Question

Observing Microorganism Through A Microscope

1. Which type of microscope would be best to use to observe each of the following? best microscope
   1. A stained bacterial smear
   2. Unstained bacterial cells when the cells are small and no detail is needed.
   3. Unstained live tissue when it is describe to see some intercellular details
   4. A sample that emit light when illuminated with ultraviolet light
   5. Intracellular detail of a cell that is 1um long
   6. Unstained live cells in which intracellular structures ae shown in color.

2. An electron microscope differs from a light microscope in that _________ focused by _____ is used instead of light, and the image is viewed not through the ocular lenses but on _________.The maximum magnification of a compound microscope is ______; that of an electron microscope, ________. The maximum resolution of a compound microscope is ______; that of an electron microscope, _______. one advantage of scanning electron microscope over an electron transmission is ( 10 pts) fill in the blank
3. Why do basic dyes stain in bacterial cells? Why don’t acidic dyes stain bacterial cells?
4. When is it most appropriate to use each of the following?
   1. simple stain
   2. differential stain
   3. negative stain
   4. flagella stain
5. Why is a mordant used in a Gram stain? In the flagella stain?
6. What is the purpose of a counterstain in the acid fast stain?
7. What is the purpose of decolorizer in the Gram stain? In the acid fast stain?
8. Choose from the following terms to fill in the blanks; counterstain, decolorizer, mordant, primary stain. I the endospore stain, safranin is the ______.In the Gram stain, safranin is the ________.
9. Fill the following table regarding the Gram stain:

	Appearance After This Step of
Steps	Gram Positive Cells	Gram-Negative Cells
Crystal violet
Iodine
Alcohol-acetone
Safranin

complete the table

Answer 1

Which type of microscope would be best to use to observe each of the following? best microscope

1. A stained bacterial smear

Answer: Compound light microscope

2. Unstained bacterial cells when the cells are small and no detail is needed.

Answer: Dark field microscope

3. Unstained live tissue when it is describe to see some intercellular details

Answer: Phase-contrast microscope

4. A sample that emit light when illuminated with ultraviolet light

Answer: Fluorescence microscope

5. Intracellular detail of a cell that is 1um long

Answer: Electron microscope

6. Unstained live cells in which intracellular structures as shown in color.

Answer: Differential interference contrast microscope

An electron microscope differs from a light microscope in that they produce higher-resolution images _ focused by _ a beam of electrons ____ is used instead of light, and the image is viewed not through the ocular lenses but on an electrostatic or electromagnetic lens. ...

The maximum magnification of a compound microscope is 2,000x; that of an electron microscope, _100,000x.

The maximum resolution of a compound microscope is 2µm; that of an electron microscope, _ 0025µm_.

One advantage of scanning electron microscope over an electron transmission is

its wide-array of applications, the detailed three-dimensional and topographical imaging and the versatile information garnered from different detectors.

Why do basic dyes stain in bacterial cells? Why don’t acidic dyes stain bacterial cells?

A basic dye is a stain that is cationic (positively charged) and will therefore react with material that is negatively charged. Basic dyes have a positively charged chromogen that forms an ionic bond with the negatively charged molecules.

Acidic dyes have a negatively charged chromogen that causes the chromogen and the molecules to repel and bacterial form is not distorted.

When is it most appropriate to use each of the following?

1. simple stain

To highlight the entire microorganism so that cellular cells and basic structures are visible.

2. differential stain

Differential stains react differently with different kinds of bacteria and thus can be used to distinguish between them

3. negative stain

Used to demonstrate the presence of capsule. Because capsule don’t accept most stains, the capsule appear as unstained halos around bacterial cells and stain out against a contrasting background.

4. flagella stain

Used to demonstrate the presence of flagella. A mordant is used to build up the diameters of flagella until they become visible.

Why is a mordant used in a Gram stain? In the flagella stain?

The mordant combines with the CV to form a complex that will not wash out of gram + cells. It stains the colorless non-acid fast cells so that they can be seen with the microscope.

The cell walls for Gram-positive microorganisms have a higher peptidoglycan and lower lipid content than gram-negative bacteria. Bacteria cell walls are stained by the crystal violet. Iodine is subsequently added as a mordant to form the crystal violet-iodine complex so that the dye cannot be removed easily.

What is the purpose of a counterstain in the acid fast stain?

A counterstain is a stain with colour contrasting to the principal stain, making the stained structure easily visible using a microscope.

Acid fast bacteria have a high content of mycolic acids in their cell walls. Acid fast bacteria will be red, while nonacid fast bacteria will stain blue/green with the counterstain with the Kinyoun stain.

What is the purpose of decolorizer in the Gram stain? In the acid fast stain?

The decolorizer in acid fast stain is acid/alcohol whereas the decolorizer in gram stain is acetone/ethanol.

Exposing gram negative cells to the decolorizer dissolves the lipids in the cell walls, which allows the crystal violet-iodine complex to leach out of the cells. This allows the cells to subsequently be stained with safranin.

The smear is rinsed with a very strong decolorizer, which strips the stain from all non-acid-fast cells but does not permeate the cell wall of acid-fast organisms.

Choose from the following terms to fill in the blanks; counterstain, decolorizer, mordant, primary stain.

In the endospore stain, safranin is the primary stain.

.In the Gram stain, safranin is the _counter-stain

Appearance After This Step of
Steps	Gram Positive Cells	Gram-Negative Cells
Crystal violet	purple	safranin.
Iodine	purple	purple
Alcohol-acetone	purple	colourless.
Safranin	purple	Pink/red.