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Hi, I'm Lisa. I'm an illustrator at Minute Earth, but I'm also a microbiologist. So, I'm absolutely fascinated by the invisible world all around us and how it influences our lives. So, I'm going to take you on a tour of some of my favorite Minute Earth videos about the microbial world. Some are good, some are bad, and some are really tasty. Some of our favorite foods are closer to this than this. That's because coffee, bread, cheese, beer, even chocolate are all home to millions of microbes. In fact, these foods only the taste, smells, and textures we love because of tiny bacteria and fungi. The vast majority of microbes, about 99%, are actually quite harmless to humans. But, the other 1% are nasty enough that our
ancestors and the ancestors of various other mammals and birds evolved a natural repulsion to stuff that might harbor nasty germs. In general, we think rotten stuff looks and smells disgusting, which considering what's at stake isn't overly cautious. Fortunately, if friendly microbes get to our food first, they can keep the bad guys at bay. Meats left out on the counter provides the perfect conditions for pathogens to flourish. It's warm, moist, and protein-rich, just like our bodies. But, with some micromanagement, adding lots of salt for instance, we can help harmless salt-tolerant microbes outcompete their dangerous but salt-sensitive relatives.
A few unrefrigerated months later, we get salami rather than salmonellae. Our ancestors stumbled on this kind of controlled spoilage thousands of years ago, either by lucky accidents or out of serious desperation. And we humans have been intentionally spoiling food ever since. Not only to keep our food safe to eat, but also because the microbes we culture can transform it almost magically into awesome deliciousness. Yeast, for example, gorge on the sugary starch in bread dough, then burp out carbon dioxide that helps give loaves their lift. In a more exotic transformation, bacteria and fungi take turns munching on piles of cacao, mellowing out bitter polyphenols, and helping create the complex and delicious
taste of chocolate. And deep in cheese caves, mold spores populate small holes and cracks in soon-to-be blue cheese, digesting big protein and fat molecules into a host of smaller aromatic and flavor compounds that give the final product its smoothness and rich funky flavor. But to some, stinky cheese is about as appetizing as licking someone's toes, which isn't that far off since the bacteria that make some cheeses super stinky are the same ones that cause foot odor. Yum. Even so, these flavors tend to grow on us, not just literally, but also figuratively. The more we're exposed to particular microbial funks, which can even start in the womb, the more we tend to like them. As a result, people around
the world have some very different ideas about how to microbify foods, but every culinary culture involves fermentation in one way or another. If we didn't let food spoil just a little bit, we'd have no sauerkraut, soy sauce, pickles, or prosciutto. Not to mention kefir, kimchi, kombucha, kumis, katsuobushi, and plenty of other delicacies that don't start with K. What's more, spoiled food may well have changed far more than our tastes. Historical evidence suggests that when our ancestors gave up their wandering ways and settled down to grow grain, it was likely for love of either bread or beer. Whatever the case, one thing is clear. Without the help of friendly
fermenting microbes, we humans would be terribly uncultured. After our lovely microbe-fueled coffee, let's take a walk in the forest. I love the way the forest smells. And if you are smelling this scent called petrichor, what you're really smelling is a tiny compound called geosmin that's produced by gazillions of bacteria. These all live in the soil, a place that I would consider alive. Here's a bear. We probably agree that the bear is alive, but how about the soil it's sitting on? That definitely isn't a living thing, right? It doesn't do a lot of the key things living things do, like moving and reproducing. But ask scientists
whether or is alive, and the answer more often than not is yes. What's going on? Welcome to Minute Earth. Soil actually has a lot more in common with a bear and all other living things than you might think. Just like all the stuff that makes up the bear, living stuff, dead stuff, minerals, air, and water are constantly working together and sustaining each other so the bear can keep doing its berry things. Soil is also made up of a system of living stuff, dead stuff, minerals, air, and water. That's right, these things don't just exist in soil, they are the soil. And they're constantly working together as a dynamic self-regulating system. You might call it a living system. Then there's the fact that living things interact with
their surroundings in all sorts of ways. A bear, for instance, gobbles up resources from its habitat and spreads nutrients around. And soil, too, is a dynamic link in its ecosystem. Its air-filled pores help regulate a fluctuating water flow. Soil helps transform an ecosystem's dead stuff into easily accessible nutrients like nitrogen, phosphorus, and carbon that other life needs. And it serves as a storehouse for extra nutrients until they're required. And maybe the most compelling argument for soil being alive is that it can die. Like a bear, soil can lose its ability to carry out all its internal processes and external interactions. Like if soil's air-filled pores get too smashed, it starts losing its ability to hold water,
