Science Friday
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A newly identified amoeba can survive at the temperature of a medium-well steak. Plus, a distant lava planet shows signs of an atmosphere.
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Hi, I'm Flora Lixman, and you're listening to Science Friday. New extremophile alert: Meet the Fire amoeba. This single-celled goo ball was found in a steamy stream in Lassen Volcanic National Park in California's Cascade Mountains. And the amoeba was still growing and oozing at about 145 degrees Fahrenheit. That's like the temperature you shoot for when you cook a steak to medium. And it is the new survival record for a eukaryotic cell. Here to tell us more is one of the researchers who identified the microbe. Angela Oliverio is a microbiologist at Syracuse University. Angela, welcome to Science Friday.
Hi, Flora. Thanks so much for having me on today.
Give me the origin story on the Fire amoeba. Where did you find it?
Sure. We went sampling at Lassen Volcanic National Park. And on our way to Boiling Springs Lake, which is one of Lassen's sort of claims to fame, there's this little tributary coming off of a stream. And we stopped to sample it because it was kind of like the first hot geothermal feature that was on our hikes. We were really excited, even though to anyone else's eye, it was quite boring to what else we saw that day, right? But it was of interest to us because it was pH neutral. And we just suspected that different types of organisms would live there relative to everything else we were sampling, which was going to be super acidic. But honestly, it's the most unremarkable feature that you'd see in Lassen.
Like, probably people hike by every single day, including microbiologists, and don't really stop here usually, right? Because relative to everything else, it's just kind of a boring little stream.
And what did you find?
So, we actually didn't find anything for a while. We go back to our lab at Syracuse. And I should say the "we" is myself and Beryl Rapaport, who's the first author on the manuscript and is currently a PhD student in the lab. So, we were in the lab. We scanned on the microscope. We didn't see anything, but we put them in an incubator, checked every day. And then after a week, we saw an amoeba emerge. And this was very exciting to us. We were like, oh, my gosh, this trip wasn't a waste, right? And the amoeba was OK, it was alive, right? Yeah, which honestly, in and of itself, was pretty remarkable to us. And so we started at 57 degrees Celsius.
And this was the previous known temperature limit for amoeba type of organism. Why can this amoeba survive the heat? Do we know? Right, oh, it's such a good question. We have some ideas. So we have some hints. Hit us. As to what it might be doing. So one of the things that we did was we sequenced the genome of incendi amoeba, or fire amoeba. And then we can look at what genes are in the genome. And we can say, what's different about this amoeba? Right? And a few of the things that we found were it seemed to have elevated numbers
of genes related to thermal stress signaling pathways, and genes enriched that were related to proteostasis, which is kind of the cell's system to make sure that proteins are synthesized and folded correctly, and that they're removed if damaged. So on a sort of molecular level, that's giving us some insight about genes that are probably really important when you're living at high temperature. Like, because you could, if you're living at high temperature, maybe your proteins would get messed up, but there's a system for clearing them out. That's right, yeah. Because proteins have different melting temperatures,
and can denature if they're exposed to temperatures that are too hot. And then at a kind of cellular level, one of the interesting things that we noticed is there's this rapid shifting. So incendi amoeba has this form that basically looks like a really long skinny worm. And it also has a form that looks kind of like, more like a classic amoeboid form, which would be sort of... A blob? Like a blob. I know, I hate the word blob, but I'm like, I have to say the word blob, right? I mean, that is what it is, Angela. It's a blob.
We'll say classically amoeboid blob.
And it can switch between these two forms super, super quickly. And we think that this might be a way in which it can react really fast. And if temperatures become too hot, then it can shift forms and escape more quickly. So that's just a hypothesis at this point.
Wait, like it turns into its skinny worm-like self and then just like wriggles away more fast.
Yeah, that's our hypothesis.
Yeah. Oh, that's interesting. So that it shape shifts to get away from the heat.
Exactly. And then another sort of mechanism that we know is happening is what we call insistment. And basically lots of amoeba, actually lots of organisms can form cysts, which are basically like hard little shells that protect them when conditions become unfavorable. And that could be that the temperature is too hot. Insistment is also triggered by lots of other things. Like if there's not enough nutrients available to eat, or desiccation can trigger insistment. And lots of different organisms can insist. But the cool thing that we found about-
Insist. I love the double entendre there. Okay.
The cool thing that we found out about incendi amoeba is when it forms this cyst, the tolerance to high temperatures is much higher than other amoebas. So we can expose it to 70 degrees Celsius.
158 Fahrenheit.
Okay, so we can expose it to 158 Fahrenheit.
We're getting into well-done steak at this point.
