Lab Exam 1

Question 1

Identify the organism, morphology, and arrangement. What stain was used?

Answer 1

Micrococcus luteus
Tetracoccus
Negative stain

Question 2

Identify the organism. What’s the morphology? What stain was used?

Answer 2

Rhodospirillum rubrum
Spirillum
Negative stain

Question 3

Identify the organism. What is the morphology? What stain was used?

Answer 3

Citrobacter freundii
Bacillus
Gram stain (G-)

Question 4

Identify the organism. What is the morphology? What is the arrangement? What stain was used?

Answer 4

Staphylococcus aureus
Staphylococcus
Gram stain (G+)

Question 5

Identify the organism. What stain was used? What was the result?

Answer 5

Klebsiella pneumoniae
Capsule stain
Positive

Question 6

Identify the organism. What stain was used? What was the result?

Answer 6

Bacillus cereus
Endospore stain
Positive

Question 7

Identify organism B. What stain is used? What is the result?

Answer 7

Mycobacterium phlei
Acid-fast stain
Acid-fast

Question 8

Identify organism A. What stain was used? What is the result?

Answer 8

Staphylococcus epidermidis
Acid-fast
Non-acid-fast

Question 9

What organism is the red colony? What is its colony morphology?

Answer 9

Serratia marcescens
Moist, entire and round, convex, opaque

Question 10

What organism is the “colorless” colony? What is its colony morphology?

Answer 10

Escherichia coli
Entire round, moist, flat, opaque

Question 11

What organism is the yellow colony? What is its colony morphology?

Answer 11

Micrococcus luteus
Entire round, moist, convex, opaque

Question 12

What organism is the yellow colony? What is its colony morphology?

Answer 12

Micrococcus luteus
Entire round, moist, convex, opaque

Question 13

What staining technique was used?

Answer 13

Basic (simple) stain

Question 14

What do basic stains dissociate into?

Answer 14

OH- and cationic chromagen

Question 15

What ingredients/dyes were used for basic (simple) stains?

Answer 15

Methylene Blue
Crystal Violet

Question 16

What organisms were viewed using basic (simple) stain?

Answer 16

Staphylococcus aureus
Bacillus subtilis

Question 17

What staining technique is used?

Answer 17

Acidic (negative) stain

Question 18

What do acidic stains dissociate into?

Answer 18

H+ and anionic chromagen

Question 19

Why do we heat fix smears?

Answer 19

• kill all cells on slide
• adheres cells to slide
• makes cells more visible (protein denatures and conjugates)

Question 20

What ingredients/dyes were used for a negative stain?

Answer 20

Nigrosin

Question 21

What organisms were viewed with a negative stain?

Answer 21

Rhodospirillum rubrum
Micrococcus luteus

Question 22

What do we use negative stains for?

Answer 22

1. Hard to stain species (non-polar cell walls)
2. Observe true size, morphology, and arrangement

Question 23

Why does a negative stain show truer size?

Answer 23

No heat fixing which can distort and shrink cells

Question 24

What staining technique is used?

Answer 24

Gram stain

Question 25

What ingredients/dyes are used for gram stain?

Answer 25

Primary stain: Crystal Violet (basic) Mordant: iodine Decolorizer: Acetone-alcohol Counterstain: Safranin (basic)

Question 26

What organisms did we view under gram stain? What were the results?

Answer 26

Citrobacter freundii (G-B) Bacillus cereus (G+B) Staphylococcus aureus (G+C)

Question 27

What is the differential step in a Gram stain?

Answer 27

Decolorization

Question 28

What is a mordant for?

Answer 28

Color enhancer

Question 29

What stain is used?

Answer 29

Endospore stain

Question 30

What dyes/ingredients are used in an endospore stain?

Answer 30

Primary stain: Malachite Green (basic) Decolorizer: water Counterstain: Safranin (basic)

Question 31

What genera produce endospores?

Answer 31

Bacillus and Clostridium

Question 32

What organisms did we use Endospore stain on? What was the result?

Answer 32

Bacillus cereus: positive for endospores Staphylococcus aureus: negative for endospores

Question 33

What staining technique is used?

Answer 33

Capsule stain

Question 34

What dyes/ingredients are used for capsule stains?

Answer 34

Primary stain: Tyler’s capsule stain (crystal violet) Decolorizer: Copper sulfate

Question 35

What organisms did we view with capsule stain? What were the results?

Answer 35

Klebsiella pneumoniae (capsule positive) Staphylococcus epidermidis (capsule negative)

Question 36

Do capsule stains use heat fixation?

Answer 36

No, capsules are heat-liable

Question 37

What staining technique is used?

Answer 37

Acid-fast stain Magenta: acid-fast Blue: non acid-fast

Question 38

What dyes/ingredients are used for acid-fast stain?

Answer 38

Primary stain: Carbolfuchsin (basic) Decolorizer: Acid-alcohol Counterstain: Methylene blue

Question 39

What organisms did we view under acid-fast stain? What were the results?

Answer 39

Mycobacterium phlei (acid-fast) Staphylococcus epidermidis (non-acid fast)

Question 40

What are other common acid-fast bacteria? What disease do they cause?

Answer 40

Mycobacterium tuberculosis: tuberculosis Mycobacterium leprae: Hansen’s disease Mycobacterium smegmatis: smegma

Question 41

What staining techniques require steam?

Answer 41

Acid-fast and Endospore stains