leading to floods and erosion. If certain nutrients get depleted, soil loses its ability to support life. And soil that can't support life can't support us. It can't grow the food we need to stay alive or store the carbon needed to stave off climate change. So, whether or not you actually believe soil is alive, it's useful to think about it as being alive since that can help us understand how soil functions as a complex dynamic system and how it can change over time, especially as a result of our actions. What's more, it gives us a vocabulary to talk about those changes. In fact, it can be helpful to think and talk about all sorts of maybe not technically living things, from the ocean to the economy, as having living properties. In the end, that may
help us ensure these things can stay alive and that we can stay alive, too. Some of the most obvious living things in the soil are mushrooms. We can see their fruiting bodies as we walk around, but that's only the tip of the fungi-sberg, Nilda. Underneath their fruiting bodies is a vast network, and that network is at war. A long time ago, almost all forest mushrooms used to feed on decomposing stuff on the forest floor. You could say they were death eaters. But, over the past few million years, a bunch of different species from different parts of the mushroom kingdom have defected and evolved a new strategy, and now a mushroom civil war is raging.
It's the death eaters versus the sap suckers. Hi, I'm David, and this is MinuteEarth. Instead of relying on dead stuff for food, the sap suckers have struck up an alliance with trees. These mushrooms grow long, thin tendrils that wind together and hook into a tree's roots, extending the tree's reach underground and helping them grab even more nutrients and water. In exchange, the mushrooms get to tap into the tree's delicious sugary sap. That's why we're calling them sap suckers. If you're a mushroom fan, you're probably already familiar with sap suckers because their sugary diet makes them great for eating. But, before they make it onto our plate, they're in conflict with the death eaters. The two sides' strategies are so different that
it seems like they'd have little reason to compete, but there's one critical resource that sap suckers don't get from their alliance with trees, nitrogen, which is left over when stuff decomposes. It turns out that all mushrooms need nitrogen to form proteins and other critical molecules. So, sap suckers have to search for nitrogen in the surrounding soil, setting up a battle. Since death eaters aren't tied to trees and spread their feelers out everywhere, they're often the first to encounter nitrogen, and they use their specialized decomposing enzymes to quickly break it down and hoard it before the sap suckers can grab much at all. Sap suckers who can't get enough nitrogen die, and to add insult to injury, deatheaters are happy to feast on the corpses of any
sapsuckers who don't make it. The sapsuckers though have some tricks under their caps. They send out sneaky straw-like tendrils to siphon the hoarded nitrogen away from the deatheaters. And some sapsuckers have developed some nifty chemical weapons. Black truffles, for example, can produce a toxin strong enough to kill other nearby mushrooms. And these sapsucker strategies are working to outmaneuver the deatheaters. Sapsuckers now dominate more than 2/3 of forests worldwide. That's actually been good for the forests since sapsuckers supercharge trees' ability to grow big and survive droughts, which is good for us humans. Forests dominated by sapsuckers are 20% better at removing planet-warming carbon from the air than
those controlled by deatheaters. But humans might be inadvertently helping out the deatheaters. The huge amounts of nitrogen we use to grow food ends up seeping into nearby forests, where deatheaters are able to quickly find it and use it, which helps supercharge their growth. And the pollution we release into the air is harming the trees with which the sapsuckers partner, preventing them from thriving. So, while the sap- suckers are winning, the deatheaters have the momentum, at least for now. In other words, it's still not clear which side, if any, will win the fungal rumble in the jungle. Fungi don't just influence the ground where they live. Their almost invisible spores also have huge influences up in the sky. If you've ever come across a mushroom
like this one, it may not surprise you that mushrooms are the reproductive organs of fungi. In a single day, one mushroom can catapult billions of tiny spores into the air. And not only do these spores help seed baby fungi, they also help seed clouds. That's because in order to form clouds, moisture in the air needs microscopic particles to glom onto, like airborne dust, sea salt, or pollution. But in places with lots of life, rain-making particles are often biological in origin, like bacteria, pollen, plant fragments, and spores from mushrooms. In fact, Earth has so many mushrooms intent on reproducing that there are a billion spores above every square meter of its surface.