That's right. That's right. And when we take the temperature back down, it's perfectly fine. It's happy.
Wow.
Yeah.
That seems very useful in a warming world, I have to say.
It sure does. It sure does.
That is really cool. Does this change where you look for life? You know, you stop in the most boring spring in Lassen, and you find this very cool new creature, you know, new to us creature, I should say. Does this change how, you know, where people should be looking for new life?
Yeah, absolutely, right? We thought that eukaryotic life could not get above 60 degrees Celsius.
Since the 70s, that's been the paradigm. Like, no organism since very early on has been able to grow above 60 degrees. And this was a longstanding paradigm in science. And I think to sort of show that theoretical limit isn't true opens up a lot of questions in terms of, well, how hot can eukaryotic life get? And what sort of mechanistic ceiling is there on eukaryotic life? And we really don't have the answer for that yet.
I can't wait to find out.
Me too.
Angela Oliverio is an assistant professor in the Department of Biology at Syracuse University. Thanks for joining me today.
Thank you for having me.
Coming up, we take you to a nice, cozy, warm planet where the ground is lava. Find out why scientists aren't interested in this faraway world. That's after the break.
Science Friday is supported by PBS, presenting Going Wild. If you love learning about the natural world and meeting the scientists who help us understand it, be sure to check out the new season of Going Wild with Dr. Ray Wynn Grant. It's the chart-topping and Webby Award-winning podcast from the folks at Nature on PBS, now with a video companion series. In this season of Going Wild, host acclaimed wildlife ecologist Dr. Ray Wynn Grant heads out into the field to explore the animals, people, and stories that make nature worth saving. Stops include a hibernating black bear den in Arkansas and an underwater shipwreck site off the Florida coast. If you're looking for a place to start, check out the season's debut episode, where Ray joins beloved biologist and influencer Jordan King in the Florida Everglades to learn
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Turning to deep space and a fiery planet where even the most dedicated Earthling extremophiles probably couldn't find a home. We're taking a trip to the charmingly named exoplanet TOI 561b. Recently observed by the James Webb Space Telescope, which found the strongest evidence yet for an atmosphere on a rocky planet outside of our solar system. The planet is also a ball of lava. Joining me now to talk about it is Johanna Tusky, a staff scientist at Carnegie Science Earth and Planets Laboratory in Washington DC. Johanna, welcome.
Thanks, I'm happy to be here.
Take me to this planet. Give me the tourist brochure version.
Yeah, so this is definitely, you should imagine, a lava-type world. The planet goes around its star in 0.4 days, so less than a day orbital period, so it's zipping around.
Their year is four days, okay.
No, their year is 0.4 of a day. So it's less than a day.
Their year is 0.4 days, wow, okay.
So zipping around the star, very hot. The star is a little bit smaller and dimmer than our sun, but it's very old. And so the star has been around for a long time. We think the planet has then also been around for a long time, something like twice the age of our solar system. What was surprising about our finding, which maybe we'll get into, is you would think that such a hot planet would just be completely devoid of any atmosphere. But the surprising thing was we found that wasn't completely true. We had some inkling of that because the bulk density of the planet is not the same as just a pure ball of iron or even like iron mixed with rock. It's a little bit less dense than that.
And so that means that we thought there could be some volatiles hiding somewhere in the planet, but we weren't sure where. So that was the point of the observation.
Let's get into this. Yeah, because I thought the prevailing wisdom was that if you're small and close, very close to your star and super hot, you probably don't have much of an atmosphere.
Yeah, that is totally correct. And we have lots of other evidence of planets where that's true. They're typically a little bit cooler even than this planet. But again, this planet's a little weird. It has this low density. And not only is the star old, but the stellar composition is quite different than our sun's composition. And so this star has less iron than our sun. Iron goes into forming, you know, planet cores, the densest part, but has more elements like oxygen and more rock forming elements like magnesium and silicon. And so that was also maybe a clue that something different could have happened with this particular very hot planet versus other very hot planets.
But does any of that have to do with why this planet would have an atmosphere?
Yeah. Indirectly, there's been some work that has shown that these ultra short period planets, that's what we call these planets that are at less than one day orbital period, they might have actually migrated to this orbital period late. And so the fact that we have a very old star could have given the planet a lot of time to be hanging out farther away from the star where it's a little bit cooler. And then it only recently through some, you know, dynamical interactions with other planets in the system, for example, moved into this very short orbital period.
And it brought its atmosphere with it?
Well, yeah, maybe, maybe. That's still somewhat of a mystery because, because these models suggest that even in that type of scenario, it's not like the planet was hanging out. At, you know, a hundred day orbital period or much, much farther away. The idea is that it was stuck more at a few day orbital period for a long time and then moved super close. So even there, it's hard for it to hang on to an atmosphere.
