L19 Virulence, Adherence, and Antigenic Diversity Flashcards
Many pathogens use ___ as a defense against the host’s mechanical cleansing devices (blinking, peristalsis, etc.).
Adherence
Adherence requires the interactions of what two factors?
- Host cell surface receptor (typically a specific carbohydrate residue)
- Bacterial adhesin (typically a surface protein structure)
Adhesions can be appendages called ___ composed of ___ protein subunits assembled as a polymer.
Pili; pilin
Pili are utilized for attachment at a distance; what is used for intimate attachment?
Non-fimbrial adhesins (outer membrane proteins)
True or false - many bacterial species possess a variety of adhesins.
True
In E. coli, Type 1 pili are used to adhere to ___; Type P pili are used to adhere to ___.
Liquids (bladder); solid surfaces (kidney)
N. gonorrhea avoid the immune system by varying ___.
Adhesin composition
Each N. gonorrhea cell possesses genetic information for a large number of variant pilin proteins. What are the implications of this?
Each cell can produce progeny that synthesize pili that exhibit different epitopes that did its parent.
Silent cassettes (pilS) have three relevant features - what are they?
- Promoterless
- Incomplete
- Oriented in the same direction as the expressed gene (pilE)
What are the two major mechanisms of antigenic variation of pilin genes?
- Gene conversion
2. Transformation
What happens in gene conversion?
A silent pilS cassette can be copied into the expressed pilE site (genes are from the same cell, thus pilS is an endogenote); the original pilS locus is unchanged.
What happens in transformation?
PilS is an exogenote and comes from a lysed donor.
True or false - antigenic possibilities are infinite.
True
