ADAPTATION 



16-3 



To study these phenomena in more detail strain No. 97 was cul- 

 tured on a series of media containing lactate or glucose in different 

 concentrations or the two substances combined in different propor- 

 tions added to the synthetic medium. The growth in 10 cc. volumes 

 in 6 X 3/4 -inch test tubes was measured photometrically at suitable 

 intervals. Some typical results with an adapted strain, isolate No. 

 322, are included as parts B of the figures. 



Considering first the growth on media with lactate alone added 

 it may be seen (fig. 16-1) that the growth of strain No. 97 is greater 

 the lower the concentration of lactate between 4 and 0.5 per cent, 

 whereas with the glucose -adapted strain No. 322, the reverse is 

 true. The results with No. 97 might appear to mean that lactate is 

 not utilized but rather interferes with the utilization of some other 

 component of the substrate. However, the fact that only traces of 

 growth are obtained in control tubes without lactate excludes this 

 interpretation and indicates rather that the concentration of lactate 

 tends to decrease both the growth rate and final yields. In the case 

 of strain No. 322 on the other hand even 4 per cent, the highest 

 concentration used, may not be sufficient for optimum growth. 



1^0.322 



40 80 UO 160 aX) 240 280 320 360 4O0 440 480 520 



A Hours 



40 80 120 160 



B 



Fig. 16-1 A. Growtli on eight subcultures of No. °1 

 (previously maintained on lactate) on different concentrations 

 of lactate in synthetic medium. Ordinates, density of yeast 

 suspension; abscissae, hours. 



B. Growth of four subcultures of No. 322 under 

 similar conditions. 



Comparing next the growth on lactate with that on glucose 

 (figs. 16-2A, 16-3A, 16-4A, and 16-5A) the following striking dif- 

 ferences are to be noted: 



