Background show artwork for Surprisingly Awesome

Mold giveth, and mold taketh away. The same not-quite plant, not-quite animal that causes cancer can also cure infections and unite long-lost family members.

The Facts

Original music for this episode by Mark Phillips and Elori Kramer

Our theme music is "How We Do," written, performed, and produced by Nicholas Britell

Our ad music is by Build Buildings

Further Reading

“Magical Mushrooms, Mischievous Molds” by George Hudler

"Protecting Peanuts from Aflatoxin"

"Killer Fungi"

"Freeze-Drying is Key to Saving Fungal Collection"

"Beneficial Fungus Formulated Into Bioplastic 'Bullets'"

"A Fungal Fight in the Desert - A little competition among fungi could help save the Southwest's cotton crop"

"Antifungal Peptides Could Protect Cotton"

"Beneficial Yeast: A New Weapon for Keeping Tree Nuts Safe To Eat"

Thanks to

Geromy Moore

Justin Trosclair of the St. James Cheese Company

David Nally

Where to Listen


Adam Davidson (AD): From Gimlet, I am Adam Davidson.

Adam McKay (AM): I am Adam McKay.

AD: And this is Surprisingly Awesome. This is a podcast where you and I try and convince each other that something that seems like it might be really boring is actually really awesome.

AM: That was well said. That's it. And we want you to know that even though that's the format, if it's boring, we're gonna end by saying it's still boring. We're not gonna, like, manufacture excited outcomes. So there's a real risk here.

AD: Yeah. You know there's no risk. Like, we edited the tape. We're gonna record like an hour. Even if it is boring, we're gonna take like 12 minutes and make it seem...

AM: So even if my voice is disinterested, you'll just pitch me up and post and I'll say like, "oh that wasn't that great", and it'll be like, "that was great!"?

AD: Yeah, we can do that.

AM: Alright. Okay, so it's gonna end with one of us thinking it's awesome, without a doubt.

AD: Yeah.

AM: Alright, so I understand you have a subject that, uh, is pretty boring. I've been told what the subject is. It's mold.

AD: Yeah. Mold.

AM: I know mold messes up houses. I know mold, when you leave food out, gets green, gets blue. It's the byproduct of neglect. Sincerely and honestly, I find that a very boring subject. And I'm a little bit thinking, how long is this gonna be?

AD: Okay, Dr. McKay. Are you ready to have your mind blown?

AM: Go ahead. Say your feelings about mold.

AD: Alright. Mold is a sporulating material that utilizes elongated hyphae to pursue both its food...


AD: If you know anything about mold, the one thing you've probably heard is that penicillin comes from mold. I knew this too, but I did not know the full story. The basic story starts in 1928 in St. Mary's Hospital in London. There was a scientist named Alexander Fleming and he was studying a particular kind of bacteria that kills human beings. And he left a petri dish full of this bacteria out on the counter and left for a while and when he came back, he saw that there was a mold growing on it. That's pretty common. Mold is everywhere and every scientist in the world who deals with petri dishes knows that sooner or later, their petri dishes will get infected by mold. But, when he looked at this particular petri dish, with this particular type of mold, he saw something remarkable. The mold was killing the bacteria. That's very unusual. And, as he studied it more and more, he realized that this particular mold, which just happened to be floating in the air of his lab at St. Mary's Hospital, creates a compound that kills all sorts of bacteria that are harmful to human beings. So he knows he has this, like, crazy compound. There's this one moment that I find funny, which is, so, he's like, "Oh, we gotta name this thing." And so, he wrote down, he was like, "penicillium", okay, but would that be penicillin or pen-i-cill-in? And so he asked in his lab, there's 10 people in his lab, he's like, "Who likes pen-i-cill-in?", and three people raised their hand. And he said, "Who likes penicillin?" and seven people raised their hand. He said, "Okay! Penicillin!".

AM: So, that's a mold, we can conservatively say has probably saved a hundred million lives.

AD: Easily. Easily. So, there's sort of this amazing journey. So, he discovers this in 1928 and it's a constant, like, almost failing. Like, just one example, when they were, the very first time they gave, like, "okay, we're gonna do a randomized control trial, we're gonna...". So what they did was they, like, "okay we're got some mice, we got some guinea pigs. Alright, like, let's grab the mice. We're gonna get them sick with bacteria and 25 of 'em we're gonna just not do anything, 25 of 'em we're gonna inject with penicillin." And so they do this. And the 25 that they do nothing, they all die. The 25 that they inject with penicillin, 24 of them are completely healed.

