l^c'coinposition of Ligniiis 119 



iherclore, the greater the relati\e eoneentratioii ot the carbohy- 

 drates to the proteins, the less ammonia will be liberated. 



The decomposition of different proteins by pnre cnltnres of dif- 

 ferent microorganisms is bronght ont in Table 22. In comparison 



T.MM.K '2'2. Im)I(.\I VTIO.N OK AmMOMA (M(i) HY MlCKUOlUiAMSMS FHOM O..') (]\l OK 



PwoTKiNs IX 40 Days (from AVaksman and Starkeyj 



Organism 



with the fungus and actinomyces cultures, the bacterium synthesized 

 less cell material and liberated the greatest amount of ammonia. 



Plant and animal residues contain, in addition to proteins, various 

 other nitrogenous substances, such as urea, purine bases, hippuric 

 acid, lecithin, choline, cyanamide, cyanide, alkaloids, and chitins. 

 These compounds are also decomposed by a great variety of micro- 

 organisms in soils and in composts; the mechanism of their decompo- 

 sition depends upon the nature of the organism and conditions of 

 decomposition (Table 23). 



Cyanamide is first changed in the soil to urea, which is decom- 

 posed further; it may also polymerize to give dicyanodiamide, which 

 is toxic to some bacteria, such as the nitrifying forms. Choline is 

 transformed to trimethylamine by a variety of bacteria. Urea is 

 decomposed to ammonia: 



/NH2 

 C0< + H2O = 2NH3 + CO2 



\NH2 



Decomposition of Lignins 



Lignins are complex plant materials characterized by a benzol 

 ring structure with certain side chains. This is shown by the fol- 

 lowing formula: 



C4oH3o06(OCH3)4 • (0H)5 CHO 



