Lecture 10 - Bacterial Invasion Flashcards

1
Q

Why might bacteria invade?
1)
2)
3)

A

1) Obligate intracellular parasite
2) Avoid immune system
3) Penetrate to deeper tissues

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2
Q

Two mechanisms of invasion

A

1) Zipper

2) Trigger (ruffling)

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3
Q

Host cell function exploited by zipper

A

Receptor-mediated endocytosis.

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4
Q

Host cell function exploited by trigger

A

Macropinocytosis

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5
Q

Which invasion mechanism does Listeria use?

A

Zipper

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6
Q

Basic principle of zipper
1)
2)
3)

A

1) High-affinity binding to host cell
2) Induces receptor immobilisation and crosslinking
3) Results in receptor-mediated endocytosis

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7
Q

Basic principle of trigger
1)
2)
3)

A

1) Resembles cell ruffling caused by hormones or hormones
2) Bacteria induces large-scale actin polymerisation, ruffles on host cell membrane
3) Macropinocytosis

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8
Q

Is Listeria monocytogenes Gram + or -?

A

Gram +

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9
Q

How does Listeria normally enter the body?

A

Food-borne

Soft cheeses

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10
Q

Why can Listeria be very dangerous?

A

Can cross maternoplacental barrier, blood-brain barrier

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11
Q
How does Listeria enter host cells?
1)
2)
3)
4)
5)
A

1) Zipper
2) Bacterial surface covered with internalin protein
3) Internalin binds to E-cadherin
4) E-cadherin binds to internalin all over bacterial surface, causing host-cell membrane to envelop bacterium (receptor clustering)
5) Bacterium is internalised

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12
Q

Proof of internalin effectiveness

A

Beads coated with internalin can invade cells

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13
Q

Another term for internalin

A

InIA

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14
Q

E-cadherin function

A

In tight junctions

Connects actin to structures external to cell

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15
Q

Is zipper or trigger more complex?

A

Trigger
Trigger uses far more proteins (~50) than zipper (as few as one)
Zipper is a passive process. Trigger is an active process

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16
Q

Bacterium that uses zipper

A

Listeria monocytogenes

17
Q

Bacteria that use trigger

A

Shigella flexneri

Salmonella enterica

18
Q

Is Shigella Gram + or-?

19
Q

Shigella spread

A

Person-person

Water-borne

20
Q

Effects of Shigella infection

A

Bacillary dysentery

Bloody diarrhoea

21
Q

How does Shigella differ from other E. coli?
1)
2)

A

1) Acquired virulence plasmid, pathogenicity islands

2) No flagella or fimbriae, to reduce inflammatory response from bacterial proliferation

22
Q

Protein making up Shigella T3SS shaft

23
Q

What does MxiH do?

A

Makes up shaft of Shigella T3SS

24
Q

Functions of ipaB, ipaC, ipaD

A

Inserted into host cell by Shigella, induce membrane ruffling (particularly ipaC)

25
Shigella proteins that induce membrane ruffling
ipaB, ipaC, ipaD ipaC most important
26
Which cells does Shigella invade?
M cells
27
Host cell proteins activated by Shigella to polymerise actin
RhoGTPases
28
Does Salmonella use zipper or trigger?
Trigger
28
Host cell proteins targeted by Shigella
Actin, vinculin, tubulin (cytoskeletal proteins)
28
Proteins used by Salmonella to invade
Sip proteins, encoded on SPI-1
28
Proteins encoded by SPI-1
``` Sip proteins (for Salmonella) T3SS ```
28
Targets of Sip proteins
Host cell cytoskeleton, GTPases
28
Number of T3SS's possessed by Salmonella
Two
28
What are the different Salmonella T3SS functions?
T3SS 1 - Induce host cell membrane ruffling | T3SS 2 - Escape from endosome, secrete Ssa
28
Ssa proteins
Effector proteins secreted by Salmonella T3SS number 2
28
``` SPI-1 effects 1) 2) 3) 4) ```
1) Invasion 2) Cytoskeletal rearrangements 3) Inflammation 4) Diarrhoea
28
SPI-2 effects 1) 2) 3)
1) Avoid intracellular antimicrobial defences 2) Modification of vacuole trafficking 3) Intracellular replication and survival
28
Broadly different roles of SPI-1 and SPI-2
SPI-1 - Invasion | SPI -2 - Intracellular survival