MIDTERM 2 MOTILITY

Question 1

What is motility defined as?

Answer 1

Self-directed movement of a cell from one position to another without involvement of physical forces such as agitation of the medium

Question 2

What form of motility is the most common and well understood?

Answer 2

Flagellar motility is most common and the mechanisms of movement are well understood

Question 3

What is Flagellar motility?

Answer 3

Whip-like structures anchored in the cell membrane and can rotate CW or CCW to produce tumbling or running movements of the cell.

Question 4

What are positive chemotaxis?

Answer 4

Movement towards a favorable chemical environment

Question 5

What are Negative Chemotaxis?

Answer 5

Movement towards an unfavorable environment

Question 6

Positive and Negative phototaxis?

Answer 6

in response to light

Question 7

Positive and Negative Geotaxis?

Answer 7

In response to gravity

Question 8

Positive and Negative Magnetotaxis?

Answer 8

in response to earths magnetic fields

Question 9

Why are flagella so hard to see? whats their size?

Answer 9

theyre well below the limit of resolution of a light microscope with a diameter of 0.01 to 0.05 uM

Question 10

What happens in the Leifson Flagellar Stain?

Answer 10

Tannic acid precipitates along the flagellar surface and serves to hold the basic fuschin stain. The accumulation of stain on the flagellum amplifies the size and increases its visibility under the light microscope

Question 11

What shapes are most flagellated bacteria?

Answer 11

They are rods with few examples of cocci

Question 12

What is Monotrichous?

Answer 12

Single Flagella inserted at the ends of a cell (polar flagella)

Question 13

What is polytrichous

Answer 13

Numerous flagella inserted at the ends of the cell or distributed over the entire surface (peritrichous)

Question 14

Does having flagella ensure motility? if no, Why?

Answer 14

No it does not.

1. Cultures in stationary phase of growth may consist of dead cells or cells that are unable to efficiently utilize nutrients in the environment to produce energy required for motility
2. Cells that are young and flagellated may lose their flagella in the process of making a wet mount and show little to no motility under microscope

Question 15

What can affect motility?

Answer 15

1. Presence/Absence of some nutrients
2. Changes in the growth Temperature
3. Degree of Aeration

Question 16

Basic requirements for detecting motility?

Answer 16

1. Cells must be inherently capable of producing flagella
2. Cells must be growing in conditions appropriate for motility
3. Cultures should be young and capable of growth and physiological activity
4. the culture must be handled gently

Question 17

What form of microscopy is best to observe motility?

Answer 17

Phase Contrast

Question 18

How can motility be determined indirectly?

Answer 18

By observing that organisms that were inoculated in one place have moved and grown in a region of the medium that was not inoculated.

Question 19

Explain Swarming motility

Answer 19

Bacteria capable of high levels of motility may spread rapidly across the surface of an agar plate ( SPREADING)

Question 20

Why does swarming occur?

Answer 20

Nutrients are exhausted in the region of inoculation, stimulating organisms to spread out in direction of higher nutrient concentration

Question 21

Problem with swarming colonies?

Answer 21

Swarming introduces complications in attempts to produce isolated colonies on a plate as the swarmer may rapidly overgrow other non swarming colonies

Question 22

What medium is used to test Motility ?

Answer 22

Soft Agar Deeps

Question 23

What is the property of a soft agar deep?

Answer 23

its more of a viscous medium than a solid agar

Question 24

How does viscosity affect motility?

Answer 24

only the stronger , higher level motile microbes can move through it

Question 25

Positive test for motile organisms in the soft agar deep?

Answer 25

Growth present away from the stab

Question 26

Soft Agar Deep can be used to test for motility, but what makes it so special that it can test for something else?

Answer 26

The soft agar can close up along the stab so that the path of the stab is no longer visible and cannot serve as a path for entry of oxygen from the airspace in the deep.

1. If bacterium is an obligate aerobe, growth will stop after the oxygen runs out in the deep.
2. Only organisms that are facultative will continue to grown in absence of oxygen.

Question 27

When can the Soft agar Deep only be used as a motility test?

Answer 27

if the organism is a facultative anaerobe and it will only exhibit motility if its actively motile as well