Virulence Mechanisms of gene regulation 1

Question 1

What is a virulence factor?

Answer 1

any bacterial property required for entry, growth, or survival in a host

-examples-capsule, adhesins, acid tolerance factors, enzymes to synthesize unavailable nutrients, adapt to stomach

Question 2

What are pathogenicity islands?

Answer 2

large, localized regions of chromosomes missing in related non-pathogens

Question 3

What are the steps of transcription initiation?

Answer 3

STEP 1: formation of closed complex
-core RNA polymerase+sigma factor (promoter-binding)= holoenzyme

STEP 2: formation of open complex (RNA polymerase pulls strands apart)

STEP 3: Initiation and elongation
-sigma factor falls off

Question 4

What does the sigma factor do?

Answer 4

enables specific binding of RNA polymerase to gene promoter

Question 5

What is the glucose cAMP relationship?

Answer 5

decrease glucose increase cAMP

Question 6

What does the lacR do?

Answer 6

expressed constitutively and makes repressor protein

Question 7

Where does the repressor bind and what does it do?

Answer 7

the operon and blocks binding of RNA polymerase by steric hindrance

Question 8

What happens when lactose is present and glucose is low?

Answer 8

1. inducer (lactose) binds the repressor
2. repressor doesn’t bind operon
3. activator interacts with RNA polymerase increasing RNA polymerase binding affinity
4. co-activator-cAMP binds activator (CRP) and increases affinity for binding site

Question 9

The probability of transcription initiation increases as the stability of what increases?

Answer 9

closed complex

• activators increase stability
• repressors decrease stability

Question 10

PhoQ and Tox S are?

Answer 10

sensors

Question 11

What are PhoP and ToxR ?

Answer 11

regulators