Ancient Viruses Found in Melting Tibetan Glaciers
As though from a horror film, ancient species are emerging from the now-melting permafrost’s cold storage: from superbly preserved extinct megafauna such as the woolly rhino, to the 40,000-year-old remains of a big wolf, and microorganisms dating back 750,000 years.
Not all of them are no longer alive. Centuries-old moss was resurrected in the laboratory’s warmth. Similarly, small 42,000-year-old roundworms were discovered.
These enthralling views of species from Earth’s distant past are shedding light on the history of ancient ecosystems, including specifics about their surroundings. However, the thaw has raised concerns about old pathogens resurfacing.
“Melting will not only lead to the loss of those ancient, archived microbes and viruses, but also release them to the environments in the future,” researchers wrote in a new study conducted by Ohio State University microbiologist Zhi-Ping Zhong.
The researchers are aiming to gain a better knowledge of what exactly exists within the cold using new metagenomics tools and new methods for sterilizing their ice core samples.
The new research identified an archive of dozens of unique 15,000-year-old viruses from the Tibetan Plateau’s Guliya ice cap and gained insight into their functions.
“These glaciers were formed gradually, and along with dust and gases, many, many viruses were also deposited in that ice,” Zhong explained. The team adds in their research that these bacteria may represent those prevalent in the atmosphere at the time of their deposit.
Microbial communities have been proven to correlate with variations in dust and ion concentrations in the atmosphere and can also provide information about the climate and environmental conditions at the time.
The researchers revealed that 28 of the 33 viruses they identified had never been observed previously in these ancient frozen records located 6.7 kilometers (22,000 feet) above sea level in China.
“These are viruses that would have thrived in extreme environments,” said scientist Matthew Sullivan of Ohio State University. “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.”
By comparing their genetic sequences to a database of known viruses, the researchers discovered that the most prevalent viruses in both ice core samples were bacteriophages that infect Methylobacterium – a type of bacteria critical for the methane cycle within ice.
They were most closely linked to viruses identified in Methylobacterium strains found in plant and soil habitats, which corroborated a prior research that the primary source of dust deposited on the Guliya ice cap is likely soils.
“These frozen viruses likely originate from soil or plants and facilitate nutrient acquisition for their hosts,” the study found.
While the threat of ancient viruses is particularly concerning in the midst of a pandemic, the greater danger comes from what the melting glacier is unleashing — vast reserves of trapped methane and carbon. However, it is evident that the ice may potentially include information about past environmental changes and the evolution of viruses.
“We know very little about viruses and microbes in these extreme environments, and what is actually there,” Earth scientist Lonnie Thompson argues, noting that numerous critical questions remain unsolved.
“What are the responses of bacteria and viruses to climate change? What occurs when we transition from an ice age to a warm period such as the one we are currently experiencing?”
There is still more to be discovered.
This research was published in the journal Microbiome.