PRINCIPLES OF MICROBIAL METABOLISM 



379 



shows 26 that both the nature of the organism and the presence of non- 

 nitrogeneous substances are of great importance in this connection. 



The nitrogen content of some fungi may be as low as 1 per cent, 27 

 in the absence of available nitrogen and in the presence of an excess 

 of energy compounds. It may be as high as 8-11 per cent, 28 in the 

 absence of sufficient energy and in the presence of an excess of nitrogen. 

 The wide variation is due to the adaptation of the organisms to the 



TABLE 20 

 Nitrogen content of some typical soil organisms 



NAME OF ORGANISM 



Bad. fluorescens 



Act. viridochromogenus 

 Zygorhynchus molleri.. 



Trichoderma koningi . . 



TABLE 21 

 Influence of age of culture upon the nitrogen content of a fungus"' 1 ' 



media. Nikolsky 25 demonstrated that the age of the organism (Mucor 

 amylomyces) , even grown on the same medium, influences its composition. 

 The nature of the organism itself, even among related forms, is of 

 great importance, as shown 29 for two organisms grown in a synthetic 

 medium, with 2 per cent xylose as the source of energy (table 22). 



26 Waksman, S. A., and Lomanitz, S. Contribution to the chemistry of de- 

 composition of proteins and amino acids by various groups of microorganisms. 

 Jour. Agr. Res., 30: 263-281. 1924. 



27 Gerlach, M., and Vogel, I. Weitere Versuche mit stickstoffbindenden Bak- 

 terien. Centrbl. Bakt. II, 10: 636-643. 1903. 



28 Czapek, 1902 (p. 502). 



29 Peterson, W. H., Fred, E. B., and Schmidt, E. G. The fermentation of 

 pentoses by molds. Jour. Biol. Chem., 54: 19-34. 1922. 



