ENERGY AND NITROGEN TRANSFORMATION 513 



its rapid decomposition is accompanied by a greater disappearance of 

 the ammonia nitrogen. Casein contains more nitrogen in comparison 

 to the carbon; therefore, the amount of nitrogen liberated as the waste 

 product (ammonia) from the casein will be greater. When sufficient 

 carbon is added to the casein, the amount of ammonia is the same as 

 that of the cottonseed meal and linseed meal. 



The influence of the carbon content of the nitrogenous material 

 itself upon ammonia formation can be readily studied with simple 

 amino acids. According to Jodidi, 10 the formation of ammonia from 

 various amino acids differs with the composition of the amino-acid 

 molecule. In the case of glycocoll, 80 per cent of the nitrogen was 

 transformed into ammonia, while in the case of leucine only 49 per 

 cent nitrogen was changed to ammonia, under the same conditions. 

 This difference was ascribed to the inert paraffin character of the com- 

 paratively long chain of the leucine molecule. However, the results 

 presented 11 in table 50 show that the greater the carbon content of 

 the acid the more abundant is the growth of the organism and 

 the less is the relative amount of nitrogen liberated as ammonia, i.e., 

 the ammonia liberated from the decomposition of a definite amount 

 of amino acid does not depend upon the absolute amount of nitrogen 

 of the material decomposed, but upon the relative carbon-nitrogen 

 content. The lower the ratio of carbon to nitrogen, the greater is the 

 amount of ammonia liberated per unit of material decomposed. 



Different groups of microorganisms as affecting the carbon-nitrogen 

 ratio in the medium. Fungi, as a rule, can readily obtain their energy 

 from carbohydrates, using inorganic salts as sources of nitrogen, as well 

 as from proteins and may even prefer the former. Actinomyces and 

 heterotrophic bacteria, however, prefer as sources of energy proteins, 

 peptones and certain peptides to carbohydrates, especially to the polysac- 

 charides. This accounts for the difference in behavior of these 

 organisms towards various organic compounds added to the soil. 

 When ground alfalfa, which contains about 2.5 to 3.0 per cent nitro- 

 gen, is added to the soil, sterilized and inoculated with fungi, only 

 a slight accumulation of ammonia takes place, while the alfalfa is 

 rapidly decomposed as indicated by the abundant C0 2 production. 

 This is due to the fact that the fungi produce an abundant growth 

 and use as much as 50 to 60 per cent of the carbon for structural 

 purposes. Since the fungi contain about 4 to 5 per cent nitrogen in 



10 Jodidi, 1912 (p. 501). 



11 Waksman and Lomanitz, 1925 (p. 379). 



