Staining Techniques

Question 1

What is the simplest preparation method for specimens?

Answer 1

The simplest preparation is the wet mount.

Question 2

What is fixation in specimen preparation?

Answer 2

Fixation is the process of attaching cells to a slide, often achieved by heat or chemical treatment.

Question 3

What does fixation do to microorganisms?

Answer 3

Fixation kills microorganisms, stopping their movement and preserving cellular integrity for observation.

Question 4

What are some chemical agents used for fixation?

Answer 4

Chemical agents include acetic acid, ethanol, methanol, formaldehyde (formalin), and glutaraldehyde.

Question 5

Why are chemical agents preferable to heat for tissue specimens?

Answer 5

Chemical agents are preferable because they denature proteins, stop biochemical reactions, and stabilize cell structures.

Question 6

What is the purpose of staining specimens?

Answer 6

Staining is applied to color features of a specimen before examination.

Question 7

What are the components of stains/dyes?

Answer 7

Stains/dyes contain salts made of positive and negative ions.

Question 8

What is a chromophore?

Answer 8

Chromophore is the colored ion in a dye.

Question 9

What is a counterion?

Answer 9

Counterion is the uncolored ion in a dye.

Question 10

What is the difference between basic and acidic dyes?

Answer 10

Basic dyes have a positive chromophore, while acidic dyes have a negative chromophore.

Question 11

What is a positive stain?

Answer 11

A positive stain adds color and is absorbed by the cell/organism, making them stand out against the background.

Question 12

What is negative staining?

Answer 12

Negative staining is absorbed by the background but not the cells, producing an outline or silhouette.

Question 13

What types of dyes are used as positive stains?

Answer 13

Basic dyes such as basic fuchsin, crystal violet, malachite green, methylene blue, and safranin are used.

Question 14

What types of dyes are used as negative stains?

Answer 14

Acidic dyes such as acid fuchsin, eosin, and rose bengal are used.

Question 15

What is simple staining?

Answer 15

Simple staining uses a single dye to emphasize structures, making all organisms appear the same color.

Question 16

What is differential staining?

Answer 16

Differential staining distinguishes organisms using more than one stain, resulting in different colors for different organisms.

Question 17

What is Gram staining?

Answer 17

Gram staining distinguishes between bacteria with different cell walls (gram negative and gram positive).

Question 18

What are the steps in Gram staining?

Answer 18

1. Add crystal violet stain (cells turn blue/purple). 2. Add iodine (mordant). 3. Add decolorizing agent (ethanol/acetone). 4. Add safranin (counterstain).

Question 19

What happens to gram positive and gram negative cells during Gram staining?

Answer 19

Gram positive cells remain purple, while gram negative cells become pink after safranin is added.

Question 20

What is acid-fast staining?

Answer 20

Acid-fast staining determines between two types of gram-positive bacteria based on the presence of waxy mycolic acids.

Question 21

What are the two methods of acid-fast staining?

Answer 21

The Ziehl-Neelsen technique and the Kinyoun technique.

Question 22

What is capsule staining?

Answer 22

Capsule staining identifies a microbe’s virulence and often uses negative staining techniques.

Question 23

What is the common technique for identifying encapsulated yeast?

Answer 23

Adding drops of India ink or nigrosin.

Question 24

What is endospore staining?

Answer 24

Endospore staining differentiates endospores from the rest of the cell using two stains.

Question 25

What is the Schaeffer-Fulton Method?

Answer 25

The Schaeffer-Fulton Method uses heat to push the primary stain (malachite green) into the endospore, followed by counterstaining with safranin.

Question 26

What is flagella staining?

Answer 26

Flagella staining thickens the flagella using a mordant before adding a stain, commonly pararosaniline.