SciShow Tangents - Yeast

Episode Date: January 18, 2022

These little, bubbly guys help us make such perennial favorites as 'bread' and 'beer.' If you're saying to yourself "what is yeast, Alex," I got good news for you: you're right! Come learn about the microscopic fungus amung us on this week's Tangents!Head to https://www.patreon.com/SciShowTangents to find out how you can help support SciShow Tangents, and see all the cool perks you’ll get in return, like bonus episodes and a monthly newsletter!And go to https://store.dftba.com/collections/scishow-tangents to buy your very own, genuine SciShow Tangents sticker!A big thank you to Patreon subscriber Garth Riley for helping to make the show possible!Follow us on Twitter @SciShowTangents, where we’ll tweet out topics for upcoming episodes and you can ask the science couch questions! While you're at it, check out the Tangents crew on Twitter: Ceri: @ceriley Sam: @im_sam_schultz Hank: @hankgreen[Trivia Question]Yeast mitotic arresthttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC4255140/[Fact Off]Stinking hellebore flower and yeast relationshiphttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC2871880/https://www.newscientist.com/article/mg20527473-900-stinky-flower-is-kept-warm-by-yeast-partner/#ixzz7HEPFjzKBFruit fly and yeast relationshiphttps://www.cell.com/cell-reports/fulltext/S2211-1247(14)00777-3https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0196440https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4556146/https://www.sciencedirect.com/science/article/abs/pii/0300962983906011https://www.cell.com/current-biology/fulltext/S0960-9822(12)00075-9https://blogs.scientificamerican.com/guest-blog/fruit-flies-use-alcohol-to-self-medicate-but-feel-bad-about-it-afterwards/[Ask the Science Couch]History of yeasthttps://www.sciencedirect.com/topics/agricultural-and-biological-sciences/yeastshttp://www.faculty.umb.edu/gary_zabel/Courses/Spinoza/Texts/WAW%20Moll%20Antonie%20van%20Leeuwenhoek.htmhttps://books.google.com/books?id=gy_SAAAAMAAJ&pg=PA228&lpg=PA228https://books.google.com/books?id=XILwDwAAQBAJ&pg=PA72&lpg=PA72http://e-malt.com/statistics/ScientificDigest/Beginnings_of_microbiology_and_biochemistry_yeast_research.pdf

Hello and welcome to SciShow Tangents. It's the lightly competitive science knowledge showcase. I'm your host, Hank Green, and joining me this week, as always, is science expert Sari Reilly. Hello. Not as always. You got to take that out of the description. Icase. I'm your host, Hank Green. And joining me this week, as always, is science expert, Sari Reilly. Hello. Not as always. You got to take that out of the description. I feel like I'm truant. That's true. As sometimes. And also our resident everyman, Sam Schultz. I'm always here. We can't get rid of you. No.

You're always there. You're always right down the street from me. Uh-huh. In that house I've never been inside of because it's COVID. Yeah. Stay out. right down the street from me and that house i've never been inside of because it's covid yeah stay out um you should come over sometime when there is not a pandemic i would love to i'd love to meet your cat especially he's so cute he looks extremely freaking cute all the time he's very cute but he is a wild man i think I think that he got neutered today. Oh no.

Oh yeah. I'm pretty sure it said on the schedule, gummy bear vet. And I think that that was about. It's definitely time. He has this great habit of being really relaxed and adorable. And then you stand up to do something and then he runs head first into your legs. Uh-oh. Why?

I don't know. Like a mountain goat. He gives you a butt? Yeah. It's very, and he'll do it to like the wall sometimes. Cool. He's either not coordinated

or he just really likes to run into stuff. His head is very hard. He doesn't seem to mind at all. And he also will attack, but without claws. So that's okay. He just like goes and he just like bear hugs your ankles.