AM: Right.

AD: And so they're like, "oh, okay. There's something going on with penicillin." And they might've grabbed the guinea pigs. It wasn't a big choice. It turns out we now know, years later, penicillin kills guinea pigs.

AM: Come on.

AD: So if they happened to do guinea pigs, all of the guinea pigs would've died, and they would've been like, "oh, eh. Penicillin’s not that great."

AM: Guinea pigs, man.

AD: Yeah. It's now 1940. World War II is breaking out, the Germans are bombing London. They know they have this valuable thing. They don't know how to mass produce it yet. At one point, this team of scientists in Oxford were, um, so worried about Germany conquering England and destroying this, so they started rubbing it all over the linings of their clothes so that if their lab was destroyed, if some of them were killed, the other ones would have it on their clothes, somewhere, and they could, like, bring it back to life. So, as you can see, there's such a limited supply of this stuff, but right then is when they need it so badly. People are getting injured in war, millions of people. We need penicillin more than ever. But we haven't figured out how to mass produce it. What happened is, the particular strain of mold that Dr. Fleming discovered in that hospital in London just wasn't particularly good at growing fast. It killed bacteria, but it didn't grow fast. So, here in the U.S., in a government lab in Illinois, a group of scientists got together and they said, "we bet there's another strain of mold out there, there's so many different strains, there's gotta be a strain out there that has all the positive benefits, it kills bacteria, but also grows really, really fast." Now, if you're a bunch of scientists in Illinois in the 1940's and you want lots and lots of mold to look at, you go to the grocery store. There is always, in a grocery store, mold somewhere, on some moldy piece of fruit. So, they hired this woman named Mary and she just went out asking everybody for moldy produce. That was her job, find anything that has mold on it and bring it back to the lab for testing. And one day, she returned with a cantaloupe, a rotten cantaloupe that had a mold on it and they scraped that mold, and that was a particular type of penicillium, penicillium chrysogenum, and it just grew way faster and heartier than any other. And so, most penicillin used is from that cantaloupe, and they call her Moldy Mary. If you talk to any mold researcher, they know Moldy Mary. She found the rotten cantaloupe that just happened to have that particularly strong mold.

AM: That's an amazing story. That changes the world in some ways forever, right? Saves millions and millions and millions of lives. That's pretty cool.

AD: And this story reveals what's so awesome about mold, what's so surprisingly awesome about mold. In fact, it made me realize mold really is the perfect topic for this podcast, because mold is around us all the time. Every breath you take, you're breathing in huge numbers of mold spores. Everything you touch, every surface you touch, you are touching mold spores. You are bathed in a world of mold. But we never think about mold, except every once in a while we open our fridge and are like, “oh man. My bread's all moldy,” and we throw it out. But mold is amazing. There is a mystery in every one of those breaths you take. Just to give you one sense of it, each type of mold creates all sorts of different chemical compounds. Some of them are used to fight off predators, some of them are used to digest food, to break down plant and animal matter so the mold can eat it. And then most of the compounds, dozens for each mold, millions and millions and millions for molds altogether, we have no idea what they're doing, we have no idea why the mold produces them. But, every once in a while, we find out that one of those compounds can have a huge effect on our lives. They can create penicillin, they can do amazing things. In fact, you might, this very second, be breathing in a mold that is creating a compound that could cure cancer or prevent depression. Or, more likely, you're breathing in countless molds, each of which produces dozens of compounds that have no impact on our lives at all. But, some of these compounds, they don't save lives. They do the opposite. And so, the U.S. government has set up a special mold police system designed to figure out which molds produce compounds that will kill us, and how do they kill us, and how can we stop them from killing us. So we went to the front lines of the U.S. government's war against mold, which happened to be in this beautiful old art deco building in New Orleans.

Shannon Beltz: So, in each drawer, there's a little frozen chunk in there and you can, it's dehydrated, and it holds the spores in stasis.

AD: Oh wow. That's mold. Hey! Hi, mold!

SB: Green fuzzies, yes!

AD: It's funny, it's both cool and kinda gross.

SB: Oh it's not gross. It's not gross. It's just cool.

