Oil immersion

Question 1

Which lenses are considered to be the air objectives?

Answer 1

The 4x, 10x, and 40x lenses

Question 2

Which lens is the oil objective?

Answer 2

The 100x lens is an oil objective, and so a drop of immersion oil must be used. ONLY USE IMMERSION OIL ON THIS OBJECTIVE

Question 3

How should a person us the immersion oil

Answer 3

Rotate objectives and stop in between the 40x and 100x
Put 1 drop of immersion oil on the slide
Continue rotating to the 100x lens
Focus your image
When you are done, rotate away from the 100x objective and remove the slide. Use lens paper to blot the oil off the 100x objective

Question 4

What are the 3 types of bacteria under the microscope?

Answer 4

Cocci (spheres)
Baccilli (rods)
Spiral

Question 5

How do we make slides?

Answer 5

First, we spread thinly spread some bacteria on a slide
(This is called a bacterial smear)

Then, we dye the bacteria so that it can be seen against a background
-This is called staining
-Stains are usually positively charged dyes that are attracted to the negatively charged nucleic acid and cell wall
-Common basic stains include methylene blue, crystal violet, and carbol fuchsin

Question 6

With field of view: What do we always start with?

Answer 6

Always start with 4x objective lens to find specimen, then move to the other objectives

• Center the specimen so it stays in view

Question 7

What is the difference between simple and differential stains

Answer 7

Simple staining uses one color to help us see bacteria against the background

Differential stains help to identify and differentiate different types of bacteria
Gram stains are a type of differential stain
Other differential stains include
Negative Staining
Acid-Fast Staining
Endospore Staining

Question 8

List the differential sains

Answer 8

-Gram stains
-Negative
-Acid-fast
-endospore

Question 9

Bacterial smears from both medium

Answer 9

1. Place one to two loopfuls of the cell suspension on the clean slide
2. With a circular movement of the loop, spread large suspension into a thin area approximately the size of a dime

Question 10

Bacterial smears from solid medium

Answer 10

1. Place one to two loopfuls of water in the center of the slide
2. Transfer a small amount of the bacterial inoculum from the slant culture into the drop of water. spread both into a thin area approximately the size of a nickel

Question 11

Simple stains 1-3

Answer 11

1. Place slide on the staining tray and flood the smear with methylene blue. Allow 1-2 minutes of exposure to the stain.

2.Gently wash the smear with tap water

3. Blot the slide dry with bibulous paper