8 LABORATORY MANUAL OF MICROBIOLOGY 



GENERAL MEDIA FOR ISOLATION AND CULTIVATION OF 



BACTERIA 



Medium 1 



Nutrient Broth or Bouillon 



Beef extract 3.0 gm. 



Peptone 5.0 gm. 



Distilled water 1,000.0 cc. 



Heat until extract and peptone are dissolved. 



Adjust reaction to pH 6.6 to 7.0 using Brom thymol blue. 



Medium 2 



I 

 Nutrient or Beef-extract Agar 



The same composition as nutrient broth (Medium 1) plus 15 

 grams of agar. 



Medium 3 



Nutrient or Beef-extract Gelatin 



Gelatin 100.0 to 150 . gm. 



Beef extract 3.0 gm. 



Peptone 5.0 gm. 



Distilled water 1,000.0 cc. 



In a convenient vessel measure 1,000 cubic centimeters of 

 nutrient broth. 



Add 10 to 15 per cent gelatin. Let the gelatin soak 5 to 10 

 minutes. 



Heat over water bath until dissolved. 



Adjust the reaction as directed in the preparation of nutrient 

 broth. Gelatin is decidedly acid and has a high buffer value; 

 it will, therefore, require more NaOH for neutralization than 

 bouillon or agar. 



If properly prepared, gelatin may be filtered through filter 

 paper. Otherwise it will be necessary to use an absorbent- 

 cotton filter. 



