Virulence Regulation I

Question 1

What is an example of how bacterial genes adapt to the host environment?

Answer 1

Siderophores allowing them to scavenge the host for Fe

Question 2

Virulence Factor

Answer 2

Any bacterial property required for entry, growth, or survival in a HOST - not necessarily required for life in the lab

Question 3

What are examples of virulence factors?

Answer 3

• capsule - inhibits killing by complement
• adhesins - permit adherence to host cells
• acid tolerance factors (ASPs) - adapt pathogen to stomach
• enzymes - synthesize unavailable nutrients

Question 4

Virulence Gene

Answer 4

Genes that encode virulence factors

Question 5

Pathogenicity Islands

Answer 5

Large, localized regions of chromosome missing in related non-pathogens

Question 6

Operator

Answer 6

Binding site for a transcription factor

Question 7

Operon

Answer 7

Operon is a unit of transcription that includes more than one cistron

Question 8

Multicistronic mRNA

Answer 8

It is the mRNA that results from transcription of a multicistronic operon

Question 9

RNA polymerase

Answer 9

Transcribes DNA into mRNA.

Question 10

σ (sigma) Factor

Answer 10

It is subunit of RNAP that specifically recognizes and binds the promoter

Question 11

What binds to the promoter?

Answer 11

The RNAP holoenzyme (entire unit binds via sigma factor)

Question 12

Closed Complex

Answer 12

The product of the RNAP/DNA interaction

Question 13

Open Complex

Answer 13

Once bound, RNAP causes the double strand of DNA to open

Question 14

What part of transcription is primarily regulated?

Answer 14

Initiation

Question 15

What happens to cAMP as glucose decreases?

Answer 15

cAMP increases

Question 16

What happens to cAMP as glucose increases?

Answer 16

cAMP decreases

Question 17

What happens in the lac operon with glucose present and cAMP absent?

Answer 17

Repression of the operon by steric hindrance as lacR is transcribed and made into the repressor protein.

Question 18

How does induction occur in the lac operon?

Answer 18

The inducer, in this case, lactose, will bind to the represser to prevent it from binding DNA.

Then, conditions need to be right with glucose absent and cAMP present, which will lead cAMP to bind CRP into cAMP-CRP which is the activator and recruits RNAP.

Question 19

What is required for induction of the lac operon?

Answer 19

1) Lactose presence

2) Glucose absence -> high cAMP

Question 20

What does RNAP bind?

Answer 20

Promoter

Question 21

What does the repressor bind?

Answer 21

Operator - repressor binding will reduce the affinity of RNAP binding

Question 22

What does the inducer bind?

Answer 22

Repressor - inducer binding will decrease the repressor’s binding affinity

Question 23

What does the activator bind?

Answer 23

Activator interacts with RNAP and increases RNAP affinity

Question 24

What does the co-factor bind?

Answer 24

In the lac operon, cAMP is the co-activator.

Co-activator binds the activator and increases the activator’s binding affinity

Question 25

What happens to the probability of transcription as the stability of the closed complex increases?

Answer 25

The probability of transcription initiation increases as the stability of the closed complex increases.

activators increase stability
repressors decrease stability

Question 26

Holoenzyme

Answer 26

σ + core enzyme (RNAP)

Question 27

Core Enzyme

Answer 27

2 α subunits, 1 β subunit, β’ subunit

Question 28

Regulon

Answer 28

A group of operons (also called a global control system) subject to the control of a common (or global) regulator

Question 29

What is the purpose of a regulon?

Answer 29

It allows simultaneous activation and inactivation of a series of related genes

Question 30

Can a repressor protein at Operator A be an activator at Operator B?

Answer 30

Yes

Question 31

Repressors inhibit transcription by
A. increasing the affinity of RNAP for the promoter
B. interfering with the binding of RNAP to the promoter
C. causing RNAP to fall off the promoter
D. none of the above
E. all of the above

Answer 31

B. interfering with the binding of RNAP to the promoter