Virulence and Antigenic Diversity

Question 1

What is the structure of N. gonorrhea?

Answer 1

Diplococcus

Question 2

Adherence

Answer 2

Many pathogens use adherence as a defense against the host’s mechanical cleansing devices.

Question 3

What 2 factors does adherence require?

Answer 3

• host receptor

* bacterial adhesin

Question 4

What are the 2 types of adhesins?

Answer 4

1) pilus (fimbria) - for attachment at a distance

2) non-fimbrial adhesin (outer membrane protein) for intimate attachment

Question 5

What is the main function of Adhesin Diversity?

Answer 5

Each adhesin plays a different role. Such diversity permits cells to adapt to an ever changing environment whether its binding to different classes of host receptors or different hosts.

Question 6

What is an additional function of adhesin diversity?

Answer 6

Differential expression of adhesins also helps cells escape the host immune response.

Question 7

What is the organization of the piling gene?

Answer 7

Expressed gene (pilE)
Silent cassettes (pilS) - lack promoters and are incomplete

Question 8

What are the mechanisms that can introduce pilS into pilE?

Answer 8

Gene Conversion

Transformation

Question 9

How does gene conversion function?

Answer 9

A silent pilS cassette can be copied into the expressed pilE site. The original pilS locus remains unchanged. However, the pilE locus now expresses a new pilus that is antigenically distinct from the old pilus.

Question 10

How does transformation function?

Answer 10

Piliated gonococci lyse easily, releasing DNA into the environment. They also are naturally competent for DNA transformation. Therefore, the silent cassettes can come from outside the cell as the result of transformation.

Question 11

The following genetic mechanisms can alter the antigenicity of adhesins, EXCEPT:
A. Recombination 
B. Attenuation
C. Gene conversion 
D. Transformation

Answer 11

B. Attenuation