Lecture 11 - Bacterial Cell-Cell spread Flashcards

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

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

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2
Q

What is a chemoheterotroph?

A

Organisms that use carbon sources as energy.

EG: Compounds from host cell interior

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3
Q

Intracellular niches
1)
2)
3)

A

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

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4
Q

Professional phagocytic cells

A

Macrophages, neutrophils, dendritic cells (kind of)

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5
Q

Which niche does Listeria live in?

A

Intracellular, cytosolic

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6
Q

How does Shigella escape vacuoles?

A

Phospholipases digest vacuole membrane

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7
Q

How does Shigella cause macrophages to undergo apoptosis?

A

Stimulate inflammosomes

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

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8
Q

Shigella protein used for actin recruitment

A

IcsA

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9
Q

Which bacteria is IcsA found in?

A

Shigella

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10
Q

Protein type of IcsA

A

Autotransporter

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11
Q

IcsA function
1)
2)
3)

A

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

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12
Q
N-WASP interaction domains
1)
2)
3)
4)
A

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

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13
Q

Which part of IcsA binds N-WASP?

A

Glycine-rich region

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14
Q

What does the glycine-rich region of IcsA do?

A

Recruit N-WASP

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15
Q

N-WASP function
1)
2)

A

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

2) Supplies monomeric actin to Arp2/3

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16
Q

Protein expressed by Listeria for intracellular motility

A

ActA

17
Q

What is ActA?

A

Protein expressed by Listeria

Causes polar actin polymerisation

18
Q
Differences between ActA and IcsA
1)
2)
3)
4)
A

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

19
Q

What are LLO and phospholipase C?

A

Used by Listeria to digest vacuole wall

20
Q

What does Listeria use to digest vacuolar wall?

A

LLO

Phospholipase C

21
Q

Proteins recruited by IcsA

A

1) N-WASP

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

22
Q

Proteins recruited by ActA

A

VASP, monomeric actin, Arp2/3

23
Q

Other bacteria which recruit actin intracellularly
1)
2)

A

1) Ricketsia conorii

2) Burkholderia pseudomallei

24
Q

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

A

No

25
Q

Advantages to living in macrophages
1)
2)
3)

A

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

26
Q

Oxygen-dependent killing

A

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

27
Q
Oxygen-independent killing
1)
2)
3)
4)
5)
A

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

28
Q

Vesicles involved in phagosome maturation
1)
2)
3)

A

1) Early endosome
2) Late endosome
3) Lysosome

29
Q

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

A

Kiss and run