404 



PRINCIPLES OF SOIL MICROBIOLOGY 



deff, 40 who found that the growth of Bac. hydrogenes in an inorganic 

 medium resulted in an exchange of gases (reduced to 0° and 760 mm.) 

 with the H 2 :0 2 varying from 2.00 to 2.62. 588 to 1860 cc. H 2 are oxi. 

 dized .for every 100 cc. C0 2 assimilated. The oxidation of H 2 is not 

 necessarily connected with the reduction of C0 2 . The ratio H 2 :C0 2 de- 

 pends upon the age of the culture. Since the organisms utilize the 



Fig. 21. Culture vessel for study of hydrogen utilization by bacteria (from 

 Iluhland). 



energy obtained from the oxidation of the H 2 for the reduction of C0 2 , 

 the H 2 :C0 2 ratio is wider in older than in younger cultures. The 

 energy process was believed to be independent of the process of assimi- 

 lation of carbon and could be expressed by the equation: 



2 H 2 + 0-2 = 2 H 2 



