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

18. 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