Ancient microbes frozen for 40,000 years revive, reorganize, and begin to devour carbon

Microbes entombed in deep permafrost, ground that stays frozen for at least 2 years, can switch back on after thawing when warmed. Experiments with Alaskan cores show they start releasing carbon dioxide within months of thaw, even from layers once thought safely inert.

Some of these organisms have slept for roughly 40,000 years. The work centers on samples taken in a research tunnel near Fairbanks, Alaska, where frozen ground records ancient climates and ecosystems.

Thawing microbes and carbon

The work was led by Tristan Caro, a postdoctoral research associate in geobiology at the California Institute of Technology (CIT). His research focuses on how dormant microbes endure frozen, low oxygen conditions and switch back to active growth.

Northern soils store a vast stockpile of organic carbon, roughly twice the amount now in the atmosphere. Unlocking even a fraction threatens to add more heat trapping gases to the air during seasons when soils stay warmer for longer.

Permafrost underlies nearly 85 percent of Alaska, a reach that shapes roads, rivers, and ecosystems. That scope helps explain why a deep tunnel there offers an unusual window into ancient life, and why its findings matter well beyond Alaska.

Most of the frozen ground lies deep below the summer thaw zone and has been cut off from daylight and oxygen for thousands of years. That isolation means the biology that wakes up down there does not match the communities near the surface.

Studying thawed microbes

Researchers collected cores from an underground facility north of Fairbanks and kept them in carefully sealed, oxygen poor chambers to prevent contamination. They incubated samples at 39 and 54 degrees Fahrenheit for up to six months.

To track fresh cell parts, the team added deuterium, a heavy form of hydrogen, to the water. That marker shows how microbes build new fatty membranes as they thaw and wake up, which is a direct sign of growth.

They also used lipid stable isotope probing, a lab method that traces new cell membranes. The approach ties biochemical activity to shifts in community makeup over time, revealing which survivors seize the moment first.

The heavy hydrogen label let the team separate actively growing cells from holdouts as the weeks ticked by. Many cells favored glycolipids, sugar bearing fats that help stiffen membranes in cold conditions, which hints at how they survived long freezes.

What changed after months

The first month was almost a crawl, with only 0.001 to 0.01 percent of cells replaced each day. That lag suggests a buffer when short warm spells pass, especially in places that still refreeze each winter.

By month six, microbial communities reorganized, lost diversity, and produced sticky biofilms, slimy layers that microbes build to stick together.

The activity matched modern surface soils even though the species mix differed, a reminder that function can persist as membership changes.

The researchers emphasized that the samples were far from lifeless, showing clear signs of microbial activity and revival.

Over time, the once-dormant microbes thawed, then began rebuilding their communities and forming visible biofilms, evidence that ancient life can quickly regain strength when conditions turn favorable.

Early gas pulses can also come from ancient bubbles trapped in the ice, not fresh respiration. That nuance matters when field teams measure carbon flows during the first weeks after thaw.

Longer summers raise the stakes

According to a NOAA report, arctic seasons are stretching as the region warms faster than the global average. A longer warm season means deeper layers stay thawed long enough for the slow reawakening to finish.

As the surface active layer, the top soil that thaws each summer, deepens, fresh oxygen and water percolate into older zones. That opens buried organic matter to microbes that turn it into carbon dioxide and methane, gases that trap heat in the air.

If warming continues, more thaw could create a dangerous feedback loop, a process where warming fuels even more warming. Researchers cautioned that this remains one of the greatest uncertainties in predicting how climate systems will respond to rapid Arctic change.

Scientists explained that a single hot day in the Alaskan summer matters far less than the steady lengthening of the warm season. As summers extend into spring and autumn, microbial communities that once stayed dormant during brief thaws can remain active for much longer, accelerating carbon release.

Lessons from thawed microbes

The experiment used one facility and a handful of cores, so other regions may behave differently. Cold soils in Siberia or the Canadian Arctic hold distinct communities with their own pace of waking and growth.

Even so, the work points to a crucial timing issue for climate models. Warming that turns weeks of autumn into thaw time could push deep microbes past their lag and into full activity during a single season.

Field tests that track thaw depth, gas flux, and lipid markers side by side would sharpen forecasts for near term and long term planning.

Engineers also want better maps of ice rich layers to plan roads, pipelines, and buildings that can handle longer thaws and higher settlement risk.

Teams will also need to separate old gas bubbles from new microbial emissions during field surveys to avoid mixing different signals. That distinction helps agencies estimate near term risks to climate targets and decide where mitigation dollars go first.

The study is published in the Journal of Geophysical Research.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–