168 Transformation of Nitrogen 



4. Ammonia formation without reduction. Anaerobic bacteria may 

 produce ammonia from amino acids, without reduction. 



RCH2 CH NH2 COOH = R CH:CH COOH + NH3 (8) 



5. Oxidative deaminization: 



R • CH • NH2 • COOH + O2 = R COOH + NH3 + CO2 (9) 



This process is carried out by aerobic organisms, especially by fungi. 

 As examples of this reaction, the transformation of leucine into iso- 

 valeric acid, as shown above, and of glutamic acid into succinic 

 acid may be cited: 



COOH CH2 • CH2 • CH • NH2 COOH + O2 



Glutamic acid 



= COOH •CH2CH2- COOH + NH3 -f CO2 



The decomposition of one amino acid may involve the reactions of 

 oxidative deaminization, decarboxylation, and reduction. The same 

 organism may bring about a series of these reactions, while different 

 results may be obtained by the same organism under different con- 

 ditions. 



The action of microorganisms on proteins and amino acids results 

 in the formation of various indols, some of which, such as indol- 

 acetic acid, act as growth-promoting substances, hormones or auxins, 

 upon plants. The favorable effect upon plant growth of organic 

 manures and animal excreta may thus be due to the action of these 

 plant hormones, or, as they have been called, "phytohormones." 

 Certain fungi and probably bacteria are able to synthesize these 

 hormones, as in the case of rhizopin. 



In addition to proteins, other organic nitrogen compounds, like 

 lecithin, methylated amines, purine bases, and other substances pres- 

 ent in plant or animal tissues and found in the soil, are acted upon 

 by microorganisms to form simpler compounds. Ammonia is one 

 of these. 



Lecithin is first split to choline, glycerophosphoric acid, and fatty 

 acids. 



The choline is decomposed into ammonia, trimethylamine, carbon 

 dioxide, and methane. Betaine, creatinine, guanidine, and purine 

 bases, like uric acid, also undergo decomposition by microorganisms. 



Uric acid can also be decomposed by various bacteria according 

 to the following reaction: 



C5H4N4O3 -f 8H2O + 1^(02) = 4NH4HCO3 -I- CO2 



