Lab Exam 1

Question 1

Where are cells in lab grown?

Answer 1

closed or batch system

Question 2

Nutrient solutions used to grow microbes in the laboratory

Answer 2

Culture medium

Question 3

Where is culture medium typically sterilized?

Answer 3

In autoclave

Question 4

Introduction of microbes into a medium

Answer 4

Inoculum

Question 5

Microbes growing in or on a culture medium

Answer 5

Culture

Question 6

What is a liquid culture media called? solid?

Answer 6

liquid: BROTH media
Solid: broth media w/ agar

Question 7

What temperature does agar liquefies and solidifies?

Answer 7

Liquid: above 95 degrees C
Solid: 45 degrees C

Question 8

T/F Agar is generally not metabolized, nor degraded by microbes
Laboratory Culture

Answer 8

TRUE

Question 9

Exact chemical composition
of media is known

Answer 9

Chemically defined media

Question 10

Extracts and digests yeast, meat, or plants; chemical composition varies batch to batch

Answer 10

Complex media:

Question 11

All pure culture cells are genetically identical T/F

Answer 11

TRUE

Question 12

What do cells grown in pure culture allow you to study?

Answer 12

the activities of a specific species

Question 13

Pure culture obtained using _________ _________

Answer 13

aseptic technique

Question 14

_______ acid = waxy layer on acid fast stain

Answer 14

mycolic

Question 15

Define Resolving Power

Answer 15

The ability of a microscope to distinguish two close objects as separate.

Question 16

How do you calculate the scale of a drawing?

Answer 16

Scale = Drawing size / Actual size

Question 17

Q: How can you recognize a capsule stain?

Answer 17

A: clear halo around the stained bacterial cells.

Question 18

1 mm = ___ μm
1 cm = ___ mm = ___ μm
1 μm = 10^-3 mm = ____ cm
1 m = _____ cm = 10^___ μm’
1 μm = 10 ^ __ m

Answer 18

1 mm = 1000 μm
1 cm = 10 mm = 10,000μm
1 μm = 10^-3 mm = 10^-4 cm
1 m = 100 cm = 10^6 μm
1 μm = 10 ^ -6 m

Question 19

Q: What 2 reagents are used in a capsule stain?

Answer 19

A: Primary stain (Congo red) and a counterstain (Maneval’s stain).

Question 20

Q: What molecules might be found in a capsule?

Answer 20

A: Polysaccharides or polypeptides.

Question 21

Q: How do you recognize gram-positive and gram-negative bacteria?

Answer 21

A: Gram-positive: stains purple, retained by the thick peptidoglycan layer.

Gram-negative: stains pink, thin PTG layer

Question 22

What ingredient makes nutrient broth solidify?

Answer 22

agar

Question 23

Provide an example of a gram + and a gram - bacteria we looked at in lab

Answer 23

gram+ : S. epidermidis, S. aureus
gram- : Ps. fluorescens, E. coli

Question 24

At what temperature and pressure are things autoclaved?

Answer 24

121° C, 15 psi

Question 25

Why are plates incubated upside down?

Answer 25

To prevent condensation from dripping onto the agar.

Question 26

Q: What dyes are used in a Gram stain and their purposes?

Answer 26

1. Crystal violet: Primary stain. 2. Iodine: Mordant. 3. Alcohol: Decolorizer. 4. Safranin: Counterstain.

Question 27

What is a negative stain used for?

Answer 27

To visualize cells without heat-fixing; used for delicate cells like spirochetes.

Question 28

What dye is used in a negative stain, and is it neutral, basic, or acidic?

Answer 28

Nigrosin, an acidic stain.

Question 29

Name three basic dyes.

Answer 29

1. Crystal violet 2. methylene blue 3. safranin

Question 30

Q: What are the differences between the cell walls of gram-positive and gram-negative bacteria?

Answer 30

A: Gram-positive: Thick peptidoglycan layer. Gram-negative: Thin peptidoglycan layer and outer membrane.

Question 31

Name an acidic dye

Answer 31

1. Eosin 2. Nigrosin 3. India Ink 4. Congo Red 5. Acid Fuchsin

Question 32

Q: How do you recognize a spore/Schaeffer-Fulton spore stain under a microscope?

Answer 32

A: Spores appear as green in a spore stain, with the vegetative cells appearing pink/red.

Question 33

Q: What reagents are used in a Schaeffer-Fulton spore stain?

Answer 33

A: Malachite green (stains spores) and safranin (counterstains cells).

Question 34

Q: Why do bacteria form spores?

Answer 34

A: To survive harsh conditions (e.g., heat, lack of nutrients).

Question 35

What is a simple stain?

Answer 35

uses a single dye to visualize cells.

Question 36

Why are slides heat fixed before staining? (2 reasons)

Answer 36

1. kill bacteria 2. adhere bacteria to slide

Question 37

What shape is cocci? bacillus?

Answer 37

cocci: spherical bacilli: rod-shaped

Question 38

Q: Name a genus of a spore-forming bacterium.

Answer 38

A: Bacillus or Clostridium.

Question 39

Q: What cell wall component makes an acid-fast bacterium acid-fast?

Answer 39

A: Mycolic acid.

Question 40

Q: What reagents are used in an acid-fast stain?

Answer 40

1. Basic fuchsin (stains red) 2. acid alcohol (decolorizer) 3. methylene blue (counterstain).

Question 41

What color do acid-fast bacterium stain?

Answer 41

Acid-fast bacterium stain red

Question 42

Q: What is the purpose of the acid-fast stain?

Answer 42

A: To identify bacteria with waxy, resistant cell walls (e.g., Mycobacterium).

Question 43

Q: Name an acid-fast and non-acid-fast bacterium.

Answer 43

A: Acid fast: Mycobacterium tuberculosis, M. smegmatis (stains red, positive, pathogenic) Non-acid-fast: S. aureus (stains blue, negative)

Question 44

Q: How do you do a bacterial dilution problem?

Answer 44

A: Use serial dilutions to calculate the concentration of bacteria based on colonies counted. Follow the formula: CFU/mL = (Number of colonies × dilution factor) / volume plated.

Question 45

total mag μm/div _____ 25 μm/div 100x ________ _______ 2.5 μm/div 1000x ________

Answer 45

total mag μm/div 40x 25 μm/div 100x 10 μm/div 400x 2.5 μm/div 1000x 1.0 μm/div