PREPARATION OF MEDIA ii„.19 



following fermentable carbon sources are usually suflBcient for 

 differentiation of the common species: lactose, glucose, salicin, sucrose 

 and maltose. The next most useful list includes: mannitol, glycerol, 

 starch, pectin, and cellulose. If there is question concerning the 

 effect of heat on the carbon compound, a concentrated solution may 

 be sterilized by filtration and added aseptically to the basal medium 

 after heat sterilization. In the establishment of the characteristics 

 of new species list the reaction on all the commonly available carbo- 

 hydrates.^ 



Fermentation Basal Medium of Reed and Orr (19/^1). Dissolve the 

 following in 1,000 ml. of distilled water; 



Peptone or proteose peptone 20 g. Sodium thioglycollate 1-0 g. 



NaCl 5 g. Agar 1.0 g. 



Carbohydrate 10 g. 



Use: Recommended for pathogenic group but not for butyric- 

 butyl group. 



Fermentation Basal Medium of Spray (19S6). Dissolve the follow- 

 ing in 1,000 ml. of distilled water: 



Neopeptone 10 g. Agar 2.5 g. 



Tryptone 10 g. Carbohydrate 10 g. 



Adjust to pH 7.3 or 7.4. 



Use: Recommended for all types. 



Medium for Testing Action on Litmus Milk. This medium is as 

 important with the anaerobes as it is with the aerobes and in fact 

 Spray (1936) used the reactions in this medium as one of the primary 

 characters in his system of classification. 



Use either fresh skimmed milk or spray-dried milk powder. In 

 the latter case, mix 90-100 g. of powder with 1000 ml. of distilled 

 water. Prepare a paste with a small amount of water and then dilute 

 this with the remainder of the water. Use the Waring Blendor^ or 

 other mixing machine if available. Strain through cheesecloth and 

 adjust to pH 6.8. Dispense in tube to which 0.05-0.1 g. of reduced 

 iron^'' is added before the tubing process. If reduced iron is not 

 available, replace the iron powder with a strip of No. 26 gauge black 

 stove-pipe iron. Sterilize by intermittent process or by autoclaving 

 for 15 minutes at 15 pounds. Immediately on removal from auto- 

 clave cool the tubes by standing them in cold water. Anaerobic 

 seal is unnecessary as the reduced iron keeps the oxidation-reduction 

 potential at a low level. 



*When interpreting results, make note of the following: 



If an organism fails to grow in the basal medium, unless a fermentable carbon source 

 is present, presence of growth indicates ability to ferment the compound in question. 



Gas production, per se, is not proof of carbohydrate fermentation, as many anaerobic 

 species are highly proteolytic and may produce gas in the cleavage of protein. 



'Waring Corporation, 1697 Broadway, New York City. 



^"Iron reduced by hydrogen, from Merck Company, Rahway, New Jersey. 