Many of these spores drift high up into the atmosphere, where they provide a scaffolding for water to condense onto, seeding raindrops and ice crystals, and resulting in literal mushroom clouds. Small things can influence some of the biggest systems on Earth. And it turns out that some of the chemicals produced by bacteria and fungi that they use to protect themselves have a massive impact on us humans. For every 10 medications used by humans, seven contain chemical compounds that originally came from the natural world, mostly from bacteria, fungi, and plants. That's because these unassuming organisms are masters of chemical warfare.
Unlike more mobile creatures, which can flee when they're threatened, plants, fungi, and bacteria are more or less stuck. So, they've evolved machinery that makes specialized chemical weapons as defense against threats, both from predators and from each other. The battle plays out everywhere, on the tops of mountains, bottoms of oceans, and even under our feet. There, soil bacteria looking to deter hungry worms produce compounds that interfere with invertebrate's nerve impulses. Other dirt-dwelling bacteria fend off fungi by turning out a chemical that makes fungal cells leaky, causing an oozy death. In exchange, one group of fungi create a compound that breaks down the cell walls of their bacterial nemeses. We humans have co-opted
all of these compounds for our own use. You've probably taken the medicine known as penicillin to treat a bacterial infection. And if you, or more likely your pet, has had a brush with parasitic worms, you may have used a drug from the ivermectin family. If you've gotten a serious fungal infection, doctors probably treated you with amphotericin. These co-opted drugs are some of the best pathogen-fighting drugs on the market, which stands to reason. Nature is essentially doing drug research and development all the time. And while nature's R&D is simply a series of blind experiments that don't always end up successful. Enough of these experiments have happened all over the planet over billions of years to result in an incredible range
of effective weapons. And pathogen-fighting drugs derived from nature are just the beginning. We have found painkillers in poppies and willow trees, an eczema treatment in bacteria, anti-cancer medicine in Pacific yews, cholesterol drugs in fungi, asthma medication from the ephedra plant, and many, many others. What's more, there are so many organisms out there that we haven't even identified, much less put to pharmaceutical use. One teaspoon of soil can contain tens of thousands of species, most of which are unknown to science, each pumping out dozens of defensive compounds that might, one day, end up in your chemical arsenal. So, yes, microbes produce many of the compounds that we use for medicine. But
one particular microbe that used to be incredibly helpful for us has now turned to the dark side. Hi, this is Julian from Minute Earth. 3 billion years ago, the land was lifeless and the air oxygen-free, but rich in CO2. The oceans were hot and loaded with nitrogen and phosphorus, and aquatic microbes called cyanobacteria were loving it. These microbes would later turn out to be our enemies, but at this point in time, humans didn't exist yet. In fact, cyanobacteria actually helped make our existence possible in the first place. But back to early life on Earth. In addition to being heat-tolerant, the cyanobacteria grew in thin mats that were good at soaking up light and nutrients like nitrogen and phosphorus,
and built nasty toxins to poison their competitors. And in one of the most profound steps in all of evolution, they figured out how to combine carbon dioxide with water to make tasty sugar, a process called photosynthesis. But that fancy new photosynthesis also happened to release oxygen, which was poisonous to organisms that had evolved under oxygen-free conditions, which meant pretty much all life on Earth at that time, including most of the cyanobacteria themselves. But over time, the surviving cyanobacteria evolved to not just tolerate oxygen, but to use it with a sort of reversal of photosynthesis, which we now call aerobic respiration. This helps cyanobacteria grow to dominate the
Earth's oceans for another billion years. Eventually though, as the Earth began to cool and nutrient supplies got used up, some algae well adapted to those conditions also stole cyanobacteria's metabolic secrets. The algae outcompeted cyanobacteria, pushing them into the shadows across much of Earth's waters for the next billion years or so. This long interval also saw the evolution of more complicated life forms, including oxygen breathers like us. And we have held center stage ever since. But our success today is now making things awesome again for cyanobacteria. We've done this by pumping CO2 into the air, which has warmed the atmosphere and oceans, which cyanobacteria like. Also, because we over-fertilize our farm fields, the rain
