Bacterial motility

Question 1

Monotrichous flagella

Answer 1

Single flagella at pole

Question 2

Amphitrichous

Answer 2

2 flagella at poles

Question 3

lophotrichous flagella

Answer 3

many at both poles

Question 4

Peritrichous

Answer 4

many everywhere

Question 5

what is the ‘run’ motility pattern?

Answer 5

motor rotates CCW to bundle flagelllar fillaments, and propel cell forwards.

Question 6

what is the ‘tumble’ motility pattern?

Answer 6

Motor rotates CW, unwinding bundle to generate forces that change the orientation of the cell.

Question 7

what is Aerotaxis?

Answer 7

Movement in response to oxygen, usually towards.

Question 8

What is Chemotaxis ?

Answer 8

Movement in response to nutrients (towards) and toxins(away)

Question 9

What is Magnetotaxis?

Answer 9

movement in response to magnetism, usually towards ions.

Question 10

What is Phototaxis?

Answer 10

Movement in response to light(towards)

Question 11

In context of chemotaxis, what detects/measures changes in environment?

Answer 11

Methyl-accepting chemotaxis(MCP)

Question 12

What are MCPs?

Answer 12

Methyl-accepting chemotaxis, which are transmembrane proteins that detect changes in the environment, aka transducer proteins.
and they interact with cytoplasmic proteins.

Question 13

What proteins do MCPs interact with?

Answer 13

Che proteins, specifically CheA

Question 14

What do Che proteins do?

Answer 14

Interact with the motor dictating the direction of the motor.

Question 15

What does CW rotation of the motor cause.

Answer 15

‘tumble’ of the cell, changing its orientation

Question 16

what does CCW rotation of the motor do?

Answer 16

‘run’-ing of the cell causing it to propel forward.

Question 17

If the MCP comes in contact with a Repellent, what happens to CheA?

Answer 17

it interacts with protein CheA, a sensor kinase, which autophosphorylates MORE

Question 18

If the MCP comes in contact with an attractant, what happens to CheA?

Answer 18

it autophosphorylates LESS

Question 19

Which protein allows causes the ‘tumble’ movement and how

Answer 19

phosphorolated CheY(Chey-P) which binds to the flagellar motor, switching it from CCW to CW( the ‘tumble’)

Question 20

Can CheY bind to the flagellar motor?

Answer 20

NO, it must be phosphorylated.

Question 21

how does the motor return to CCW motion from CW motion? ‘tumble’ to ‘run’

Answer 21

the phosphatase CheZ, dephosphorylates CheY-P, causing it to undbind from the motor, returning it to CCW motion(‘run’)

Question 22

What affect does attractants have on CheY-P and the effect on the movement of the cell?

Answer 22

attractants DECREASE CheY-P, therefore LESS CW motion(‘tumbling’) and MORE CCW motion(‘running’)

Why? because attractants decrease autophosphorylation of CheA (i.e LESS CheA-P) therefore less CheA-P to phosophorylate CheY into CheY-P so overall DECREASE in CheY-P

Question 23

What affect does REPELLENTS have on CheY-P and the effect on the movement of the cell?

Answer 23

repellents INCREASE CheY-P, therefore MORE CW motion(‘tumbling’) and LESS CCW motion(‘running’)

Why? because repellents increase autophosphorylation of CheA (i.e MORE CheA-P) therefore more CheA-P to phosophorylate CheY into CheY-P so overall INCREASE in CheY-P

Question 24

What is the function of methylating MCP

Answer 24

Methylation of MCP acts as bacterial ‘memory’.

Question 25

What is the function of CheB?

Answer 25

it is a methylesterase, it demethylates MCP only when phosphorylated by CheA-P

Question 26

What is the result of low conc. attractant on MCP sensitivity to attractant and why?

Answer 26

Increase of sensitivity to the attractant. because low conc of attractant, means more CheA is being autophosphorylated into CheA-P, therefore more CheB can be phosphorylated by it into CheB-p, which demethylates MCP making it More sensitive to attractants. Longer runs

Question 27

what happens if MCP is fully methylated?

Answer 27

it will become insensitive to attractants.