That's cute. But he got his little gummy bears cut off today. So now he'll be a different guy. Oh, wow. I was just inside and I didn't ask, but I didn't see gummy bear. Oh, no. Or his gummy bears. Anyway, every week here on SciShow Tangents,

we don't usually talk about the testicles of our pets but we do try to one up a maze and delight each other with science facts while trying to stay on a topic our panelists are playing for glory but they're also playing for Hank Bucks which I will be awarding as we play and at the end of the episode

one of them will be crowned the winner with one of those Burger King crowns that you get when you are a child. Now, as always, we introduce this week's topic with the traditional science poem this week from Sari. When you're baking a loaf or doing the most for a feast, that's yeast. That's it. You don't need any more. I'm happy. I'm done. I'm satisfied. That was a full meal. I feel like i just i just feel like i just had a number four mcdonald's that was great well just like a mcdonald's where i order a size larger fries than i ever want but i'll eat it anyway i got more five more stanzas

or you're in the lab at work for eukaryotic quirks knowledge increased that's yeast oh yeah or you're brewing an ale before you set sail west or east that's yeast or you're shopping in a store buy a pouch of some spores they're not deceased that's yeast or your biome is thrown off and your skin starts to slough and wrinkles creased. That's yeast. Or you're just breathing air. Yes, it's there too, I swear. A tiny beast. That's yeast.

That's yeast! We're like 100% of the way through a children's book. Yeah, that was pretty good. Oh man, that's yeast. That was pretty good. They're so good. Oh, man. That's yeast. So the topic for today's episode is yeast, which is a single-celled fungus.

And that's basically all I got. Sari, what's yeast? That's basically all you need to know. They've been around for a while. But interestingly, I didn't dig into this, but I should have probably. But they evolved from multicellular ancestors. I guess that makes sense. So they are single cells, but at some point their ancestors were multicellular.

And they were like, actually, no. We'll go back to being a little bit simpler. Why does that make sense? So like because yeast is a fungus, this is a thing that people say all the time. There's like these two kinds of organisms. There's autotrophs who make their own food and heter They're just, they get food the same way. But a single-celled fungus indicates that it is an ancestor of a fungus. So like, did we draw the line at fungus before or after the sort of multicellular portion

of evolution on earth? And I always sort of assumed that it was after, which I guess is the case, is why that makes sense to me. It's more of a vibe what else do you know about yeast though some more fun facts most of the yeasts

reproduce asexually so they bud off of each other so like create a little bud and bloop but one of my favorite words in biology some yeast cells reproduce sexually by mating and they produce a nodule so almost like budding but instead of splitting in half it's just a nodule with like sex chromosomes and stuff called a shmoo and the

cells join together in a process called schmooing. What? The schmoo is from Lil Abner. It was a comic strip. The schmoo was an animal that you could milk or eat or it could like do labor for you. It was like the perfect animal. And it was like a pet and you could do anything you wanted to with the schmoo and they loved to be eaten as well. So they wouldn't be sad when you ate them. Wow.

Schmoo. Well, that's again, I'm satisfied. What a satisfying episode we've had now that I know about schmooves. Who did that? Who made that decision? I don't know. Someone did and it's stuck. And I guess like yeast do look like that.

They just kind of blob. They do look a little like the schmoo. I'm glad my thing I went to college for is paying off. I did take comic book history. Maybe it's named after him. I think it probably is. They do kind of look like him. Yeast is kind of similar where it does what we want it to and then we eat it when we're done.

This is my question about yeast. So we make bread and beer and stuff out of it. What is our relationship with it? Is it mutualistic or parasitic? What is it? This is a great question because a lot of the yeast that we experiment on in labs or like bread and beer, it's all one species and maybe subspecies of that called Saccharomyces cerevisiae. But there are a bunch of other, I think like hundreds to thousands of other known species of yeast. And some of them are like thrush, the disease on your tongue or like athlete's foot. That can be caused by yeast that is not Saccharomyces cerevisiae. And there are yeasts that like live at the bottom of the ocean.

