Lecture 2

Question 1

Human cell diameter:

Answer 1

10-100 mm

Question 2

Bacteria diameter:

Answer 2

1 micron

Question 3

Should a light microscope be used to study bacteria?

Answer 3

If looking for the size/shape/arrangement of bacteria. Otherwise, resolving power is not strong enough

Question 4

Virus diameter:

Answer 4

0.01-0.1 microns

Question 5

Can a virus be seen on a light microscope?

Answer 5

No, it is far too small

Question 6

List microbes in order of smallest to largest:

Answer 6

Prion < Virus < Bacterium < Yeast

Question 7

Describe bright field microscopy:

Answer 7

• Must heat-fix and stain bacteria
• Background appears light
• Bacteria are color of stain

Question 8

Describe Dark Field Microscopy:

Answer 8

• Light is refracted by organism and enters objective
• Background appears dark

Question 9

Describe Phase Contrast Microscopy:

Answer 9

• Shades of gray
• Phase Contrast converts differences in refractive indices to detect variations in light intensity

Question 10

Describe Fluorescent Microscopy:

Answer 10

Uses UV light to excite fluorescent molecules

Question 11

Describe electron microscopy:

Answer 11

• Resolution 1000x better than light microscope
• 5E-4 micron resolution

Question 12

What microscopy should you use to study organelles inside a eukaryotic microbe?

Answer 12

Phase contrast - shows differences in light refraction

Question 13

What microscopy should you use to study bacteria sample t visualize arrangement, cell shape and size?

Answer 13

Bright field

Question 14

What microscopy should you use to study bacteria to look at small internal structures?

Answer 14

Electron microscopy

Question 15

What microscopy should you use to study viruses in infected cells?

Answer 15

Electron microscopy
Fluorescent microscopy

Question 16

What microscopy should you use to study live bacteria in a water sample?

Answer 16

Phase contrast

Question 17

What microscopy should you use to study yeast cells used in the beer brewing process?

Answer 17

Phase contrast

Question 18

What is a simple stain?

Answer 18

Only one stain is used to increase visibility

Question 19

What is a differential stain?

Answer 19

Multiple stains are used to determine characteristics of one or more microbes.

Question 20

Shapes of bacteria:

Answer 20

Cocci (Spherical), Bacilli (rods), Vibrios (Commas), Spirals (Spirilla- with flagella & Spirochetes- no flagella)

Question 21

Arrangements of Cocci:

Answer 21

Diplococci - 2 cocci
Streptococci - chains of cocci
Staphylococci - groups/cluster
Tetrads - 2 planes, 4 cell groups
Sarcina - 3 planes, 8 cell groups

Question 22

Arrangement of Bacilli:

Answer 22

Coccobacillus (resemble cocci)
Diplobacillus - 2 bacilli
Streptobacillus - chains of bacillus

Question 23

Characteristics of bacterial cells:

Answer 23

• Peptidoglycan wall
• Prokaryotic

Question 24

What does a gram stain differentiate between?

Answer 24

Differentiates between Gram (+) and Gram (-) cell walls.

Question 25

Gram (+) color:

Answer 25

Purple

Question 26

Gram (-) color

Answer 26

Pink/Red

Question 27

Process of performing a Gram Stain

Answer 27

Crystal violet + Gram's iodine, acetone alcohol decolorizer, saffranin

Question 28

What does an Acid Fast stain differentiate between?

Answer 28

Bacteria that produce mycolic acid and don't produce mycolic acid

Question 29

Acid fast (+) color

Answer 29

Red/pink

Question 30

Acid fast (-) color

Answer 30

Blue

Question 31

How do you perform acid fast stain?

Answer 31

Carbol fuchsin + heat, Acid alcohol decolorizer, Methylene blue

Question 32

What does an endospore stain differentiate for?

Answer 32

Bacteria that produce endospores vs. don't

Question 33

Endospore (+) color

Answer 33

Green endospores

Question 34

Endospore (-) color

Answer 34

Pink non-endospore material

Question 35

How do you perform an endospore stain?

Answer 35

Malachite green + heat, water decolorizer, safranin

Question 36

What is mycolic acid?

Answer 36

Fatty acid chain that form walls of Mycobacteria.

Question 37

What does a flagella stain differentiate for?

Answer 37

Bacteria that have flagella vs. don't

Question 38

What part of the bacteria is stained in a flagella stain?

Answer 38

The outside of the flagella, to make it visible under the microscope.