Presentation is loading. Please wait.

Presentation is loading. Please wait.

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

Similar presentations


Presentation on theme: "Bacterial motility, chemotaxis Lengeler et al. Chapter 20, p. 514-523 Global regulatory networks and signal transduction pathways."— Presentation transcript:

1 Bacterial motility, chemotaxis Lengeler et al. Chapter 20, p 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

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

19


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

Similar presentations


Ads by Google