[MUSIC PLAYING] FLORA LICHTMAN: Hi, I’m Flora Lichtman, and you’re listening to Science Friday. New extremophile alert, meet the fire amoeba. This single celled gooball 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.

ANGELA OLIVERIO: Hi, Flora. Thanks so much for having me on today.

FLORA LICHTMAN: Give me the origin story on the fire amoeba. Where did you find it?

ANGELA OLIVERIO: 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 hike. So 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. 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 a boring little stream.

FLORA LICHTMAN: And what do you find?

ANGELA OLIVERIO: 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 Rappaport, 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?

FLORA LICHTMAN: And the amoeba was OK. It was alive, right?

ANGELA OLIVERIO: 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.

FLORA LICHTMAN: Why can this amoeba survive the heat? Do we know?

ANGELA OLIVERIO: Right? It’s such a good question. We have some ideas, so we have some hints as to what it might be doing. So one of the things that we did was we sequenced the genome of Incendiamoeba, 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?

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 the cell’s system to make sure that proteins are synthesized and folded correctly, and that they’re removed if damaged. So on a molecular level, that’s giving us some insight about genes that are probably really important when you’re living at high temperature.

FLORA LICHTMAN: Because if you’re living at high temperature, maybe your proteins would get messed up. But there’s a system for clearing them out?

ANGELA OLIVERIO: 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 Incendiamoeba has this form that basically looks like a really long, skinny worm. And it also has a form that looks more like a classic amoeboid form, which would be sort of, like–

FLORA LICHTMAN: A blob?

ANGELA OLIVERIO: –a blob. I hate the word blob, but I’m like, I have to say the word blob, right?

FLORA LICHTMAN: I mean, that is what it is, Angela. It’s a blob.

ANGELA OLIVERIO: 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.

FLORA LICHTMAN: Wait. Like, it turns into it’s skinny worm-like self and then just, like, wriggles away super fast?

ANGELA OLIVERIO: –more quickly. Yeah, more quickly than it was, yeah.

FLORA LICHTMAN: Oh, that’s interesting, so that it shapeshifts to get away from the heat.

ANGELA OLIVERIO: Yeah, exactly. And then another mechanism that we know is happening is what we call encystment. 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.

Encystment is also triggered by lots of other things, like if there’s not enough nutrients available to eat, or desiccation can trigger encystment. And lots of different organisms can incyst. But the cool thing that we found–

FLORA LICHTMAN: Incyst, I love the double entendre there.

ANGELA OLIVERIO: The cool thing that we found out about Incendiamoeba is when it forms this cyst, the tolerance to high temperatures is much higher than other amoeba. So we can expose it to 70 degrees Celsius.

FLORA LICHTMAN: 158 Fahrenheit.

ANGELA OLIVERIO: OK, so we can expose it to 158 Fahrenheit.

FLORA LICHTMAN: We’re getting into well-done steak at this point.

ANGELA OLIVERIO: That’s right. That’s right. And when we take the temperature back down, it’s perfectly fine. It’s happy.

FLORA LICHTMAN: Wow.

ANGELA OLIVERIO: Yeah.

FLORA LICHTMAN: That seems very useful in a warming world, I have to say.

ANGELA OLIVERIO: It sure does. It sure does.

FLORA LICHTMAN: 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– new to us, creature, I should say. Does this change where people should be looking for new life?

ANGELA OLIVERIO: Yeah. Absolutely, right? We thought that eukaryotic life could not get above 60 degrees Celsius since the ’70s. That’s been the paradigm. No organism since very early on has been able to grow above 60 degrees. And this was a long standing paradigm in science. And I think to 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.

FLORA LICHTMAN: I can’t wait to find out.

ANGELA OLIVERIO: Me too.

FLORA LICHTMAN: Angela Oliverio is an Assistant Professor in the Department of Biology at Syracuse University. Thanks for joining me today.

ANGELA OLIVERIO: Thank you for having me.

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FLORA LICHTMAN: Coming up, we take you to a nice, cozy, warm planet where the ground is lava. Find out why scientists are interested in this faraway world. That’s after the break.

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FLORA LICHTMAN: 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-561 b, 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 Teske, a staff scientist at Carnegie Science Earth and Planets Laboratory in Washington, DC. Johanna, welcome.

