188 PHYSIOLOGY OF BACTERIA 



tion. Table 45 shows that 9 to 14 X 10 -^^ mg. are sufficient for 

 the doubling of young cells, and that the required amount increases 

 with increasing age of the culture, approaching infinity. 



Meyerhof (1916a) determined how many mg. of nitrite nitrogen 

 must be oxidized by Nitrobacter in order to increase the organic 

 nitrogen of the culture 1 mg. This increase is a good measure 

 of the growth rate. Young cells accomplished this with 107 mg. of 

 nitrite while older cells required 135 mg. to accomplish the same 

 amount of growth. 



While with Azotobacter, no accurate data could be obtained for 

 cultures younger than three days, and with Strept. lactis, not younger 

 than nine hours, the very accurate methods of oxygen determination 

 make it possible to estimate the energy utilization right after inocula- 

 tion. A good material for this are the experiments by A. Miiller 

 (1912) with cultures of Ps. fluorescens and Bad. coli in a very dilute 

 medium, containing only 0.004% of asparagin and 0.006% of ammo- 

 nium lactate and minerals. The organisms were grown in closed 

 bottles filled completely to the stopper without leaving an air space. 

 For each test, a new bottle was used. Some of the data on Ps. 

 fluorescens will be given in Table 130, p. 390 while the data on Bad. 

 coli are shown in Table 46. 



From these data, the oxygen consumption per generation has 

 been computed (Table 47). Though there is a good deal of fluctua- 

 tion in these data, it cannot be said that there is less oxygen needed 

 at the start than a few hours later. This should be the case if the very 

 young cells could use their food more efficiently than the older 

 ones. 



(c) SUMMARY OF FACTS 



All microorganisms liberate energy during their life 

 processes. Only a fraction of this energy is accounted 

 for by the energy content of the newly formed cells: 

 the larger part is transformed to heat. 



Even when cells are formed from building material 

 which has a higher combustion heat than the cells, energy 

 is liberated by fermentation. 



Part of the total energy liberated by fermentation 

 can not be used for cell construction, for thermodynamic 



