Ammonia Formation by Microorganisms 



173 



to ammonia. Thus tluTc is a possibility that different organisms take 

 an acti\ e part in different stages of the pJrocess of protein decompo- 

 sition; bacteria hke B. ccrciis may be active in the first stages of 

 hydroKsis, and bacteria hke Ps. jiiiorescens, in the hitter stages lead- 

 ing to the formation of ammonia. 



5 10 



Days incubated 



Fig. 74. Rate of decomposition of cottonseed meal in soil, as shown by the evo- 

 lution of carbon dioxide and accumulation of ammonia (from Gainey). 



The rapidity of ammonia formation from proteins by bacteria de- 

 pends not only upon the nature of the organism but also upon the 

 kind of protein. The process of ammonia formation from casein 

 was completed in a few days, whereas it continued for more than 

 a month from gliadin. The amino-nitrogen contents of the gliadin 

 and casein media were 0.57 and 0.68 mg before hydrolysis; 42.56 

 and 99.31 mg after acid hydrolysis; and 17.03 and 46.00 after hy- 

 drolysis with B. subtilis. All the nitrogen forms of the protein mole- 

 cule are changed more or less by the action of bacteria, the end 



