96 AGRICULTURAL BACTERIOLOGY 



terial, ammonium sulphate and sodium nitrate are used as 

 fertilizers. 



It is probable that plants can make use of nitrogen in 

 a number of different compounds, varying with the kind 

 of plant. Some plants, as potatoes and rice, can use am- 

 moniacal nitrogen; oats make use of either ammoniacal 

 or nitrate nitrogen, showing no preference for either; 

 while corn and beets must have their- nitrogen needs 

 supplied in the form of nitrates. Most of our culti- 

 vated plants demand all or a portion of their nitrogen in 

 the form of nitrates, and can make a normal growth only 

 in their presence. It is thus essential that the nitrogen 

 added to the soil be changed from protein nitrogen to ni- 

 trate nitrogen before it can be generally available. This 

 process can be effected only by the action of the micro- 

 organisms of the soil. 



Ammonification. This term is applied to that portion 

 of the cycle of nitrogen in which protein nitrogen is 

 changed to ammonia. The proteins are very complex sub- 

 stances of high molecular weight. Legumin, the charac- 

 teristic protein of leguminous plants, has been held to have 

 the following formula: C 718 H 1158 O 238 N 214 S 2 . The path 

 from this complex molecule to carbon-dioxide, water, hy- 

 drogen sulphide, and ammonia is a long and largely un- 

 known one, both chemically and biologically. 



The organisms that use the native proteins as food must 

 form proteolytic enzymes which will change the protein 

 into more soluble and diffusible compounds that can pass 

 into the cells. The intermediate products are divided into 

 three great classes, the proteoses, the peptones, and the 

 amino acids, the simplest of which is glycocoll or amino- 

 acetic acid, having the formula CH 2 (NH 2 )COOH. From 

 such compounds ammonia is easily formed. 



A great number of molds and bacteria, aerobic, faculta- 



