15,000-Year-Old Viruses Were Pulled From a Tibetan Glacier Leave a comment

A team of microbiologists studying glacier ice in Tibet found 33 different viruses dating back to the Pleistocene in the core samples they pulled up. They suspect that the viral communities may have been active on glacier surfaces before being frozen and that some may be active even within the ice cores.

The viruses found in the ice cap, called Guliya, are thought to have infected the microbes that inhabited the same ice. The team is not sure when those infections occurred, though—whether the viruses were most active before the ice cap formed or only thrived once it did. Their complete analysis of the viruses’ ecology was recently published in the journal Microbiome.

Based on the genetics of the various viruses, the team was able to attribute different bacterial hosts to some of them. The team notes that climate change means those pathogens are melting out of their stasis in the glaciers, which could be a problem in multiple ways. “Such melting will not only lead to the loss of those ancient, archived microbes and viruses but also release them to the environments in the future,” according to the new paper.

The team’s cores were wrapped in plastic and put into cardboard sheathes encased in aluminum. They were then shipped out of the ice cap in freezers on a truck, then a plane, then another plane, and then a truck again, and are now stored at the Byrd Polar and Climate Research Center at The Ohio State University at a cool -30 degrees Celsius (-22 degrees Fahrenheit). Those cores—and the viruses inside them—are likely of no threat to us. “The way we work with these cores, [the viruses] are immediately ‘killed’ by the chemistry of nucleic acids extraction, so the viruses are not active,” said co-author Matthew Sullivan, a microbiologist at Ohio State and director of the university’s Center of Microbiome Science, in an email.

Of the 33 viruses identified in the ice, 28 were novel, meaning they had not previously been documented by science. The frozen viruses came from families that typically infect bacteria. The team identified the viral elements after decontaminating the ice in a multi-step process: After scraping off the ice cores’ surfaces in a lab environment with a sterilized saw, they washed the cores in ethanol and water and bathed them in ultraviolet light. Then, the core samples were filtered, concentrated, and sampled for genetic material. Detected genetic material was then compared to virus gene sets in a widely used database.

About half of the viruses had genetic signatures that indicated they were built for ice ages. “These are viruses that would have thrived in extreme environments,” Sullivan said in a press release. “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.”

“These glaciers were formed gradually, and along with dust and gases, many, many viruses were also deposited in that ice,” said Zhi-Ping Zhong, lead author of the study and a researcher at The Ohio State University Byrd Polar and Climate Research Center, in the same release. “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.”

On the one hand, there’s a non-zero chance that melting glacier ice will release active viruses not seen since the Pleistocene into the world. On the other hand, as reported by Vice, frozen biomasses are often in such small quantities that it’s the outside world that presents a threat to them, not the other way around.

Based on the amount of genetic evidence the team found in the cores, the researchers suggest that the resident viruses could still be active in the glacier. It’s also possible that so much viral material ended up in the ice that enough was available for extraction and sequencing thousands of years later.

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