And there are yeasts in the air. And there are yeasts in all kinds of environments so i think a lot of our relationship with yeast is non-existent or like just we we coexist in the world like we coexist with a lot of other microorganisms but as far as like us cultivating it for beer and bread we like farm it i don't know what what is our relationship with animals we like grow it to eat yeah there's tiny livestock really really tiny livestock do we have a parasitic relationship with livestock oh gosh i think that that's its own it's its own thing okay it is a agricultural relationship okay but i don't know do we parasitize farms farm animals i feel like we kind of do yeah certainly feels that way sometimes but i don't know yeast is it just feels like a tool

to me even though of course it is alive so maybe that's mean to think but it is a single-celled organism where does the word yeast come from so the only interesting thing about the etymology of yeast that I could found is that it comes from the same root word as eczema, which is like bizarre to me. That seems bad. And it comes from what we know of the Proto-Indo-European root Y-E-S. I don't know if it's pronounced yes or not. To boil, foam, or froth. or not to boil, foam, or froth. So we define yeast by the thing that it does because we didn't know what it was back in the day of early fermentation. We were just like, ah, this thing, this goop bubbles. And so we're going to call it the bubbly thing. What's eczema have to do with this?

Eczema is like a bubbly skin condition. I guess your skin doesn't actually bubble, but it's itchy and it flakes off and it froths as much as skin can froth. And I think eczema used to be a term for any sort of skin condition. So when Greek physicians were using eczema, it was any sort of pus-filled thing. So if you're a real pussy, they'd be like, you're a bit yeasty. Yeah. Well, I guess that means it's time to move on to the quiz portion of our show this week. We're going to be playing a good old game of this or that. So yeast has been a faithful companion of humans since before we knew that yeast existed.

And as we have learned more about yeast and genetics, we've also learned how to add genes and engineer a yeast's own pathways to get the organism to brew up medicines and biofuels and lots of other useful stuff for people. So this is why I think of yeast as a tool, not just because it's good at bread, because you can do lots of different stuff with it. Another popular option isn't yeast. It's E. coli, a bacteria, which like yeast is easy to grow, easy to engineer. But which one is better? It depends. Sometimes the bacteria is better.

Sometimes the yeast. And for today's game of this or that, I'm going to tell you something that scientists have made using yeast or bacteria. And you're going to have to guess which of those two things was better at it. Are you ready to play? Sure. Yes. Round number one.

Psilocybin is a psychedelic that is currently mostly illegal, though that's starting to change because scientists are exploring its potential applications for treating a bunch of different mental illnesses. But it is expensive to extract from its original mushroom sources, and it's expensive to synthesize it chemically. Now, you might just say, let them chew on the mushrooms. That makes sense. But maybe it's good to have it direct so that you know exactly what you're getting. So scientists have engineered biological pathways

in both E. coli and in yeast to get them to successfully produce psilocybin. However, one of them is notably cheaper than the other one. Which one is it? Oh, cheaper. Oh, I feel like yeast being a fungus is a trick kind of right do you feel that's what i was wondering that that was my only thread of logic because otherwise these are all complete guesses but like yeast is a fungus a mushroom's a fungus

i'm gonna guess yeast i think i am too yeast is you know it's everywhere that's a cheap thing they're both cheap but you are correct so a team of scientists was able to engineer e coli to get it to produce psilocybin but there was a notable cost involved because prokaryotes like e coli aren't able to express a key enzyme that is needed in the pathway so they had to add that ingredient extra and it costs 288 dollars a gram so that's not great that That's no good. The yeast, however, doesn't have that problem because it's a eukaryote that is fully capable of expressing that enzyme. So you bet you are exactly right that you were looking for something that was

more akin to the thing that originally created psilocybin. So yeah, yeast is better at making psilocybin without that expensive reagent. So it can just churn it out. Round number two, this one's about human milk, which has a lot of valuable nutrition in it, including a sugar called 2-FL. It might help combat the growth of pathogens in our gut. Unfortunately, there's not a whole lot

of this sugar in human milk. So scientists have been trying to see if we can get bacteria and yeast to make it for us. So if you want to milk some milk sugar from yeast or E. coli, which one would you be more likely to do that from? Because it's better at it. Which teat do you want to grab? I think that's what you were going to ask. Who is your single-celled cow in this situation?

