120 K. V. KossiKOv 



cells of this type readily ferment maltose and less readily 

 ferment sucrose. Therefore, the enzyme developed in these 

 cells must be a-glucosidase. Cells of the second altered form 

 readily ferment sucrose, and ferment one-third of raffinose, 

 but do not ferment maltose; therefore, the enzyme developed 

 in these cells must be p-D-fructosidase. Thus, sucrose, as the 

 specific substrate, may cause the appearance in yeast cells of 

 two enzymes — a-glucosidase and p-D-fructosidase — and these 

 enzymes can activate not only sucrose and maltose but also 

 one-third of raffinose, i.e. three different carbohydrates. 



It follows from the scheme shown in Fig. 1 that the forma- 

 tion in yeast cells of the active enzymes, a-glucosidase and 

 p-D-fructosidase, is due to the presence of certain carbo- 

 hydrates in the cultural medium, and the biochemical speci- 

 ficity of these carbohydrates conforms completely to the 

 specificity of the enzymes which they cause to appear in the 

 cell. The mechanism of formation of these enzymes is not 

 known. 



Inheritance of Fermentative Properties developed by 

 Yeasts as a result of Directed Changes 



Because of the specificity of the reproduction of yeasts 

 (sexual reproduction), in making a detailed study of the 

 inheritance of fermentative properties developed in these 

 yeasts we carried out experimental investigations of the 

 following questions: 



(a) Inheritance of sugar-fermenting properties in sexual re- 

 production {spore formation) : Cells which fermented a specific 

 sugar were isolated from the previously adapted culture and 

 seeded into wort-agar, where they formed asci. The spores 

 from these asci were selected by means of a micromanipulator, 

 and cultures obtained from single spores were tested for their 

 ability to ferment their corresponding sugars. Observations 

 were carried out over a period of one month. 



Five different cultures adapted to fermentation of sucrose 

 were studied. All five gave similar results showing that in 



