Scientists studying the glacier’s ice have found viruses nearly 15,000 years old in two samples taken from the Tibetan plateau in China. Many of these viruses, which have survived because they remained frozen, are unlike any virus cataloged to date.
The findings, published in the journal Microbiome, may help scientists understand how viruses have evolved over the centuries. For this study, the scientists also created a new ultra-clean method of analyzing microbes and viruses in ice without contaminating it.
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“These glaciers were gradually formed, and along with the dust and gases, many, many viruses were also deposited on that ice,” said Zhi-Ping Zhong, lead author of the study and researcher at Ohio State University Byrd Polar and Climate Research Center which also focuses on microbiology. “The glaciers in western China are not well studied and our aim is to use this information to reflect previous environments. And viruses are part of these environments.”
The researchers analyzed ice samples taken in 2015 from the Guliya ice cap in western China. The cores are collected at high altitudes – the Guliya summit, where the ice originated, is 22,000 feet above sea level. The cores of the samples contain layers of ice that accumulate year after year, trapping whatever was in the atmosphere around them when each layer froze. These layers create a kind of timeline, which scientists have used to understand more about climate change, microbes, viruses and gases throughout history.
The researchers determined that the ice was nearly 15,000 years old using a combination of new and traditional techniques to date this ice core. When they analyzed the ice, they found genetic codes for 33 viruses. Four of these viruses have already been identified by the scientific community. But at least 28 of them are new. About half of them seemed to have survived the moment they were frozen not despite the ice, but because of it.
“These are viruses that would have thrived in extreme environments,” said Matthew Sullivan, study co-author, Ohio State professor of microbiology and director of the Ohio State Center of Microbiome Science. “These viruses have gene signatures that help them infect cells in cold environments – just surreal genetic signatures of how a virus is able to survive in extreme conditions. These signatures are not easy to extract, and the method that Zhi-Ping developed to decontaminate nuclei and study microbes and viruses in ice could help us to research these genetic sequences in other extreme icy environments – Mars, for example, the moon, or more close to home, in the Atacama Desert, on Earth.”
Viruses don’t share a common universal gene, so naming a new virus — and trying to figure out where it fits into the known virus landscape — involves several steps. To compare unidentified viruses with known viruses, scientists compare sets of genes. Sets of genes from known viruses are cataloged in scientific databases.
These database comparisons showed that four of the viruses in the Guliya polar cap cores had been previously identified and belonged to virus families that normally infect bacteria. Researchers found the viruses at much lower concentrations than those found in the oceans or in the ground.
The researchers’ analysis showed that the viruses likely originated from soil or plants, not animals or humans, based on the environment and databases of known viruses.
The study of viruses in glaciers is relatively new: only two previous studies have identified viruses in old glaciers. But it’s an area of science that is becoming more important as climate changes, said Lonnie Thompson, senior author of the study, distinguished university professor of earth science at Ohio State, and senior research fellow at the Byrd Center.
“We know very little about viruses and microbes in these extreme environments and what really exists,” Thompson said. “Documenting and understanding this is extremely important: How do bacteria and viruses respond to climate change? What happens when we move from an ice age to a warm period like we are now?”
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