1. Flagella
Slender rigid structures
Approx. 20 nm across and up to 20 m long
Used for locomotion
(Hair is m across)

2. Flagella distribution
Bacteria differ regarding the arrangement of flagella
Monotrichous = one
Polar = located at the end
Amphitrichous = one on each pole

3. Flagella distribution
Lophotrichous = tuft at one or both ends
Peritrichous = spread evenly over the entire surface
Arrangement can be useful in identification

4. Flagella ultrastructure
Composed of three parts:
Filament
Hook
Basal body
Some bacteria have sheaths surrounding their flagella

5. Flagella ultrastructure

6. Flagella ultrastructure

7. Flagella ultrastructure
C-ring contains proteins involved in the rotation of the flagella

8. Flagella ultrastructure
Gram negative Gram positive
Have four rings Have two rings

9. Flagella synthesis
Involves more than 20 genes
Mechanism related to type III secretion systems
Filament is a hollow tube composed of flagellin and ending with a capping protein

10. Flagella synthesis
The hook is made of different protein subunits
Basal body is composed of several different proteins

11. Flagella synthesis
Other proteins are involved in the transport of subunits across the membrane
Protein subunits travel down the hollow filament and are incorporated into the end of the growing flagella

12. Flagella synthesis

13. Chemotaxis
Rotation of flagella propels cell through the environment
E. coli flagella can rotate 270 rps
V. alginolyticus flagella can rotate 1,100 rps

14. Chemotaxis
Rotation of flagella in counter-clockwise direction usually results in running/swimming
Rotation in opposite direction results in tumbling (random movement)

15. Chemotaxis
When in the presence of a gradient of attractant, amount of time spent in run vs. tumble mode increases

16. Chemotaxis
Exact mechanism of flagella movement not yet understood
Basal body may rotate within a membrane bound ring of proteins (rotor and stator)

17. Chemotaxis
Rotation is driven by proton and sodium ion gradients and not ATP

18. Chemotaxis
Controlled by a two-component phosphorelay system
Chemicals bind to chemoreceptor on cell surface
Che A = sensor kinase
Che Y = response regulator

19. Chemotaxis
Different levels of phosphorylation of proteins in response to the presence of attractant or repellent influences the direction of rotation

20. Chemotaxis
Attractant Repellent

21. Archaeal flagella
Are quite different from bacterial flagella
Subunits may be added to filament from the cytoplasmic side (like pili)

22. Pili/fimbriae
Conjugation pili differ from other pili/fimbriae
Conjugation pili are usually wider and longer than other pili/fimbriae (9-10 nm wide vs nm wide)

23. Pili/fimbriae
Are composed primarily of a single protein
Many have special adhesive proteins located on the tip
Can aid in attachment to various surfaces

24. Pili/fimbriae
Many pathogenic bacteria are dependent on pili/fimbriae for their ability to cause disease
e.g. urinary tract and kidney infections
Pili also help bacteria to attach to surfaces in the environment
Attachment often followed by production of a slime layer/biofilm

25. Pili/fimbriae
Unlike flagella, pilus subunits are added to the growing rod from the bottom
Outer membrane complex required in gram-negative bacteria

26. Pili/fimbriae
Some pili/fimbriae are responsible for a type of motility referred to as twitching motility (Type IV pili)
Caused by extension and retraction of adherent pili