Module 3: Section 1C

Question 1

What is phenotypic adaptation in bacterial infection?

Answer 1

• When bacteria alter their metabolism to survive in changing host conditions
• Ex: they shift metabolic pathways to balance biosynthesis and ATP production, using available host nutrients

Question 2

What do persister cells do during antibiotic exposure?

Answer 2

They shift their metabolism to make just enough ATP to stay viable but not grow, so antibiotics targeting metabolic intermediates have no effect

Question 3

Presister cells

Answer 3

Bacterial cells that temporarily survive exposure to antibiotics without undergoing any genetic change

Question 4

How do resistant cells differ from persister cells?

Answer 4

Resistant cells grow in the presence of antibiotics, and their resistance comes from genetic changes that block antibiotic activity

Question 5

What is bacterial communication called?

Answer 5

Quorum sensing

Question 6

Quorum sensing

Answer 6

Method for bacteria to sense things like culture density and to respond by changing their metabolic activity

Question 7

What are the signalling molecules used in quorum sensing called?

Answer 7

Autoinducers

Question 8

Step 1 of quorum sensing in gram-positive bacteria

Answer 8

The autoinducer binds to a protein that is exposed on the cell surface

Question 9

Step 2 of quorum sensing in gram-positive bacteria

Answer 9

• The interaction activates the receptor, which initiates a series of signalling events
• Activates a transcriptional regulator that binds to DNA and alters gene expression

Question 10

Step 1 of quorum sensing in gram-negative bacteria

Answer 10

Autoinducter is taken into the cell

Question 11

Step 2 of quorum sensing in gram-negative bacteria

Answer 11

Autoinducter binds to an intracellular receptor which activates the protein

Question 12

Step 3 of quorum sensing in gram-negative bacteria

Answer 12

The receptor protein now acts as a transcriptional regulator by binding to DNA and altering gene expression

Question 13

Low population density and the virulence of bacteria

Answer 13

• At low population density the concentration of autoinducer is too low to interact with the quorum sensing receptor
• No effect on gene regulation

Question 14

High population density and the virulence of bacteria

Answer 14

• More autoinducer enters cells and interacts with QS receptors, forming a QS complex that regulates expression of survival genes

Question 15

Step 1 of using quorum sensing to make biofilm

Answer 15

• When a small microcolony forms, the local concentration of autoinducer becomes high enough to start the signaling process between cells.
• To form biofilm, cells must up regulate expression of polysaccharide synthesis and down-regulate genes involved in motility

Question 16

Step 2 of using quorum sensing to make biofilm

Answer 16

Cells in a biofilm talk to each other via quorum sensing to build micro colonies and to coordinate gene expression