Matthew Sullivan, the study’s co-author, explained:
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.
Since contamination by modern microbes is a significant problem for this type of study, the researchers developed a new process for sterilizing the ice cores. They eliminated half-centimeter (0.2-in) layers of the outer material with three different techniques – the first involved band saw scraping, then an ethanol wash, and finally, sterile water wash. Once this sterilization process was completed, the inner section of the core could then be examined contamination-free.
The team tested this sterilization method on artificial ice cores coated in DNA, viruses, and bacteria. After conducting their three-step process, no traces of these contaminants were found in the inner ice cores. Interestingly, this sterilization method could also be used to detect traces of viral genetic sequences in samples taken on Mars or the Moon.
While the idea of the melting ice freeing ancient microbes is troubling amid the pandemic, the greatest danger lies in the massive reserves of sequestered methane and carbon that it’s releasing. However, studying these ancient microbes and ice samples could shed light on the history of their evolution, past environmental changes, as well as how they handled climate change in the past – and how well they might in the future.
In February 2020, scientists at the University of Colorado at Boulder found that abrupt permafrost thawing in the Arctic could double carbon emissions, thus, speeding up climate change. However, by March 2020, scientists in Hamburg concluded that resettling massive herds of large herbivores, including reindeer, horses, and bison, could curb this effect and save up to 80% of the world’s permafrost soils until 2100.
Like a horror movie, all kinds of ancient creatures emerge from the melting permafrost as global temperatures rise.
Not all of them are lifeless. For example, microscopic 24,000-year-old multicellular invertebrates called Bdelloid rotifers, a class of rotifers entirely made up of females were able to spring back to life and reproduce in the warmth of the laboratory. These microscopic worm-like creatures are labeled an “evolutionary scandal” by biologists for having thrived for millions of years without having sex.
Now, scientists led by a team from Ohio State University have identified dozens of viruses from nearly-15,000-year-old ice samples collected from Tibetan glaciers. Remarkably, dozens of unearthed species were unknown to science, potentially providing insight into the history of viral evolution.
When it comes to preserving history, glaciers are ideal, as they trap whatever was in the atmosphere around them when each layer froze. As a result, these layers accumulate year after year, creating a sort of timeline. Scientists drill and study ice cores from these glaciers to learn more about ancient climates, climate change, the atmosphere, and the kinds of life and gases that existed at various points in history.
In the new study, published in Microbiome, ice cores were drilled from the Guliya ice cap of the Tibetan Plateau, which were dated back to 14,400 years. When the team analyzed these cores for viruses, they identified the genetic codes of thirty-three viruses. Four belonged to known types of bacteriophages, viruses that prey on bacteria. However, at least twenty-eight of them didn’t match any known type.
The team suspects that the viruses originated in plants and soil. Interestingly, these ancient viruses weren’t necessarily thwarted by the cold – instead, around 50% of them were well suited to life on the freezing ice. “These frozen viruses likely originate from soil or plants and facilitate nutrient acquisition for their hosts,” concluded the team.