washes a lot of that fertilizer into rivers and oceans, providing a level of delicious nutrients that cyanobacteria haven't seen for perhaps billions of years. And that's bad for us because these heat-loving, nutrient-gobbling microbes are once again forming sludgy, gross-smelling mats that release nasty toxins that keep their algal competitors at bay, but also make animals and people sick. And since cyanobacteria live short lives and die in large groups, floating mats of their dead bodies serve as food for oxygen-breathing decomposers who temporarily use up all of the available oxygen in the water, killing fish, shrimp, insects, and plants in sometimes dangerously massive dead zones. To keep cyanobacteria at bay, we
need to stop warming the planet and to farm in a way that doesn't send nutrients into waterways. Until we do, the little creatures that first gave us oxygen are going to keep on blooming and dying and turning our oceans and lakes to the dark side. Okay, so some microbes are good and some are bad. And some are like history teachers. These small single-celled forams have helped us figure out how the temperatures on Earth has changed over the past half a billion years. Let's see the popular T-Rex do that. Hi, this is Emily from Minute Earth. Each of these seashells is in fact really, really tiny because each was once home to a tiny single-celled marine life form called a foram. Though they don't have eyes or brains or limbs, forams somehow managed to pull
ingredients from seawater and stack them together into houses made out of the mineral calcium carbonate. Even cooler, each little house ends up with a number written into it that tells us how much ice and snow there is on Earth. That's right, a single-celled sea creature knows how much combined snow and ice there is on all the mountaintops and ice sheets and glaciers on our entire planet. Crazy, but it's true. Here's how it happens. The number in the foram shells comes from the two types of oxygen forams pull from seawater. The regular kind with eight protons and eight neutrons and the heavy kind with eight protons and 10 neutrons. H2O molecules with regular oxygen are slightly lighter and less sluggish than H2Os with heavy oxygen. So
they're more likely to evaporate from the ocean surface and go gallivanting around in clouds. And since all the ice in the ice sheets comes directly from clouds, the ice sheets act as a kind of storage facility for regular oxygen. The colder the global climate, the more regular oxygen the ice sheets store and the less is left behind in the oceans. As they built their shells, forams effectively capture the ratio of regular oxygen to heavy oxygen in seawater and we can read that ratio back to figure out how much ice there is at the poles and thus what the average global temperature is. Of course, we can also just measure those things directly, but our thermometers and can only tell
us what's going on right now. Forams, on the other hand, have been recording this data for hundreds of millions of years, and their archives have been slowly piling up on the seafloor. So, by drilling down and pulling up a big long core of ancient sediment, we can recover an almost continuous record of how Earth's temperature has gone up and down and up and down, etc., over time. In fact, we owe most of what we know about our planet's past climate to these tiny brainless seafarers and their tiny, beautiful homes. Whenever I'm at the beach, I love watching the waves mix and churn. And I can't help but wonder what life is like for the smaller things that live at the top of the ocean. How do they evolve?
Well, we don't know. This is one of science's biggest mysteries. Let's find out why. One of the biggest mysteries in biology centers, perhaps surprisingly, around one of its smallest organisms, single-celled ocean-dwelling plankton. Specifically, why are there so many different species? Welcome to Minute Earth. In most instances, when similar species live in the exact same place and compete for the exact same resources, only one species succeeds, and the other ones either go extinct or have to try something different. In California, for example, when almost identical plants known as tarweeds and rosinweeds start growing on the same rocky hillside, the rosinweeds will take over and the tarweeds will die off.
