Motility

Question 1

What are external structures?

Answer 1

• extend beyond the cell envelope in bacteria and archaeons
• function in protection, attachment to surfaces, horizontal gene transfer, and cell movement
• ex: fimbriae, pili, and flagella

Question 2

What is are sex pili?

Answer 2

• similar to fimbriae except longer, thicker, and less numerous (1-10/cell)
• genes for formation are found on a plasmid (called fertility plasmid)
• required for conjugation
• one bacteria sends the fertility plasmid to another bacteria via the sex pilus

Question 2

What are fimbriae and pili?

Answer 2

• short, thin, hair-like proteinaceous appendages (up to 1,000 per cell)
• mediate attachment to surfaces
• some (type IV pili) required for motility or DNA uptake

Question 3

How are sex pili seen under the microscope?

Answer 3

• use a virus as a mordant

- makes the pilus appear thicker so it can be viewed under the microscope

Question 4

What are flagella?

Answer 4

• thread-like appendages extending outward from the plasma membrane and cell wall
• functions in motility and swarming behavior and attachment to surfaces
• may be a virulence factor because the flagella allows the bacteria to burrow themselves into tissues

Question 5

monotrichous

Answer 5

one flagellum

Question 6

polar flagellum

Answer 6

flagellum/flagella at the end of the cell

Question 7

amphitricous

Answer 7

one flagellum at each end of the cell

Question 8

lophotricous

Answer 8

cluster of flagella at one or both ends

Question 9

peritrichous

Answer 9

flagella spread over entire surface of cell

Question 10

What are the three parts of the flagella?

Answer 10

• filament
• hook
• basal body (motor)

Question 11

What provides the energy for rotation of the flagellum?

Answer 11

proton motive force

Question 12

What is the mechanism of flagellar movement?

Answer 12

• the flagellum is a motor that produces torque
• the rotor is a C ring and an MS ring that turn and interact with the stator
• the stator is made of Mot A and Mot B proteins that H+ ions flow through in order to move the C and MS rings

Question 13

What is the biosynthesis of the flagella?

Answer 13

• MS/C ring
• Mot proteins
• P ring
• L ring
• early hook
• late hook (with cap)
• filament and hook-filament junction

Question 14

How does the filament grow?

Answer 14

from tip to base

Question 15

What is the difference between gram positive and gram negative flagella?

Answer 15

• gram negative flagella have 4 rings (L,P,MS, and C)
• gram positive flagella have 2 rings (MS and C)
• L and P ring offer stability to gram negative bacteria that have a thin layer of peptidoglycan

Question 16

What happens when the flagella rotates counterclockwise?

Answer 16

forward motion (run)

Question 17

What happens when the flagella rotates clockwise?

Answer 17

• disrupts run causing cell to stop and tumble

- tumbles allow the cell to change direction (but the new direction is random)

Question 18

How do spirochetes move?

Answer 18

• spirochetes have multiple flagella (endoflagella) that form an axial fibril that winds around the cell
• the flagella remain in the periplasmic space inside the outer sheath
• exhibits flexing and spinning movements
• good for pathogens because they can burrow into tissues

Question 19

What is twitching motility?

Answer 19

• pili at the ends of cell
• short, intermittent, jerky motions
• cells are in contact with each other and the surface

Question 20

What is gliding motility?

Answer 20

• smooth movements
• often involves slime
• usually social
• glide proteins pull the bacteria forward

Question 21

What is chemotaxis?

Answer 21

• movement toward a chemical attractant or away from a chemical repellant
• concentrations of chemoattractants and chemorepellants detected by chemoreceptors on surfaces of cells
• complex but rapid
• responses occur in less than 20 milliseconds
• 2-over 60 cell lengths/sec

Question 22

What is positive chemotaxis?

Answer 22

• going toward an attractant
• runs are longer
• tumbles are less frequent

Question 23

What is negative chemotaxis?

Answer 23

• going toward a repellant (trying to move away)
• runs are shorter
• tumbles are more frequent