Lecture 3: Motility and Chemotaxis in Bacteria

Question 1

Ways Microbes Respond to Environment

Answer 1

Physical signals : temp, pH, osmolarity
Chemical signals : nutrients, toxins, signaling molecules
Responses at level of gene expression
Responses at level of cellular structure

Question 2

How do Bacteria move

Answer 2

Respond at level of cellular structure

• Bacteria use proton motor force to cause flagella to rotate in anticlockwise direction
• Flagella bundle up and propel forward, aka run
• Flagella rotate clockwise, bundle unravels and bacteria tumbles

Question 3

Master Regulators of Flagellum Expression

Answer 3

flhC & flhD
Expressed from flhD C operon
Positively enhanced by cAMP CRP activation complex
Complex links to cellular glucose levels

Question 4

flhD and flhC proteins

Answer 4

Create transcriptional activation complex and activates expression of middle genes

Question 5

Sigma Factor

Answer 5

Forms part of RNA polymerase complex and directs complexes towards specific classes of promotors
*Responsible for directing polymerase complex towards late genes and FliA

Question 6

Phase Variation

Answer 6

Helps Salmonella to evade host defenses