Photomicrographs

Section:MICROORGANISMS Subsection:METHODS
6 The capsule stain
Date Composed: 12-19-95 Date Modified:01-18-96

VI. The capsule stain

A. Materials

1. Microscope slides

2. Capsule staining solutions 1 and 2

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 1% congo red solution (capsule staining solution 1) in the center
of the slide with your inoculating loop.

3. Transfer some of the bacteria to be used from the culture to the drop of congo red
solution on the slide. Mix.

4. Spread the drop of congo red solution containing the bacteria out over the slide with
your inoculating loop to form a thin smear about the size of a nickel. Allow the smear
to air dry. Do not heat fix the smear.

5. Cover the dried smear with capsule staining solution 2. Allow this solution to remain
in contact with the smear for 2 to 3 minutes.

6. Pour off the capsule staining solution 2, rinse the slide in gently running water, and
then carefully blot the slide dry.

7. Examine the slide under the oil immersion lens of your microscope. The background
will stain a grayish color. The bacteria cells will stain red. The capsule, if one is pres-
ent, will not stain and will appear as an unstained halo around the cells.