Quiz 2

Question 1

Simple stain (3A)

Answer 1

Consists of one dye that stains a component of the microbial cell

Question 2

What is the most commonly used basic dye? (3A)

Answer 2

Methylene blue

Question 3

Why is methylene blue a commonly used dye? (3A)

Answer 3

It dyes the more acidic components of the cell more deeply than less acidic parts of the cell

Question 4

What are two common things that are smeared with methylene blue? (3A)

Answer 4

Raw milk & throat smears in the diagnosis of diptheria

Question 5

What yeast was used in exercise 3A?

Answer 5

Saccharomyces cerevisiae

Question 6

Briefly describe how to prepare a simple stain (3A)

Answer 6

-Place a dot of water on the slide -Smear in a bit of the bacteria/yeast/etc -Let it air dry, then fix it by passing through flame -Apply several drops of methylene blue & let sit for about a minute -Rinse with water, dry, and examine

Question 7

About how large is a yeast cell? (3A)

Answer 7

7 x 15 microns

Question 8

Differential stain (3B)

Answer 8

Uses two or more dyes that can be used to categorize cells into groups

Question 9

What are the four dyes used in a gram stain? (3B)

Answer 9

i) Crystal violet ii) Gram’s iodine iii) Decolorizer iv) Safranin (counter-stain)

Question 10

What color do gram-positive cells stain? (3B)

Answer 10

Purple – hold onto the crystal violet b/c of the thick peptidoglycan layer

Question 11

What color do gram-negative cells strain? (3B)

Answer 11

Pink – decolorizer penetrates lipid membrane, but holds the saffranin

Question 12

Why might a cell be gram-variable? (3B)

Answer 12

-Depending upon how long the culture has been growing, it might appear gram-positive or gram-negative. -For example, many gram-positive bacteria will appear gram-negative in later stages of growth. -Young growths shouldn’t be gram variable (less than 12-18 hrs).

Question 13

What three bacteria were used in the gram-staining procedure? (3B)

Answer 13

-Staphylococcus epidermis - Gram positive -Bacillus subtilis - Gram variable -Escherichia coli - Gram negative

Question 14

Briefly describe the gram staining method (3B)

Answer 14

-Apply water to slide, apply bacterial strains to the water, let air-dry, and heat-fix -Stain with crystal violet for ~1 min, rinse w/ water -Stain with iodine for ~1 min, rinse w/ water -Decolorize for 2-5 sec -Stain w/ Safranin for ~30 sec, rinse, dry, & examine

Question 15

Cell capsule (3C)

Answer 15

-Protects the cell, does not provide any necessary functions though -Often destroyed in some methods of staining -India ink is often used to do a negative stain & stain the background, leaving the cells white so we can see the capsule

Question 16

Name a genus that contains a capsule (3C)

Answer 16

Klebsiella

Question 17

Name two genus that make spores (3D)

Answer 17

Bacillus & Clostridium

Question 18

What are the dormant structures that are made during sporulation called? (3D)

Answer 18

Endospores

Question 19

What triggers the formation of endospores? (3D)

Answer 19

Usually, lack of nutrients in the environment. Sporulation causes the cells to become dormant & they will become active again once there are more nutrients available

Question 20

What bacterium was spore-stained in 3D?

Answer 20

Bacillus subtilis -Sub-terminal spore -Gram positive

Question 21

Briefly describe the spore-staining technique (3D)

Answer 21

-Swab bacterial culture & place whole swab into malachite green, place in boiling water bath ~10 min -Rub swab onto a slide, heat fix -Decolorize with water 2-5 sec -Stain w/ Safranin ~20 sec -Rinse w/ water, dry, & examine

Question 22

Why would a person want to do a spore stain? (3D)

Answer 22

Can determine size, shape, & position of the spore in the cell. The dye will not penetrate the spore, but it will penetrate the vegetative cell, & the counterstain will colorize the spore

Question 23

What technique was done on the spore stain? (3E)

Answer 23

Leifson’s technique -Uses a mordant to increase cell size

Question 24

What kind of flagella did the microbe in 3E have?

Answer 24

Polar monotrichous

Question 25

What two microbes were used in 3F (acid-fast staining)?

Answer 25

-Mycobacterium phlei - Acid-fast (resists decolorization), gram + -Staphylococcus epidermis - Not acid-fast

Question 26

Briefly describe the technique for acid-fast staining (3F)

Answer 26

-Collect S. epidermis on swab, rotate in tube of carbol fuschin, discard -Collect M. phlei on swab, put in tube, incubate tube in boiling water bath for 10 minutes -Wipe swab on slide, heat fix -Decolorize w/ acid alcohol 2-5 sec, rinse w/ water -Counterstain w/ methylene blue ~20 sec, rinse, dry, observe

Question 27

Metachromatic granules (3G)

Answer 27

-Reserves of polumerized meta phosphates & sometimes called volutin

Question 28

Give two examples of a bacterium that contains metachromatic granules (3G)

Answer 28

-Cornyebacterium diptheriae -Cornyebacterium xerosis

Question 29

Describe what will happen to a cell in a hypotonic solution (3H)

Answer 29

Solute (edit: SOLVENT (water) moves with osmosis, not solute) will flow into the cell and it will swell & lyse due to its inability to resist the high osmotic pressure

Question 30

Describe what will happen to a cell in a hypertonic solution (3H)

Answer 30

Solute (edit: SOLVENT (water) moves with osmosis, not solute) will flow out of the cell & the cytoplasm will shrivel up

Question 31

Protoplasts (3H)

Answer 31

-A cell devoid of a cell wall -Still bound by a plasma membrane

Question 32

What is it called when the solute concentration is the same both inside and outside of the cell? (3H)

Answer 32

Isotonic

Question 33

What does a lysozyme do? (3H)

Answer 33

It’s an enzyme that attacks the peptidoglycan by hydrolyzing the glycosidic bond that connects NAM & NAG

Question 34

What bacteria was used in 3H?

Answer 34

Bacillus subtilis

Question 35

What are the two chemical groupings attached to benzene rings that define a dye? (3)

Answer 35

Chromophores & auxochromes

Question 36

Auxochrome (3)

Answer 36

-Increase the solubility of the molecule & augment the effects of the chromophore

Question 37

Chromophore (3)

Answer 37

-Responsible for the color in dyes