244 DIFCO MANUAL 



BACTO 



WORT AGAR (Bill) 



DEHYDRATED 



Bacto-Malt Extract 15 g 



Bacto-Peptone 0.78 g 



Maltose, Technical 12.75 g 



Dextrin, Difco 2.75 g, 



Glycerol 2.35 g 



Dipotassium Phosphate 1 g, 



Ammonium Chloride 1 g 



Bacto-Agar 15 g, 



Bacto-Wort Agar is a medium prepared particularly for the cultivation of 

 yeasts. The reaction is adjusted so that after sterilization it will be pH 4.8, which 

 is near the optimum for most yeasts and at the same time will inhibit most 

 bacterial growth. 



The study of yeasts is one of the oldest branches of the science of micro- 

 biology, and it remains today one of the most important. A variety of processes 

 in industry are performed by yeasts. A study of the pathogenic activities of 

 yeasts (blastomycetes) has revealed them to be the causative organisms of 

 such conditions as certain skin ulcers, tumors, infections of the upper and 

 lower respiratory and gastrointestinal tract etc. As a rule, the yeasts grow well 

 upon culture media containing dextrose or maltose, particularly if the reaction is 

 somewhat acid. The formula of Bacto-Wort Agar closely duplicates the composi- 

 tion of wort, which is a favorable medium for the cultivation of yeasts. Growth- 

 promoting qualities have been increased by the addition of salts and other nutri- 

 ments. 



Parfitt^ reported satisfactory results with Bacto-Wort Agar in his study of the 

 influence of culture media on the mold and yeast counts of butter, and in order 

 to procure comparative yeast and mold counts he suggested that dehydrated 

 Bacto-Whey Agar, Bacto-Malt Agar or Bacto-Wort Agar should be used. 



To rehydrate the medium, suspend 50 grams of Bacto-Wort Agar in 1000 ml. 

 of cold distilled water and heat to boiling to dissolve the medium completely. 

 Distribute in tubes or flasks, and sterilize in the autoclave for 15 minutes at 

 15 pounds pressure (121°C.). The final reaction of the medium will be pH 4.8. 



Due to the high acidity of the medium the heating process should be com- 

 pleted in as short a period of time as possible. Excessive heating of this acid 

 medium causes a breaking down of the agar, resulting in an inability to solidify 

 properly when cool. Normally, medium prepared from Bacto-Wort Agar is 

 soft and is ideal for plating purposes. However, if a medium of solidity satis- 

 factory for streaking is desired, it can be prepared by using 60 grams of Bacto- 

 Wort Agar per 1000 ml. of water or including 5 grams Bacto-Agar. 



One pound of Bacto-Wort Agar will make 9 liters of medium. 



1 J. Dairy Science, 16:141:1933. 



BACTO 



MALT EXTRACT AGAR (B112) 



DEHYDRATED 



Some laboratories have used Bacto-Malt Extract Agar for the cultivation of 

 yeasts and molds. We will continue to carry this medium in stock for those 

 laboratories where it has been in routine use or where it is desired for compara- 

 tive purposes. 