And in the American Northeast, different bird species that once competed for the same resources in the same spruce trees now don't. The Cape May warbler has come to dominate the valuable top of the tree, while other warbler species have had to carve out a different living lower in the tree. In these situations, a tiny little difference, like rosinweeds' marginally quicker growth in shallow soil, gives them a slight advantage again and again. It's enough to result in one species coming out on top. These KOs are backed up by math. We figured out equations that simulate how matchups between similar species will play out. And in almost every case, the models agree that there's going to be a winner,
and that winner will take all. Over time, one species will apply its small advantage again and become the champion. Plankton seem like they should follow this winner-take-all rule, too. After all, most plankton species compete for the same resources within the same surface layer of the ocean. One species should come to dominate, and the other should scram, right? But instead, thousands of very similar plankton species all seem to coexist in relative harmony. What gives? One possibility is that the models are wrong, at least for plankton, because they don't account for the unpredictable conditions in which plankton live. Wind and waves may be mixing up the water enough and regularly enough that no one plankton
species has enough time to exploit whatever tiny advantage they have and outcompete their rivals. Perhaps every disturbance simply puts all the competitors back on nearly equal footing, just like when tar weeds and rosin weeds first start growing on that rocky hillside. The second possibility is that the models are right, but we're using them wrong. When scientists collect plankton from the ocean, they often use what's called a plankton net, basically a stocking attached to a bottle. When they pull this contraption through the water, they may actually be sampling several different micrometer-thick microenvironments, each with a slightly different combination of resources. So, while it appears that several species of
plankton are coexisting peacefully, perhaps what we're actually seeing is a jumbled-up collection of species that, in their natural state, actually dominate their own tiny, just different enough microenvironments. It's as if we counted all the birds in the spruce tree together and said, "These trees are shared by many similar species of warblers," without realizing that they specialize in different parts of the tree. Recently, though, many researchers have come to favor a third possibility. The model is right, but occasionally spits out something weird. It turns out that when you model five or more species competing for three or more resources, the entire system can occasionally get caught in a chaotic
loop, and no clear winner ever emerges. It seems like this is the case for certain groups of cave-dwelling bats. Maybe the coexistence of thousands of species of plankton is the result of that chaos, too. One thing is for sure, as much as we know about the world, to truly understand its inhabitants, even those as seemingly simple as single-celled sea dwellers, we've got a plankton more to learn. Oof. Plankton puns. While we're in the ocean, though, let's have a look at why the most famous shipwreck in the world is rapidly disappearing. It turns out that some microorganisms have a taste for luxury metal.
The Titanic was once thought to be indestructible, and we all know how that turned out. And now it's dying a second death on the seafloor as it erodes. It's disappearing so quickly that experts predict that by 2050, there will be no sign of it. Meanwhile, this Greek merchant ship, which sank 2,400 years ago, is super well preserved. What the wreck is going on here? Hi, I'm Cameron, and this is Minute Earth. There are two main factors that determine how long a shipwreck might last on the seafloor. Now, there's a lot to consider, but in general, it comes down to what the ship is made of and how
much oxygen there is on the seafloor where it sank. For most of seafaring history, ships, both above and below the water, were made mostly of wood. But during the Industrial Revolution in the 1840s, people started making ships out of metals, mostly iron and steel, that gave us bigger, stronger ships like the Titanic, the Lusitania, and modern luxury cruise ships. It stands to reason that these big metal ships should outlast the wooden ones, even underwater. And under some conditions, like if there's oxygen around, they do. Warm, shallow, oxygen-filled water tends to be full of animals and microbes searching for organic matter to gobble up. A wooden ship that sinks in these waters is a buffet for these
decomposers. They'll start breaking down the wreck almost immediately. Shipworms, which are so named for their incredible ability to burrow holes in wooden ships, can completely break down a wooden shipwreck in as little as 2 years. That's not the case for a metal ship that sinks in shallow waters because there aren't any critters there capable of digesting iron or steel. Sure, the metal ship will eventually rust, but in these conditions, it will last tens of times longer than the wooden ship. In deeper, colder waters with less oxygen, the rules are reversed. Wooden ships that sink here just live on.
That's because in the depths, the water has so little oxygen that most organisms, including those wood-chomping decomposers, can't survive. The Black Sea, a particularly oxygen-poor body of water, is home to at least 60 known immaculately preserved ancient shipwrecks from as far back as the time of ancient Greece. Some are in such good shape that archaeologists can literally read the engravings in their planks. Iron ships that sink in similarly cold, deep water aren't so lucky. That's because although wood chompers can't survive in these oxygen-poor waters, other, weirder decomposers can.
