Mirror cells could threaten life on Earth. Why are we building them?

For people with two hands, one is usually dominant. On a molecular level, earthly life takes this to the extreme. All of the DNA in living things twists to the right, whereas the protein building blocks favor a kind of left-handed chemistry. The rules of life are based on this chemistry. In recent years, scientists have worked toward a kind of mirror version of life. Currently, the technology doesn't exist to make mirror life at the cellular level — and likely won't for at least a decade. Still, a group of scientists is concerned enough about the possibility that they've published a 299-page technical report https://purl.stanford.edu/cv716pj4036 calling for a stop to the science. In this encore episode for our Tech Camp series, host Regina Barber https://www.npr.org/people/1082526815/regina-g-barber talks to Carl Zimmer https://www.nytimes.com/by/carl-zimmer, a science reporter at The New York Times, about his reporting on mirror cells — and why creating them could lead to devastating consequences for life on Earth. Check out Carl's full article https://www.nytimes.com/2024/12/12/science/mirror-life-microbes-research.html. Curious about other controversial research? Email us at [email protected] mailto:[email protected]. Support public media with NPR+ and enjoy perks for over 25 podcasts like this one. This show’s perks include sponsor-free listening. Learn more at plus.npr.org http://plus.npr.org/. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

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• 0:21Speaker 01

  Hey, everyone. Regina Barber here with another installment of our summer series Tech Camp, and it's just for you because it's Monday. And every Monday through mid-August, we're dropping episodes about the frontiers of tech, tracking down the breakthroughs, experiments, and innovations that could change everything. Today, that means checking out cells. And I don't mean the ones that make up you, me, or every living thing you see. Nope, it's something different that gets two very different reactions from scientists, that it's either the future of biology or possibly the end of life as we know it. Okay, let me back up. So I'm right-handed. Not everyone is.

• 1:05Speaker 01

  My whole life, I've heard the woes of my left-handed friends, that the world is just not made for them. And working on this story, I learned about a whole new level to that. Handedness affects the very building blocks of life, all of life on Earth picks a side.

• 1:21Speaker 02

  The building blocks for our DNA, they're all right-handed. They could be left-handed, but they're not. And that's just a rule across all of life.

• 1:31Speaker 01

  That's Carl Zimmer. He's an author of many books on science and a reporter for The New York Times.

• 1:37Speaker 02

  I'd say my beat is life, basically what it is and what it could become.

• 1:42Speaker 01

  This handedness of molecules and life is called chirality. It's the mirror image of a molecule, like how your face is flipped in the mirror. On Earth, all the DNA we see, aside from some transient exceptions, all the helixes turn to the right. And so far, scientists haven't seen any evidence that life is ambidextrous either. But in the last decade, researchers have been getting closer and closer to understanding how life can be on the other side of that mirror by creating mirror molecules, like in pharmaceutical drugs, some of which are even in clinical trials. Since enzymes in the body didn't evolve to recognize mirror molecules, the thought is that these drugs last longer.

• 2:24Speaker 01

  But Carl says manufacturing these molecules can be a painstaking process, like, say, a scientist hypothetically wanted to manufacture mirror insulin in the hope it lasts longer.

• 2:34Speaker 02

  Now, if you want to make mirror insulin, there's no cellular factory around that you can use to make those molecules. You have to make them by hand, basically.

• 2:42Speaker 01

  Unless you make a mirror cell. That cell could make those mirror molecules. And he says seeing a mirror cell, a form of mirror life, would just be cool.

• 2:53Speaker 02

  I mean, no one has ever seen a mirror cell, ever. As far as biologists can tell, the chemistry should all work in the mirror, but we don't know that.

• 3:05Speaker 01

  Right now, scientists can't even make a regular cell from scratch, much less a mirror cell. But many scientists do see a path to mirror cells, even though it's likely a decade away at the earliest.

• 3:18Speaker 02

  At this point, it's not just science fiction.

