Bacteria Chapter 11: Regulation of Genes Encoding Virulence Factors

Question 1

What do bacteria need to do to live in many different environments?

Answer 1

regulate expression of components needed for survival in different environments — they can turn components (including virulence factors) only when needed

Question 2

What environmental factors do bacteria sense in regulating the expression of their various virulence factors?

Answer 2

• temperature
• nutrients
• oxygen
• pH inside the cell
• iron availability
• osmolarity

Question 3

What are some common processes regulated at the genetic level?

Answer 3

• metabolism
• response to environmental stresses and conditions
• cell division

Question 4

What are global regulatory systems?

Answer 4

regulatory systems that control the production of multiple different virulence factors at once

Question 5

What is the 2-component system?

Answer 5

system that coordinately regulates virulence factors

comprises a sensory protein and a regulator protein

common system for signal transduction

Question 6

Two-component Regulatory System for Signal Transduction — Process

Answer 6

1. sensor (kinase) protein in cytoplasmic membrane detects changes in environment that indicate that bacterium is residing inside a human host – signal molecules
2. sensor protein is phosphorylated by kinase
3. sensor protein phosphorylates regulator protein
4. phosphorylated regulator protein transcriptionally activates or represses the virulence factors (ie. flagella genes, toxin genes, adhesin genes) by binding to a DNA sequence in regulatory regions of each of the operons for these virulence factors

Question 7

Does the 2-component system activate or block transcription of operons?

Answer 7

depends on the particular virulence factor

Question 8

What happens if the transcription of virulence genes are to be repressed?

Answer 8

response regulator protein blocks transcription of DNA by RNA polymerase

Question 9

What happens if the transcription of virulence genes are to be promoted?

Answer 9

response regulator protein bonds to regulatory region of the operon and recruits RNA polymerase

Question 10

Does gene regulation always play a part in production of virulence factors?

Answer 10

yes — production of virulence factors that bacteria use to enter and colonize the host, resist host immune defences, and cause damage in host, all result from DNA ⟶ RNA ⟶ Protein

Question 11

What would be the consequence if the sensor protein was always in an active state?

Answer 11

cell would not be able to respond to changes in its environment by changing gene expression

• sensor protein would be constantly phosphorylated and transferring phosphate to regulator protein
• gene will constantly be expressed or repressed

Question 12

What is an example of a one-component system?

Answer 12

lac operon in E. coli

Question 13

Focusing on the signal molecule, how do one-component and two-component systems differ?

Answer 13

one-component system:

• signal molecule acts with regulatory protein to activate or repress transcription
• signal molecule must enter into cell cytoplasm

two-component system: (signal molecule does not directly interaction with regulator protein)

• signal molecule acts on sensor (cell membrane protein), which causes it to get phosphorylated
• sensor protein relays information that signal molecule is present by transferring phosphate group to regulator protein
• regulator protein activates or represses gene expression