Lab 11 - Motility

Question 1

what is brownian motion?

Answer 1

small, random movements exhibited by bacterial cells due to collisions with water molecules or other cells in their vicinity

Question 2

how do the cells look during brownian motion?

Answer 2

they look like their vibrating, or moving slow in a floating type of motion

Question 3

what is motility?

Answer 3

purposeful movement of bacterial cells using structures like flagella

Question 4

define chemotaxis

Answer 4

motility in response to a chemical concentration gradient

Question 5

what is an example of how chemotaxis happens?

Answer 5

when the cells are moving towards a nutrient or moving away from a toxin

Question 6

what are two examples of chemotaxis sub examples?

Answer 6

chemoattractant - towards something (nutrients)
chemorepellent - away from something (a toxin)

Question 7

what are four types of motility?

Answer 7

-twitching
-gliding
-flagella
-axial filaments

Question 8

what does twitching use to move?

Answer 8

it uses its pili

Question 9

how does twitching work?

Answer 9

the pili attach to a solid surface; as some pili extend at one edge, other pili retract from another edge causing the cell to crawl on the surface

Question 10

what is an example of bacteria that use twitching to move?

Answer 10

Pseudomonas aeruginosa

Question 11

what is gliding?

Answer 11

it is similar to twitching, except no pili are involved

Question 12

what is an example of a bacteria that uses gliding to move?

Answer 12

Flavobacterium psychrophilum

Question 13

what are the 3 parts of the flagella?

Answer 13

-Basal body: PMF-driven motor (proton-motor force).
-Hook: hinge, changes position with respect to the rotation of flagella; it is either perpendicular or parallel to the cell surface.
-Filament: the corkscrew-like structure made of flagellin protein subunits (also called H-antigen)

Question 14

what are the H-antigens?

Answer 14

the flagellin protein subunits within the filament of the flagella

Question 15

what do the proteins in the basal body act as?

Answer 15

they act as a motor, rotating when energy is supplied. The source of energy for the basal body is the proton motive force

Question 15

what do the proteins in the basal body act as?

Answer 15

they act as a motor, rotating when energy is supplied. The source of energy for the basal body is the proton motive force

Question 16

how does the flagellar movement happen?

Answer 16

??

Question 17

what is the run-and-tumble?

Answer 17

it is a biased random walk

Question 18

what is the run part of the run-and-tumble?

Answer 18

when the basal bodies all run in one direction - all filaments get flexed to form a superflagellum; the cells move in a straight line

Question 19

what is the tumble part of the run-and-tumble?

Answer 19

when the basal body reverses directions - the filaments point in different directions - the cell moves randomly in all directions

Question 20

T/F: the bacteria swims using run and tumbles sequentially

Answer 20

true

Question 21

how long does the bacteria swim during run-and-tumble if they’re running in the direction of the nutrients?

Answer 21

runs long if it’s swimming in the right direction (like towards the nutrients)

Question 22

If during the run, nutrient concentration is increasing, what will happen?

Answer 22

If during the run, nutrient concentration is increasing, it will be a long run (4-6 seconds)

Question 23

If during the run, nutrient concentration is decreasing, what will happen?

Answer 23

If during the run, nutrient concentration is decreasing, it will be a short run (1-2
seconds)

Question 24

where is the overall movement toward for run-and-tumbles?

Answer 24

towards the nutrients

Question 25

what happens in axial filaments?

Answer 25

The whole cell rotates like a microscopic drill helping the bacterium to drill through human tissues

Question 26

what are examples of bacteria that perform axial filaments and the disease they cause?

Answer 26

Spirochetes: like Treponema pallidum (syphilis) and Borrelia burgdorfi (Lyme disease)

Question 27

??

Answer 27

Endoflagella or periplasmic flagella

Question 28

what is the purpose of viewing motility?

Answer 28

Motility is viewed to help identify unknown organisms; it helps to narrow down the possibilities, since not all organisms are motile

Question 29

what is the procedure for viewing motility?

Answer 29

-Make a hanging drop slide that suspends bacteria upside-down from a cover slip into a depression slide -Using the 40X objective, focus on bacteria at the edge of the drop to assess for motility

Question 30

motility usually involves flagella, but can we see flagella under the microscope?

Answer 30

No, flagella are too small to be seen with a light microscope (without staining)

Question 31

are all bacteria in a culture alive?

Answer 31

No, not all bacteria in a culture are alive, so if you see any motility at all, the culture is motile

Question 32

is brownian motion motility?

Answer 32

Brownian motion is NOT motility, but represents water molecules colliding with cells, making them rock back-and -forth