Researchers have brought ancient microorganisms back to life from permafrost cores dating back up to 40,000 years, extracted from four sites within the permafrost research tunnel near Fairbanks, Alaska. They found that as underground permafrost melts, microbial activity begins with a slow “awakening”, but significant transformations in the microbial community occur within six months.
Archaeal abundance in whole samples collected from a permafrost research tunnel near Fairbanks, Alaska. Image credits: Caro et al., doi: 10.1029/2025jg008759.
Currently, permafrost across the globe is melting at an alarming pace due to climate change driven by human activities.
Scientists are concerned that this could initiate a dangerous feedback loop. When permafrost thaws, the microorganisms within the soil begin to decompose organic matter and release it into the atmosphere as carbon dioxide and methane, both potent greenhouse gases.
“This is one of the biggest uncertainties in climate response,” stated Professor Sebastian Copp from the University of Colorado at Boulder.
“How does the thawing of this frozen ground, which contains significant amounts of stored carbon, impact the ecology and climate change rate in these areas?”
To investigate these uncertainties, researchers visited the US Army Corps of Engineers’ permafrost tunnels, a distinctive research setting.
The facility has been extended over 107 meters (350 feet) and continues toward the frozen ground below central Alaska.
Scientists have gathered permafrost samples ranging from thousands to tens of thousands of years old from the tunnel walls.
The samples were then treated with water and incubated at temperatures of 4°C and 12°C (39°F and 54°F).
“We aimed to replicate scenarios that would occur during Alaska’s summers under projected future climatic conditions that allow these temperatures to penetrate deeper into permafrost,” explained Dr. Tristan Caro, a postdoctoral researcher at Caltech.
The researchers utilized water containing unusually heavy hydrogen atoms, referred to as deuterium, to track how microorganisms absorbed water and used hydrogen to construct lipid membranes surrounding all living cells.
In the initial months, these colonies grew slowly, with some even replacing only one cell for every 100,000 daily.
In laboratory settings, most bacterial colonies can be entirely replenished in a matter of hours.
However, by the six-month mark, everything had transformed. Some bacterial colonies even developed visible biofilms.
“These microorganisms likely pose no threat to human health, but they were kept in sealed environments nonetheless,” remarked Dr. Karo.
“The colonies don’t seem to wake up quickly in warmer temperatures.”
“These findings may provide insights regarding thawing permafrost in real-world conditions. It appears that after a warm period, microorganisms can take several months to start emitting significant quantities of greenhouse gases into the atmosphere.”
“This means that a longer Arctic summer increases risks for the planet.”
“While a single hot day might occur during an Alaskan summer, the primary concern is the prolonged summer season, with warm temperatures extending into autumn and spring.”
“Many questions remain unresolved about these microorganisms, such as whether ancient organisms exhibit similar behavior in different global locations.”
“There is an abundance of permafrost worldwide. In Alaska, Siberia, and other northern cold regions, our sampling covered only a small fraction of that.”
The findings were published on September 23rd in the Journal of Geophysical Research: Biogeosciences.
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Takaro et al. 2025. Microbial resuscitation and growth rates in deep permafrost: Lipid-stable isotope probing results from the permafrost research tunnel in Fox, Alaska. JGR Biogeosciences 130 (9): e2025jg008759; doi: 10.1029/2025jg008759
Source: www.sci.news
