GROWTH 183 



Linhart (1920) found for Azotobacter an efficiency of only about 

 1%, but Baas-Becking and Parks believe that 7% is more 

 probable. 



Similar calculations based on the total energy liberated rather than 

 on the "free energy" have been made by Tangl as early as 1903. 

 One compilation of his data has already been given on p. 28. From 

 his data on B. anthracis, we obtain an energy utiUzation of 49%. 

 This seems very high in comparison with the above data calculated 

 by Baas-Becking and Parks. It must be remembered, though, that 

 the former data referred to synthesis of protoplasm from CO 2, 

 H2O and either NH3 or HNO3 while here, the food has even a higher 

 energy level than the cells. The energy content of 1 gm. of broth 

 solids was 4.4 calories while 1 gm. of bacteria solids represented only 

 4.23 calories. It is quite evident that even with the same species 

 of bacteria, the energy required for synthesis will vary with the kind 

 of building material used. More data on this subject may be found in 

 Putter's book (1911, p. 121-129). 



(6) EFFICIENCY OF YOUNG AND OLD CELLS 



All these experiments, from Tangl to Baas-Becking 

 and Parks, disregard the time factor. It is generally- 

 known that fermentation continues for a considerable 

 time after the multiplication of cells has stopped. This 

 must be of considerable influence upon the efficiency of 

 energy utilization. If one experimenter discontinues 

 his experiments with beer yeast after 2% of alcohol has 

 been formed and multiplication has practically ceased, 

 and the other waits until the fermentation is over, and 

 6% of alcohol has been formed, the former's efficiency 

 will be three times that of the latter, both using the 

 same organism in the same medium. After growth has 

 ceased, fermentation will be needed for nothing but 

 repair and upkeep; after completion of growth, the 

 efficiency must be practically zero. 



This would be the one extreme ; we are more interested 

 in the other extreme, i.e., the maximum efficiency. 



