12 BULLETIN 819, U. S. DEPARTMENT OF AGRICULTURE. 



Litmus milk. — Same as broth cultures. No coagulation nor pep- 

 tonization. 



Blood semm. — Growth moderate. Similar to agar slant. No 

 liquefaction. 



Potato. — Growth moderate. Similar to agar slant. No destruction 

 of starch. 



BIOCHEMICAL FEATURES OF THE PINK YEAST. 



ACID PRODUCTION. 



To determine whether or not acid was produced by the pink or- 

 ganism, cultures were made in various carbohydrate media, and 

 titrations made daily. Dextrose, maltose, lactose, raffinose, saccha- 

 rose, and glycogen broths were used. Of these the first four were 

 prepared according to the standard methods of the American Public 

 Health Association. 



Inasmuch as the pink yeast was found growing in and was iso- 

 lated from oyster liquor which contains a large amount of glycogen, 

 it was thought necessary to test its acid production in this car- 

 bohydrate. Owing to the scarcity of glycogen in pure form and to the 

 difficulty in preparing it, a special medium containing glycogen 

 was made. An infusion of oysters was prepared by infusing finely 

 ground oysters over night with double the quantity of water. The 

 mixture was allowed to boil for 2 minutes over the flame, after 

 which it was strained through a cloth. To the resulting oyster in- 

 fusion 1 per cent peptone was added, and the broth made neutral. 

 As oysters contain glycogen in amounts varying from 3 per cent 

 to 25 per cent of the total solids according to the season, food supply, 

 etc., the broth prepared no doubt contained a fairly high percentage 

 of glycogen. Growth in this oyster broth at room temperature re- 

 sembles the conditions under which the yeast occurs, and it is of 

 special interest to test for acid production in this medium. All these 

 media were titrated after sterilization and before inoculation. There- 

 after titrations of the cultures and controls were made daily for 7 

 days. The titrations were made against N/20 sodium hydroxid, using 

 phenolphthalein as an indicator. 



In addition, acid production was determined in cultures grown 

 anaerobically, in order to approximate the conditions afforded for 

 the growth of the pink yeast in oysters packed in sealed glass jars. 

 The cultures were grown under paraffin oil and titrated daily as de- 

 scribed. 



In none of the carbohydrate media used was there any acid pro- 

 duction by the pink yeast when grown either aerobically or anaero- 

 bically. 



