MODULE 3 - MODULE 3 3a Motility The Flagellum Amazing...

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MODULE 3 3a) Motility The Flagellum Amazing structure, within what we consider to be a simple bacterial cell When looking under light microscope don’t see much structure at all, need higher resolution Paradigm for complexity of bacterial structure- flagellum Special structure found only in bacterial cells (in eukaryotes, flagella have different structure) Flagella are embedded in cytoplasmic membrane, rotate Ring proteins embed the flagella within cytoplasmic membrane Mot proteins are associated with ring proteins (mot=motor) Mot proteins use proton motive force to cause flagellum to rotate Requires estimated 1000 protons for each rotation event Over 40 genes required for formation and function of flagellum Some proteins make up structural proteins, others are regulatory proteins controlling expression of the proteins Other ring proteins involved in stabilization of flagellum within cell wall and membranes o P ring associated with peptidoglycan o L ring associated with outer membrane and LPS Hook protein connects filament to the rest of the structure o Filament: part of flagellum on outside of bacteria Flagella can rotate fast enough to propel bacteria at relatively high speeds, estimated 60 cell lengths per second Must be some selective advantage to cell to move so quickly b/c requires lots of energy
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Formation of Flagellum Proteins associated with cytoplasmic membrane formed first MS ring Motor proteins assmebed adjacent to them P ring L ring Early hook Cap protein directs formation of filament made up of protein called flagellin Filament is made up of single type of protein, forms btwn cap and hook Expression of genes controls process of flagellum formation Genes must be expressed at correct time in order for flagellum to assemble properly Organisms can have different types of behaviour depending on types of flagella they have Peritrichous Flagella “periotrichous”: hairs surround the cell (peri=around) Flagella rotate CCW, become bundled at one end of cell propelling cell forward Flagella rotate CW, become unbundled causing cell to tumble b/c being pulled in diff directions, can reorient itself during tumble phase
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