DORMANCY 8-2 



STORAGE OF GLYCOGEN UNDER DIFFERENT CONDITIONS 



The effects of low and moderate aeration and different concen- 

 trations of sugar, on glycogen deposition, were studied by comparing 

 growth in 50 cc. of nutrient broth placed in an Erlenmeyer of 500 cc. 

 capacity with growth in 30 cc. broth placed in an 8 x 1 inch test tube. 

 The following percentage concentrations of sugar were used: 12, 

 8, 4, 2, and 1. Each culture was observed daily to determine the 

 percentage of dead cells and the percentage containing glycogen. 

 The final dry weight of yeast in mgm./cc. was measured. Table 

 8-1 shows that (1) in low concentrations of sugar glycogen disap- 

 pears much more rapidly than in high, (2) the cells die much more 

 rapidly in high than in low concentrations of sugar, and (3) the ef- 

 ficiency of converting sugar to yeast is much higher in low sugar 

 concentrations than in high. 



After the granular glycogen had disappeared from the cells 

 grown in 12 or 8 per cent sugar solutions, the cytoplasm still con- 

 tains the nongranular carbohydrate which is not found in yeasts 

 grown in 1 or 2 per cent sugar. 



DORMANT VEGETATIVE CELLS 



After most yeasts have grown for several weeks on slants of 

 our pre-sporulation agar, the cells contain an abundance of mito- 

 chondria and glycogen, and although all the cells are alive, they 

 are dormant (fig. 8-1). Subsequent experiments were undertaken 

 to reproduce dormancy by loading the cells with reserve materials 

 in broth cultures, but we were unable to obtain cells with precisely 

 the appearance of those taken from pre-sporulation agar, which ap- 

 pear to be much more heavily packed with larger mitochondria. The 

 vacuoles in a dormant cell from pre-sporulation agar are usually 

 spherical, and centrally located, indicating that deposition of re- 

 serves on this medium occurs without deformation of the vacuole. 

 After an hour in nutrient medium, most of the mitochondria break 

 down and after the second hour half of the cells show buds and some 

 contain only a few mitochondria. The vacuoles appear to be multi- 

 ple or obscured in the growing cells. In three hours there are very 

 few granules left in the cells, nearly all of which contain lobed or 

 obscured vacuoles. Practically all the cells bud, proving that the 

 culture is viable. 



Manometric studies were made with the cells taken directly 

 from the pre-sporulation slant (fig. 8-1) and shaken with phosphate 

 buffer containing 4 per cent glucose, but with no other nutrients. 

 The respirometer values showed that the cells were incapable of 

 taking up oxygen and incapable of producing CO2 either aerobically 

 or anaerobically over a 150-minute period. During the same per- 

 iod, all the cells in the nutrient broth budded. Ninety -eight per 