Instead of using oxygen to make their bodies run, these microbes run on iron. They usually get their iron from geologic vents on the seafloor, but when an iron ship like the Titanic reaches their depths, they will happily feast on it. Scientists estimate that by 2050, these iron chompers will have consumed the entire Titanic. In other words, my heart may go on, but this ship will be gone. All the videos we've shown you so far are about microorganisms in their natural environments, but everything we know about microorganisms is from laboratory studies in Petri dishes, where they don't behave like they would
in nature at all. And that's a problem. When I was working as a microbiologist, a day in the lab would go like this. I would mix a powder called nutrient agar with water in a beaker and then chuck it into a fancy oven to make it sterile. I would then pour the warm liquid into little containers called Petri dishes, where the liquid would cool and solidify into jello. And once that was done, I would do it all over again, and again, like a hundred times a day. That's what I spend most of my time doing, and that's because Petri dishes are amazing. They're easy to prepare, they stack nicely, and the jello inside then provides the perfect nutrient-filled habitat for well-studied bacteria like E. coli to grow on top of. Petri dishes
are basically the perfect research tool. But, as great as they are, they have a huge drawback. Only a tiny percentage of bacterial species will grow on the jello. The other 98% of them simply refuse to. Hi, I'm Lisa, and this is my new Earth. E. coli are easy to please. I would know. I've grown literally billions of them. In the human gut, they live on warm, smooth surfaces with easy-to-access nutrients. In the lab, Petri dishes can mimic that lifestyle pretty well. But, while it's easy to think of bacteria as all really similar, in reality, they are a super-diverse group of organisms with incredibly different lifestyles. I mean, consider animals for a second. You wouldn't build
an aquarium, throw a monkey in it, and be surprised that it isn't happy. An aquarium is just too different from a monkey's natural habitat. Similarly, most types of bacteria cannot grow on nutritional jello in a Petri dish because it's just too different from their natural environment. For example, these bacteria grow in marine sediment where the bottom layer has sulfur but no oxygen, and the top layer has oxygen but no sulfur. So, its food is at the bottom, and its air is at the top. These bacteria form a vertical conga line where the top one breathes and the bottom one eats. Then, they exchange energy in the form of literal electricity. The flat, horizontal surface of Petri dish jello doesn't allow them to do the things they need to survive. Some bacteria, like Vibrio
fischeri, are really good friends with other organisms. They grow in the light-producing organs of the bobtail squid. It's so cute! The luminescent bacteria help the squid camouflage itself. If you want to study these friendships in the lab, you'll have to actually build an aquarium full of squid to grow together with these bacteria. And some bacteria are parasites that will only grow within living animal cells, but not in a friendly way. This is the case for the bacteria that causes syphilis. Putting a bacteria on a plate of jello is like feeding them candy bars, which does work for some species, but other species, like syphilis, are pickier. They need a constant supply of fresh nutrients, like you can only get inside a host cell. And
some bacteria grow in environments that we can't replicate because we still don't know enough about them. All organisms need something from their environment, like how the bacteria that live in thermal vents need a ton of heat, while others need high amounts of salt, and still others need blood. These things aren't difficult to provide in petri dishes, but the key is knowing what the little bugs need, which can create a catch-22 situation. We can't figure out what it is that the bacteria specifically needs to grow because we can't study it because we simply don't know how to grow it. Because of all these difficulties, the vast majority of what we know about bacteria comes from the easy-to-please
E. coli that thrives in petri dishes, which have been a huge boon to microbial science. But at the same time, my mind boggles at the thought of all the species we don't know about simply because they don't grow on petri dishes. But lab techniques evolve, and we are now learning more about the world of bacteria by bringing the lab outside or by bringing some of the outside world inside. One day, petri dishes might even become obsolete, but I will still love them. I mean, look at this jello. It's alive. As you can tell, that last one was personal. I've spent so much time trying to get bacteria to behave in petri dishes. And you know, the more I learn about microorganisms, the more I love them. They play such big roles in human
health, climate, and in producing my favorite snacks. Thank you for watching this compilation with me. I hope you love the microbial world a little bit more as well. And you know what? I don't just love the microbial world, I also love you. Thank you for being here and watching this with us. And see you again soon. And if you're not gone yet, this is my plushy collection. This is Candida. That's a fungus that's really bad for you. This is cholera that swims through the sea. This is a cancer cell that you can turn inside out and then it's health. This is syphilis.
