Scientists have discovered over 900 previously unknown species of microbes living within glaciers on the Tibetan Plateau. An analysis of the genomes of these microbes revealed that some have the potential to produce new epidemics if rapid melting caused by climate change "releases" them from their icy prison.
In a new study, researchers from the Chinese Academy of Sciences collected ice samples from 21 glaciers on the Tibetan Plateau—a high-altitude region in Asia located between the Himalayas to the south and the Taklamakan Desert to the north. The team subsequently sequenced the DNA of the microorganisms trapped in the ice, creating a massive database of microbial genomes that they termed the Tibetan Glacier Genome Catalog (TG2G).
The team identified 968 microbial species frozen within the ice—mostly bacteria but also algae, archaea, and fungi—as reported by the researchers on June 27 in the journal Nature Biotechnology. Perhaps most surprising was that about 98% of these species were completely new to science. The researchers noted that this level of microbial diversity was unexpected due to the challenges associated with living inside glaciers. The study authors wrote, "Despite harsh environmental conditions, such as low temperatures, high levels of solar radiation, periodic freeze-thaw cycles, and nutrient limitation, glacier surfaces support a diverse array of life."
Researchers seem unsure about the exact age of some of these microbes. Previous studies have shown that it is possible to revive microbes that have been trapped in ice for up to 10,000 years, according to the study. This is not the first time scientists have found an unexpected abundance of microbes living in Tibetan glaciers. In January 2020, a team analyzing ice cores from a single glacier revealed 33 different groups of viruses living inside the ice, 28 of which had never been seen before.
Scientists have indicated that the remarkable microbial diversity within glaciers, combined with increasing glacial melt due to climate change, enhances the chances of potentially dangerous microbes—most likely bacteria—escaping and causing chaos. The authors wrote that "pathogenic microbes trapped in ice could lead to local epidemics and even pandemics" if released into the environment. Evidence suggests that some newly discovered bacteria could be highly harmful to humans and other living beings. The team identified 27,000 potential virulence factors—molecules that help bacteria invade and colonize potential hosts—within the TG2G catalog. Researchers warned that around 47% of these virulence factors had never been seen before, leaving no way to determine how harmful these bacteria might be.
The researchers stated that even if these pathogenic bacteria do not survive long after escaping from their glaciers, they can still cause problems. Bacteria have a unique ability to exchange large portions of their DNA, known as mobile genetic elements (MGEs), with other bacteria. So even if the glacial bacteria die shortly after thawing, they can still transfer some of their virulence to other bacteria they encounter. The scientists wrote that this genetic interaction between glacier microbes and modern microorganisms "could be particularly dangerous."
The glaciers on the Tibetan Plateau could be hotspots for unleashing future epidemics because they feed freshwater into several waterways, including the Yangtze River, the Yellow River, and the Ganges River, which supply two of the most populated countries in the world: China and India. Epidemics can spread rapidly in densely populated areas, as the world witnessed during the COVID-19 pandemic.
However, this potential problem will not only affect Asia. There are over 20,000 glaciers on Earth covering about 10% of the Earth's landmass, and each glacier likely hosts unique microbial communities. A study in April 2021, using satellite imagery of glaciers, found that nearly every glacier showed an accelerating rate of ice loss between 2000 and 2019, increasing the risk of microbes causing epidemics anywhere on the planet. Researchers warned that "the potential health risks of these microbes need to be assessed before they escape from their icy prison."
Nonetheless, there is a bright side to this new study. The genetic records of microbial communities, such as the TG2G catalog, can serve as "toolkits" for bioprospecting—exploring natural systems to find valuable new compounds that can be used in medicine, cosmetics, and other beneficial technologies. This makes databases like TG2G extremely important, especially if the newly discovered species go extinct in the future; researchers noted that this outcome is highly probable if they cannot adapt to changes in their frozen environment.
