Virus adaptations to extreme weather conditions provide insights into climate change

Ancient viruses preserved in glacial ice hold valuable information about changes in Earth’s climate, a new study suggests.

For decades, the Guliya Glacier, located more than 6,000 meters above sea level in the far northwest of the Tibetan Plateau, has been one of the richest archives available to scientists to study large-scale paleoclimate changes. Now, by analyzing ice core samples recovered from the glacier, microbiologists have reconstructed fragments of viral DNA that remained there and identified nearly 1,700 viral species, about three-quarters of which are newly discovered.

Drilling into prehistoric ice has no implications for the health of modern humans, as these long-dormant viruses likely infected other dominant microbes rather than animals or humans, but the researchers found that their adaptations significantly influenced their hosts’ ability to survive extreme conditions during Earth’s changing climate cycles.

“Prior to this work, the links between viruses and large-scale climate change on Earth had not been studied,” said ZhiPing Zhong, lead author of the study and a research associate at the Byrd Polar and Climate Research Center at Ohio State University. “Glacier ice is so precious, and we often don’t have the large amounts of material needed for virus and microbe research.”

As unprecedented global warming continues to accelerate glacier melt, the race to collect these ice cores before they disappear forever has only increased their scientific value. For example, the ice sheets examined by the researchers in this paper provided precise snapshots of how viruses behaved during three periods of cold to warm weather over the past 41,000 years.

The study was published today in Geosciences of nature.

Among the different types of new viruses reported, the most distinct viral community observed by the team dates back to about 11,500 years ago, a time when a major climate transition occurred from the cold of the last glacial stage to the warm Holocene.

This suggests that microorganisms are responding to climate change as global temperatures shift from cold to warm, but it’s too early to say for sure, Zhong said. “This at least indicates the potential link between viruses and climate change,” he said.

Using advanced sequencing technologies to look more closely at their genetic signatures, the team’s results also showed that while most of the viruses discovered in the glacier were specific to Guliya, about a quarter of them overlapped with organisms known from other parts of the world. “This means that some of them were potentially transported from regions like the Middle East or even the Arctic,” Zhong said.

The researchers believe that taking the time to better understand how viruses evolved during periods of intense climate change can provide insight into how modern viruses are likely to respond and adapt to future warming ecosystems. And because the organisms found in ice cores expand the diversity of information researchers can gather about these periods, the discovery and sequencing of new swaths of ancient viral DNA could lead to an explosion of new mysteries and new conclusions.

“To me, this science is a new tool that can answer fundamental climate questions that we wouldn’t have been able to answer otherwise,” said Lonnie Thompson, study co-author and professor of earth sciences at Ohio State.

Improving these techniques on Earth will likely provide scientists with new tools to expand the search for life in space environments, aiding efforts to find microbes in the ice fields of Mars or beneath the icy shells of other planetary bodies, Thompson said.

Researchers seeking to make new connections between viruses and climate here on Earth could also benefit from future technological advances and diverse scientific approaches to research, the study notes. Yet, the authors say, time is running out: These techniques must be implemented before warming compromises the glacial ice needed to preserve and further explore Earth’s rich history.

“I’m optimistic about what can be done here, because if we work together, these techniques have great potential to help us begin to tackle a broad range of scientific questions,” Thompson said.

Matthew Sullivan, a study co-author and professor of microbiology and civil, environmental and geodetic engineering at Ohio State, said the study’s success can be attributed to how the interdisciplinary approach taken by Ohio State’s Byrd Polar and Climate Research Center and Center of Microbiome Science helped incubate new science.

“This kind of opportunity represents the coming together of multiple disciplines, each with their own scientific language, which is a barrier to progress,” he said. “But being able to study ancient viruses and microbes in ice with this team is a testament to the support we’ve had to explore new interfaces.”

Other co-authors include Ellen Mosley-Thompson, Olivier Zablocki, Yueh-Fen Li and Virginia Rich of Ohio State, and James Van Etten of the University of Nebraska.