Glaciers have long served as nature’s deep freezers, preserving the physical features of past climates and the genetic blueprints of ancient life, including viruses. As the planet’s climate continues to change, scientists are increasingly turning to these frozen archives to understand how pathogens have historically responded to environmental changes. By studying viral genomes extracted from glacial ice, Ohio State University researchers have uncovered how these ancient viruses have adapted to Earth’s changing climate over the past 41,000 years.
Insights into Ancient Viral Societies
The team, comprised of microbiologists and paleoclimatologists such as Lonnie Thompson, Virginia Rich, Matthew Sullivan, and Ellen Mosley-Thompson, focused their efforts on the Guliya Glacier on the Tibetan Plateau. This glacier is an invaluable resource, containing layers of ice that have captured genetic material from viruses from different periods in Earth’s history. The researchers drilled through the glacier, collecting ice cores that represent nine distinct time periods spanning more than 41,000 years. As outlined in a study published by The Conversation, by analyzing the viral genomes in these samples, they were able to track the evolution and adaptation of viral communities over three major cold-to-warm cycles.
Their analysis led to the recovery of 1,705 viral genomes, a discovery that significantly expands the known catalog of ancient viruses preserved in glaciers. Interestingly, only about a quarter of these viral species share any similarity to viruses previously identified in global metagenomic data sets. This suggests that many of the viruses found in the Guliya glacier may have originated locally, underscoring the exceptional viral biodiversity in this region.
Virus Evolution and Climate Change
One of the key findings of the study was the significant variability in viral communities between cold and warm climate periods. For example, the viral community from about 11,500 years ago, which coincides with the transition from the last glacial stage to the Holocene, was found to be different from communities from other periods. This suggests that climate change played a key role in shaping viral communities. Changes in wind patterns, temperature fluctuations, and other environmental factors likely influenced which viruses were preserved and how they evolved over time.
To delve deeper into these interactions, the researchers used computer models to compare the virus genomes with those of other microbes present in the same environment. They found that many of these ancient viruses often infected Flavobacterium, a genus of bacteria common in glacial environments. The study also found that the viruses carried accessory metabolic genes that they likely stole from their bacterial hosts. These genes, associated with essential metabolic functions such as synthesizing and breaking down vitamins and amino acids, may have helped the viruses survive the extreme conditions of the glacier, boosting the fitness of their hosts.
Implications for Understanding Climate Change
This research offers a unique perspective on how life has responded to climate change over tens of thousands of years. By studying these ancient viral communities, scientists gain valuable insights into how viruses may continue to evolve in response to ongoing global climate change. The findings also underscore the importance of glaciers as repositories of Earth’s climatic and biological history.
As glaciers melt due to modern climate change, the genetic material they preserve is at risk of being lost. It is all the more urgent to study these ancient records while they are still available. The work by Thompson, Rich, Sullivan, and Mosley-Thompson of Ohio State University underscores the critical role glaciers play in revealing the long-term interactions between climate and life on Earth.
Understanding how ancient viruses adapted to past climates can help inform future virological and climatological studies by shedding new light on potential challenges and changes that may arise as Earth’s climate evolves.
