A PINK YEAST CAUSING SPOILAGE IN OYSTERS. 11 



light pink in color. The control can was normal. All 3 cans were 

 placed in cold storage, and in 2 days the 2 cans were decidedly pink, 

 the control remaining normal. In this experiment also the pink 

 yeast was recovered from the pink oyster liquid. 



These experiments, together w4th the fact that the pink yeast 

 was isolated from every shipment of pink oysters examined, are 

 good evidence that the pink yeast is, without question, the cause 

 of the pink color in shucked oysters. The experiments have also 

 shown that when oysters are pink they are close to the stage of spoil- 

 ing, as it takes 5 or 6 days for the color to develop at a temperature 

 of about 10° C. When kept at a temperature as low as 0.5° C. about 

 1 month is required to produce the pink color, in which time the 

 oysters become decidedly stale. 



MORPHOLOGY OF THE PINK YEAST. 



Shape cuul size. — Elliptical. Maximum measures 9.8 by 7 micra; 

 minimum measures 4.1 by 2.8 micra. Average measurement, 6 by 4 

 micra. No mycelium. Often grouped in gelatinous framework. 

 Granules, fat globules, and vacuoles present. Budding forms com- 

 mon. 



Spor'ulation. — Yeast grown for 1 month on sterilized gypsum 

 blocks and examined at intervals showed no spores, either when 

 unstained or when stained with carbol fuchsin. 



Staining reactions, — Stains readily with methylene blue, safranin, 

 or gentian violet. Not acid fast. Staining by Gram's method is 

 very similar to that reported by Henrici (1914). Decolorized with 95 

 per cent alcohol, the cells are Gram positive, but a few cells in the 

 field are partly decolorized, showing a number of fine black par- 

 ticles in a red matrix. When 30 per cent acid (HCl) alcohol is used 

 the cells are completely decolorized. 



CULTURAL FEATURES OF THE PINK YEAST. 



Temperature. — Optimum temperature, 22° C. Will not grow at 

 37° C. Grows at 6° C, but growth not as abundant nor as charac- 

 teristic as at 22° C. 



Dextrose hroth. — Growth first appears as precipitate in bottom of 

 tube. Later a ring forms around wall of tube at surface of medium. 

 Precipitate flocculent. No film formation. 



Dextrose agar slant. — Growi:h along the streak, heavy, moist, and 

 glistening. Later growth collects at base of slant in heavy mass. 

 Growth of slimy consistency. 



Gelatin stab. — Growth fair. Uniform along the stab. Pigment 

 production not pronounced. No liquefaction. 



Dextrose agar colonies. — Visible about third or fourth day. Kound, 

 smooth,. moist, and glistening. 



