Lecture 1B: Cell Locomotion (Archaella, gliding motility and Taxis Flashcards
Archaella, Gliding Motility and Taxis
- even thinner than the flagellum.
- about half the diameter of the bacterial flagellum (around 10-13 nm).
Archaella
Movement of archaella
By rotation
Have a very ______ ________ to the bacterial flagellum.
little homology
To what structure does the Archaellum similar?
type IV pilus
Common cell wall of the Archaea
S-layer
Instead of L, P, MS, and C ring, what structure (?) stabilizes the filament of the archaea?
FlaJ
Protective and Adaptive mechanism of Bacteria
Gliding motility
Does archaea exhibits gliding motility?
No. Bacteria can only exhibit gliding motility.
Gliding motility is _______ and ________ than swimming.
slower and smoother
Why does the movement of gliding motility occurs away from colony?
to avoid the crowd.
Gliding requires _______ ________ (semi-solid or solid) but there has to be moisture.
surface contact
Mechanisms of gliding motility
-Excretion of polysaccharide slime.
-Structure is similar to type IV pili
-Movement is twitching motility
-Gliding specific proteins involve in adhesion complexes and other specialized proteins.
On the outer membrane you can find proteins interspersed in the membrane that serve as _________ ________.
Gliding proteins
Where does the gliding proteins connected?
to the transmembrane proteins in cytoplasmic membrane.
The movement of outer membrane glide proteins moves _________ to the movement of the cell.
oppositely
The opposite movement of glide proteins to the movement of cell creates _________ that kind of pushes the cell in opposite direction.
friction
Directed movement in response to chemical or physical gradients.
Taxis
Response to chemicals
Chemotaxis
Response to light
Phototaxis
Response to oxygen
Aerotaxis
Response to ionic strength
Osmotaxis
Response to water
Hydrotaxis
- Best studied in E.coli.
- “run and tumble’ behavior.
- Move by rotation
- Bacteria respond to temporal difference in chemical concentration
- Monitor/sample environment with (?) that sense attractants and repellants
Chemotaxis
Smooth forward motion, and the flagellar motor rotates counterclockwise (right to left)
Run
Cell stops and jiggles, flagellar motor rotates clockwise (left to right), flagellar bundle comes apart.
Tumble
- Similar but not identical to peritrichous cells.
- Many (e.g., Pseudomonas) can fully reverse flagellar rotation, avoid tumbling and reversing direction.
- Some (e.g., Rhodobacter) stop and are affected by Brownian motion.
Chemotaxis in peritrichous flagellated bacterium
Allows phototrophic organisms to optimize position for light harvest.
Phototaxis using Photoreceptors
Entering darkness causes cell to tumble, reverse direction, head back to light.
Scotophobotaxis
