2-6: Movement of Bacterial Cells Flashcards
What is motility
The ability to propel your own movement
What is the flagellum
Large, complex, multi-protein (~50) machine that powers movement
How does the flagellum work
Long, thin filament that acts as propeller, rotated by motor anchored in cell envelope
What is swarming
Coordinated multicellular movement across a solid surface
What are the different flagellar arrangements
Peritrichous = many across body/pole
Monotrichous = single at pole
Lophotrichous = many, all at one pole
Amphitrichous = both poles
Atrichous = none
“runs” in peritrichous bacteria
Counterclockwise, flagella bundle at tail, cell moves forward
Rotation of short “tumbles”
Peritrichous only: One or more flagella rotate clockwise, therefore bundle falls apart, tumbles, assumes new random orientation
How do monotrichous bacteria move
Reversible flagellums, can rotate clockwise or CCW (runs)
OR
Unidirectional flagella, rotation stops/starts, movement during stops = direction change
What are the three segments of the flagella
1) Filament (long, thin propeller driving movement)
2) Hook (adaptor that connects filament to basal body)
3) Basal body (core of structure, powers rotation, motor is part of)
What drives motor rotation
Proton motive force
What are the parts of the gram negative flagellar motor
Central rod, MS ring, C ring, P ring, L ring, stator
Where are the MS, C, P and L ring located
MS = cm
C = cytoplasm
P = peptidoglycan
L = om
What does the stator do
couples flow of protons to rotation of MS
What does the MS do
Rotates rod, ultimately the hook and filament
What do the L/P rings do
Bearings to help rotation
What does the C ring do
Generate torque, switch motor direction, flagellin secretion
What does gram positive flagellum lack
P/L rings
What is flagellin
Proteins, thousands of which make up the filament
How long and wide is the filament
5-10um long, 20nm wide
Is the filament highly conserved
Yes
How is flagellin detected by our immune systems
It is an important antigen (H antigen)
How is flagellum made
Inside -> out
Produced in cytoplasm, secreted via “export apparatus” (type 3 secretion system), through thin pore in basal body.
Variations in some bacteria flagellar motility?
Some use Na+ gradient, spirochetes have axial filament that resides in periplasm, rotates like a crokscrew
What is a taxis
Directed movement of bacteria towards attractant
what is chemotaxis
Movement in direction of gradients (increase or decrease) in concentration of a chemica
what is chemotaxis
Movement in direction of gradients (increase or decrease) in concentration of a chemical
Detected by chemoreceptors
What is phototaxis and aerotaxis
P = movement towards/away from light
A = directed motility in response to O2
What is twitching motility
Non-flagellar
Type 4 pilus attaches to surface then retracts “grappling hook”
