80 



PHYSIOLOGY OF BACTERIA 



would be considered very poor. It is evident that this 

 supply must soon be exhausted. 



Table 10. — Solubility of Oxygen in Water 



A. Miiller (p. 187) has shown that Bad. coli growing in a poor 

 medium requires about 1.6 X 10~^° mg. of oxygen per hour; Pseudo- 

 monas fluorescens needs considerably more oxygen, A full-grown 

 culture of Bad. coli contains about 10^ cells per c.c, or 10^^ cells per 

 100 c.c, and these cells would require 1.6 X lO-^" X lO^i = 16 mg. 

 of oxygen per 100 c.c. of medium per hour. Since only 1 mg. is 

 available in the medium, the supply will be exhausted in a short 

 time. Diffusion of oxygen is far too slow to provide the bacteria 

 in the lower layers. 



There can be no doubt that in a testtube culture or 

 flask culture of aerobes, all cells will exist under prac- 

 tically anaerobic conditions except those in the very top 

 surface layer. 



SUMMARY OF FACTS 



The processes that yield energy to the cell involve 

 shifting of oxygen, either within the molecule of the 

 substrate, or between two different kinds of molecules. 



