DECOMPOSITION OF PROTEINS 493 



teins is very large; when tested in pure culture upon native proteins, 

 the spore-forming bacteria are most active. When protein derivatives, 

 like peptone, amino acids, and urea, are used, various non-spore form- 

 ing bacteria will be found to play an important role in the process. In 

 the soil itself, all of those organisms probably contribute to a greater 

 or less extent to this process, depending upon the nutrients available 

 and environmental conditions. 



The rapidity of ammonia formation from proteins by bacteria depends 

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

 protein. The process of ammonia formation is completed in a few days 

 in the case of casein, while it continues, even after a month, from 

 gliadin. 61 The amino-nitrogen content of the gliadin and casein media 

 was 0.57 and 0.68 mgm. before hydrolysis; 42.56 and 99.31 mgm. after 

 acid hydrolysis, and 17.03 and 46.00 after hydrolysis with Bac. sub- 

 tilis. All the nitrogen forms of the protein molecule are changed more 

 or less by the action of bacteria, the end product being ammonia; in 

 no case, however, is one form of nitrogen completely destroyed. A 

 similarity was found in the chemical change produced by acid hydroly- 

 sis and bacteria. 



Ammonia formation by fungi and actinomyces. The actinomyces 

 develop on artificial culture media and in the soil slower than the 

 fungi and, when a short period of incubation is used, their intense ac- 

 tivity in breaking down proteins and forming ammonia may be over- 

 looked. When a long period of incubation (30 days or more) is used, 

 they are found to be very active in this respect. 62 The important point 

 in this connection is that these organisms are capable of allowing a 

 large accumulation of ammonia even in the presence of available 

 carbohydrates; in other words, they prefer proteins to carbohydrates 

 as sources of energy. According to Guittonneau, 63 actinomyces pro- 

 duce, from proteins, not only ammonia, but also urea, both in the 

 presence and absence of dextrose. 



Fungi can decompose proteins very vigorously. Different species 

 vary greatly in this respect, and the nature of the protein, reaction of 



81 Robinson, R. H., and Tartar, H. V. The decomposition of protein sub- 

 stances through the action of bacteria. Jour. Biol. Chem., 30: 135-144. 1917. 



82 Fousek, 1912 (p. 302); Mace, E. De la decomposition des albuminoides par 

 les Cladothrix (actinomyces). Compt. Rend. Acad. Sci., 14: 147-148. 1905; 

 Waksman, 1920 (p. 299). 



63 Guittonneau, G. Sur la production de l'uree au cours de rammonifica- 

 tion par les Microsiphonees. Compt. Rend. Acad. Sci., 178: 1383-5. 1924. 