AD: I was talking to Shannon Beltz. She's a lab technician at the USDA's Agriculture Research Center, that's where we were. And what she showed me was her mold storage system. Filed away in hundreds of little yellow envelopes were different strains of mold. So this lab focuses on one species of mold, aspergillus flavus.

SB: We have more flavus than anything else, so they're all uniquely numbered. 2000, 2001, 2002.

AD: This is a mold that is everywhere. Every breath you take, aspergillus flavus. It's all around us. Right now. Grab your hand, run it through the air. You're touching little microscopic aspergillus flavus mold.

SB: Your body is acclimated to breathing these things and dealing with them.

AD: But when it gets into food, especially corn and peanuts, it creates these compounds that break the food down. And one of the compounds it creates is extremely toxic. If you ingest a fair bit of it, it will give you liver cancer.

AM: Oh, I see. Okay.

AD: That's one of the worst cancers there are. And if you ingest enough of it, it will kill you.

Deepak Bhatnagar: The most recent episode was in Kenya in 2004, where they were eating moldy corn.

AD: This is Deepak Bhatnagar. He runs the USDA lab Shannon works in.

DB: They were storing it in the ground, under high moisture, warm temperatures, and the fungus was growing merrily on that corn and producing large amounts of toxins. And these people were eating that corn, and there were at least 200 deaths reported.

AD: That's not over time, getting liver cancer? That's just...

DB: No, that's right away.

AD: And that's why this lab exists.

SB: Absolutely, yes.

AD: To make sure that I don't eat that toxin.

SB: Yes, we are its enemy.

AD: You have devoted your lives to...

SB: We have. Very willingly.

DB: Many, many people around the globe have devoted their lives. That's why we get up in the morning and run to the lab, so that we can find new things and try to, you know, find a solution that'll affect a lot of people around the world. Gets us going every day.

AD: Here in the U.S., we have a lot of precautions to make sure these toxic crops never get to market. We test them, we make farmers throw the bad crops out. But, that doesn't come free. It costs farmers a lot of money. So, to prevent outbreaks like this, these scientists are taking a different mold, one that's very similar but does not produce the cancer-causing toxin, and they're spreading that other, safer mold all over the crops. It basically creates mold on mold warfare. The safe mold acts as a shield, keeping the bad mold out. And now that we've developed this in America, we're sharing the research with other, less developed countries, hoping that this will stop outbreaks in those countries too, and save lives.

AM: That's really amazing. They're heroes!

AD: Now, for anyone listening in America or Europe, aspergillus flavus is not a threat. The government efforts to prevent it from getting into your mouth are very robust. However, there is a very close cousin of aspergillus flavus, almost genetically identical, and you eat the product of that mold all the time. In fact, if you're my four-year-old son Ash, you eat it almost every day because it is your favorite thing. And right here, you have the paradox that is mold. Aspergillus flavus, the one that makes the compound that gives us liver cancer, is nearly genetically identical to one that makes food way more delicious. And it's used by companies like Kikkoman and others to make soy sauce. My son can't eat almost anything unless he dips it in soy sauce. And it's used by sake producers to make sake.

AM: So it's consumed by the, just, millions of gallons of it. This fungus which kills hundreds of thousands of people around the world, with little differences, people are just guzzling it in Japan.

AD: Yeah, and a couple of years ago, Kikkoman got concerned because their mold was so similar to the dangerous mold, they were worried, "could our mold, like, mutate and start producing the cancer-causing toxin?". So, Deepak Bhatnagar and other scientists at this lab we were visiting, they did the DNA sequencing on the special good Kikkoman mold, and they looked at the entire genome.

DB: They are very, very closely related to this fungus. The genes that were there for making this toxin, they're there, but they're all so heavily mutated. All the genes in there, that it can never revert back to making the toxin.

AD: Oh, so it's like a machine that has the parts to make the poison but it just, it's so broken that it...

DB: It's so broken that it'll never make the toxin.

AD: And he found there were 22 specific changes, but those 22 specific changes were sufficient to deactivate the machinery that creates that toxic chemical. And he said it's basically mathematically impossible for it to spontaneously, genetically make all 22 changes.

AM: Wow. If it did, but it's impossible, then there would be the great Kikkoman massacre of 2027.

