Microbiology Lab practical: microscopy and basic handling techniques and Isolation of Pure cultures

Identify the numbered parts on the microscope

1. Ocular lens 

2. Body Tube

3. Nose piece

4. Condensor lens

5. Objective lens

6. Coarse knob

7. Fine knob

8. Stage

9. Illuminator

10. Iris Diaphragm 

What is the function of the ocular lens?

The part you see through to view the specimen on the slide

What is the function of the Body Tube?

Connects the eye piece to the objective lenses

What is the function of the objective lenses?

They are the different magnifications you are able to use to view the specimen

What is the difference between the coarse knob and the fine knob?

• The coarse knob is the one you use to start with and it helps bring the stage up towards the objective to see better, also helps bring into focus but still need the fine knob to view better

• The fine knob is used to make the image clearer/ bring into focus better

What is the function of the Iris Diaphragm?

Controls the amount of light that passes through the condenser lens

• contrasts

What does the condenser lens do?

Focus’ the amount of light from the Iris diaphragm onto the specimen

What is the total magnification for the 4X objective?

40X magnification

What is the total magnification for the 10X objective?

100x magnification

What is the total magnification for the 40X objective?

400x magnification

What is the total magnification for the 100X objective?

1000x magnification

which focus knobs should you use for the 4x, 40x, 10x, and 100x

Always start st the 4x objective and use the coarse knob to bring the image into focus, then use the fine knob to further bring the image into focus

• You will then continue to use the fine knob the bring the image into focus with the 40x, 10x, and 100x 

What do you need to add when transtioning from the 40x to the 100x objective?

Oil immersion

what does oil immersion do?

Helps improve the resolution to help sharp focus

• prevents the light to get refracted

Describe how to use the par-focal nature of your microscope when observing a sample?

par focal, which means that if one objective lens has the object in focus, and you go to the next objective lens, only a minor adjustment

• So start with the 4x objective and use the coarse knob and the fine knob to make the image clear

• Then move onto the next objective and you now only have to use the fine focus knob to adjust the image a little ()

How do you properly carry a microscope?

Always handle with 2 hands one at the bottom on the microscope and the other at the body tube

• Make sure the objective are at the lowest setting

What kind of paper do you use to clean oil off a microscope lens?

Lens paper

How do you properly store a microscope?

Store the objective lens facing the back of the case

• objective lens at the lowest setting (4x)

• With proper covering on

When looking at your wet mount under the microscope what did you notice about the difference in size between the bacterial cells and the cheek cells?

The cheek cells were significantly bigger than the bacterial cells

Are blood cells or bacterial cells bigger?

Blood cells

What tool should be used to inoculate a plate? What about an agar deep?

• Plate= use an inoculated loop

• Agar deep= use an inoculated needle

What are these types of medias?

1. Broth culture

2. Agar slant

3. Agar deep

4. Agar plate

what are the 4 things needed when labeling a sample?

1. Name

2. Date

3. Section

4. Culture

How should your plates be stored?

Upside down

What part of the microscope would need to be adjusted to increase or decrease the contrast during a wet mount? Where on the microscope is this part located?

The Iris Diaphragm is used for contrast

• Below the stage

Why would a coverslip be used to observe bacteria?

To contain the bacteria onto the slide

• stabilize it 

Order the following organisms from largest to smallest: E. coli, S. cerevisiae, cheek cell

• Cheek cell

• S. cerevisiae/ yeast cell

• E.coli

What are the advantages and disadvantages of using a wet mount?

Advantages:

• Able to see living cells

• Types of movement (true motility vs. Brownian Motion)

Disadvantages

• Not able to see structures of cell bc we can’t stain

• Only able to view up to 40x

What is a pure culture?

A culture containing ONE species of bacteria

What is the method called used in lab for isolating organisms on the plate?

T-streak method