Postdoc Laura Perini from Aarhus University‘s Department of Environmental Science and her colleagues have discovered giant viruses living on the ice beside the algae.
According to her suspicions, the viruses serve as natural regulators of algal blooms by feeding on snow algae.
This newly discovered virus is bigger than bacteria. Typically, viruses are substantially smaller than bacteria. A normal bacteria is 2-3 micrometers, while regular viruses range in size from 20 to 200 nanometers. Otherwise, a typical virus is around 1000 times smaller than a bacterium.
However, that is different with large viruses. Giant viruses can enlarge to 2.5 micrometers in size. That surpasses the majority of bacteria.
However, giant viruses are not just larger. They have a far larger genome than other viruses. Bacteriophages, viruses that infect bacteria, have genomes containing anywhere from 100,000 to 200,000 letters. There are about 2.4 million giant viruses.
Laura said, “We don’t know a lot about the viruses, but I think they could be useful to alleviate ice melting caused by algal blooms. We do not know how specific they are and how efficient they would be. But by exploring them further, we hope to answer some of those questions.”
The first giant viruses were detected in the ocean in 1981. These viruses had become experts in infecting marine green algae. Giant viruses were later discovered in human tissue and terrestrial soil.
However, this is the first time giant viruses have been shown to reside in snow and ice, mostly made up of microalgae.
Scientists examined samples from melting holes (cryoconite), crimson snow, and dark ice. They detected signs of active giant viruses in the crimson snow and dark ice. Additionally, this is the first time they have been discovered on snow and surface ice with a significant concentration of colored microalgae.
Laura said, “A few years ago, everyone thought this part of the world to be barren and devoid of life. But today, we know that several microorganisms live there—including giant viruses.”
“There’s a whole ecosystem surrounding the algae. Besides bacteria, filamentous fungi, and yeasts, there are protists eating the algae, different fungi parasitizing them, and the giant viruses we found infecting them.”
“In order to understand the biological controls acting on the algal blooms, we need to study these last three groups.”
Despite their enormous size, the viruses are invisible to the unaided eye. Laura Perini has yet to use a light microscope to view them, but she intends to do so later.
Scientists discovered them by analyzing the DNA of the samples. They found sequences that are highly similar to known giant viruses by sifting through this huge dataset, looking for specific marker genes.
They also extracted the mRNA from the sample to confirm that the viral DNA originated from live, active viruses rather than long-dead bacteria.
When genes are activated, the DNA sequences that makeup them are translated into single-stranded units known as mRNA. These fragments serve as building blocks for the proteins required by the virus. If they are detected, the virus is living.
Laura said, “We discovered the same markers in the whole DNA and total mRNA sequences from the samples, indicating transcription. It indicates that there are living, functioning viruses on the ice.”
“Which hosts the giant viruses infect, we can’t link exactly. Some may infect protists, while others attack the snow algae. We simply can’t be sure yet.”
She’s working hard on discovering more about the giant viruses and has more research coming out soon.
Journal Reference:
- Laura Perini, Katie Sipes, Athanasios Zervas, Christopher Bellas, Stefanie Lutz, Mohammad Moniruzzaman, Rey Mourot, Liane G. Benning, Martyn Tranter, Alexandre M. Anesio. Giant viral signatures on the Greenland ice sheet. Microbiome, 2024; 12 (1) DOI: 10.1186/s40168-024-01796-y