380 



PRINCIPLES OF SOIL MICROBIOLOGY 



The concentration of nutrients is also of great importance in deter- 

 mining the composition of fungus mycelium, as shown by Raulin 30 

 (table 23). 



In general, the nitrogen content of bacteria and yeasts is found to be 

 about 10 per cent or more, indicating that their cells consist largely 

 of proteins. The nitrogen content of fungi is much lower showing 

 that the nitrogen-free substances predominate in the mycelium. The 

 same is true of higher fungi, Zopf 31 having found that the dry weight 

 of these consists of 11-51 per cent protein, 2.15 per cent ash, 1 to 10 

 per cent fat and 37 to 82 per cent carbohydrate. The nitrogen con- 



TABLE 22 

 Influence of nature of fungus upon its composition 



TABLE 23 

 Influence of concentration of minerals in solution upon the nitrogen content 



of fungi 



tent of invertebrates has been reported 32 as 10.65 to 11.2 per cent for 

 insects and insect larvae, 9.4 per cent for earthworms, and 4.9 per 

 cent for myriapods. 



The mineral composition of microorganisms depends also on the 

 mineral composition of the medium. It has been shown, 33 in the case 

 of cholera bacteria cultivated in nutrient bouillon, that, with an ash 

 content of 2.1 per cent P2O5 in the medium, the ash of the bacterial 



30 Raulin, 1869 (p. 415). 



31 Zopf. Pilze. Breslau. 1890, p. 119-121. 



32 Morris, 1922 (p. 342). 



33 Cramer, E. Die Aschenbestandtheile der Cholerabacillen. 

 28: 1-15. 1897. 



Arch. Hyg., 



