hey everybody dr. L 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 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 bacterial flagella can't but I just wanted to show it to you because kind of a cool one okay so here we see the two different types of flagella and I just want you to know again I'm not going to talk about state tours and row tours and secretion proteins but I want you to see if they're different so 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 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 the function or what allows the rotation to occur is a flow of hydrogen ions or protons through through the the flagella very similar to the way that the flow of protons are hydrogen ions through your ATP synthase enzyme and the electron transport system produces ATP so the flow of protons causing a rotation is not it is not something that only flagella can do is use another place 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 periplasmic space then you have the outer membrane so the gram-negative flagella is gonna 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 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 gonna contract together but first let's talk about why right why did bacteria have flagella well it's for motility motility is the ability ability of an organism to move so why would why would an organism move similar to the reasons we get off the couch I guess it we move towards things we need and a thing from things 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 etc there's also phototaxis so some are gonna move towards her 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 gonna 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 gonna 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 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 when you when they rapidly stop and rapidly change directions by changing the direction the flagella are moving from counterclockwise to clockwise so alright so that's the basic structure of flagella why they have flagella and why they use them and then they run and tumble which is how bacteria use flagella to move okay I hope that helps have a wonderful day be blessed