Using samples gathered from a permafrost tunnel north of Fairbanks, researchers have awakened microbes that were last active as far back as 40,000 years ago.
If that sounds like the opening scene in a sci-fi horror movie, don't worry, say the researchers, who take precautions against unleashing anything dangerous. Plus, the process of ancient microbes reawakening is already happening on a much larger scale, as climate warming thaws permafrost all across the Arctic.
And that's what they're really trying to get at: How long does it take the microbes, which themselves produce greenhouse gases, to wake from their slumber?
That's a question Tristan Caro, a postdoctoral research scientist at the California Institute of Technology, aimed to answer in a recently published paper he co-authored as a graduate student at the University of Colorado Boulder.
But first, Caro says, he and his colleagues had to venture into the permafrost tunnel in Fox, Alaska.
This interview has been lightly edited for length and clarity.
Tristan Caro: The first thing you'll probably notice is the smell. It smells very musty. It smells like a very, very old basement, which is the result of all this degrading carbon that's been locked away for thousands of years. And you're kind of walking through time, in a way. It's called a chronosequence for that reason. And you can see these ancient environments layered in the permafrost around you, so there's bones and leaves and branches of trees that are preserved over millennia, that are from essentially the Ice Age.
Casey Grove: How do you actually collect the samples?
TC: Essentially, what it looks like, this corer, it's kind of like a chainsaw motor that's hooked up to a drill that's about a meter long. And we would mount the corer horizontally on the wall and drill horizontal cores. The core of solid permafrost and ice hosted within, we pack up in a kind of a PVC tube and ship it back on ice so that these cores can stay intact.
CG: Cool, yeah. I guess cool, literally.
TC: Yeah.
CG: So then what do you do? I mean, I've heard this described as, like, awakening the sleeping ancient microbes. But how do you actually do that?
TC: Microbes need two things. They need water, and they need a temperature that they can live at, and when permafrost thaws, it provides both of those. So the ice that's locked up in permafrost becomes liquid water again, which rehydrates the sample. And then, once the permafrost thaws, they also get a slightly elevated temperature. And you don't even need to go to, you know, particularly human-comfortable temperatures. These microbes are perfectly happy growing at 39, 37 degrees Fahrenheit. And so yeah, when we bring these cores back to the lab, we take a small chunk of it, put it in a sealed jar, and then slowly bring that jar up to a slightly above freezing temperature and let the microbes do the work of waking up after a 40,000-year nap.
CG: So do they just spring back to life? If we're describing this as a nap, do they just, like, pop out of bed? Or is it like how I get out of bed and I'm slowly, like, crawling out of bed with my eyes half closed, that kind of thing?
TC: Yeah, it's probably more like the second one. So that was part of the question we went into research, the rate at which these microorganisms resuscitate, or awaken, after a long period of dormancy. And we found that it did indeed take months for these organisms to wake up, to really convince themselves that, yes, it's time to start processing carbon and exhaling CO2 and methane. Somewhere between one and six months. And that's an important finding. It really shows that these ecosystems, even though they're in suspended animation, they're very much still capable of supporting life from a microbiological or a climate perspective.
The Arctic warms, the permafrost thaws, permafrost contains CO2 and methane and will produce more CO2 and methane by the activity of microorganisms, which will cause the Arctic to continue to warm. And that's really a concern, this kind of self-amplifying cycle, and we're starting to see it occur. So our research paper was getting at the rates, or the speed, at which microorganisms awaken after thaw, almost like a traffic cop with a radar gun. You know, we're shooting the radar gun at these microbes and seeing how fast they're acting and putting a number to it.
CG: Yeah, it's just fascinating. I mean, just 40,000-year-old microbes in such a cold environment, and being able to wake them up, is fascinating. I think some people would wonder, is this safe to bring these microbes back to life? It sort of sounds like the plot to a movie or something. I wonder what you think about that.
TC: Yeah, it's certainly a fair question, and it's something that I've thought about, and our collaborators have thought about, this concept of emerging pathogens from thawing permafrost, and these environments that have been in suspended animation for a while. But it's not something we are too worried about for a variety of reasons.
One, at least in terms of the lab experiments, we take back just a tiny portion of permafrost, back to the lab, and thaw it under extremely controlled conditions in bottles. And compared to the quantity of permafrost that is naturally thawing in the cold regions and naturally interacting with humans and animals and plants, this tiny — imagine a mason jar's worth of permafrost that we've thawed — is not even a drop in the bucket, compared to what is currently happening across the northern cold regions and the Arctic.
And then on a personal level, like, as I'm handling these samples, I'm an environmental microbiologist by training, and they are just common sense safety procedures that you undertake when you're handling any kind of environmental sample, including, you know, natural soils, like just in your yard.
But even so, yeah, it's still worth being careful, and it's still worth understanding that as these regions continue to warm, they're going to release novel organisms and strains that maybe we haven't really observed in modern environments. And so it's certainly worth monitoring and keeping track of, but it's not something that keeps me up at night.
