Biologists from the Ohio State University analyzed two cores that were taken from the Giulia Glacier in western China in 2015. The age of the ice is estimated at 15 thousand years. It revealed the genetic codes of 33 viruses, four of which were already known, and 28 — completely new, unlike modern ones.
Glaciers preserve a lot of information about the history of the Earth, because they capture dust particles, traces of gas, microbes and plant matter from the environment. From the cores taken during the drilling of glaciers, it is possible to obtain data on the ancient climate, the composition of the atmosphere and what biological species existed at various points in history.
“These glaciers formed gradually, and along with dust and gases, many viruses were deposited in the ice,” the lead author of the article Zhi-Ping Zhong, a microbiologist from the Center for Polar and Climate Research and the Center for Microbiome Studies at Ohio State University, is quoted in a press release. – Glaciers in western China are poorly studied, and our goal is to use this information to reflect the environment of the past. And viruses are part of this environment.”
According to the researchers, at least half of the detected viruses returned to life after the ice melted. This is very important information, since every year the glaciers of Tibet decrease in size and as they melt, ancient viruses come to the surface.
“These are viruses that can thrive in extreme conditions,” explains another study participant, Dr. Matthew Sullivan, professor of microbiology at Ohio State University and director of the Center for the Study of the Microbiome. — They have gene signatures that help them infect cells in very cold conditions.”
To decipher these signatures, scientists have developed a new ultra-pure method of ice sterilization, which allows avoiding contamination of the sample with modern microbes (this is a serious problem for such studies).
“Perhaps this method will help us find genetic sequences in other extreme ice environments, for example, on Mars, the Moon, or closer to us — in the Atacama Desert,” says Sullivan.
Viruses do not have a common universal gene, so their identification and naming takes place in several stages. To do this, they compare the sets of genes of new viruses and known ones that have already been entered into databases.
The analysis showed that only four viruses from the Giulia ice cap had previously been encountered by scientists. They belong to bacteriophages-viruses that infect bacteria. According to the researchers, they most likely originated in the soil or plants, and not in animals or people.
The authors hope that their discovery will help to trace the history of the evolution of viruses and better understand what changes occurred in the environment in the past.