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Friday, 24 January 2020

Unknown ancient viruses discovered in a Tibetan glacier


A set of unknown viruses has been discovered in a glacier in the northwest of the Tibetan plateau in China. Researchers recently dissolved samples after examining two ice cores from the site, revealing the existence of 28 groups of viruses never seen before.

Studying these mysterious viruses could provide researchers with crucial information to determine which viruses have thrived in different climates and environments over time.



" However, in the worst case scenario, this melting ice [due to climate change] could release pathogens into the environment, " wrote the researchers in the study, which has not yet been peer reviewed. . If this happens, it's best to know as much as you can about these viruses, the researchers wrote. The results of the research have been available for consultation on the bioRxiv server since January 7.

Studying ancient glacial organisms can be difficult. Indeed, it is extremely easy to contaminate samples of ice cores with current bacteria. Thus, the researchers created a new microbial and viral sampling protocol.


A new sampling protocol to avoid contamination

In this case, the two samples of ice cores, from the Guliya ice cap on the Tibetan plateau, were collected in 1992 and 2015. However, at that time, no specific measures were taken to avoid microbial contamination during drilling, handling or transporting carrots.

In other words, the outside of these ice cores was contaminated. But the interior was still pristine, the researchers wrote in the study. To access the inner part of the carrots without contaminating it, the researchers installed themselves in a cold room (at -5 degrees Celsius) and used a sterilized band saw to cut 0.5 cm of the ice from the outer layer. They then washed the ice cores with ethanol to melt another 0.5 cm of ice. Finally, they washed the next 0.5 cm with sterile water.

After this work (removal of 1.5 cm of ice), the researchers reached an uncontaminated layer which they were able to study. This method has proven to be effective even during tests in which they had coated the outer layer of the ice with other bacteria and viruses.

The experiment revealed 33 groups of viruses (or genera) in ice cores. Of these, 28 were previously unknown to science, the researchers said. " The microbes differed considerably across the two ice cores, presumably representing very different climatic conditions at the time of deposition, " the document said. It is not surprising that the glacier has kept these mysterious viruses for so long, they add.

" We are very far from sampling all the diversity of viruses on Earth, " says Chantal Abergel to Vice , researcher in environmental virology at the National Center for Scientific Research, who did not participate in the study.



Since human-induced climate change is melting glaciers around the world, these viral archives could be lost, the researchers noted. The study of ancient viruses “offers a first window on viral genomes and their ecology linked to glaciers. It also highlights their likely impact on today's abundant microbial groups, ”the researchers wrote.


Bibliography:

Glacier ice archives fifteen-thousand-year-old viruses

Zhi-Ping Zhong, Natalie E. Solonenko, Yueh-Fen Li, Maria C. Gazitúa, Simon Roux, Mary E. Davis, James L. Van Etten, Ellen Mosley-Thompson, Virginia I. Rich, Matthew B. Sullivan, Lonnie G. Thompson

doi: https://doi.org/10.1101/2020.01.03.894675

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