Lecture 11 - Bacterial Cell-Cell spread

Question 1

Advantages to intracellular pathogenesis
1)
2)
3)
4)
5)

Answer 1

1) Privileged environment (no competition)
2) Inaccessible to attack by complement, antibodies
3) No need to adhere to host cell
4) Readily available nutrients
5) Necessary, if obligate intracellular pathogen

Question 2

What is a chemoheterotroph?

Answer 2

Organisms that use carbon sources as energy.

EG: Compounds from host cell interior

Question 3

Intracellular niches
1)
2)
3)

Answer 3

1) Intralysosomal (low pH, hydrolytic)
2) Intravacuolar (neutral pH)
3) Cytosolic

Question 4

Professional phagocytic cells

Answer 4

Macrophages, neutrophils, dendritic cells (kind of)

Question 5

Which niche does Listeria live in?

Answer 5

Intracellular, cytosolic

Question 6

How does Shigella escape vacuoles?

Answer 6

Phospholipases digest vacuole membrane

Question 7

How does Shigella cause macrophages to undergo apoptosis?

Answer 7

Stimulate inflammosomes

Causes pro-caspase 1 activation, IL-1b, IL-18 release, pyroptosis

Question 8

Shigella protein used for actin recruitment

Answer 8

IcsA

Question 9

Which bacteria is IcsA found in?

Answer 9

Shigella

Question 10

Protein type of IcsA

Answer 10

Autotransporter

Question 11

IcsA function
1)
2)
3)

Answer 11

1) Binds N-WASP to glysine-rich region
2) N-WASP has two binding grooves, one for monomeric actin, one for Arp2/3 complex
3) Arp2/3 complex nucleates actin, actin chain begins formation

Question 12

N-WASP interaction domains
1)
2)
3)
4)

Answer 12

1) CDC42
2) Nck
3) Actin
4) Arp2/3

Question 13

Which part of IcsA binds N-WASP?

Answer 13

Glycine-rich region

Question 14

What does the glycine-rich region of IcsA do?

Answer 14

Recruit N-WASP

Question 15

N-WASP function
1)
2)

Answer 15

1) Has binding site for monomeric actin, Arp2/3

2) Supplies monomeric actin to Arp2/3

Question 16

Protein expressed by Listeria for intracellular motility

Answer 16

ActA

Question 17

What is ActA?

Answer 17

Protein expressed by Listeria

Causes polar actin polymerisation

Question 18

Differences between ActA and IcsA
1)
2)
3)
4)

Answer 18

1) Acta is used by Listeria, IcsA by Shigella
2) ActA recruits VASP, IcsA recruits N-WASP
3) IcsA recruits actin at pole from start. ActA initially recruits actin all over cell, then begins recruiting polarly
4) ActA directly recruits VASP, actin and Arp2/3. IcsA recruits N-WASP, which then recruits actin and Arp2/3

Question 19

What are LLO and phospholipase C?

Answer 19

Used by Listeria to digest vacuole wall

Question 20

What does Listeria use to digest vacuolar wall?

Answer 20

LLO

Phospholipase C

Question 21

Proteins recruited by IcsA

Answer 21

1) N-WASP

2) N-WASP recruits monomeric actin, Arp2/3

Question 22

Proteins recruited by ActA

Answer 22

VASP, monomeric actin, Arp2/3

Question 23

Other bacteria which recruit actin intracellularly
1)
2)

Answer 23

1) Ricketsia conorii

2) Burkholderia pseudomallei

Question 24

Do R. conorii and B. pseudomallei use actin polymerisation as efficiently as Shigella and Listeria?

Answer 24

No

Question 25

Advantages to living in macrophages
1)
2)
3)

Answer 25

1) Professional phagocytes, so easy to enter cell
2) Long-lived
3) Migrate through the body, so can help with dissemination

Question 26

Oxygen-dependent killing

Answer 26

Respiratory burst using NADPH oxidase
Generates radical oxygen species
EG: H2O2, OCl-, O2-

Question 27

Oxygen-independent killing
1)
2)
3)
4)
5)

Answer 27

1) Low pH (in lysosome)
2) Proteolytic enzymes
3) Lysozyme
4) Lactoferrin
5) Membrane-damaging proteins

Question 28

Vesicles involved in phagosome maturation
1)
2)
3)

Answer 28

1) Early endosome
2) Late endosome
3) Lysosome

Question 29

By which mechanism do EE, LE and Ly help in phagosome maturation?

Answer 29

Kiss and run