Lecture 11

Question 1

What are the roles of adhesion for extracellular pathogens?

Answer 1

Colonisation of host cell surfaces or artificial surfaces

efficient delivery of exotoxins into the host cell

Question 2

What is the role of adhesion for intracelular pathogens?

Answer 2

Critical step that preceeds internalisation

Question 3

How do bacteria directly adhere to host cells?

Answer 3

Pili

Question 4

What are pili made up of? What is the major subunit?

Answer 4

Large, long multisubunited proteins. The major subunit is the pili protein.

Question 5

What bacteria expresses the P pili? What disease is this bacteria responsible for?

Answer 5

Europathogenic E.coli. Responsible for 80% of UTIs

Question 6

What are the 4 subunits of the P pilus and what are their functions?

Answer 6

PapG- adhesin (protein) that binds to a receptor on the surface of a human cell

PapA- major structural component of the pilus

PapC- outer membrane protein that forms a channel for the other components to be transported through

PapD- a chaperone that binds to P pilus proteins in the periplasm to prevent them from being degraded and to transport them to the Pap C channel

Question 7

How are P pili assembled?

Answer 7

Occurs in an ordered fashion. Starts with PapG (tip protein), then PapA (major structural protein)

Question 8

What is a drug that inhibits pilus proteins? How do they work?

Answer 8

Pillicides are chemicals that bind and inhibit the functioning of PapD which prevents folding of the pilus proteins and assembly of the proteins. This prevents adhesion of the bacteria to the host cells.

Question 9

What is the receptor for the p pilus?

What is the receptor made out of?

Where is it found?

Answer 9

Globoside. Made out of a galactose containing glycolipid. Found on the surface of epithelial cells in the kidney and bladder.

Question 10

What are two examples of bacteria that have the type IV pilus?

Answer 10

Nesseria, Enteropathogenic E.coli (EPEC)

Question 11

What does the type IV pili help with?

Answer 11

Mediate binding of bacteria to protein or glycolipid receptors on the surface of host cells

Can also promote the internalisation of bacteria into human cells (Nesseria)

Question 12

Where does Nesseria meningitidis colonise?

Answer 12

Nasopharynx

Question 13

How does type IV pili aid in N.meningitidis to cause disease? What two diseases can it cause?

Answer 13

Type IV pili play a critical role in internalisation of the bacteria into the nasopharynx epithelial cells. They can then spread into the blood to cause septisemia and then pass through the blood brain barrier into the meninges to cause meningitis.

Question 14

What are the two subunits of the type IV pilus?

Answer 14

PilC- binds to the surface of human cells

PicE- main component of the pilus. Can be added or subtracted from the pilus to cause it to grow or shrink.

Question 15

Describe what ‘twitching motility’ is. How does it work and what bacteria use this form of motility?

Answer 15

“Twitching motility” is named that bc it looks like the bacteria are twitching across the cell surface. N.meningitidis use this to move. Caused by the polymerisation and depolymerisation of pilus proteins from the type IV pili. Pulls the bacteria along the cell.

Question 16

What are single protein adhesins?

Answer 16

Adhesins are bacterial surface proteins that bind to the host surface proteins to lead to internalisation of the bacteria into the cell.

Question 17

What is the single protein adhesin produced by Yersinia enterocolitica and what cells does it invade? What does invasion of these cells cause?

Answer 17

Invasin protein used to invade M cells in the intestine.

Question 18

Describe the two step adhesion of enteropathogenic E.coli that leads to the formation of a bacterial pedestal.

Answer 18

1. binding of a type IV bundle forming pilus to the host cell causes vili to degrade and pili can drag the bacteria closer to the cell
2. bacterial injection of translocated intimin receptor (TIR) into the host cell plasma membrane. EPEC then binds TIR through its bacterial protein adhesin, Intimin. TIR/intimin interaction illicits the formation of a pedestal

Question 19

True or false: Type III excretion systems are only found in gram positive bacteria?

Answer 19

False

Question 20

True or false: Type III excretion systems are found on all gram -ve pathogens

Answer 20

False- they are found on many gram -ve bacteria but not all

Question 21

What are type III excretion systems and how do they work?

Answer 21

Multiprotein complexes that form a needle like apparatus that can inject several bacteria effector proteins into the host cytosol or plasma membrane.