IRA FLATOW, host:
For the rest of the hour, we're going to talk about what the melting ice - what of ice melting around the world and these glaciers - what some of that ice might tell us about the origins of life on Earth. Because locked in the ice in Antarctica is sort of a biological catalog. It's a record of the microorganisms that inhabited this icy climate thousands, hundreds of thousands, millions, millions of years ago. So what happens if you melt the ice? If, for instance, the climate were there to warm up? You know, what about global warming? If all these ice starts melting, would the organisms locked in the ice come back to life?
To find out, researchers collected samples of ice from glaciers in Antarctica. The ice ranged in age from a hundred thousand years old to eight million years old. They took the ice samples back to the lab, melted the ice, to see if they could get any of the ancient organisms trapped in the ice to grow. What happened? Well, joining me now to talk about what they found is Kay Bidle, assistant professor of marine and coastal sciences at Rutgers University in New Brunswick, New Jersey.
Thanks for talking with us today, Dr. Bidle.
Dr. KAY BIDLE (Assistant Professor, Marine and Coastal Sciences, Rutgers University): Oh, my pleasure, Ira. Thanks for the interest.
FLATOW: Well, I started you off down there. Tell us what happened when you melted that ice and started to grow, what was in it?
Dr. BIDLE: Well, we actually examined a couple of different types of ice ranging in ages. Well, the youngest was about 100,000 years old and the oldest was about eight million years old, which represents the oldest ice on Earth that we know of. And so we were interested in looking to see if we could find microorganisms encased in the ice and if they were potentially viable.
So we melted both of these ices, after, of course, we decontaminated them from potential surface contamination of microbes that are around today. And we first looked to see who was in the ice and who could grow. What we found is that the organisms that were in the ice were a variety of organisms that you would find are closely related to organisms that we find in soils and in ice - a variety of ice environments today. So they're closely related to those. And what we also found was that organisms in the young ice were much more viable, they grew faster. We could recover them easier. The organisms in the old ice, we also saw some evidence of growth, but they were severely retarded. Very, very slow growth, doubling - dividing about once every 70 days, which is quite slow for a bacterium.
FLATOW: And that was quite a difference, wasn't it?
Dr. BIDLE: Yes, of course. And we sort of expected that type of difference because these two ice samples differ quite dramatically in the amount of time they've been frozen and locked up in the glaciers. And then with that, they would be exposed to different levels of - or doses of cosmic radiation that comes in to the Antarctic. And that region receives the highest cosmic radiation flux on the planet, along with the Arctic.
FLATOW: So the cosmic rays sort of disrupted DNA and chop it up.
Dr. BIDLE: That's right. So one of the things that we looked at in the paper was to examine the state of the DNA locked up in ices of various ages ranging from those 100,000 years to 8,000,000-year range. And we found that the longer you are exposed over geologic time, you do have much more degraded or deteriorated DNA. In the old ice, the average age or size was about 200 base pairs, which is 200 of the genetic code letters - A, T, C, G - strung together. Just for comparison, the average bacterium would have something like 3 million base pairs.
FLATOW: So that argue - the argument is made in your paper that possibly the theory that's been around for a while, circulating around, that life on Earth might have been seeded with bacteria or life forms from outer space.
Dr. BIDLE: Right.
FLATOW: You sort of have thrown cold water on that a bit because the DNA is so disrupted after all those years, or the exposure to all that cosmic radiation.
Dr. BIDLE: That's right. Yeah. So what we were able to do in this study was to at least get a relationship for the rate at which DNA degrades over geologic time. And so what we were able to get is sort of a half-life or a time over which a piece of DNA would be chopped in half. And that was about 1.1 million years, based on our data from the variety of ice samples that we collected over the entire age range. And so what we like to do is extend that to organisms or genetic material that might be locked up in icy comets. Comets are essentially dirty ice balls.
Dr. BIDLE: And our buried glaciers in this environment are also dirty ice packs as well. So, what that allows us to do is severely constrain the possibility that a comet from a different solar system may have traveled into our solar system and it would, of course, have been exposed to even higher levels of cosmic radiation in outer space. And the time it would take to do that would essentially degrade all of that material and essentially sterilize it.
FLATOW: So it couldn't seed - sort of seed life here on Earth.
