Bacterial motility, chemotaxis

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Bacterial motility, chemotaxis

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

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

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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

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• 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

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

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Locations of flagella

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

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swimming

• Mechanism
• Rotation of flagella
• Energy pmf
• H flux drives rotation of motor
• Long filaments

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rotation

• Directions of movement
• changes frequently
• CW, CCW
• Expt 1
• Latex bead
• Coat with a flagellin antibodies
• Bead binds to flagella
• Spinning of bead ? rotation of flagella

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• Expt 2
• Glass slide
• Coat with a flagellin antibodies
• Cells tethered by layer of abs
• Cells rotate 100 Hz 100 cps
• Spinning of cells ? rotation of flagella

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• 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

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

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gradients

• Chemical stimulus
• Attractants
• Nutrients aas, sugars
• Repellents
• Phenol, organic acids, Ni, Co, some aas
• Response biased random walk
• Chemotaxis directed movement
• Towards an attractant, away from repellent

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• 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

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Chemotaxis system

• 10 different proteins
• Detect and respond to changes
• Different attractants, repellents
• Send signals to flagellar motor
• Controls motility system

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Motility system

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

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• 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

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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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