Lecture 4: Motility & Chemotaxis

Question 1

Peritrichous bacteria

Answer 1

Numerous flagella around the body

Question 2

Monotrichous

Answer 2

Singular flagella

Question 3

Lophotrichous

Answer 3

Many flagella on one end of the bacteria

Question 4

Trade off between flagellar motility and efflux driving heterogeneity in antibiotic resistance

Answer 4

-Flagellar rotation & efflux pumps both use the proton gradient
-Cells expressing flagellar have a lower proton gradient and thus a lower efflux activity, resulting in higher concentrations of intracellular antibiotics
-Flagella-expressing cells are more sensitive to antibiotics
-Some bacteria slow flagella when exposed to antibiotics to allow efflux to remove them

Question 5

Bimodal expression of flagella in salmonella

Answer 5

Causes 2 distinct subpopulations that can be dynamically regulated depending on their environment as flagella are useful in escaping harsh environments

Question 6

Mechanism of twitching motility

Answer 6

-Type IV pili
-Pilus fiber made of pilins can extend or retract by polymerization and depolymerization
-Powered by cytoplasmic ATPase and proton gradients
-Cell body extends its pili to latch to a surface in order to pull bacteria forward

Question 6

Repellent

Answer 6

Signal that allows movement down gradient (AWAY)

Question 7

Chemotaxis

Answer 7

Movement of an organism or cell in response to a chemical stimulus

Question 7

Attractant

Answer 7

Signal that allows movement up gradient (TOWARDS)

Question 8

Counterclockwise rotation of flagella

Answer 8

Cell moves toward attractant

Question 9

Clockwise rotation of flagella

Answer 9

Stops forward motion so that cell tumbles and changes direction

Question 10

Biased random walk

Answer 10

Sometimes random walk that is overall directional due to the controlling of tumbles

Question 11

Excitation stage of chemotacis

Answer 11

Mostly run

Question 12

Chemoreceptors

Answer 12

-Direct binding and indirect binding possible
-Allows for signal amplification within the cytosol

Question 12

CheA

Answer 12

Histidine Kinase

Question 12

Adaptation stage of chemotaxis

Answer 12

Stable run & tumble combination

Question 13

CheW

Answer 13

Adapter that controls autophosphorylation of CheA

Question 14

CheY

Answer 14

Accepts phosphate from CheS

Question 15

CheY-P

Answer 15

Induces clockwise rotation of flagellar motor and tumbles

Question 15

CheZ

Answer 15

Dephosphorylates CheY-P to inactivate it (Constitutively expressed)

Question 16

CheR

Answer 16

Methylates cytoplasmic receptor to decrease sensitivity

Question 17

Receptor methylation

Answer 17

Covalent attachment of methyl group to a specific glutamate side chain

Question 17

CheB-P

Answer 17

Demethylates cytoplasmic receptor to increase sensitivity