Lecture 10: Bacterial Motility

Question 1

What is meant by swarming

Answer 1

“multicellular movement of bacteria across a surface powered by flagella”

Question 2

What is meant by twitching?

Answer 2

“surface movement of bacteria powered by extension of pili; by attaching to the surface followed by retraction”

Question 3

What is meant by gliding?

Answer 3

“Active surface movement no requiring pili or flagella - involve focal adhesion complexes”

Question 4

What is meant by sliding?

Answer 4

“Passive surface translocation powered by growth and facilitated by surfactant”

Question 5

What are the different forms of bacterial motility?

Answer 5

1. Swimming
2. Swarming
3. Twitching
4. Gliding
5. Sliding

Question 6

Give an example of a bacteria that moves via twitching

Answer 6

Neisseria gonorrhoeae

Question 7

How does the gliding mechanism work?

Answer 7

1. Large focal adhesion complexes extend
   from the cell
2. connect to the extracellular surface to
   actin-like cytoskeletal filaments
3. motor proteins attached to intracellular
   portion push backwards and move focal
   adhesion along cytoskeletal filament -
   moving the cell forward (whilst they stay
   fixed)

Question 8

What is the structure of flagella?

Answer 8

1. Basal body attached in the cell 
   membrane and cell wall
2. Hook anchored in the basal body
3. Long fine filament, helical protein made 
    of 'flagellin' subunits

Question 9

How does the flagellum rotate?

Answer 9

1. Energy is required, comes from proton
   motive force
   a. H+ movement across membrane
   through “Mot” complex
   b. 1000 H+ must be translocated per
   single rotation

Question 10

What is the result of counter-clock wise flagella rotation?

Answer 10

run

Question 11

What is the result of clock wise flagella rotation?

Answer 11

tumble

Question 12

What is meant by the term chemotaxis?

Answer 12

“ability of cell to sense external concentration of a chemical species and migrate (directed movement) towards/away from higher concentrations”

Question 13

What is the mechanism of chemotaxis with no chemical gradient?

Answer 13

1. Runs - cell swims forward in smooth 
   fashion
2. Tumbles - when cell stops and jiggles 
     about
3. Direction of next run is random
4. Cell moves randomly but can go 
     anywhere

Question 14

What is the mechanism of chemotaxis with a chemical gradient?

Answer 14

1. Biased movements
2. Run time > tumble time
3. Organism moves up or down
   concentration gradient

Question 15

How does the flagella switch between clockwise and counter-clock wise rotation?

Answer 15

1. FliM
2. Binding of CheY-P to CCW FliM causes
   the flip resulting in CW rotation
3. Binding of CheY to CW FliM causes the a
   flip resulting in CCW rotation
4. CheyY is frequently being converted (“switched”) to Chey-P using CheZ
5. Sensed by the sensor complex
6. CheB-P de-methylate’s the sensor complex (‘makes it responsive to attractant’)
7. CheR methylate’s the sensor complex (‘makes it inactive to sense attractant’)

Question 16

What is the series of events when the is no attractant (tumbling)?

Answer 16

1. MCPs - methyl accepting protein sensing the presence/absence of attractants
2. CheW with MCP’s - regulate activity of CheA (histidine kinase)
3. Phospho-CheA - donates phosphoryl groups to CheY (response regulator, messenger protein)
4. Phospho-CheY - interacts with flagella (M protein) to induce CW rotation
5. tumble

Question 17

What is the series of events when there is attractant (run)?

Answer 17

1. MCPs - methyl accepting protein sensing the presence/absence of attractants
2. CheW with MCP’s - regulate activity of CheA (histidine kinase) - NO KINASE ACTIVITY
3. CheY - response regulator, messenger protein is not phosphorylated
4. No CheY-M protein interaction
5. CCW rotation
6. Run