LAB: Differential stains Flashcards
1
Q
Gram Stain Procedure
A
- Prepare a smear of the bacteria
- Apply Crystal violet. Sit for 1 minute and rinse with distilled water
- Apply Gram’s Iodine. Sit for 1 minute and rinse with distilled water
- Rinse gently with ethyl alcohol. Do not over rinse - rinse for few seconds. Rinse with distilled water for 10-15 seconds
- Apply Safranin. Sit for 1 minute and rinse with distilled water
- Blot dry with bibulous paper
- Observe on high power
- Sketch and label Gram + control and Gram - control
2
Q
Gram Stain Procedure cont…
A
- Purple indicates Gram-positive (Staphylococcus; cocci in clusters)
- Pink indicates Gram-negative (E. coli; individual rods)
3
Q
Gram-Positive Composition of cell wall
A
- thick peptidoglycan
- no outer membrane
- stained purple
- cells are stained
- uncolored around the cell is the capsule
4
Q
Gram-Negative Composition of Cell Wall
A
- thin peptidoglycan
- outer membrane (highly negative)
- stained pink
5
Q
Capsule Stain
A
- background purple stained
- capsule is halo-like
6
Q
Importance of capsule
A
- Hides bacteria from immune system; gives some bacteria its virulence
- adhesion
- made of polysaccharides
- thick rigid layer
7
Q
Endospore Stain
A
- differentiate between spores and vegetative cells
- pink stained cells = vegetative cells
- light greened stained cells = endospores
- Schaeffer-Fulton endospore slide
8
Q
Central location
A
- Central endospores are located in the middle of the vegetative cell
9
Q
Terminal location
A
- Terminal endospores are located at the end of the vegetative cell
10
Q
Examples of bacteria that forms endospores
A
- Bacillus
- Clostridium
11
Q
Differential Stains
A
- use 2 different dyes
- differentiate between cell types or cell structures
12
Q
Primary Stain
A
- Crystal Violet - stains all cells purple
13
Q
Mordant
A
- Gram’s Iodine - fixes crystal violet into cell wall of G+ cells
14
Q
Decolorizer
A
- Ethyl Alcohol - removes crystal violet from G- cells
15
Q
Counterstain
A
- Safranin - stains G- cells pink
