Photomicrographs

Section:MICROORGANISMS Subsection:METHODS
5 Crystal violet stain
Date Composed: 12-19-95 Date Modified:01-18-96

V. Crystal violet stain

A. Materials

1. Sample to observe

2. Crystal violet stain

B. Procedures

1. Flame one side of the slide in the flame of your Bunsen burner to remove any oil
or grease. Allow the slide to cool.

2. Place a drop of water in the center of the slide with your inoculating loop.

3. Transfer some of the bacteria to be stained from the culture to the drop of water on
the slide as demonstrated by your laboratory instructor. Mix.

4. Spread the drop of bacterial suspension out over the slide with your inoculating loop
to form a thin smear about the size of a nickel.

5. Allow the smear to air dry. Do not attempt to hasten the drying of the smear by blow-
ing on it or heating the slide.

6. Heat fix the dried smear by passing the slide, smear side up, quickly through the
flame of your Bunsen burner two or three times. Heat fixation kills the bacteria in
the smear and causes them to stick to the side so that they will not be washed off
the slide during staining,

7 Place the slide on your staining rack with the side containing the smear up.

8. Cover the smear with crystal violet stain. Leave the stain on the slide for 1 minute.
Pour off the stain, rinse in gently running water, and then blot the slide dry.

9. Examine the slide under the oil immersion lens of your microscope. The bacterial
cells will be purple and the background unstained.