Saccharomyces Cerevisiae. 



I 



OfRiGiN. — Beer or bakers' yeast; at times in the air. ^ 



Color. — White. 



Form. — Cells spherical or egg-shaped 8-10 p. broad. The 

 ■cells are colorless and when actively growing have a homo- 

 geneous protoplasm. Later, granules and vacuoles develop. 

 Owing to a gelatinous exudate it may form zoogleal masses. 

 The cells maybe single or may have several buds; at times 

 long branching forms may be found, especially if the tem- 

 perature is about 30°. 



Motility. — None. 



Sporulation. — Usually several spores form. Can be 

 •double stained. Spores develop between 11 and 37°. 



Anilin dyes. — Stain readily; so does Gram's method. 



Growth. — Thick white growth, especially abundant on 

 glucose media and in wort. 



Oelatin plates. — Small, opaque, white, circular colonies wMcli are 

 very coarsely granular and slimy. 



Stab cultwre. — The growth is confined to the upper portion of the 

 tube and spreads over the surface. It is thick and opaque white. 



Streak cullwre. — On agar and on potato it forms a thick, somewhat 

 raised white growth. 



Temperature. — As an "upper yeast" the most rapid 

 fermentation takes place between 14 and 18°. 



Behavior to gelatin. — Does not liquefy gelatin. 

 I 

 Aerogenesis. — It gives rise to a ferment (invertin) which 



changes cane-sugar into glucose. The latter is then 



■changed by another ferment, zymase, to carbonic acid and 



alcohol (4-6 per cent.). It does not ferment lactose. 



JPathogenesis. — It has no effect on animals. A large 



amount may produce a catarrhal condition in the alimentary 



tract. 



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