming. Researchers, including postdoc Laura Perini from Aarhus University, have discovered giant viruses living alongside the algae on the ice, which might serve as a natural control mechanism for algae blooms and help reduce ice melting.
Giant viruses are much larger than regular viruses, growing up to 2.5 micrometers in size, which is larger than most bacteria. Their genomes are also much bigger, with around 2,500,000 letters compared to the 100,000-200,000 in regular viruses. Giant viruses were first discovered in 1981 in the ocean, where they specialized in infecting green algae, and have since been found in various environments such as soil, land, and even humans. However, it is the first time that giant viruses have been found on the surface ice and snow dominated by microalgae, indicating a previously unknown ecosystem thriving in these harsh conditions.
Researchers analyzed samples from dark ice, red snow, and melting holes and found active giant viruses in both dark ice and red snow. These viruses were infecting the microalgae, showcasing a diverse ecosystem on the ice surface, including bacteria, fungi, yeasts, protists, and the giant viruses. Despite their size, these viruses are not visible to the naked eye and have not been observed even with a light microscope. However, genetic analyses have revealed the presence of giant viruses actively infecting the microalgae, which indicate their role in the ecosystem and potentially in controlling algal blooms.
Giant viruses contain DNA at their core, which includes genetic information needed to create proteins that carry out various functions within the virus. Unlike regular viruses that rely on the host cell for transcription, giant viruses can transcribe the DNA into mRNA themselves, indicating their ability for self-sufficiency. This unique trait allows them to actively replicate, repair, and translate DNA within their own structure. While the exact hosts infected by the giant viruses are not known, ongoing research aims to uncover more about these mysterious viruses and their interactions within the Arctic ecosystem.
Laura Perini and her team are continuing their research on giant viruses to learn more about their role in the ecosystem and their interactions with the microorganisms on the ice surface. Further studies aim to understand the specific hosts infected by the giant viruses, whether they target protists or the snow algae themselves. Perini’s upcoming research will focus on revealing more information about giant viruses infecting cultivated microalgae thriving on the surface ice of the Greenland Ice Sheet, shedding light on the dynamics between viruses and microorganisms in these extreme environments.
In conclusion, the discovery of giant viruses living on the ice in the Arctic alongside microalgae opens up new possibilities for understanding the complex relationships within these ecosystems. By studying these giant viruses, researchers hope to uncover their potential as natural controls for algae blooms and their effects on ice melting rates. As these viruses continue to be a relatively new area of research, ongoing studies aim to reveal more about their genetic makeup, interactions with other organisms, and their impact on the delicate balance of life in the Arctic environment.