Viral genomes from glaciers reveal Earth’s climate history

As humans alter the planet’s climate and ecosystems, scientists study Earth’s history to predict what climate change may bring. To this end, massive ice structures such as glaciers serve as Nature's freezersArchiving detailed records of past climates and ecosystems – including viruses.

We are a team of Microbiologists And Paleoclimatologists who study ancient microorganisms, including viruses preserved in glacier ice. Together with our colleagues Lonnie Thompson, and Virginia Rich and other researchers at Ice Core Palaeoclimatology Group At Ohio State University, we study interactions between viruses and their environment that are observed in ice cores from the Guliya Glacier on the Tibetan Plateau.

By linking the genomes of ancient virus communities to specific climate conditions preserved in glacier ice, our newly published research provides insights into how these Viruses have adapted to the changes on Earth climate in the last 41,000 years.

The ice cores that preserve the history of the Earth are themselves disappearing.

Read the story of viral genes

We primarily Metagenomes used – genome collections that capture the entire genetic content of all microorganisms present in environmental samples – to reconstruct viral genomes from nine different time intervals within the Guliya ice core. These time horizons span three major cold-warm cycles and provide a unique opportunity to observe how viral communities have changed in response to different climatic conditions.

Through our analyses we were able to identify the genomes of Equivalent of 1,705 virus speciesThis has resulted in a more than fifty-fold increase in the number of known ancient viruses preserved in glaciers.

Only about a quarter of the virus species we found shared species-level similarities with all viruses identified in nearly 1,000 metagenomes previously collected in global datasets. Most of these overlapping species were also from the Tibetan Plateau. This suggests that at least some of the viruses preserved in Guliya Glacier originated from the region, but also speaks to the relative paucity of glacier viruses in available databases.

Using these new reference genomes, we tried to “read” their stories.

One of the most important results was viral communities varied clearly between cold and warm climate periods. The most distinct community of viral species on the glacier emerged about 11,500 years ago, coinciding with the major transition from the last ice age to the Holocene. This suggests that the unique climate conditions during cold and warm periods strongly influenced the composition of viral communities. We suspect that these influences are likely due to viruses being blown in from other locations by changing wind patterns and being subjected to selection pressure from the changing temperatures on the glacier.

Next, we investigated how viruses interact with their hosts. We used computer models to compare viral genomes with the genomes of other microbes that also exist in that environment. We found that viruses constantly infected Flavobacteriaa lineage of bacteria commonly found in glacial environments.

We also learned that viruses on the Guliya Glacier must “steal” genes from their hosts to manipulate their metabolism. The following genes are encoded in the viral genomes: 50 auxiliary metabolism genes related to metabolism, including the synthesis and degradation of vitamins, amino acids and carbohydrates. Some of these genes were abundant in all nine time intervals studied, suggesting that they help microbial hosts cope with the harsh conditions on glacier surfaces and thereby enhance viral fitness.

Viruses not only infect and kill cells, but probably also alter the fitness of their hosts during infection, thereby influencing their ability to survive under the extreme conditions of a glacial environment.

Climate change over time

Our findings provide a new perspective on how life in the form of viruses has responded to climate change over tens of thousands of years.

Understanding these ancient interactions provides a unique opportunity for future research in both virology and climate science. By studying the response of ancient viruses to past climate changes, researchers can gain valuable insights into how viruses adapt to ongoing global climate change.

We believe that glacial ice, because it contains information about microorganisms and their ecosystems over time in each layer, continues to be an important resource for studying Earth’s climate history and the life that made it possible – especially as glacial ice reserves lose weight quickly.

Zhi-Ping Zhong is a research associate at the Polar and Climate Research Center at Ohio State University. Ellen Mosley-Thompson is a professor of geography at Ohio State University. Lonnie Thompson is a Distinguished University Professor of Earth Sciences at Ohio State University. Matthew Sullivan is a professor of microbiology at Ohio State University. Virginia Rich is an associate professor of microbiology at Ohio State University. This article was republished from The conversation under a Creative Commons LicenseRead the Original article.