CULTURE MEDIA FOR CULTIVATION OF MICROORGANISMS 



743 



tint with brom thymol blue instead 

 of titrating to +1.0% as in 1917. 

 (g) Committee A. P. H. A. (1925) pre- 

 pared the medium as follows: 



(1) Add 3.0 g. of beef extract, 5.0 g. 

 peptone and 120.0 g. gelatin (un- 

 dried market product as stored in 

 the ordinary cupboard) to 1000.0 cc. 

 distilled water. 



(2) Heat slowly on a steam bath to 

 65°C. until the ingredients are dis- 

 solved. 



(3) Make up the lost weight with dis- 

 tilled water and adjust the reaction 

 so that after the final sterilization 

 the pH value will be between 6.2 

 and 7.0. 



(4) Bring to a boil, stirring vigorously. 

 Make up the lost weight with dis- 

 tilled water and clarify. 



(5) Distribute in the desired containers. 



(6) Sterilize in the autoclave at 15 

 pounds (120 °C.) for 15 minutes, 

 after the pressure has reached 

 15 pounds. 



References: Heinemann (1905 p. 23), 

 Wherry (1905 p. 318), Bahr (1916-17 

 p. 21), Committee A. P. H. A. (1917 p. 96), 

 Committee S. A. B. (1918 p. 115), Ball 

 (1919 p. 77), Tanner (1919 p. 55), Com- 

 mittee A. P. H. A. (1920 p. 95), Levine 

 (1921 p. 109), Treece (1920 p. 9), Com- 

 mittee A. P. H. A. (1923 p. 95), Park, 

 Williams and Krumwiede (1924 p. 131), 

 Committee A. P. H. A. (1925 p. 97). 



2299. Frost's Peptone Extract Gelatin 



Constituents : 



1. Distilled water 1000.0 cc. 



2. Beef extract, Lie- 



f: big's 3.0 g. 



3. Peptone (Witte) 



(1.0%) lO.Og. 



4. NaCl (0.5%) 5.0 g. 



5. Gelatin (Gold Label 



sheet) (10.0 or 15.0%) . 100.0 or 150.0 g. 

 Preparation : 



(1) Weigh out 3.0 g. of beef extract such 

 ^ as Liebig's. 



(2) Add a liter of distilled water. 



(3) Place in a cooking vessel. 



(4) Add 1.0% peptone (Witte) 0.5% 

 NaCl and from 10.0 to 15.0% the best 

 gold label sheet gelatin. (Add 10.0% 



gelatin in winter and 15.0% in 

 summer.) 



(5) Weigh the solution and the vessel. 



(6) Heat until solution is complete. 



(7) Neutralize the phenolphthalein. 



(8) Boil 5 minutes and restore the weight 

 lost by the addition of distilled water. 



(9) Test the reaction and readjust if 

 necessary. 



(10) Cool below 60°C. and thoroly stir 

 in an egg. 



(11) Boil until the albumin coagulates 

 and floats in the clear fluid. 



(12) Filter thru cotton supported on a 

 coil of wire using a suction pump to 

 hasten filtration. 



(13) Add 5.0 cc. (0.5%) of a normal HCl 

 solution. In water analysis a +1.0 

 reaction is used and +0.5 for patho- 

 genic bacteria. 



(14) Tube. 



Sterilization: Sterilize in the steamer for 

 30 minutes on 3 consecutive days or in 

 the autoclave at 110° for 15 minutes. 



Use: General culture medium. 



Variants : 



(a) Stoklasa isolated radiobacter and 

 Azotobacter chroococcuni on a me- 

 dium containing 100.0 g. gelatin, 

 20.0 g. peptone, 5.0 g. NaCl and 5.0 g. 

 Liebig's meat extract per liter of 

 water. 



(b) Day and Baker cultivated bacteria 

 causing ropiness in beer on a medium 

 adjusted to +1.0, containing 0.5% 

 Lemco meat extract, 0.5% NaCl, 

 1.0% Witte's peptone and 12.0% 

 gelatin. 



(c) Abel prepared the medium as follows: 



(1) Dissolve 10.0 g. Lemco meat ex- 

 tract, 10.0 g. Witte's peptone and 

 5.0 g. NaCl in 1000.0 cc. water. 



(2) Steam for 30 minutes. 



(3) Filter when cool. 



(4) Add 900 parts (3) to 100 parts gela- 

 tin and allow to soak and soften. 



(5) Place in a steamer until solution 

 is complete (not longer than 30 

 minutes in the steamer). 



(6) Neutralize to litmus. 



(7) Heat for 15 minutes. 



(8) Readjust the reaction if necessary. 



(9) Add 1.5 parts of crystalline un- 

 decomposed soda. 



