Lecture 11 Flashcards
What are the roles of adhesion for extracellular pathogens?
Colonisation of host cell surfaces or artificial surfaces
efficient delivery of exotoxins into the host cell
What is the role of adhesion for intracelular pathogens?
Critical step that preceeds internalisation
How do bacteria directly adhere to host cells?
Pili
What are pili made up of? What is the major subunit?
Large, long multisubunited proteins. The major subunit is the pili protein.
What bacteria expresses the P pili? What disease is this bacteria responsible for?
Europathogenic E.coli. Responsible for 80% of UTIs
What are the 4 subunits of the P pilus and what are their functions?
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
How are P pili assembled?
Occurs in an ordered fashion. Starts with PapG (tip protein), then PapA (major structural protein)
What is a drug that inhibits pilus proteins? How do they work?
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.
What is the receptor for the p pilus?
What is the receptor made out of?
Where is it found?
Globoside. Made out of a galactose containing glycolipid. Found on the surface of epithelial cells in the kidney and bladder.
What are two examples of bacteria that have the type IV pilus?
Nesseria, Enteropathogenic E.coli (EPEC)
What does the type IV pili help with?
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)
Where does Nesseria meningitidis colonise?
Nasopharynx
How does type IV pili aid in N.meningitidis to cause disease? What two diseases can it cause?
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.
What are the two subunits of the type IV pilus?
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.
Describe what ‘twitching motility’ is. How does it work and what bacteria use this form of motility?
“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.
What are single protein adhesins?
Adhesins are bacterial surface proteins that bind to the host surface proteins to lead to internalisation of the bacteria into the cell.
What is the single protein adhesin produced by Yersinia enterocolitica and what cells does it invade? What does invasion of these cells cause?
Invasin protein used to invade M cells in the intestine.
Describe the two step adhesion of enteropathogenic E.coli that leads to the formation of a bacterial pedestal.
- 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
- 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
True or false: Type III excretion systems are only found in gram positive bacteria?
False
True or false: Type III excretion systems are found on all gram -ve pathogens
False- they are found on many gram -ve bacteria but not all
What are type III excretion systems and how do they work?
Multiprotein complexes that form a needle like apparatus that can inject several bacteria effector proteins into the host cytosol or plasma membrane.
