Chapter 3

Question 1

What do the terms magnification and resolving power refer to?

Answer 1

Magnification makes objects appear larger.

Resolving power refers to ability to show details.

Question 2

Why do we use oil at high magnification?

Answer 2

Oil immersion helps to improve resolving power at high magnification.

Question 3

– What is the difference between transmission electron microscopy and scanning electron microscopy?

Answer 3

TEM- Are thin slices that are from inside of the cell.

SEM- Visualize surfaces of cell.

Question 4

Be familiar with each of the six “I’s”

Answer 4

• -Inoculation
• -Incubation
• • Isolation
• • Inspection
• • Information Gathering
• • Identification

Question 5

Why does the light microscope have a resolving power that is limited to 0.2-0.5 µm? Why can’t we
improve the resolving power of the light microscope?

Answer 5

Wavelength of visible light is 400-700 nanometers. The longer wavelength, lower resolving power.

Question 6

Why is electron microscopy capable of much greater resolution than light microscopy?

Answer 6

Because the wavelengths are much shorter

Question 7

Be able to describe two ways in which we can view live specimens

Answer 7

Wet Mount & Hanging drop slides

Question 8

Why do we add dyes to our slides when viewing bacteria?

Answer 8

Because it is extremely difficult to see cells without the dye.

Question 9

What is the difference between positive staining with a basic dye and negative staining with an acidic
dye (think about what the dye molecules attach to and what the final image looks like)

Answer 9

…

Question 10

What is the difference between a simple and a differential stain?

Answer 10

Simple stain- type of positive staining technique that uses a single dye to add color to cells so that they are easier to see.

Differential stain- a technique that utilizes two dyes to distinguish between different microbial groups of cell parts by color reaction.

Question 11

Be familiar with how the Gram stain works, and what would happen if a Gram stain were performed
and one of the reagents were forgotten

Answer 11

The gram stain steps

1. Add crystal violet (primary dye)
2. Gram’s Iodine (mordant)
3. Alcohol (decolorizer)
4. Safranin (red dye counterstain)

Question 12

What are three ways in which bacteria can be isolated from the environment and grown in pure
culture?

Answer 12

streak plate, pour plate, & spread plate

Question 13

Why would one use solid, semisolid and liquid media? What purposes do each of these media serve?

Answer 13

Solid- Isolation (plates) maintenance (slants)
Liquid- we use for fermentation study’s
Semisold- motility study (shows the movement of bacteria)

Question 14

What is the difference between a defined, or simple medium, and a complex, or undefined, medium?

Answer 14

Defined (simple)- what makes it defined we know the Structure of the media. We can assign a molar value to all ingredients. It also is usually restricted range of organisms.

Undefined (complex)- Can’t put a number of molar value so makes it undefined. Grows wide range of organisms ( due to so many nutrients it can grown a lot faster)

Question 15

What are each of the following media used for?

• • General purpose media
• • Selective media
• • Differential media

Answer 15

General purpose media- Good for growing organisms.

Selective media- Only certain organisms grow in this medium.

Differential media- Allows you to tell the difference between what grows often it will be a color change.