• 3:20Speaker 01

  And that worries some scientists, so much so that dozens of biologists published a 299-page technical report on the feasibility and risks of creating mirror cells, claiming that this kind of research could potentially lead to devastating consequences for life on Earth.

• 3:37Speaker 02

  They could potentially create a kind of a pandemic that's almost like science fiction. It would potentially be a total catastrophe, not just for humans, but for maybe all animals, and maybe all plants, and maybe all ecosystems.

• 3:56Speaker 01

  So today on the show, how mirror cells could threaten life on Earth, what it would take to actually make one, and what it means for a scientific community to call for a stop on a technology before it's ever made. I'm Regina Barber, and you're listening to Short Wave, the science podcast from NPR.

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• 5:38Speaker 01

  So Carl, at the end of 2024, like, a group of biologists issued a warning against studying mirror cells. And you reported on this for The New York Times. Can you help us, like, paint a picture of what exactly they're afraid of happening?

• 5:51Speaker 02

  Their big worry is that scientists would create a mirror cell. One of these cells gets out. Maybe it actually just infects someone working in the lab. It gets into their bodies. It's possible that even though it's a mirror cell, it may be able to find some food inside of our bodies, and so that it can actually feed and grow. You would start to have this mirror cell slowly dividing inside of your body. So you can sort of imagine it as kind of like a slow-moving infection.

• 6:29Speaker 02

  The problem is that our immune systems are evolved to recognize life on our side of the mirror. And if they're coming up against cells that have, you know, proteins that are twisting the other way, it's as if these cells are invisible. So these mirror cells would just keep growing and growing and growing and growing until, you know, they kill the first person they infect, and then all of a sudden, you have this person just rife with these mirror cells, they infect other people, and on and on and on, you have this uncontrollable pandemic.

• 7:08Speaker 01

  And you're, I mean, we're talking about, like, worst-case scenario with humans, but we could even take a step back and be like, this could hurt plants, this could hurt animals, you know, this could affect our agriculture, right? Like, what would a scenario like that be? Same, right?

• 7:22Speaker 02

  Basically, if the scientists are right, any species that might be vulnerable to microbes and infections could be totally helpless against a mirror cell. So plants get lots of infections, they get lots of bacteria get into them, and they have all sorts of sophisticated ways of fending harmful bacteria so that they can grow and survive and give us food. And that all falls apart if you're dealing with a mirror cell, as far as plant biologists can tell, because the plant defense systems are all tuned to life on our side of the mirror.

• 8:06Speaker 01

  That said, this hypothetical scenario, like, won't happen tomorrow. There are definitely, like, some big steps that would need to happen before, like, any of this could become a reality. What are the hurdles to scientists making a mirror cell?

• 8:18Speaker 02

  So as of now, scientists have figured out how to make some mirror proteins. They have been able to make a mirror enzyme that can build some mirror RNA. And of course, cells are made of a vast number of parts, and so it's a long way to go before anyone is going to put a mirror cell together.

• 8:47Speaker 01

  So what's the landscape right now on, like, just making a functional cell in the lab?

• 8:54Speaker 02

  Scientists are creating very simplified versions of cells from synthetic parts. And so these have a membrane, they have an inside and outside, you can put some molecules inside of them. Those molecules may do some of the things that happen inside of our own cells. These are not full-blown cells, however. So, you know, just how far you have to go to actually boot up a cell is just a fundamental question. But there is a whole community of scientists who are going towards this goal. They sometimes call themselves the Build a Cell group, and they're headed in this

• 9:39Speaker 02

  direction. And, you know, they keep steadily making more progress. And so while no one is about to make a cell from scratch today, I don't think you can be assured that they won't be able to do it in 20 years.

• 9:56Speaker 01

  So these scientists are calling for, like, a stop to this science before it's been even created. Like, how unique is that?

• 10:03Speaker 02

  I think that this is actually unprecedented. In the 1970s, scientists invented recombinant DNA, where they could take pieces of DNA and insert them into the genes of bacteria. And they were already starting to publish results on this, where you could get bacteria to make human proteins. And then a group of scientists said, whoa, whoa, let's stop and think about this and what we're doing. But, you know, by then, the technology had been created. More recently, people have heard of CRISPR, which is a way to actually edit DNA.

