 Hey everybody, Dr. O. In this video I want to talk about just kind of the basics of flagella structure. I won't go too into the weeds here and then also talk about why bacteria would use flagella and show you a couple of things too. So this is just starting with a really cool image. This would be a flagella stained Proteus vulgaris organism. So as you can see there are lots of flagella on this organism. It actually allows it to move in special ways that even other bacteria with flagella can't, but just wanted to show it to you because it's kind of a cool one. Okay, so here we see the two different types of flagella and I just want you to note, again I'm not going to talk about stator and rotors and secretion proteins, but I want you to see their difference. I'm going to show you a more close up, but the one thing that all flagella have in common are the three things they all have in common. So they all have the filament, which is the structure you would think of as the flagella and they all have the hook, which is what attaches it to the basal body, which is where the rotation actually occurs. So that's the key is that the bacterial flagella uses a rotary motion and what's really cool about it is it's kind of, there's some unknowns here, but the function or what allows the rotation to occur is a flow of hydrogen ions or protons through the flagella very similar to the way that the flow of protons or hydrogen ions through your ATP synthase enzyme in the electron transport system produces ATP. So the flow of protons causing a rotation is not something that only flagella can do is use in other places. So I just find that kind of cool. But here, let me just go a little bit closer here and you'll see the gram positive one is relatively straightforward because if you remember, gram positive bacteria just have that thick cell wall going to the gram negative. You'll see there's the paraplasmic space, then you have the outer membrane. So the gram negative of flagella is going to have a few more pieces, but that's only because it has to travel through that outer membrane as well. So, but again, don't get bogged down here with that at all. So here's how they move. It's actually be called the run and the tumble and you see what determines if an organism is running or tumbling is which direction. All these flagella are going to contract together. But first let's talk about why, right? Why do bacteria have flagella? Well, it's for motility. Motility is the ability of an organism to move. So why would an organism move? Similar to the reasons we get off the couch, I guess. We move towards things we need and we move away from things that we want to avoid. So when you move towards something, it would be an attractant. So like they move towards food, chemotaxis would be the term you'd see most often. They move towards chemicals that they want. Could be like a source of sugar like galactose or oxygen, et cetera. There's also phototaxis. So some are going to move towards or away from light, but chemotaxis would be the most important. So they also might be repelled by something. So like a waste product or something they want to avoid would be a repellent. So just like us, bacteria are going to move towards things they want or away from things they don't want to be by. But they use this run and tumble system to do so. So running would be when a microbe, when a bacteria is moving one direction for a relatively long period of time, it would be called a run. And that's going to be from the counterclockwise turning of all the flagella. But then every so often they're going to tumble. They're going to stop, and this allows them to quickly stop and change directions by changing the direction their flagella are rotating. And they can do this in about a quarter of a turn. It's actually quite impressive. So let me show you this picture here. So in this case you see on the left-hand side, you see an organism running towards something that it's chemically attracted to. So that would be that chemotaxis. But the tumble would be when they rapidly stop and rapidly change directions by changing the direction the flagella are moving from counterclockwise to clockwise. So all right, so that's the basic structure of flagella, why they have flagella and why they use them. And then the run and tumble, which is how bacteria use flagella to move. Okay, I hope that helps, have a wonderful day, be blessed.