Bacterial motility + chemotaxis

Question 1

types of motility

Answer 1

swarming
(flagella)

swimming
(flagella)

twitching
(plis retraction)

gliding
(focal adhesion complexes)

sliding
(spreading by growth)

Question 2

flagella

- locations

Answer 2

polar

lophotrichous
(many polar)

medial
(middle)

peritrichous
(many middle)

Question 3

flagella

- action

Answer 3

propeller driven by rotary motor embedded in cell envelope

driven by proton motive force
- decrease/increase rotational speed depending on force strength

Question 4

flagella

- components

Answer 4

basal body + rings
- anchor to envelope

filament
= propeller

motor
- drives rotation

SS
- exports subunits

ATPase
- energy source

Question 5

flagella

- synthesis

Answer 5

many genes required
- in operons related to timing of generation of key structures

1. MS ring ~5mins
2. other proteins + hook
3. filament ~40mins

Question 6

flagella

- principles of regulation of biosynthesis

Answer 6

needs to be tight to ensure right proteins at right time

+ not fill cell with components that it can’t use

Question 7

flagella

- 3 tiers of biosynthesis regulation genes

Answer 7

class 1:
early genes
- control expression of regulon

2:
middle genes
- cell envelope components

3: late genes
- filament, motor force generators + chemosensory machinery

Question 8

flagella

• FliA
• FlgM

Answer 8

TF activates expression of class 3 genes

inhibits activity of FiA
-ve feedback

Question 9

Peritrichous movement

Answer 9

1. bundled flagella
   - CCW rotation
2. tumble
   - flagella apart
   - CW
3. bundled flagella (opposite direction)
   - CCW

straight line

Question 10

Polar movement

Answer 10

reversible flagella:

1. CCW rotation
2. CW rotation

unidirectional flagella

1. CW rotation
2. cell stops + reorients
3. CW rotation

circular or curved

Question 11

random walk

Answer 11

switching between run and tumble

Question 12

taxis

Answer 12

biased random walk
- move toward attractant

by regulating switch between run + tumble

change frequency of runs + tumbles)
-> longer runs as conc of attractant increases

if conc lowers –> switch to tumble quickly

Question 13

Chemotaxis example

- low signal

Answer 13

MCP assisted by CheW stimulates autoP of CheA

CheA transfers ~P to CheY

CheY~P interacts with switch complex in flagella C-ring
-> tumbling

CheR methylates receptor
-> CheA works better
= more tumbling

Question 14

Chemotaxis

- how to think about methylation

Answer 14

makes MCP less responsive to stimuli

-> ensures cells keep moving UP conc grad

as methylation makes tumbling more likely unless conc of attractant keeps getting stronger

Question 15

MCP

Answer 15

Methyl-accepting chemotaxis protein

Question 16

E. coli

- MCPs

Answer 16

span membrane + sense signals in periplasm

arranged in large array at 1 pole
- can integrate signals

Question 17

swarming

Answer 17

multicellular behaviour

surface-associated motility

Question 18

swarming

- P.mirabilis

Answer 18

use flagella as tactile sensor

• when reach solid surface, inhibits rotation
• > controls switch to swarming motility

can be initiated by chemicals

Question 19

twitching motility

Answer 19

Type IV pili

elongation + retraction

ATP dependent

exploration of surfaces