• 10:44Speaker 02

  And there again, you know, scientists did get together and meet and have been talking about the ethics of this. But really, you know, they only started talking about it after they had created the technology. And so now, we're in a situation where the scientists have done enough work that they can see down the road and say, you know, we might be able to make this. It doesn't exist yet. So let's think about what would happen if it existed. And if we think it's a bad idea, let's not do it. So I don't know of, I don't know of any case where this has happened before.

• 11:24Speaker 01

  And if the call to like, stop this science works, we might not need to worry about this potential threat?

• 11:30Speaker 02

  We surely don't need to worry about it today because it doesn't exist. And as scientists have these conversations and other stakeholders get involved, if we can come to sort of a global agreement, then, then this won't come to be. I mean, it's not easy to make a mirror cell. You cannot make a mirror cell in your garage. And so there's an opportunity here for a conversation to really think about what would be the risks and what might be the benefits of making mirror cells and then making a decision about whether to make it or not.

• 12:09Speaker 01

  So even with this warning, how popular is research into creating mirror cells? You said it hasn't happened yet, but like, who's working on it and how many people are working on it?

• 12:21Speaker 02

  Actually, one member of this team that's warning about mirror cells, Kate Adamala, she is among a group of scientists who have actually have been working towards mirror cells. You know, they thought that mirror cells would be cool. And they had, you know, grants from the US government and elsewhere to work on the, on the steps you need to take to get to creating a mirror cell. Now, they still expect it to be decades away, but, you know, they can, they can see the path. And Kate Adamala, after thinking about this and talking with her colleagues, said, you know what? This is not worth it. And she had, she had shut that program down.

• 13:06Speaker 01

  Wow.

• 13:07Speaker 02

  You know, I have not talked to any scientist who has said after this warning came out, yeah, I'm going to go ahead and do it anyway. I think that this is going to actually like be a matter of debate now that this warning has come out. And I think you, you will see public meetings happening over the next year where a lot of scientists and, and people with other kinds of expertise are going to be getting together to talk more about this. You know, are they, are they being hysterical? Are there actually real benefits? We'll see. But right now, I, it looks to me like if anybody is really

• 13:51Speaker 02

  excited about doing a mirror cell project, it's probably not looking good for them to get that next grant.

• 13:56Speaker 01

  Okay. How worried should like, let's say, a regular listener be about mirror cells? Really?

• 14:04Speaker 02

  You, you know, there are lots of things to worry about in our everyday life.

• 14:10Speaker 01

  Yeah.

• 14:11Speaker 02

  A mirror cell killing you is not something to worry about because they literally do not exist on Earth.

• 14:18Speaker 01

  Right, right.

• 14:21Speaker 02

  And if, if scientists are dealing with this transparently and, and thinking about, well, maybe we shouldn't do this at all, then, you know, you don't have to worry about getting infected with a mirror cell in 50 years. Like, it just, as far as we know, mirror cells on Earth will not exist if scientists don't make them. So, there you go.

• 14:43Speaker 01

  Thank you so much, Carl, for bringing us this story about mirror cells. I definitely learned a lot. Thank you.

• 14:52Speaker 02

  Excellent. Thanks for having me.

• 14:53Speaker 01

  Before we head out, if you liked this episode, remember to hit the follow button. That way, you'll never miss another episode of Short Wave. And if you have the time, leave us a review. It helps out the show. This episode was produced by Jessica Young and Burleigh McCoy. It was edited by our showrunner, Rebecca Ramirez, and fact-checked by Tyler Jones. Quacey Lee was the audio engineer. Beth Donovan is our senior director, and Colin Campbell is our senior vice president of podcasting strategy. I'm the regular Regina Barber, not the mirror Regina Barber. Thanks for listening to Short Wave from NPR.

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