CYTOLOGy 



6-38 



"ABNORMAL" DISTRIBUTION OF VOLUTIN IN THE YEAST CELL 



Wiame has shown that yeast cells can be starved for phosphate 

 by growing them in a medium deficient in phosphate, such as beet 

 molasses. When growth finally ceases, chemical analysis reveals 

 no metaphosphate in the cells, and the cells do not contain volutin. 

 Furthermore, the cytoplasm is colorless showing a marked diminu- 

 tion of protein in the cytoplasm. He centrifuges these cells, washes 

 them in water, and resuspends them in a 2 per cent sugar solution, 

 adding M/30 KH2PO4. Wiame kindly performed this experiment 

 with me in my laboratory and allowed me to follow the process cy- 



Fig. 6-28 Yeast cells stained for volutin; the vacuole is 

 shrunken by fixation. (a) A single large unstained nucleolus with 

 many small, light pink peripheral chromosomes. (b) A budding cell 

 with one stained and one unstained nucleolus. Two stained and two 

 faintly stained chromosomes are attached to the unstained nucleolus, 

 (c) A budding cell with a deeply stained nucleolus and very faintly 

 stained peripheral chromosomes. No nucleolus visible in bud. 



tologically. The chromosomes rapidly became coated with volutin, 

 staining red by the volutin stain. Volutin sometimes appeared on 

 the chromosomes within three minutes after the addition of the phos- 

 phate. After twenty minutes, volutin begins to appear in the cyto- 

 plasm and the volutin in the vacuole decreases rapidly as the entire 

 cytoplasm becomes faintly pink. Wiame' s chemical tests show that 

 there is a steady increase in the total metaphosphate in the cells 

 and that the overall concentration of metaphosphate in the cells con- 



