Virulence of Mechanisms of Gene Regulation

Question 1

Before ingestion, intestinal pathogens often reside in water at

Answer 1

• low temperature
• low ionic strength
• low concentration of organic nutrients
• neutral pH

Question 2

After ingestion, intestinal pathogens must adapt to

Answer 2

• higher temperature
• higher osmotic strength
• low pH
• high pH
• bile salts
• lack of oxygen and abundant nutrients
• sequestration of iron by host

Question 3

To survive this journey, the pathogen must rapidly express a variety of gene products:

Answer 3

-proteins that help tolerate low pH of stomach
-flagella and chemotaxis proteins
-for migration to suitable niche
-adhesins that permit colonization
-toxins & invasins to elicit disease
iron chelators (siderophores) to scavenge for iron

Question 4

VIRULENCE FACTOR

Answer 4

• any bacterial property required for entry, growth, or survival in a host
• —examples:
• capsule - inhibits killing by complement
• adhesins - permit adherence to host cells
• acid tolerance factors (ASPs) -
• adapt pathogen to stomach
• enzymes - synthesize unavailable nutrients
• 5 - 10 % of Vibrio or Salmonella genes
• often located on mobile genetic elements (plasmids or phage) or in pathogenicity islands*

Question 5

pathogenicity islands

Answer 5

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

Question 6

cistron

Answer 6

a sequence of DNA that encodes a polypeptide

Question 7

Bacteria organize their genes in

Answer 7

multicistronic operons.

Question 8

operon

Answer 8

-a unit of transcription that includes more than one cistron.

Question 9

multicistronic mRNA

Answer 9

-the mRNA that results from transcription of a multicistronic operon

Question 10

The typical operon

Answer 10

promoter, an operator, cistrons and a terminator

Question 11

promoter

Answer 11

the site at which RNAP binds

Question 12

sigma

Answer 12

a subunit of RNAP that specifically recognizes and binds the promoter

Question 13

closed complex

Answer 13

The product of the RNAP/DNA interaction

Question 14

open complex.

Answer 14

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

Question 15

how do cells regulate transcription

Answer 15

• Cells regulate transcription primarily at its initiation
• They make the decision to initiate or not by setting the frequency of initiation
• The frequency of initiation depends upon the ability of RNAP to bind the promoter

Question 16

repressor

Answer 16

• binds the operator, a site located close to or overlapping the promoter.
• The overlap prohibits binding of RNAP to promoter

Question 17

inducer

Answer 17

-a small molecule that binds the repressor, changing that protein’s conformation so that it can no longer bind DNA

Question 18

activator

Answer 18

-interacts with RNAP, increasing the ability of RNAP to bind the promoter

Question 19

co-activator

Answer 19

• (cAMP) binds activator

- increasing ACTIVATOR binding affinity

Question 20

The probability of transcription initiation _____ (incr/decr)
as the stability of the closed complex ____ (incr/decr)

Answer 20

• increases, increases
• activators increase stability
• repressors decrease stability

Question 21

regulon (a gene network) chain of events

Answer 21

1) through the action of some sensor molecule, a cell senses a stimulus;
2) sensor signals to activate/deactivate a regulator;
3) regulator binds to several operons;
4) binding turns some on & some off;
5) gene products respond to the original stimulus; &
6) gene products exert feedback control on their own expression.

Question 22

most of the regulation of gene expression comes from…

Answer 22

-getting the RNA polymerase to bind long enough to get transcription

Question 23

when glucose levels are high, cAMP levels are ______

Answer 23

low

Question 24

Glucose present / cAMP absent = _____

Answer 24

repression

Question 25

glucose absent/cAMP present

lactose (inducer) present = ______

Answer 25

INDUCTION

Question 26

interactions that enhance transcription initiation

Answer 26

1) sigma /DNA (promoter)
2) DNA/alpha-CTD
3) sigma/alpha-CTD
4) CRP/DNA
5) CRP/alpha-CTD