This is also kind of blowing my mind because when I think about planets orbiting a star, I don't think about them moving in closer or farther proximity to their star. I feel, I think of them as sort of stuck, you know, in their distance. Yeah.
Yeah. Yeah. I mean, exoplanets, actually, this is a totally separate topic, but they have a lot of evidence of dynamical interactions and some of them actually have orbits that are not very stable and show small variations even that we can measure right now. I think kind of a baseline assumption for planets in constant orbits is, is not a bad one for present day, but they most certainly had dynamical histories that we actually try to use their current compositions to better understand.
Do we know what this atmosphere would be made of?
Yeah. Great question. Not really yet, even though we're using the best tool that we can for these observations, JDMS T, this space-based telescope observing at near infrared wavelengths, still challenging to pull out the signal from, from the data. And so really all we're able to say right now is kind of rule out parts of parameter space for what we think the atmosphere isn't made of. So for example, we, we think there's evidence of an atmosphere because the day side temperature of the planet is cooler than what we would expect from a bare rock, much cooler.
Okay.
The planet is so hot that rocks on the surface of it would be vaporizing, like it would just be evaporating into like a rock atmosphere, right? It's sort of hard to picture, but, but like, almost like a, yeah, sandy, grainy atmosphere. But even that type of atmosphere isn't enough to cool the planet enough to the temperature that we're seeing, at least by itself. So the other options are something that has a little bit more volatiles in the, in the atmosphere, so something like water or maybe a mix of rock and water or a mix of carbon dioxide, for example. We don't have enough sensitivity to, to pinpoint that exactly, but we can, like I said, sort of rule out things that we don't think it is.
I mean, this planet seems like an intriguing place. T O I five, six, one B is not a great name. Do you have a nickname for it?
Um, not, not really. I think that's an okay name. It's now.
Sell me on it.
Well, I don't know. I, this is, this is sort of silly, but I have sort of personalities for different planets that I study in detail. And so like when someone says other TOI numbers, I have thoughts that come to mind.
So for this one, I think of it as like, like very tricksy, um, almost like a fox, right? Where, where it is like outsmarting us and has secrets to hide and we're trying to catch it almost. And we, we've gotten a little bit of a glimpse with these observations, but there's still a lot, a lot of questions that, that remain, which as a scientist is exciting for me.
Are all the TOI planets like that? Are they all tricksters?
No, no, I don't think so. Um, some of them are, at least in my, my mind are much more calm or demure. These are, um, are planets that were discovered by the TESS Transiting Exoplanet Survey Satellite. And so TOI stands for Test Object of Interest. Once planets are confirmed, uh, then they get the, the letter designation. So this is TOI 561B. They're actually sibling planets in the system too, farther out. They're a little bit larger. So I think they, they would also have different personalities, just like my personality is different from my brother's. So yeah, I, I think they're all slightly, slightly different in my mind.
So this is not a place we'd likely go. It probably couldn't support life, but I'm curious how, how it fits into the bigger picture. So why you're interested in it?
You're absolutely right. This is a very hot planet. Um, even with an atmosphere, even, you know, we're seeing it be, be cooler than a bare rock. It's still not a habitable place. However, what is so exciting for me about this system and why I wanted to observe it with JDWST, um, was the potential to better understand, uh, how rocky planets get and retain atmospheres. Um, and so a lot of people are focused on cooler planets that seem like a more natural place for them. There to be to be atmospheres. But on planets like TOI 561B, we think the atmosphere, which is what we're suggesting. We, again, this is just a suggestion, but we're suggesting from our work that this atmosphere is secondary.
So it's something that has been some combination of things being outgassed and evaporated from the surface of the planet. Um, so that gives us a glimpse into the interior of the planet. And that's a perspective that, or it's very hard to get any other way for planets, right? These are so far away, um, not places we're going to be sending spacecraft. And so to be able to have this, this way to get a glimpse of what could be inside the planet, even in a very hot, uh, not Earth-like planet, um, I think is a, a great step forward.
Joanna Teskey is a staff scientist at Carnegie Science Earth and Planets Laboratory in Washington DC. Johanna, thank you for joining us.
My pleasure. Thanks.
This episode was produced by Charles Berquist. And if you're feeling all warm and fuzzy after today's episode, please leave us a podcast review. It really does help. Or give us a call to suggest another far-off world for us to explore. 8774 Sci-Fry, the listener line is standing by. Happy Thursday. I'm Flora Lichtman, and thank you for listening.
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