ELEMENTARY BACTERIOLOGY LABORATORY EXERCISES 21 
EXERCISE 33 
NUTRIENT AGAR 
Formula 
0.3% beef extract 
0.5% peptone 
1.5% agar 
Distilled water 
Reaction, pH 7.0 
Procedure 
Follow the same procedure as in making bouillon with the following dif- 
ferences: In step (1) the ingredients should be dissolved by heating in the auto- 
clave under 15 pounds pressure for 15 minutes. In step (4) absorbent cotton may 
be used for filtration instead of paper. 
an 
EXERCISE 34 
NUTRIENT GELATIN fer 
Formula ee 
0.3% beef extract 
0.5% peptone 
12.0% gelatin 
Distilled water 
Reaction, pH 7.0 
Procedure : 
Use the same procedure as in the preparation of nutrient agar except: The 
heating in steps (1) and (3) should be in flowing steam instead of in the auto- 
clave. Sterilization should be done by the intermittent method at 100°C. Gelatin 
may be sterilized in the autoclave in which case it should be cooled immediately 
upon removal. 
EXERCISE 35 
BEEF INFUSION BROTH OR BOUILLON 
For many purposes nutrient media prepared with fresh meat are superior to 
those made with beef extract. This is especially true for the growth of a num- 
ber of the pathogenic microorganisms. 