AD: Right. Now that's a movie, where we're trying to, like, get aspergillus flavus into Kikkoman and...

AM: It's a good one-line pitch. Just walk in the room and go, "we're trying to get aspergillus flavus into Kikkoman". And you watch checks get written in Hollywood once they hear that. "Whoa, whoa! Come back here! Come back here, young man!"

AD: We're going to take a short break. When we come back, Adam and I will take our relationship to a whole new level, all because of mold. After this word from our sponsors.

[ad break]

AM: Gotcha. I'm alright with that. I'm gonna let you go on that.

AD: Okay, so mold is the most creative. It is the ultimate survivor. And let me tell you about this one mold that I love, and its really unique strategy for survival. It's called pilobolus.

AM: Okay.

AD: Now, pilobolus specializes in the poop of herbivores, of deer and other animals that eat plants. It's in the digestive tract of a deer, the deer poops, and now the mold is in the poop. Now, there's a problem. For its kids to survive, it needs to get in another deer. That's a key part of its lifecycle. So pilobolus, it's in the poop, and it starts moving. And as soon as it touches the edge of the poop, and there's some light coming from the outside, it starts growing in that direction.

AM: Growing?

AD: Growing. It has a very primitive eye and it grows until that very primitive eye is fully illuminated, and now it knows, okay, I'm clear of the poop. And then, it creates all these spores, it builds up this pressure, and then it goes "PUH-SHOOOO!" and shoots six feet in the air...


AD: One little centimeter goes "puh-shoo!", six feet in the air.

AM: Wow.

AD: It lands on leaves far away and just waits for a deer to walk by and eat it and then that deer creates the process all over again.

AM: Why does it wanna be pooped out of a deer so badly? What does that do for it?

AD: It's trying to find some niche in the ecosystem where there's not a lot of competition, where they can get food, and they can reproduce.

AM: So there's not a lot of competition...deer poop.

AD: Deer poop. For now! I mean, they might become pretty hot. So, we have one last stop here on the journey to take mold from boring to awesome. And this stop on the journey is designed to hit home, to you in particular, Mr. Adam McKay. Molds, it turns out, are a huge part of life on Earth, and human life in particular. They help break down our bodies when we die, they're instrumental in breaking down dead plants and trees. I talked to one mold scientist who said it's hard to imagine the world without mold. There would just be leaves piled up for miles and miles, mountains everywhere, and dead bodies everywhere, never breaking down, never disappearing. But I was looking for something less abstract and more immediate, a way that mold tangibly affects our lives. So, I found somebody to help figure this part out, and I wanna see if you can guess who this is. Here's clue number one.

Doris McKay: My grandpa, he didn't learn how to write, and grandma wanted to teach him, at least sign his name, but he was too proud, so he just used an X for his name.

AM: No idea.

AD: Okay. Alright, clue number two.

DM: We're here at Mary's Woods in Lake Oswego, Oregon, and it's a retirement community. I moved here four and a half years ago with my cat, Sonny.

AM: Absolutely no idea. Famous actress of some kind? Or, how would I know who this person is?

AD: Alright, um, one more clue.

DM: The McKays were fun people, and when they all got together they had a good time joking and enjoying the time they had together.

AM: So it's a relative of mine? Who...I still don't know who this is!

DM: Hi, Adam. This is your great-aunt Doris. I always wanted to meet you. Hopefully we will get to meet each other, maybe soon.

AM: Oh my God.

AD: I have been intimately involved with your family for the last two weeks. Do you remember I called you in Portland and I was like, I really wish I could tell you what I'm doing? I was driving to your great-aunt Doris.

AM: No!

AD: So, I had this idea that one of the greatest impacts of mold on the modern world is that the potato famine in Ireland in the 1840's and 1850's was caused by a particular kind of mold. A million people died and two million came to America. So most Irish people in America today came here because of a mold that killed the potatoes that their great-great-grandparents or great-great-great-grandparents ate. So I was curious about this, 'cause I was trying to figure out, like, are they McKays, I figured it's Irish, and are the McKays here because of mold? What I learned was that the potato famine did drive them here, but not in the way you might think. The original McKays were from Scotland and they were moved to Ireland in the 1600's. Your family were very poor linen weavers.

AM: I love that you know this and I don't. My great-great relatives were poor linen weavers.

