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Bacterial motility, chemotaxis

Bacterial motility, chemotaxis. Lengeler et al. Chapter 20, p. 514-523 Global regulatory networks and signal transduction pathways. Basic mechanisms of motility Flagella, rotation Chemotaxis Flagellar motor. Basic mechanisms of motility. Swimming Liquid environment, low viscosity

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Bacterial motility, chemotaxis

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  1. Bacterial motility, chemotaxis Lengeler et al. Chapter 20, p. 514-523 Global regulatory networks and signal transduction pathways

  2. Basic mechanisms of motility • Flagella, rotation • Chemotaxis • Flagellar motor

  3. Basic mechanisms of motility • Swimming • Liquid environment, low viscosity • External flagella • 10 to 20 μm / sec • = 10 to 20 body lengths / sec • bacteria: E. coli S. typhimurium B. subtilis

  4. Turning screw • Viscous environment • Endoflagella in periplasm • Anchored in CM • Extend “half way” along cell length • Twist • 1 to 2 μm / sec • Spirochetes: Treponema pallidum

  5. Gliding motility • Liquid / solid interface • No flagella • 0.2 μm / sec • myxobacteria, cyanobacteria

  6. Locations of flagella • Polar • Caulobacter • Pseudomonas • Medial • Rhodobacter • Peritrichous • Proteus vulgaris; 100s per cell • E. coli; 6 to 8 per cell

  7. swimming • Mechanism • Rotation of flagella • Energy: pmf • H+ flux drives rotation of motor • Long filaments

  8. rotation • Directions of movement • changes frequently • CW, CCW • Expt 1 • Latex bead • Coat with α – flagellin antibodies • Bead binds to flagella • Spinning of bead  rotation of flagella

  9. Expt 2 • Glass slide • Coat with α – flagellin antibodies • Cells tethered by layer of ab’s • Cells rotate: 100 Hz = 100 cps • Spinning of cells  rotation of flagella

  10. CCW  CW  CCW • 1 to 2 sec 0.1 sec 1 to 2 sec • CCW rotation of flagella • Smooth swimming • CW rotation of flagella • Somersault = tumble

  11. Random walk • Homogeneous environment; unbiased • CCW = smooth • filaments intertwine • Bundles • Propeller • CW = tumble • Each flag. pushes in different direction • No bundles

  12. gradients • Chemical stimulus • Attractants • Nutrients: aa’s, sugars • Repellents • Phenol, organic acids, Ni++, Co++, some aa’s • Response = biased random walk • Chemotaxis = directed movement • Towards an attractant, away from repellent

  13. Expt 3 • Fill capillary tube with maltose • Insert capillary in drop of E. coli • Gradient of maltose: • Diffuses [high] …….[low] • Cells swim into capillary • Longer runs in “right” direction • Shorter runs in “wrong” direction

  14. Chemotaxis system • ~ 10 different proteins • Detect and respond to [changes] • Different attractants, repellents • Send signals to flagellar motor • Controls motility system

  15. Motility system • Structural components • Basal organelle • 4 rings + central rod • Embedded in cell envelope • Rotor • 12 flg genes • 4 flh genes • 18 fli genes

  16. Energy transducing components • H+ to drive flagellar rotation • stator • MotA • Proton pore • Spans CM • MotB • Anchor for MotA • Switch components • Determines direction of rotation • FliG, FliM, FliN

  17. Assembly_basal organelle • M ring  CM • S ring (superficial) inserted • Central rod added, capped • P ring (peptidoglycan) • L ring (LPS) • Hook linked to central rod • Flagellar filament assembled • Mot proteins

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