I feel like because it's a sugar, that's relatively simple and that's something a bacteria could do. But also... Doesn't yeast eat sugar though? Yeah, that's what I was thinking because yeast ferments sugar. So yeast would probably use up the sugar.

Opposite of what you want. So I think it's the bacteria. I think you're right. Well, I'm going to guess whatever Sari's guessing. Same. I'm going to guess bacteria. Once again, not only are you correct, you're correct about why you're correct. So just go with whatever Sari says, Sam.

In 2018, scientists engineered Saccharomyces cerevisiae to produce 2-FL, resulting in a final concentration of 92 milligrams per liter. Meanwhile, previous work with engineered E. coli reported the bacteria was able to produce 2 grams per liter. It's about 23 times the concentration that the yeast was able to make. The yeast engineers gave a few possible reasons why this might be, including the lack of a particular metabolic pathway to make the sugar, and also the fact that the yeast

might be making a lot of other products while fermenting. And finally, that the yeast might just not be very good at transporting the sugar out of itself because it's hogging that sugar for itself instead. And so now it is time for your final this or that for the episode.

Snake venom is very complex and scientists have been studying venoms because they have enzymes and other chemicals in them that can be really important for developing new medicines. So they're just very biologically active. They can do a lot of different cool things. There are some obvious advantages, though, to being able to make snake venom without having a whole snake involved in the process. So scientists have engineered yeast and E. coli to produce the proteins found in snake venom. Which organism has the dubious honor of being better at making the proteins found in snake venom, E. coli, or yeast?

Oh, wouldn't it be so cool if yeast could do it? I feel like I want to guess yeast just based on how cool it would be. Just little funguses. I'm just going to go with yeast out of coolness. Yeast out of coolness. Oh, I'm going to go with yeast out of complexity because eukaryotic, but I don't have any idea this one could this one's a crap shoot well the answer is yeast one of the snake venom proteins that scientists have studied are called disintegrins and they are promising despite their origins because they can help study

cell adhesion intracellular signaling, apoptosis, and other important cellular processes. When expressed in E. coli, the bacteria were able to make one milligram per liter. Meanwhile, a species of yeast called Pitchia pastoris was able to make up to 10 to 15 milligrams per liter of a disintigrant protein. The reason E. coli is not as good at making snake venom is because snake venom proteins get a lot of their unique structure from a type of linkage called disulfide bonds. But E. coli is just really bad at making those bonds compared to yeast. Probably because it's just not as complicated an organism. So, again, Sari, right, not just because she's right for all the right reasons.

But it didn't matter because it was Ty all the way through. I'm getting smarter. Right. Well, the score is three to three. Next up, we're going to take a short break. Then it will be time for the fact off. Welcome back, everybody. It's time for the Fact Off. Our panelists have brought science facts to present in an attempt to blow my mind.

And after they have presented their facts, I will judge them and award Hank Bucks any way I see fit. Which mostly is by which one's going to make a better TikTok video. To decide who goes first, though, I have a trivia question. Here it is. Yeast are generally cells with spherical nuclei in the middle, and our bodies have cells like that too. But in our bodies, nuclei with funky shapes are more common in aging and cancer populations. So to study how nuclei turn into different shapes, researchers at the National Institutes of Health paused the yeast reproductive process in what's called a mitotic arrest. The yeast genetic material stopped separating into two nuclei, but the nuclear envelope around them didn't stop expanding. It formed a flare of excess material. It formed a flare of excess material. What percent of genetically typical wild-type yeast cells will develop a flare in mitotic arrest?

