424 PRINCIPLES OF SOIL MICROBIOLOGY 



place only when accompanied by active oxidation whereby a large 

 amount of energy is made available. 



In the synthesis of protein compounds by microorganisms, nitrates 

 are first reduced to ammonia and, if proteins or amino acids form the 

 nitrogen source, they are hydrolized to ammonia and the correspond- 

 ing oxy-acids. The combination of the ammonia with the various oxy- 

 acids, either synthesized by the autotrophic organisms from C0 2 or 

 produced by the heterotrophic organisms from the complex organic 

 substances in the medium, results in the formation of amino acids, 

 from which the microbial proteins can be formed: 



C 3 H 6 2 + NH 3 = C3H7NO2 + H 2 . 

 Propionic acid Alanine 



The propionic acid is derived from lactic acid or from glucose, so 

 that glucose and ammonia can be used directly for the synthesis of 

 alanine : 80 



C ( H, 8 6 + 2NH 3 = 2C 3 H 7 N0 2 + 2H 2 + 63 Cal. 

 Alanine 



C fl H 12 6 + NH 3 = C 6 H 13 N0 2 + H 2 + 30 - 101 Cal. 

 Leucine 



C 6 H 12 6 + 3NH 3 = 3C 2 H 5 N0 2 + 3H 2 + 11 Cal. 

 Glycocoll 



2C 6 Hi 2 8 + 3NH 3 = 3C 4 H 7 N0 4 -K6H 2 + 31 Cal. 

 Asparagine 



When proteins or amino acids form the only sources of both carbon 

 and nitrogen, the oxy-acids produced from the amino acids may be 

 utilized for the building of the protein molecule. 81 In the case of 

 carbohydrates, pyruvic acid and acetaldehyde are important sub- 

 stances in the synthesizing activities of microorganisms (Neuberg). 



Once the amino acids are synthesized, the protein molecule is formed 

 from them by the union of a carboxyl and an amino group with the 

 elimination of a molecule of water. The amount of energy required 

 is much smaller in comparison with that necessary for the synthesis 

 of the amino acids. 82 



80 Kruse, 1910 (p. xii). 



81 Czapek, 1902 (p. 502). 



82 Further information on the transformation of energy in synthetic processes 

 is given by Nathanson, A. tlber kapillarelektrische Vorgange in der lebenden 

 Zelle. Kolloid-chem. Beihefte., 11: H. 10-12. 1919. 



