A team of scientists from the United States and China have discovered a multitude of new virus groups in 15,000-year-old Tibetan glacial ice. Their research uncovered 33 groups of virus genuses in the ice cores taken from the glacier. Of these, 28 were previously unknown to science. The paper detailing their discovery, which has not yet been peer-reviewed, has been published on the pre-print server bioRxiv.
The two ice core samples came from the Guliya ice cap on the northwestern Tibetan Plateau of China. They were collected in 1992 and 2015 from about 164 feet (50 meters) down into the glacier. At those times, no special measures were taken to avoid microbial contamination during the core drilling, handling, or transport. Since it is very easy to contaminate ice core samples with modern-day bacteria, the exterior of these ice cores became contaminated.
Since the insides were still pristine, the researchers created a new three-step decontamination protocol for ultraclean microbial and viral sampling. In a cold room at about 23 degrees Fahrenheit (minus 5 degrees Celsius), the researchers first used a sterilized band saw to cut away 0.2 inches (0.5 centimeters) from the outer layer of the ice. Ethanol was used to melt away another 0.2 inches of ice, while the next 0.2 inches were washed away with sterile water.
This gave the researchers an uncontaminated layer that they could study. The researchers then used microbiology techniques to identify microbes in the samples. The researchers wrote, “The microbes differed significantly across the two ice cores, presumably representing the very different climate conditions at the time of deposition.”
The researchers warned in their paper that climate change could free the ancient viruses into the modern world. They wrote, “At a minimum, [ice melt] could lead to the loss of microbial and viral archives that could be diagnostic and informative of past Earth climate regimes. However, in a worst-case scenario, this ice melt could release pathogens into the environment.” If this happens, they wrote, it’s best to know as much about these viruses as possible.