What the fuck are you talking about? You're going to give me a number between zero and a hundred. Yeah, so mitosis is cell division. So it's like one cell turning into two cells if you break that and it just like overproduces stuff how much will get wiggly and how much will like just do nothing i assume and be completely broken uh 34 it's great five percent you said five percent sorry yeah 90 percent oh you seem so surprised, Sari. Like you knew a lot about this. No. I have no idea about it. I just can picture it very clearly.

Okay. But that means that Sam gets to choose who goes first. I think I'll go first. I have no concept of what's interesting or boring in yeast, so I'm just going to get it out of the way. Okay. Humans. We love yeast. It's such a weirdly useful

weird little guy and we've developed quite a mutualistic i don't know we talked about this earlier some kind of relationship with yeast where we eat it we make it into bread we make it into beer all kinds of yeast stuff and even the animal kingdom has gotten in on the action like there's ants that use a type of yeast in their fungus farming practices. And fairly recently we discovered another yeast slash organism relationship and a surprising one we hadn't seen before. So the charmingly named stinking hellbore is a flowering plant in the buttercup family that grows in Southwestern Europe. So instead of flowering in the spring or summer when there's bugs everywhere and all the other flowers are doing their flowering the stinking hell bore flowers in late

winter when the temperatures are generally around seven degrees celsius i think 44 degrees fahrenheit even though it's chilly these flowers do get pollinated mostly by bumblebees but around this time pollinators are pretty rare and there are also other cold weather problems like smell doesn't travel very far in cold, dry air. So these flowers need to pull out all the stops to get a bee visit. So their big trick to do this is the symbiotic relationship that they have with yeast. So as pollinators visit the flowers, they leave behind the local species of yeast, which the flowers keep alive and thriving by providing them with sugar in their nectar. So the yeast do what they do, and they eat the sugar and create heat in the process. And researchers found that the insides of these flowers could be two to seven degrees

Celsius warmer than they are outside of the flowers, depending on how much yeast they collected. And they also looked at flowers that had been prevented from being pollinated and found that they had no yeast and no extra heat. So they were collecting yeast and making heat. So the heat does a couple of things. The researchers think it makes the nectar warmer, which makes it smellier, which attracts more bees. And it possibly also just gives the bees a nice little warm place to come hang out.

It's like, hey, it's cold out there, bee. Come hang out inside of me. And they studied the bees in the area and found that when given the choice, the bees preferred a warmer flower. So that seems pretty likely too. And these flowers were the first ever plant found that relies on another organism to make heat. And I think it still holds that distinction. This was in 2010.

And I think that's still the case. There are other flowers that make themselves warm to get smellier, like some corpse flower family plants. But they warm up with a chemical reaction that they do themselves. And other flowers just rely on the good old sun to get warm. What's this plant called again? Stinking hellbore. Okay, I'm looking at it. It doesn't look stinky.

No, it doesn't look too bad. I believe it is. I don't even know if it is stinky. I didn't actually see any description of what it smells like. Nobody calls a plant a stinking hellbore if it doesn't. It's also called a dungwort. Oh, yeah. And it's hellborus fetidus, which doesn't sound good either, does it?

No. Fetid sounds funny. Oh lord. So the flower feeds yeast to create warmth for bees. Yeah. Yep. It's like a three-way mutualistic relationship. The bee thing is a little bit more sketchy than... It definitely makes heat to make itself smellier but but that's for the bees to get the bees to come oh that's for the bees for sure yeah but like that doesn't necessarily actually i guess it helps the bees because the bees get something once they get there right the bees get a little snack you get a little snack they get a little food but it doesn't

it's not necessarily a little toasty bee sleeping bag, but it might be. I'm going to say it is. I'm going to say it. Look, scientists are so conservative. Yeah. If you could go somewhere that was seven degrees warmer than it was where you were, you would go there. Yeah. All right. Sari, you got a steep hill to overcome because it's a three-way mutualism with hot, stinky flowers and cozy bee sleeping bags.

