14-6 THE YEAST CELL 



The yield of cells was determined in about the same manner as 

 in the preceding section but the peptone yeast-extract medium was 

 used. Cultures were inoculated into 20 cc. of medium contained in 

 25 X 200 mm. test tubes. Each tube contained an inverted gas tube 

 11 cm. long with a capacity of 4 cc. The openings of the gas tubes 

 were cut off at a slant to prevent a seal forming at the base. The 

 gas evolved was read at the end of 24 hours by measuring the length 

 of the gas column to the nearest 0.5 cm. The results on gas volume 

 were recorded and plotted in terms of these arbitrary units, each 

 of which is equivalent to 0.36 cc. After 48 hours the amount of 

 growth was determined. The contents of each test tube were agi- 

 tated to attain uniform distribution of yeast cells and a 10 cc. sam- 

 ple removed and placed in a graduated Hopkins vaccine tube. This 

 was then centrifuged for 20 minutes at 2,000 r.p.m. and the yield 

 read off in terms of arbitrary units of yeast volume. Each such 

 unit represents 0.012 cc. of yeast volume per 10 cc. of culture 

 medium. These arbitrary units were employed in the various plots 

 used in comparing the different strains. 



The results are summarized by spot diagrams which give a 

 pictorial survey of the distribution of the various physiological 

 types. The position of each point characterized a particular strain. 



GAS EVOLVED VERSUS GROWTH 



Figs. 14-1 to 14-6 inclusive, give the gas -yield data obtained 

 when the strains were inoculated into the "3 -sugar" broth medium 

 containing glucose, sucrose, and maltose. The data are plotted in 

 terms of the arbitrary units of gas and yeast volume described 

 above. By far the vast majority of the strains from all sources 

 can apparently utilize at least one of the sugars to support growth. 

 With a few exceptions yields of 4.5 and over were obtained. While 

 the yields under these conditions are restricted in the main to a 

 relatively narrow region lying between 4.5 and 7.0 the gas measure- 

 ments are spread over the entire range of measurements. In all 

 the pedigrees examined, there exist some members with relatively 

 high yields and poor (between and 0.5) gas production. These 

 strains are obviously different from those which, though giving the 

 same yield, produce 10-20 times as much CO2. Insofar as the gen- 

 eral distribution is concerned, there is no apparent difference in 

 the physiological types derivable from the original twelve diploids. 

 Figs. 14-7 to 14-12 inclusive show similar data for growth and 

 gas evolution on single sugars. In these and all subsequent dia- 

 grams, the strains represented in each figure do not all belong to 

 the same pedigree. Sample strains were selected at random from 

 the twelve pedigrees and these were used in the single sugar ex- 

 periments. Studies similar to those depicted in figs. 14-7 to 14-9 



