Scientists ‘reawaken’ ancient microbes from permafrost — and discover they start churning out CO2 soon after
Microbes that have been suspended in permafrost for 40,000 years could “wake up” and start reproducing. greenhouse gas whether Arctic summers are getting much longer, new research suggests.
In future climate conditions, microbes that have been dormant since the last ice age (2.6 million to 11,700 years ago) might only need a few months to reactivate, according to a study published September 23 in the Geophysical Research Journal: Geosciences. If they do so for even part of the year, scientists warn it could trigger a feedback loop that accelerates the thawing of permafrost and global warming.
“There may be a single warm day during the Alaskan summer, but what matters much more is the lengthening of the summer season until these warm temperatures extend into the fall and spring,” said the study’s lead author. Tristan Caropostdoctoral research associate in geobiology at Caltech, said in a statement.
Caro and his colleagues collected samples from the Permafrost Research Tunnel near Fairbanks. The tunnel lies 50 feet underground and extends more than 350 feet (107 m) into permafrost, offering a glimpse of life during the late Pleistocene (129,000 to 11,700 years ago).
Their goal was to determine the resuscitation and growth rates of microbes that lived at that time. But as Caro entered the tunnel, he also noticed mammoth and bison bones protruding from icy walls, according to the release.
“The first thing you notice when you walk in is that it smells really bad,” said Caro, who conducted the research as a graduate student at the University of Colorado Boulder. “For a microbiologist, this is very exciting because interesting odors are often microbial.”
Back in the lab, the researchers soaked the samples in water containing unusually heavy hydrogen atoms, also called deuterium. They then incubated the samples in refrigerators set at 25, 39, or 54 degrees Fahrenheit (minus 4, 4, and 12 degrees Celsius) and periodically examined them for changes in microbial activity.
“We wanted to simulate what happens in an Alaskan summer, under future climate conditions where these temperatures reach deeper areas of the permafrost,” Caro said.
A month into the experiment, the team didn’t notice much change, even in the two hottest samples. A handful of microbes had awakened from their long slumber, but only 0.001 to 0.01 percent of the cells were replaced daily by new, active cells.
But in the months that followed, everything changed. The deuterium in the samples allowed the researchers to track how much water the microbes consumed to build the fatty membranes around their cells. This revealed that ancient organisms preferentially produced fatty acids called glycolipids, which the researchers believe may be involved in cryopreservation.
Six months after the experiment began, microbes incubated at 39 F and 54 F had undergone “dramatic” changes in community structure and activity levels, according to the study. The samples were less diverse than active layers of permafrost, but the microbes were as active as their more modern counterparts, even producing slimy structures called biofilms visible to the naked eye.
“These are by no means dead samples,” Caro said.
The findings have implications for the Arctic and Earth’s climate in general, because microbes in permafrost survive on organic matter, which they convert into carbon dioxide and methane. Global temperatures are growing faster in the Arctic than anywhere else in the world, permafrost thawing at an alarming rate and for increasing durations. As Arctic summers are getting longer and temperatures rise in deeper layers, colonies of ancient microbes could wake up and start emitting carbon.
Permafrost in northern regions currently holds about twice as much carbon than the Earth’s atmosphere, so large-scale releases could contribute significantly to climate change. This would accelerate the thawing of permafrost, triggering a vicious cycle of warming, more thawing and more warming.
“This is one of the biggest unknowns in climate responses,” co-author of the study Sébastien Kopfassociate professor of geological sciences at the University of Colorado Boulder, said in the release. “How will the thawing of all this frozen ground, where we know there are tons of carbon stored, affect the ecology of these regions and the rate of climate change?”
But the study only looked at ancient microbes from one location, and microbes from other regions may respond differently to warming, the researchers noted.
“There is so much permafrost in the world – in Alaska, Siberia and other cold northern regions,” Caro said. “We only sampled a very small slice of it.”