Yeah. What yeast fact do you have? So to Sam's buttercup of a fact, I have the rowdy mutualism, I think. Because it's very similar, but also a little bit different. So fruit flies, specifically Drosophila melanogaster and yeast, specifically Saccharomyces cerevisiae, are both popular lab organisms because they're relatively harmless. We have a good understanding of their genetics, and we can mess around with them to learn about other eukaryotic organisms like we've talked about.

But outside of those day jobs in the natural world, they're kind of friends, too. too. When many different yeasts eat sugars for energy, they produce volatile organic compounds that have stinky or fruity aromas like isoamyl acetate and ethyl acetate. For example, think of the smell of a rotting apple or some of the notes in beer and wine that I can never detect because it all tastes gross. Unlike me, fruit flies love those stinks. The adults follow the stink to eat the yeast and preferentially lay eggs on fermenting stuff like fermenting fruits because yeast is easy food for freshly hatched larvae. And while some yeast cells get eaten, others get stuck to the fruit fly leg hairs and get carried away to more sugar-rich environments where they can grow happily. This is a well-known mutualism, and fruit flies and yeast have sorted out some of their differences along the way. For example, fermenting yeast make ethanol, which is toxic and can disrupt cell membranes in other organisms like

fruit flies and apes and whatnot. So fruit flies have enzymes called alcohol dehydrogenase, the same as us, to metabolize ethanol. And for a while, we thought that was the end of the story. The alcohol is an unfortunate hurdle that fruit flies tolerate to crunch on yeast. But in a 2012 paper, researchers found that the flies may actually be seeking out and using the ethanol as a sort of medicine. The researchers raised some Drosophila melanogaster larvae in a lab on control food with no ethanol or food that contained anywhere from four to ten percent ethanol for reference six percent is about the amount in yeast cells that grow on rotting fruits and then they offered up the fly larvae up to two kinds of parasitic wasps

both of whom just straight up lay their eggs in or on the fly larvae so that the wasp babies can eat when they hatch one of the wasps was L. heterotoma, a generalist that feeds on all kinds of Drosophila species, and it avoided laying eggs on the boozier fruit flies. When it did, though, more of the wasp babies died or were really sickly when the researchers cut open the flies and checked on the babies. The other was L. boulardii, a specialist parasite that specifically preys on Drosophila melanogaster, and it was a little more ethanol resistant. Not as much as the fruit flies, but it held up better than the generalist wasp. And in a separate test, infected fruit fly larvae

sought out more ethanol-rich food over the control food. So they basically self-medicated with alcohol when they sensed there was something wrong. Even though ethanol is dangerous, eating poison to kill off your parasite is better than getting eaten by a hungry baby wasp, I guess. This is wild. But what ill effect does a fruit fly experience from consuming poisonous alcohol? Do they get fucked up? Well, drunk babies? Yeah, I don't know.

I don't think they have the cognition to be drunk necessarily. Maybe. You could definitely experience the motor control problems. They're just falling over. Probably like drunk bees.

Stumbling out of the bar. Like drunk bees.'re really similar like just not as controlled but also probably just like damaged to their cells and they don't have as many

so it's like it feels bad because they don't have a giant liver helping filter stuff right right yeah they don't have

all that machinery so they're like their hangovers are way worse probably lifetime long yeah that's it they don't got all that machinery. So they're like, their hangovers are way worse. Probably lifetime long. Yeah. They don't got long to shake it, really. Yeah. But how do they know that the wasps are near?

Oh, they know that the wasps, once they've been infected already. Oh, okay. So like they've got a baby wasp inside them and they feel sick. And then they're like, got to drink up. Oh, okay. That's how you know because there's a baby wasp in you. Yes. Yeah. It doesn't know the wasps are near.

