Are they threats? Possibly, researchers say.
While the consequences of the rapid melting of glaciers worldwide are manifold, such as rising sea levels and habitat loss, some have pondered, If things trapped inside the ice could be unleashed into the environment?
In the northwestern Tibetan Plateau, Chinese and American researchers from Lawrence Berkeley National Laboratory and Ohio State University obtained 154-foot deep ice samples from the core of a 15,000-year-old glacier. By getting samples from the glacier core, any possibilities of contamination from outer sources can be eliminated.
Foreign and Ancient Viruses
Back in their laboratories, they employed “ultra-clean microbial and viral sampling procedures” to decontaminate the ice samples, they say. The scientists then used advanced metagenomics techniques to look for any genetic sequences of microbial origin in the ice samples.
Their results were made known to the world in 2020 as a preprint not peer-reviewed yet. They discovered 33 groups of viruses trapped inside the ancient glacier. Only 5 groups can be classified into existing virus families known as Siphoviridae and Myoviridae. The remaining 28 groups were alien to modern science. They don’t even know what to name them yet, identifying them by codes at the moment.
They Could’ve Have Been Replicating
Out of the novel 28 groups of viruses, three groups were highly abundant — suggesting that either a huge number of virus particles were deposited in the first place or that they may have been actively replicating.
They also found several psychrophilic (i.e. capable of surviving under low temperatures) bacteria commonly present in glacier ice — such as Methylobacterium, Janthinobacterium, and Herminiimona species — thus strengthening the validity of their techniques and results.
What’s more interesting is that — by using bioinformatics prediction techniques — they successfully modeled that these bacterial groups are suitable hosts for half of the alien viruses they identified.
Viruses are not considered as living organisms as they can’t replicate on their own. That’s why viruses hijack on the host’s reproductive machinery to make more copies of themselves. The presence of compatible bacterial hosts highly suggests that the newly identified viruses were replicating inside the glacier.
Are They Dangerous?
“Glaciers around the world are rapidly shrinking…,” the study authors wrote. “And this will release glacial microbes and viruses that have been trapped and preserved for tens to hundreds of thousands of years.”
But scientists still don’t know whether the glacial viruses pose any threat to humans or other animals.
“At a minimum, this could lead to the loss of microbial and viral archives that could be diagnostic and informative of past Earth climate regimes,” they say. Put it simply, they meant that evolutionary data — indicative of ancient climate — could be lost should the glaciers keep melting.
“However, in a worst-case scenario, this ice melt could release pathogens into the environment,” they wrote.
Are they dangerous? “Maybe,” answers Jean-Michel Claverie, Professor of Genomics and Bioinformatics at Aix-Marseille University in France, who was unaffiliated with the Tibetan glacier study. “There also could be viruses that caused animal — or human — extinctions in the past, and that modern medicine are not aware of.”
Prof. Claverie’s research team had previously published a paper showing that a 30,000-year-old virus — named Pithovirus sibericum — isolated from the Siberian permafrost can revive and infect amoebas in the lab but, fortunately, not animals or humans.
As mentioned, viruses are not considered as being alive. By definition, therefore, they cannot die from ageing alone.
The Unleased Anthrax
In the Siberian tundra in 2016, an anthrax — a rare but lethal bacterial infection — outbreak occurred. It killed 23,00 reindeer and a 12-year-old boy and infected 8 people.
Thorough investigations led to the conclusion that melted permafrost from a heatwave had released an ancient anthrax bacteria from a reindeer carcass into nearby water and food supply. This is possible as anthrax forms protective spores that can withstand harsh environmental conditions. And indeed, the same outbreak happened before in 1941.
Current Views
“Following our work and that of others, there is now a non-zero probability that pathogenic microbes could be revived, and infect us,” comments Prof. Claverie. “How likely that is is not known, but it’s a possibility.” The professor further says that “if the pathogen hasn’t been in contact with humans for a long time, then our immune system would not be prepared.”
But the American oceanographer and head of the Environmental Biophysics and Molecular Ecology Laboratory at Rutgers University, Prof. Paul Falkowski assures that most viruses are harmless to humans. “Viruses are everywhere — in soils, in ice, on money,” he remarks.
Though Prof. Falkowski admits that exceptions like the anthrax bacteria exist, “the risk is very low,” he says. Not to mention that most pathogenic microbes are transmitted via body fluids, direct contact or air droplets. “There is virtually no danger of long-range transmission,” the professor concludes.
Still, anything that can go wrong will go wrong — Murphy’s law.
“Warming plus more people in previously uninhabited arctic regions are the recipe for disaster — in theory,” Prof. Calverie asserts. “However, nobody knows how to estimate the probability of this to happen.”
This article was originally published in Microbial Instincts with minor modifications.