2-6: Movement of Bacterial Cells Flashcards
What is motility
The ability to propel your own movement
Give an example of a non-motile bacteria
Yersinia pestis, a bacterial pathogen
What is the flagellum
Large, complex, multi-protein (~50) machine that powers movement
Describe the general structure of a flagellum
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
Descibe flagellar rotation of short “tumbles” in peritrichous bacteria
One or more flagella rotate clockwise, therefore bundle falls apart, tumbles, assumes new random orientation
What two ways do monotrichous bacteria move
Reversible and unidirectional flagella
How do monotrichous bacteria with unidirectional flagella move?
rotation stops/starts, movement during stops = direction change
How do monotrichous bacteria with reversible flagella move
Can rotate clockwise or CCW, rotation in the opposite direction will reverse the movement
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 rotation of the flagellar motor
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 ring - acts like a turbine
What does the MS ring 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
Describe the structure of the filament
Rigid, helical, and hollow
Is the filament highly conserved in bactiera?
Yes
How is flagellin detected by our immune systems
It is an important antigen (H antigen)
How is flagellum made
Built inside -> out
Produced in cytoplasm, secreted via the hollow filament. New subunits will assemble at the end (outside the cell) with the cap proteins
What secretion system is used to export flagellin?
Type III secretion system. A related system is used as a protein toxin injection system by certain pathogens
Variations in some bacteria flagellar motility?
Some use Na+ gradient, spirochetes have axial filament that resides in periplasm resulting in corkscrew motion
What is a taxis
Directed movement of bacteria using bias random walk
what is chemotaxis
Movement in direction of gradients (increase or decrease) in concentration of a chemical
which is detected by chemoreceptors
How does tumble frequency change with moving TOWARDS a stimulus?
Tumbles inhibited, longer runs
What is phototaxis?
P = movement towards/away from light
What is aerotaxis?
directed motility in response to O2
What is twitching motility
Non-flagellar motility, uses a type 4 pilus attaches to surface then retracts like a “grappling hook”
