394 



PRINCIPLES OF SOIL MICROBIOLOGY 



creasing the amount of Na 2 C0 3 , which would lead to a lower alkalinity, 

 Boulanger and Massol 19 found that the injurious effect of ammonium 

 salt is less and concluded, therefore, that the growth of nitrate bacteria 

 is not injured by the salt but by free ammonia. This was confirmed 

 by Meyerhof who found that the injurious influence of ammonia and 

 its derivatives (aliphatic amines) consists in the penetration of the 

 base into the cell (which does not take place in the case of ammonium 

 salt) and in a specific action of the NH 3 and NH 2 group. Lipoid in- 



vzo 



no 



90 



d 



.2 80 



■3 

 •a 



o 



60 



50 



12 3 4 5 6 



Nitrate concentration, percent 



Fig. 19. Influence of nitrate concentration upon the growth ( — 

 piration (— ■) of nitrate forming bacteria (from Meyerhof). 



-) and res- 



soluble amines, like the diamines, are not injurious. The injurious 

 effect of amines and cations depends upon their ability to penetrate into 

 the cell and upon the reaction of the media; respiration is usually less 

 affected than growth. Iron salts are taken out by the organism from 

 iron poor media. Whether or not iron plays the part of a catalyzer is 

 still undecided. According to Ashby, 20 nitrification takes place in the 



"Boulanger and Massol, 1905 (p. 65). 

 20 Ashby, S. F. Some observations on nitrification. 

 67. 1907-8. 



Jour. Agr. Sci., 2: 52- 



