Observing organisms through a Microscope

Question 1

(TEM) Transmission Electron Microscope

Answer 1

Beam of electrons pass through a specifically prepared ultrathin section of the species.
Can produce magnification of 10,000-10,000,000x

Question 2

Electron Microscope

Answer 2

Observes objects smaller than 0.2 micrometers (viruses & bacteria)
Beam of electrons used instead of light
Images are always black & white
Cant be used to view living specimens

Question 3

Coarse Focusing Knob

Answer 3

Only to be used with Scanning Lens (4x)
Moves stage up and down
Big knob on arm Inner to fine focus

Question 4

Scanning Objective

Answer 4

4x

Always start with this power to focus on object

Question 5

Fine Focusing Knob

Answer 5

Ued to bring specimen into sharp focus
Smaller knob on arm
Use only after fine coarse knob is used to focus

Question 6

Ocular

Answer 6

Eyepiece
10x
Total Magnification=(10x) times objective

Question 7

Oil-Immerson

Answer 7

100x
Must use Immerson Oil
Technique used to increase resolving power of microscope

Question 8

Low Power

Answer 8

10x

Question 9

Scanning Electron Microscope

Answer 9

Provides striking 3-D image of specimen
Useful in studying surface structures of intact cells & viruses
Magnification is from 1,000-500,000x

Question 10

Acid Dyes

Answer 10

Negative charge bind to positively charged cell

structures

Question 11

Acid Fast Staining

Answer 11

Is a differential stain used to identify acid-fast organisms
Used to find Members of Mycobacterium (T.B. & leprosy)
Waxy material in cell walls of bacteria.
1)Apply stain carbo fuchsion for 30 sec.
2)Heat fix cells to slide using flame.
3)Decolorize w/acid alcohol for 15-20 sec
4)Apply countestain of methylene blue for 30 sec
5)Rince access stain.
6)Observe under microscope.

Question 12

Gram Negative

Answer 12

Bacteria have a thinner layer (10% of cell envelope), so do not retain the purple stain and are counter-stained pink by safranin.
E-coli

Question 13

Gram Positive

Answer 13

Bacteria have a thick mesh-like cell wall made of peptidoglycan (50–90% of cell envelope), and as a result are stained purple by crystal violet.
Staphylococcus epidermidis
Bacillus subtilis

Question 14

Differential Stain

Answer 14

Staining process which uses more than one chemical stain.Used for microbe identification
Gram-stain & Acid Fast stains are most frequent used.

Question 15

Simple Staining

Answer 15

1) Perform a bacterial smear,
2) Saturate the smear with basic dye for approximately 1 min. Use crystal violet, safranin, or methylene blue.
3. Rinse the slide gently with water.
4. Carefully blot dry with bibulous paper.
5. Observe the slide under the microscope,

Question 16

Gram Stain

Answer 16

Apply crystal violet to a heat-fixed smear of a bacterial culture.
Apply iodide, (mordant)
Decolorization with ethanol or acetone.
Counterstaining with safranin.
Observe under oil immersion under microscope
Either gram + or gram -

Question 17

Smear

Answer 17

Bacterial cells, spread on a slide for microscopic examination or on the surface of a culture medium.

Question 18

Heat fixing

Answer 18

Heat fixing kills the bacteria in the smear, firmly adheres the smear to the slide, and allows the sample to more readily take up stains.
Allow the smear to air dry.
After the smear has air-dried, hold the slide at one end and pass the entire slide through the flame of a Bunsen burner two to three times with the smear-side up.
Now the smear is ready to be stained.

Question 19

Negative staining

Answer 19

The background is stained, leaving the actual specimen untouched, and thus visible.

1) Remove a small amount of culture with an inoculating loop and disperse it in the drop of stain without spreading the drop.
2) Use another clean slide to spread stain
3) Allow to air dry without heat
4) Observe under oil immersion

Question 20

Staining

Answer 20

Coloring microorganisms with dyes.
Kills microorganisms and attaches them to slide.
Preserves various parts of microbes in natural state with minimal distortion.

Question 21

Basic dyes

Answer 21

This dye have positive charge to negatively charged molecules.
Crystal Violet, Methylene Blue, Safranin , basic fuchsin.

Question 22

Acidic Dyes

Answer 22

Dye which has negative charge so they bind to positively charged cell structures like some proteins.