15,000 year-old viruses discovered in Tibetan glacier

Researchers at Ohio State University have discovered ancient viruses encased in 15,000-year-old ice in Tibet, many of which have never been encountered before.

The findings, which were published in the magazine Microbiome on Wednesday, could help microbiologists better understand how diseases evolve over time.

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The research required a new method of analysing the microbes, with the team in charge of the study developing an ultra-clean method to study the microbes encased in the rise without contaminating them.

“These glaciers were formed gradually, and along with dust and gases, many, many viruses were also deposited in that ice,” said Zhi-Ping Zhong, the author's lead study and a researcher for Ohio State University.  “The glaciers in western China are not well-studied, and our goal is to use this information to reflect past environments. And viruses are a part of those environments.”

The researchers analysed ice cores recovered in 2015 from the Guliya ice cap in Tibet. The ice originates from high altitudes - roughly 22,000 feet above sea level.

These ice cores traditionally contain ice that is layered year by year and traps anything present in the local environment within them when it does, similar to rock formations layering and trapping minerals over time.

These can provide a sort of time capsule as to what conditions were like at the time.

Dating the core using both traditional and newer methods, scientists found they were at least 15,000 years old.

The genetic code for 33 viruses was recovered from the ice, four of which have already been identified. Ohio State University has revealed 28 of the viruses remain unidentified.

The researchers have also speculated the ice has gone some way to help preserve the diseases as at least half appear to have survived this long not in spite of the ice, but directly as a result of being frozen.

Matthew Sullivan, co-author of the study and a professor of microbiology at Ohio State said:  “These are viruses that would have thrived in extreme environments. These viruses have signatures of genes that help them infect cells in cold environments – just surreal genetic signatures for how a virus is able to survive in extreme conditions."

Attempting to name a new virus or figure out what it is can be a daunting step. Viruses generally do not share a common gene. Some researchers compare new viruses with known viruses, while others compare gene sets.

Analysis of the microbes has revealed many of these viruses likely originated from soil or plants, not from animals or humans.

The study of glaciers, especially when it comes to microbial research, is relatively new. Only two prior examples of researchers discovering diseases encased in ice have been noted.

However, it is likely to be an important factor going forward as it allows researchers to directly study how diseases change over time, depending on environmental factors.

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Lonnie Thompson, the senior author of the study, said this research could help scientists understand how diseases respond to climate change.

"We know very little about viruses and microbes in these extreme environments, and what is actually there,” Thompson added. “The documentation and understanding of that is extremely important: How do bacteria and viruses respond to climate change? What happens when we go from an ice age to a warm period like we’re in now?”

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