Bacterial structure 3

Question 1

Types of motility

Answer 1

Swarming
- flagella

Swimming
- flagella

Twitching
- pilus retraction

Gliding
- focal adhesion complexes

Sliding
- spreading by growth

Question 2

Flagella locations

Answer 2

polar

lophotrichous

medial

peritrichous

Question 3

flagella direction

Answer 3

lophotrichous

• rotate 1 direction
• > spread out to stop
• > rotate other direction

polar

• rotate 1 direction
• > rotate other direction

Question 4

flagella
- proton motive force

• differences in swimming motions

Answer 4

flagella increase or decrease rotational speed in relation to strength of proton motive force

peritrichous
= slowly in straight line

polar
= rapidly + spin around

Question 5

flagella synthesis

Answer 5

approx 50 genes required

1. MS ring made
2. other proteins + hook made
3. filament grows from tip

Question 6

flagella components

Answer 6

basal body + rings
- anchor to envelope

hook complex
- connects basal body to filament

filament = propeller

motor
- drivers rotation

secretion system
- exports subunits

ATPase
- energises system

Question 7

similarity between flagella + T3SS

Answer 7

derived from common ancestor
share 9 homologous constituents

both arose from a common primordial secretion system

Question 8

regulation of flagella biosynthesis

- tight gene regulation…

Answer 8

to ensure:

gene regulation, protein supply + substrate secretion are coordinated

Question 9

regulation of flagella biosynthesis

• early genes
• middle genes
• late genes

Answer 9

early
- regulatory proteins that control expression of regulon

middle
- control expression of structural components

late
- filament, motor force generators + chemosensory

Question 10

random walk

Answer 10

succession of random steps

sequence of runs + tumbles:
movement via CCW rotation
-> tumble (random reorientation)
-> movement via CW rotation

Question 11

taxis

Answer 11

= biased random walk

bacteria move toward attractant by regulating switch between run + tumble
longer runs in increasing attractant conc

Question 12

signalling and chemotaxis

Answer 12

Methyl-accepting chemotaxis proteins (MCP)
- bind to specific attractants/repellents

MCP + CheW stimulates autophosphorylation of CheA

CheA transfers P to CheY

CheY~P interacts w/ switch complex in flagella C-ring

Attractants decrease phosphorylation
-> increases runs (CCW)

Repellents increase phosphorylation
-> increases tumbles (CW)

Question 13

MCP

• function
• features

Answer 13

homodimers that sense signals in periplasm

arranged in large array

• near or at 1 pole
• > can integrate different signals

Question 14

pili

- 5 types

Answer 14

chaperone-usher
type 4
type 4 secretion 
type 5
curli fibres

Question 15

pili

- roles

Answer 15

motility 
conjugation 
virulence
biofilm formation
attachment

Question 16

pili

- attachment

Answer 16

chaperone-usher pili involved in attachment to host cells

adhesins normally bind to specific molecules
specific carbs
-> specific attachment

Question 17

twitching motility

Answer 17

type 4 pili

elongation + retraction

ATP dependent

exploration of surfaces

Question 18

gliding motility

• features
• example

Answer 18

flagella-independent motility

smoother + slower than swimming

movement along long axis of cell

requires surface contact

e.g. Pseudomonas

Question 19

gliding motility

- mechanisms

Answer 19

excretion of polysaccharide slime

gliding-specific proteins