JOHANNA TESKE: Thanks, I’m happy to be here.

FLORA LICHTMAN: Take me to this planet. Give me the tourist brochure version.

JOHANNA TESKE: 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.

FLORA LICHTMAN: Their year is four days.

JOHANNA TESKE: No, their year is 0.4 of a day, so less than a day.

FLORA LICHTMAN: Their year is 0.4 days? Wow.

JOHANNA TESKE: 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 findings, 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.

FLORA LICHTMAN: 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.

JOHANNA TESKE: 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 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.

FLORA LICHTMAN: But does any of that have to do with why this planet would have an atmosphere?

JOHANNA TESKE: 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 dynamical interactions with other planets in the system, for example– moved into this very short orbital period.

FLORA LICHTMAN: And it brought its atmosphere with it?

JOHANNA TESKE: Well, yeah, maybe. Maybe. That’s still somewhat of a mystery because these models suggest that even in that type of scenario, it’s not like the planet was hanging out at a 100 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 think of them as sort of stuck in their distance.

FLORA LICHTMAN: 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 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.

FLORA LICHTMAN: Do we know what this atmosphere would be made of?

JOHANNA TESKE: Yeah, great question– not really yet. Even though we’re using the best tool that we can for these observations, JWST– this space-based telescope observing at near-infrared wavelengths– it’s still challenging to pull out this signal from the data. And so really, all we’re able to say right now is rule out parts of parameter space for what we think the atmosphere isn’t made of.

So for example, we think there’s evidence of an atmosphere because the dayside temperature of the planet is cooler than what we would expect from a bare rock– much cooler. The planet is so hot that rock on the surface of it would be vaporizing. Like, it would just be evaporating into a rock atmosphere. It’s sort of hard to picture, but almost like a– yeah, a 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 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 pinpoint that exactly, but we can, like I said, rule out things that we don’t think it is.

FLORA LICHTMAN: I mean, this planet seems like an intriguing place. TOI-561 b is not a great name. Do you have a nickname for it?

JOHANNA TESKE: Not really. I think that’s an OK name.

FLORA LICHTMAN: Really? Sell me on it.

JOHANNA TESKE: Well, I don’t know. This is sort of silly, but I have personalities for different planets that I study in detail. And so when someone says other TOI numbers, I have thoughts that come to mind. So for this one, I think of it as very tricksy, almost like a fox, where it is, like, outsmarting us and has secrets to hide. And we’re trying to catch it, almost. And we’ve gotten a little bit of a glimpse of these observations, but there’s still a lot of questions that remain, which as a scientist, is exciting for me.

FLORA LICHTMAN: Are all the TOI planets like that? Are they all tricksters?

JOHANNA TESKE: No. No, I don’t think so. Some of them are, at least in my mind, are much more calm or demure. These 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, then they get the letter designation.

So this is TOI-561 b. There are actually sibling planets in the system too, farther out. They’re a little bit larger. So I think they would also have different personalities, just like my personality is different from my brother’s. So, yeah, I think they’re all slightly different in my mind.

FLORA LICHTMAN: So this is not a place we’d likely go. It probably couldn’t support life. But I’m curious how it fits into the bigger picture, so why you’re interested in it.

JOHANNA TESKE: You’re absolutely right. This is a very hot planet. Even with an atmosphere, even we’re seeing it 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 JWST, was the potential to better understand how rocky planets get and retain atmospheres.

And so a lot of people are focused on cooler planets that seem like a more natural place for there to be atmospheres. But on planets like TOI-561 b, we think the atmosphere– which is what we’re suggesting, 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.

So that gives us a glimpse into the interior of the planet, and that’s a perspective that it’s very hard to get any other way for planets. These are so far away, not places we’re going to be sending spacecraft. And so to be able to have this way to get a glimpse of what could be inside the planet, even in a very hot, not Earth-like planet, I think, is a great step forward.

FLORA LICHTMAN: Johanna Teske is a staff scientist at Carnegie Science Earth and Planets Laboratory in Washington, DC. Johanna, thank you for joining us.

JOHANNA TESKE: My pleasure, thanks.

FLORA LICHTMAN: This episode was produced by Charles Bergquist. 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. 877-4-SciFri, the listener line, is standing by. Happy Thursday. I’m Flora Lichtman, and thank you for listening.

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