AD: I know where. I know, like, I saw on Google Maps, like, the block. They're from...

AM: No! Where? In what area of...

AD: They were in a parish called the Grange of Dundermott.

AM: The Grange of Dundermott.

AD: Isn't that, like, the coolest name there is?

AM: Sounds like the name of a mold.

AD: The end of this journey is so crazy, but I wanna save it.

AM: This is amazing.

AD: So, we don't know of any of your family dying from the potato famine. Probably some did, but we don't know of that. I know a lot about your family, weirdly.


AD: They would've been very hungry. Though, apparently, from what we know, not yet hungry enough to leave. So, they stick it out through the famine years. But the potato famine changed Ireland in horribly negative ways. It destabilized the government and it heightened divisions between Catholics and Protestants. In other words, the potato famine helped turn Ireland into a terribly troubled country that people wanted to flee. And then, in 1882, mold finally made your family leave Ireland. What happened was, a new mold ate away all the peat moss. Peat moss, that kinda grassy, pretty thing that makes Ireland look so beautiful, was the main source of fuel. Your family and every other poor Irish family would cut the peat moss, dry it out, and that's how they would cook food, heat their homes in the winter. Well, a virulent outbreak of mold killed all the peat moss. So finally, in 1882, your family left.

AM: Wow!

AD: It's that combination of things, as far as we can tell, that brought your family to America.

AM: Oh, so the potato thing they got through.

AD: Plus the political crisis created, the violent crisis, created by the potato famine mold.

AM: Finally they said alright, we're getting outta here.

DM: There were 15 in the party and they decided to homestead in Nebraska. They had wagons and horses to pull 'em.

AD: You would just show up and if you were willing to farm, they'd just give you some acres?

DM: Yeah. And it was 160 acres and they had to dig their own wells, but one of the uncles was a great well-digger and he dug wells for everybody.

AM: This is very strange. I gotta say, I never imagined we would talk about mold and then suddenly I would be learning about my family history.

AD: So, Doris and I really hit it off. We had a great dinner. She really likes drinking, which was fun. She's really funny! She's cool. So we were talking and she was showing me her family tree and the McKays and, um, telling me, you know, "we're not all Irish. Some of us were English." So, Doris, we just discovered something and I grabbed my microphone. What did we just discover?

DM: Something about Abraham Brown.

AD: Yeah. You were showing me your family tree and it rang a bell, and I looked up Abraham Brown on my little family tree, and we're descended from the same man, Abraham Brown.

AM: [laughs]

AD: Born 1585, died 1650. See? It says your 10th great-grandfather for me.

DM: I'm so impressed that you came all the way to Lake Oswego to find out that we're really related.

AD: We're cousins! That's amazing.

AM: Are we really cousins?

AD: Yeah. We're distant cousins.

AM: Distant cousins, though. You're a dangerous individual. I like that you somehow took mold and we find out we're distant cousins. That's crazy. Who's our link? Who's the guy?

AD: Uh, an Englishman who came, he was born in the 1500's in England, came to America in the very early 1600's.

AM: He had a lot of sex.

AD: He had a lot of sex. You're a direct descendant of one of his daughters, I'm a direct descendant of another one.

AM: Man oh man. If somehow mold led to me meeting for the first time a great-aunt and learning about my family, that's insane. Thank you, mold.

AD: Thank you, mold. We're cousins!

AM: That is crazy!

AD: Today's show was produced by Caitlin Kenney, Eric Mennel, Alex Blumberg, and Robyn Wholey. It was edited by Peter Clowney. Mixing and original music by Mark Phillips, more music by Elori Kramer. Our theme song is by the great Nick Britell. Special thanks to Geromy Moore, Justin Trosclair of the St. James Cheese Company, and David Nally. George Hudler's book Magical Mushrooms, Mischievous Molds was a huge help for this episode. Thanks to our sponsor, has over 180,000 audio books and spoken word audio products. If you wanna listen to it, Audible has it. Get a free audio book and a 30-day trial by signing up at That's And thanks to PC Does Whaaaat?!, a collaboration between Dell, HP, Intel, and Lenovo. Together, the next generation of PC's is doing what no PC has done before. Learn more at We'll be back in two weeks with another episode. Until then, you can find us online at I'm Adam Davidson.

AM: I am Adam McKay.

AD: And this has been Surprisingly Awesome.