Scientists have raised ancient microbes from nuclei of late age of the Pleistocene (up to 40,000 years) collected in four locations in the Pergélisol research tunnel near Fairbanks, in Alaska. They found that the microbes of the thaw of underground permafrost present a slow “reappearance” at the start, but in six months, the microbial community is undergoing spectacular changes.
Abundance of archaea through samples taken from the permafrost research tunnel near Fairbanks, Alaska. Image credit: Caro and al., DOI: 10.1029 / 2025JG008759.
Today, the world’s permafrost thaws an alarming pace due to the climate change caused by man.
Scientists fear that this trend can launch a vicious circle. While the Pergélisol Déget, the microbes living in the ground will begin to decompose organic matter, spitting it in the air in the form of carbon dioxide and methane – both powerful greenhouse gases.
“This is one of the biggest unknowns of climatic responses,” said Professor of the University of Colorado, Sebastian Kopf.
“How does the thaw of all this frozen soil, where we know that there are tons of stored carbon, will affect the ecology of these regions and the rate of climate change?”
To explore these strangers, the researchers went to a unique location of its kind, the permafrost tunnel of American army engineers.
This search installation extends to more than 107 m (350 feet) in the soil frozen under the center of Alaska.
Scientists collected permafrost samples that had a few thousand thousands of years from the tunnel walls.
They then added water to the samples and incubated them at temperatures of 4 and 12 degrees Celsius (39 and 54 degrees fahrenheit) – cold for humans, but downright boiling for the Arctic.
“We wanted to simulate what is happening during a summer in Alaska, in future climatic conditions where these temperatures reach deeper areas of permafrost,” said Dr. Tristan Caro, a postdoctoral researcher in Caltech.
The authors relied on the water composed of unusually heavy hydrogen atoms, also known as Deuterium.
This allowed them to follow how their microbes drank water, then used hydrogen to build the membranes in fatty materials surrounding all living cells.
During the first months, these colonies increased to a flipper, in some cases, replacing only one cell over 100,000 per day.
In the laboratory, most bacterial colonies can completely turn around in a few hours.
But at six months, everything has changed. Some bacterial colonies have even produced biofilms that you can see with the naked eye.
“These microbes probably couldn’t infect people, but we kept them in sealed rooms despite everything,” said Dr. Caro.
“The colonies did not seem to wake up much faster at warmer temperatures.”
“The results could contain lessons to defrost permafrost in the real world: after a hot spell, it can take several months so that microbes become active enough to start emitting greenhouse gases in the air in large volume.”
“In other words, the more arctic summers are developing, the higher the risks for the planet.”
“You may have a single hot day in the summer of Alaska, but what matters much more is the extension of the summer season until these hot temperatures extend in the fall and spring.”
“There are still a lot of open questions about these microbes, as if ancient organizations behave in the same way on sites around the world.”
“There are so many permafrosts in the world – in Alaska, Siberia and other northern regions of the cold. We have only sampled a small slice of this.”
The results were published on September 23 in the Journal of Geophysical Research: Biogeosciences.
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Your caro and al. 2025. Microbial resuscitation and growth rates in deep permafrost: the survey results of the stable lipid isotopes of the permafrost research tunnel in Fox, in Alaska. Biogeoscience JGR 130 (9): E2025JG008759; DOI: 10.1029 / 2025JG008759