Dr. BIDLE: Right. So one of the things that we argue in the paper is that it's still possible for life to have come from, you know, other planets within our solar system, for example, but it constrains the possibility of things coming in from outside of solar system, for example.
FLATOW: Now, the fact that some of the - the hundred-thousand-year-old DNA and the organisms are pretty viable.
Dr. BIDLE: Right.
FLATOW: Does that mean we're going to see, as these ice - polar ice caps melt, or ice around the world melts in different places and different glaciers, a pooling and mixing in of these ancient bacteria with modern day bacteria?
Dr. BIDLE: Yeah, very, very likely. So in those ices of different ages, you do have both viable microorganisms that we detected and actually show in the paper, but as well as a whole mix of genomic information. And in the paper, we sort of refer to these things as gene popsicles. So basically, you would have encased ancient DNA of some age period that once these glaciers would melt ultimately can end up in the oceans. And then it would provide a source of new genetic material, for example, which can then be taken up by current microorganisms. And this is - we know that this happens a lot in natural microbial communities. It's called lateral gene transfer. And it's a mechanism by which microbes can take up new pieces of DNA that may contain useful information, incorporate it into their DNA. And then it can confer some advantage or it can be deleterious. It's up to natural selection to sort that out.
But this is one of the primary ways by which microorganisms on the planet gain new traits and evolve. So this melting would not only potentially add viable members to a community, but also significantly affect the tempo of microbial evolution on the planet.
FLATOW: Talking about microbes in ancient ice this hour on TALK OF THE NATION: SCIENCE FRIDAY from NPR News. Talking with Kay Bidle, assistant professor of marine and coastal sciences at Rutgers University.
Who came up with this popsicle name? That's an interesting name.
Dr. BIDLE: The gene popsicle?
Dr. BIDLE: Well…
FLATOW: It's a vision you could actually see. Is it actually shaped like a popsicle?
Dr. BIDLE: Like a popsicle on a stick?
Dr. BIDLE: No, of course not.
Dr. BIDLE: But functionally, it's very similar. So my close colleague here at Rutgers, Dr. Paul Falkowski - who was recently elected to National Academy of Sciences a few months ago - him and I sort of talked about this possibility of, you know, a way of actually conceptualizing, you know, this idea. So that's where the gene popsicle term came from.
FLATOW: Now, people are going to start thinking, oh, my goodness, we have a science fiction movie here. Right? I'm sure you've thought about that.
Dr. BIDLE: We have. But the important thing to realize is that these processes of glaciers forming and melting have happened many times over the course of Earth's history. So this isn't something that Earth hasn't seen before. And it's very likely that these processes have affected the tempo of evolution and the diversification of species over geological time. And in fact, we do see some of that evidence in the fossil record. But with microorganisms, you don't - they generally don't leave a fossil record. So we've never been able to really assess what processes might influence their diversification and proliferation.
And so here's a mechanism by which that might be able to happen. And now we're sort of in a position, of course, melting glaciers, as you mentioned, in the lead up, this is a very relevant situation to our current climate. So now we're in a position to actually address this experimentally with some sophisticated techniques, including molecular biology.
FLATOW: How close to the surface are these thousands or hundred-thousands-year-old bacteria? How far down? I mean, will they just naturally melt out now in puddles, flow into the ocean?
Dr. BIDLE: Well, the actual - so the ice that we obtained, the ice was actually collected by a co-author on the paper, Dr. Dave Marchant from Boston University - he's a geologist and he studied this particular region for some time, both its age and its formation. And so his team has been going to the Dry Valleys region of the Antarctic. So that's up in high altitude. But ultimately, all glaciers - and of course there have been a lot of glaciers and ice that have already disappeared from the Antarctic continent, and they ultimately end up in the oceans.
FLATOW: Right. I want to thank you for taking time to talk with us.
Dr. BIDLE: Oh, my pleasure. I really appreciate the interest.
FLATOW: Good luck to you. And one of my favorite places you've been in, the Dry Valleys there in Antarctica.
Dr. BIDLE: Thanks, Ira.
FLATOW: You're welcome. Kay Bidle is assistant professor of marine and coastal sciences at Rutgers University in New Brunswick.
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