It knows that it's already got got. Okay, I got confused. Oof. A challenge has been laid at my feet and now I, the great King Hank, have to decide which one of you I will execute for not having a good enough fact. I think that the bee is uh cuter

and stinkier and we're a little weirder that's what people love on tiktok cute stinky and weird that's why they like me um uh all right wow now it's time to ask the science couch where we've got some listener question for our virtual couch of finely honed scientific minds. What is it? It's from Emily 17 on Discord who asks, when and how did we first classify yeast as a fungus? And what did we think about it before then? What a great question. You look at a single thing, you're like, ah, it's just like a single cell thing. And then do you have to like do the genome first can you look at it and be like oh it's organelles look like fungus organelles who figured this out who indeed i i realized now

i have three pages of notes i got way too excited about this freaking question and i'm gonna distill it down because i've found google books where people just talked about the history of microorganisms and i'm like i actually love this this is i'm a nerd back when we uh didn't know really what yeast was we knew it was important because brewers would like scrape the dregs from the bottom of jars or the scum at the top and reuse it oh my god that's great that nobody's gonna die of that yeah no weum at the top and reuse it. Oh my God, that's great. Nobody's going to die of that. Yeah.

No, we were like, that's what makes it foamy. That's the fizz. That's the good stuff. They were like, wow, a precipitate. But at least in written material that we can find, didn't think too hard about the chemical reaction. They were just like, we need this fizz. Better put it in the next fizz to keep it going. And so, I don't know

if the general consensus was this, but my understanding was that it was just a chemical that hung around and helped with reactions. Kind of like, I don't know, baking powder. You had it,

didn't want to get rid of it, and you could just like keep generating more. And then, in literature in the 1600s to 1700s, scientists were trying to figure out like quantify the fizz they described what they called quote a ferment and defined it as quote a body existing in a state of internal motion that then like transferred that motion to other particles so they thought the fizz was an inherent trait. And they were describing yeast kind of like we describe temperature, where it's like the motion of molecules, like the wiggles.

They were like, yeast is the wiggles. And so it's transferring the wiggles to our bread and our beer. And that's what makes it fizz. So it's just like a fundamental force of nature to them or something? We didn't know anything. Everything was very confusing and people were doing their best with the information they had. That's so funny that it took us that

long to look at it and be like, maybe we should figure out what that is. Well, we didn't know about microbes. We didn't know that there were small things that were alive that you couldn't see. We were just like, beer exists? That's enough for me. Is that all there is? I worry about it and then I drink some and I stop worrying about it.

The first time someone observed yeast was in 1680. It was a man named Antony van Leeuwenhoek who lived in Holland. And he was like you, Sam, was like, I got a look in beer. He took a rudimentary microscope and was like, what the heck is in here? Well, he was like the Sam was like I gotta look in beer he took a rudimentary microscope and was like what the heck is in here well he was like the first guy who had microscopes yeah and so he found these globules what he called globules in beer that were made of like six separate little lumpy things that were about the same size and shape of a red blood cell. So about like seven micrometers. And what he saw, what that was, is yeast that had divided,

but which is still like clustered up into different cells. But he was like, yeast? This is yeast, I think. But he wasn't sure what it was. He was like, it's inanimate maybe and derived from flour. But like, I can see it now. I can see these like little animals which are bacteria but then there's like yeast and then more chemists came into play lavoisier

in 1789 came up with an equation for fermentation and we started to understand like okay this is how sugar is converted into ethanol and carbon dioxide by yeast. And other chemists chimed in and were like, okay, we've got the idea of alcoholic fermentation. Didn't really think about yeast during this time. They were just like, it's there also. We're chemists. We want to know what's happening with the CO2 in the C6H12O6. Then in 1838, Charles Cagnard Latour, I pronounced a French man's name in a very English way, used a better microscope to observe yeast cells. And he sat in a brewery and like sampled them over time. So it was like, oh, you're brewing beer.

I'm going to take one every hour. And saw the same globules, but then saw the process of budding. And so he saw them protruding. He found some schmooze. He saw some schmooze. And he was like, holy shit, this is not an inanimate thing. It's an animate thing. And he described it as vegetable activity.

