6- Chapter 7

Question 1

What are the two proteins that make up two component regulatory systems?

Answer 1

Sensor kinase (in cytoplasmic membrane)- detects environmental signal and autophosphorylates
Response regulator (cytoplasm)- DNA binding protein that regulates transcription

Diagram on slide 3 sept 28

Question 2

What are the 3 steps in the response to signal in chemotaxis?

Answer 2

1. Sensory proteins in cytoplasmic membrane sense attractants and repellents
   MCPs bund attractant or repellent and initiate flagellar rotation
2. Controlling flagellar rotation
   Controlled by CheY protein
3. Adaptation- feedback loop
   Allows system to reset itself to continue to sense the presence of a signal

Diagram on slide 7 on sept 28

Question 3

What two Che proteins result in which direction of flagellar rotation?

Answer 3

CheY is counterclockwise rotation and runs
CheY-P results in clockwise rotation and tumbling

Che proteins also play roles in phototaxis and aerotaxis

Question 4

What is quorum sensing?

What was it first discovered as?

Answer 4

Mechanism by which bacteria assess their population density
Ensures that a sufficient number of cells are present before initiating a response that requires a certain cell density
First discovered as mechanism regulating light production in bacteria

Question 5

What is an autoinducer molecule?

Answer 5

It diffuses freely across the cell envelope
Reaches high concentrations inside cell only if many cells are near
Binds to a specific activator protein and triggers transcription of specific genes
Diagram on slide 11 sept 28

Question 6

What are examples of quorum sensing?

Answer 6

Virulence factors

Switching from free living to growing as a biofilm

Question 7

What is a heat shock response and heat shock proteins?

Answer 7

Heat shock response- largely controlled by alternative sigma factors
Heat shock proteins- counteract damage of denatured proteins and help cell recover from temperature stress
Picture on slide 16 of sept 28

Question 8

What is sporulation in bacillus?

Answer 8

Regulation of development in model bacteria
Endospore formation in bacillus
Controlled by four sigma factors
- forms inside mother cell
- triggered by adverse external conditions (starvation or desiccation)
Picture on slide 18 of sept 28