ESSENTIAL XON METALLIC ELEMENTS 



107 



involved and the specific fungus used. Leonian and Lilly (1940) tested 

 the growth of Phycomyces blakesleeanus upon five single amino acids and 

 upon a mixture of these five amino acids with the following results : mix- 

 ture of five amino acids, 214; asparagine, 209; DL-alanine, 151; arginine, 

 50; aspartic acid, 203; glycine, 201; and glutamic acid, 189 mg., respec- 

 tively. Arginine is a poor nitrogen source for P. blakesleeanus, but the 

 presence of arginine in the amino-acid mixture did not depress growth. 

 More complex relations were found with yeast (Lilly and Leonian, 1942). 

 Ten strains of yeast were grown upon media containing a mixture of six 

 amino acids (aspartic and glutamic acids, arginine, asparagine, alanine, 

 and leucine). Upon this mixture of amino acids two strains grew as well 

 as or better than upon the best single amino acid (aspartic acid). The 



Table 21. Comparison of Various Soi'rces of Nitrogen for Six Strains of 



Yeast 

 Milligrams of dry yeast cells produced in 72 hr. Each culture received 8 mg. of X. 

 (Lilly and Leonian, Proc. West Va. Acad. Sci. 16, 1942.) 



Nitrogen source 



Ammonium sulfate 



Urea 



L- Aspartic acid . . . 



L-Aspargine 



Glycine 



DL-Norleucine 



Yeast strain 



18.7 

 33.2 

 60.7 

 49.4 

 3.0 

 29.3 



21.2 

 31.5 

 59.9 

 45.8 

 1.2 

 17.6 



22.3 

 32.9 

 65.6 

 50.0 

 2.0 

 33.0 



17.5 

 27.3 

 62.0 

 49.2 

 2.1 

 18.4 



21.7 

 32.0 

 52.4 

 47.6 

 1.0 

 1.2 



23.8 

 35.1 

 70.6 

 35.0 

 1.1 

 4.2 



amount of growth of one strain was 70.6 mg. on aspartic acid alone, while 

 on the amino-acid mixture only 38.6 mg. was produced. Omission of 

 asparagine from the mixture increased the yield to 52.0 mg. These 

 results show that the effects of multiple nitrogen sources upon growth, and 

 perhaps other functions, are complex. 



Organic acids, especially the four-carbon dicarboxylic acids, affect the 

 utilization of some amino acids much as they do that of ammonium com- 

 pounds. Phycomyces hlakesleeamis on a medium containing arginine 

 produced 43 mg. of mycelium per flask. Addition of 0.1 per cent succinic 

 acid to the medium increased the yield to 192 mg. (Leonian and Lilly, 

 1940). 



Nitrogen utilization by the fungi has been studied for almost a century, 

 but many of the problems involved are not yet solved. Brenner (1914) 

 has reviewed the early work in this field, especially with reference to the 

 divergent views of Raciborski and Czapek on the mode of utilization of 

 amino acids. Raciborski held that amino acids were deaminat^d before 



