Chapter 4 lecture notes

Question 1

Stains are dyes made of?

Answer 1

Organic salts

Question 2

Dyes carry ___ or ___ _____ on the molecule. The molecule binds to?

Answer 2

(+) or (-) charge

Certain cell structures

Question 3

Dyes divided into _____ or _____ based on charge

Answer 3

basic or acidic

Question 4

These dyes carry positive charge and bond to cell structures that carry negative charge

Answer 4

Basic dyes

Question 5

• Commonly stain the cell
• Simple stains are these dyes which are simple to use
  – Simply soak a smear and rinse off

Answer 5

Basic dyes

Question 6

These dyes carry negative charge and are repelled by

cell structures that carry negative charge

Answer 6

Acidic

Question 7

• Commonly stain the background

* Negative stains are these dyes

Answer 7

Acidic dyes

Question 8

Common basic dyes include

Answer 8

– Methylene blue
– Crystal violet
– Safranin
– Malachite green

Question 9

Uses one basic stain to stain the cell

Answer 9

Simple stain

Question 10

• Allows for increased contrast between cell and background
• All cells stained the same color
• no differentiation between cell types

Answer 10

Simple stain

Question 11

• Used to distinguish one bacterial group from another

* Uses a series of reagents

Answer 11

Differential stains

Question 12

Two most common differential stains

Answer 12

• Gram stain

* Acid-fast stain

Question 13

Most widely used procedure for staining bacteria

Answer 13

Gram stain

Question 14

– Developed over century ago

– Dr. Hans Christian Gram

Answer 14

Gram stain

Question 15

Bacteria separated into two major groups

Answer 15

Gram stain. The two groups are Gram positive (Stained purple) and Gram negative (stained pink)

Question 16

The Gram stain involves four reagents

Answer 16

1) Primary stain- crystal violet, stains all cells
2) Mordant- Grams iodine
3) Decolorizer- usually alcohol, removes primary dye from gram negative cell
4) Counter or secondary stain- Safranin, recolors cells that lose stain through decolorization

Question 17

Used to stain organisms that resist conventional staining

Answer 17

Acid fast stain

Question 18

Used to stain members of genus Mycobacterium (High lipid (wax) concentration in cell wall prevents uptake of dye)

Answer 18

Acid-fast stain

Question 19

• Uses heat to facilitate staining

* Once stained difficult to decolorize

Answer 19

Acid-fast stain

Question 20

Can be used for presumptive identification in diagnosis of clinical specimens

Answer 20

Acid fast stain

Question 21

Acid fast staining requires multiple steps

Answer 21

1) Primary dye- Carbol fuchsin, colors acid-fast bacteria red
2) Decolorizer- Generally acid alcohol, removes stains from non acid-fast bacteria
3) Counter stain- Methylene blue, colors non acid-fast bacteria blue

Question 22

• Example of negative stain
• Only stains the background
• Allows capsule to stand out around organism

Answer 22

Capsule stain

Question 23

• Staining enhances endospore

* Uses heat to facilitate staining

Answer 23

Endospore stain

Question 24

• Staining increases diameter of flagella

* Makes them more visible

Answer 24

Flagella stain