Bacterial Flagella and Motility Overview

Bacterial Flagella and Motility Overview

• Bacteria can have single or multiple flagella, which can be located at one or both poles.
• Flagellar movement in peritrichous bacteria like E. coli and S. enterica involves rotation in both directions, leading to longer "runs" and short "tumbles".
• The direction of movement in bacteria with monotrichous flagella can be reversed by rotating the flagellum in the opposite direction.
• The flagellum is composed of around 50 different proteins and has three segments: filament, hook, and basal body.
• The flagellar motor, powered by the proton motive force, consists of over 20 proteins anchored in the cytoplasmic membrane and cell wall.
• Gram-positive bacteria lack P/L rings in their flagellum and their flagellin filament is made of a single protein called flagellin.
• The flagellum is built from the inside out, with flagellin being produced in the cytoplasm and secreted through the hollow filament.
• Variations of flagellar motility include the use of Na+ gradient instead of proton motive force, and spirochetes having a flagellum in the periplasm resulting in corkscrew motion.
• Taxis is the directed movement of bacteria, achieved using a "bias random walk" and can include chemotaxis, phototaxis, and aerotaxis.
• Chemotaxis involves movement in the direction of gradients of specific chemicals, with longer runs and less frequent tumbles if moving towards desirable nutrients.
• Other types of motility, such as twitching motility, involve non-flagellar movement, like the use of Type IV pili as a grappling hook.
• The text provides links to YouTube videos demonstrating flagella, motility, and chemotaxis in bacteria.