 Most of us, when we think of bacteria, we think bad, bad bacteria, dirty bacteria, kill the bacteria, antibacterial madness, like squirt antibacterial, everything on every surface, please, bacteria, bad. Well, I just have to make sure that everyone's super clear about a couple things. First of all, you have 10 trillion cells in your body. You never take a 10 trillion or so or 20 trillion, whatever. Those are you, your cells. Okay? You're cool with that. Do you know how many bacterial cells are in or on your body? 100 trillion bacteria in or on you. What? True story, dog pounds. Most of them are found in your gut. However, they're everywhere. They're in your skin, they're in your eyebrows, they're like up your nose, they're everywhere. And there's 10 times as many of them in your body as you. Now, right off the bat, we do not want to get rid of them. One of the problems with antibiotics is that antibiotics often target and kill the good bacteria that are living in our system. And I say good because they serve some pretty important functions. It makes you wonder, what are you? Because it's not really like you are this brilliant human organism. It's like you're a walking ecosystem for a whole bunch of other kind of critters that are like hanging out and living in there, including like little mites and stuff that live in your eyebrows. All right, so our friends with bacteria, what are they doing? Oh, wait, I was going to tell you how much they weigh because don't you want to know? Some of you may know this fact already. Three pounds, three pounds of your body weight actually is your friendly troop of bacteria. So the next time you go to the doctor and you get weighed, just go ahead and say would you please subtract three pounds from that because it isn't me. That might make you feel a little bit better sometimes. I always subtract three pounds when I step on the scale. So my 100 trillion bacteria, I'm telling you that they're good, but dude, somebody's got to convince me, like why are they good? I'm just going to tell you right now, there's a couple of things that happen. First of all, they compete with bad bacteria. And so actually, if you have good bacteria, they use resources, they take up space, and those are resources and space that can't be taken up by bad bacteria, bacteria that make you sick if they're healthy and doing their thing. So you take some antibiotics, you kill some of the bad bacteria, and then you kill a bunch of the good bacteria and now it's like a ghost town down there and other bacteria come in and they're like woo-hoo. We were having to work really hard being kind of kept in check by the presence of all these other bacteria, but now nothing's here, so let's totally go to town. We can build like massive cities now. And bad bacteria, the reason why they're considered bad is because they make you sick. That's, I mean, that's relationships amongst critters. Your 100 trillion that are living here, what would happen if they made you sick? You wouldn't be alive. You probably would be like, dude, there's 100 trillion people trying to kill me, and so you probably would not make it through that. So these are 100 trillion that are either just chilling and not bugging you at all or possibly doing some good things. So they compete with the bad guys, which makes it harder for bad guys to come in. Sometimes they make stuff. And one of the things, there's a bacterial species that makes vitamin K. What? And you wouldn't have vitamin K if you didn't have it produced by these bacteria. And the bacteria that make vitamin K live in your large intestine and then your large intestine cells suck the vitamin K out of your poop before it gets pooped out. You suck out the vitamin K that the bacteria made for you. Thanks, guys. And then vitamin K, I mean, it makes sense, vitamins. If it's called vitamin, you probably need it for something. Vitamin K is involved in blood clotting. So if you don't have vitamin K, you're going to like bleed to death. So take a second and think the fellas in your guts that are making you vitamin K. That's pretty much brilliant. They also, dude, of course, I mean, this kind of makes sense. They help us digest our food. Now, think about this for a second. This is a strategy used by a whole bunch of critters. For example, critters like termites. Termites eat wood. No one eats wood. Can you eat wood? I mean, even if it's like sawdust, if you tried to yumstralize some sawdust, it's going to like go down. First of all, how is it going to get down? So you're going to have to drink a whole lot of water to make that sawdust go down. And then your intestines are going to be like, dude, why you got to eat wood? Because we got nothing. We have no enzymes that can break down wood. We're going to get nothing out of this wood that you just sent through your system. Well, termites, we know they eat wood. They're going to eat your house if you let them. How do they do that? How do they digest wood? They have bacterial friends that hang out in their guts. A bacteria can digest the wood. And then they digest the wood and the termites absorb it. And the bacteria are like, this is a sweet deal. We get to live inside this awesome, warm little termite house. We like how it smells. We like how we get to decorate in here in these termite guts. It's awesome. And we get this steady supply of food like delivered right to our house. And all we have to do is just start eating it. And then the bacteria are stoked. We don't have wood-eating bacteria in our guts. I mean, this would be really interesting. What would happen if you stuck some in there? I mean, I guess if you modified the environment and made it so that they could live in there, that'd be kind of cool. Then you could start eating wood. Sounds pretty exciting. There could be some advantages of eating wood. So they actually help us digest our food. And even though it's not food, they do help us digest some things. Many herbivores, many critters that eat lots of grass, they have bacteria that help them break down the grass. And in fact, one of the appendix that is the little wormy thing hanging off of their large intestines, the appendix is, in humans, we aren't sure exactly what it does, but we think that it might be a home for some of our 100 trillion bacteria. But in rabbits, it's like a special zone for digesting plant matter. And so rabbits will let their food hang out in their appendices for long periods of time and let the bacteria go to town on the grass, because grass is hard to digest. That's why dogs and cats, when they want to puke, they go eat grass, because their bodies are like, what were you thinking? You might as well eat wood, because we can't send this through, so it makes you puke. That's why it's good for you, because it's fiber. That's why they say eat lots of fiber, because it goes right through you. Hopefully the fiber doesn't make you puke, it just makes the dog puke. Okay. We can talk about antibiotics, because sure, there are some good ones, but we're kind of obsessed with fighting the ones that we interpret as bad, and how do we decide what's bad and what's good? Let's find out.