So he was like, they're not animal-like. They're vegetables. They're the other thing so we got another step on the path not necessarily closer yeah but similar maybe closer and then around the same time theater schwan who did a lot as far as microbiology and developing the idea that living structures uh came from cells and like differentiation of cells and those are what make organisms and they don't generate spontaneously he was like ah yes yeast is an is a moving living thing and it is a sugar fungus i don't know how he came to the term fungus but

i don't think it came through intense taxonomy he was just like a little plant a fungus and then it feeds on sugar so that's where the word uh saccharomyces comes from so it's like sugar saccharin and then myases which is like mycology i think that's study of mushrooms or fungus yeah so he was just like sugar fungus and then we just kind of kept it as a fungus from there. I guess a fungus would be like probably maybe the kind of vibe around a fungus was a plant that eats. Yeah. Rather than a plant that makes its own stuff. It's kind of the situation with a fungus. If you like look at it with fuzzy eyes that isn't aware of the last 200 years of science. You're like, it's weird.

There's some plants that eat stuff and some plants that make their own food. And those ones are fungus and those ones are plants. Yeah. And so he kind of classified it as a fungus. And 1800s were a mess. There was like a denunciation of yeast as a living organism. A bunch of people were like, no, it can't be alive. Like fermentation is like a reaction between air and plant juice and whatnot.

And yeast is just a byproduct. And then eventually Louis Pasteur of pasteurization was like, no, microbes really exist, guys. of pasteurization was like no microbes really exist guys and uh like established more about fermentation like aerobic and anaerobic which is oxygen using or not oxygen using um in 1883 emil christian hansen isolated pure strains of yeast and i think at that point we like started diving into genetics and like understanding them the 1900s are just like learning about the genetic sequencing of yeast and also learning about what enzymes yeast have to help with fermentation. But that early stuff was a wild roller coaster. Thank you for sitting with me through it. Yeah, it feels a little bit like we kind of lucked into the right answer.

Where I was like, okay, so this thing is consuming sugars and it's more plant-like and less animal-like and so we're gonna be like that seems like a fungus to me and uh and so we named it correctly for once saccharomyces for sugar mushroom nice well thank you uh emily for your question if you want to ask the science couch your question you can follow us on twitter at scishow tang, where we will tweet out topics for upcoming episodes every week, or you can join the SciShow Tangents Patreon and ask us on Discord. Thank you to at Wancho Bros,

at Scribe of Stories, and everybody else who asked us your questions for this episode. If you like this show and you want to help us out, it's so easy to do that. First, you can go to patreon.com slash SciShow Tangents to become a patron and get access to things like our newsletter and our bonus episodes and our Cars 2 commentary, which we are recording this week. Yeah, I have to prepare a lot for it, but we'll get there. Second, you can leave us a review wherever you listen.

That's very helpful and it helps us know what you like about the show. And finally, if you want to show your love for SciShow Tangents, just tell people about us. Thank you for joining us. I've been Hank Green. I've been Sari Reilly. And I've been Sam Schultz. SciShow Tangents is created by all of us and produced by Sam Schultz,

who edits a lot of these episodes, along with Hiroko Matsushima. Our story editor is Alex Billow. Our social media organizer is Paola Garcia Prieto. Our editorial assistants are Deboki Chakravarti and Emma Dowster. Our sound design is by Joseph Tuna-Medish. And our executive producers are Caitlin Hoffmeister and me, Hank Green. And of course, we could not make any of this without our patrons on Patreon. Thank you. And remember, the mind is not a vessel to be filled, but a fire to be lighted. But one more thing.

Yeast is a fungus that populates our gastrointestinal tracts and our poop. So a study published in the journal Microbiome analyzed the fungal makeup of poop samples from about 300 pairs of moms and their babies, and they found that babies were more likely to have detectable fungal DNA in their poop if their mothers did too. And baby poop had more D. hansiniae, which is a yeast also found in cheese and might have something to do with breastfeeding. Then, when they are three months old, they join everyone else in having more S. cerevisiae or baker's yeast

in their poop. So, turns out, you are what you eat. Poop. Eat shit. Eat shit, SciShow Tangents listeners.