Ancient ice filled with viruses may reveal the future of Earth’s microbiome

Trees, rocks, and ice are united by a quintessential job: Each catalog climate history.

Lonnie Thompson, a paleoclimatologist who’s studied ice core records since the late 1970s puts it this way: Frozen in ice, like snapshots stacked within the pages of a photo album, are bits of the environment. This means that glacial water — considered the cleanest water on Earth — is filled with millions of microscopic and novel microbes. Much like rings within redwoods or layers of limestone, ice can be a time capsule.

“Most of the biodiversity on our planet exists as microbes, most of which we know very little about,” Thompson tells Inverse. Whether they’re swimming in the ocean, living inside our guts, or held frozen in a glacial sleep — microbes are everywhere.

In a new study, Thompson, a professor at Ohio State University, and colleagues present evidence of these elusive microbes: 33 viruses, 28 of which have never been seen before.

These viruses became entombed in ice at least 15,000 years ago — and most of them are still alive. (Viruses are a type of microbe.)

This research was published on July 20 in the journal Microbiome. Apart from allowing scientists to reconstruct history and the environmental conditions these viruses encountered, the work also validates a new ultra-clean sampling technique.

Visiting a glacier — Guliya ice cap is located in western China as part of the Tibetan Plateau. It is some 22,000 feet above sea level and can reach below 40 degrees Fahrenheit at its coldest.

Thompson and colleagues experienced this chill as they collected high-altitude ice cores. Layers of ice trap what is in the atmosphere when they freeze, allowing researchers a peek at what was going on in the world during the entrapment.

“Microbes have played vital roles in the evolution of our planet,” Thompson says. “For example, around 3 billion years ago, cyanobacteria increased the oxygen levels in the Earth's atmosphere, which would allow the evolution of large organisms like us.”

“Viruses and bacteria play vital roles both good and bad and thus we need to understand those roles much better,” he explains. “Glacier ice provides one way in which we can do that.”

Regardless of their microbe content, Thompson says that glacial water is still some of the purest you can find on Earth.

“These samples come from one of the coldest, highest radiation, and cleanest environments on our planet,” he says. “Glacier water is considered amongst the purest water on Earth. Our research team has been drinking the meltwater from Guliya since our first expedition to the western Kunlun mountains in 1990.”

Keeping it clean — The purity of glacial water means it’s essential to ensure modern-day contaminants don’t make their way into these samples. Contaminants can include more recent viruses that could confuse the analysis.

Applying new rigor to this challenge was the work of Zhi-Ping Zhong, a postdoctoral scholar at Ohio State University’s Byrd Polar and Climate Research Center.

Using a mix of deep-sea techniques for amplifying low-mass sea microbe genomes and decontamination techniques for preventing terrestrial contamination on Mars, a group led by Zhong probed how well they could prevent contamination using an artificial ice sample. This sample was covered in a special cocktail of microbes, including viruses.

“The glacier ice contained unique viruses.”

In their artificial trials, the team found that nearly all contaminant microbes, viruses, or DNA were removed from the surface of the ice sample and left a pristine inner core. With this success achieved, the team then applied the technique to their 2015 ice sample.

“The uniqueness was evaluated by comparing glacier viruses to the available viruses in the database today,” Zhong tells Inverse.

“The glacier ice contained unique viruses,” he says. “This may be due to the fact that the glacier viruses were frozen or archived many thousands of years ago. They are unique from the viruses in the database mostly from the modern environments that have probably been evolving for a long time.”

The discovery — Analysis suggests the ancient viruses identified here likely originated with soil or plants.

While we typically associate a virus as something that infects us and leads to illness, not all viruses are bad. For example, the ocean contains at least 200,000 marine viral species, some of which influence the ocean’s ability to temper the effects of climate change. Viruses in soil, meanwhile, can benefit biodiversity.

“A good piece of context is that there are a huge number of viruses on Earth,” co-author Matthew Sullivan, director of Ohio State’s Center of Microbiome Science, tells Inverse. “If you put them end to end, tiny as they are, they would stretch light-years away from Earth.”

“Science, to date, has sampled only a few hundred deeply and has genomic information on maybe a few hundred thousand,” he explains. “Virtually every virus studied in nature is ‘unique.’”

Now, the team wants to catalog microbes across different ice samples from around the world to get a better idea of what the global climate might’ve looked like 15,000 years ago. This could help us better anticipate, and understand, what will happen in future periods of freezing and melting.

As our climate continues to warm, and glacial ice sheets continue to melt, this question is becoming only more pertinent: both because of the predictive nature of the study, and the literal melt.

“Since we have a global collection of ice cores here at the Byrd Polar and Climate Research Center stored at -30F we should be able to develop a global picture of microbes and how they have evolved through time,” Thompson says.

“How do microbes vary between ice ages and warm periods like the one we currently live in is the question we will be exploring,” he says. “The answer to that question is in part frozen in the ice cores.”

The trick is collecting, extracting, and analyzing before the ancient evidence melts away.