514 



PRINCIPLES OF SOIL MICROBIOLOGY 



their protoplasm (3 to 9 per cent as extremes), the nitrogen made 

 available from the decomposition of the alfalfa may be just sufficient 

 for the synthesis of the fungus protoplasm, without any excess left 

 as ammonia. 



When the same amount of alfalfa (0.5 to 2 per cent) is added to 

 soil, sterilized and then inoculated with actinomyces or bacteria, some 

 ammonia will be readily formed. This is due to the fact that these 

 organisms synthesize a considerably smaller amount of protoplasm 

 than do the fungi. The nitrogen content of those organisms is higher 

 than that of fungi, viz., 7 to 12 per cent, but because of the considerably 

 lower carbon assimilation, a great deal of the nitrogen is liberated as 

 ammonia. In a series of detailed studies on the decomposition of organic 

 matter by pure cultures of microorganisms, Neller 12 (figs. 32-33) found 



TABLE 50 

 Influence of composition of amino acid upon ammonia productionby microorganisms 



AMINO ACID 



Glycocoll 

 Glycocoll 



Alanine 



Alanine 



Glutamic acid 

 Glutamic acid 

 Glutamic acid 



ORGANISM 



Trichoderma 

 Actinomyces 

 Trichoderma 

 Actinomyces 

 Trichoderma 

 Actinomyces 

 Bad. fluorescens 



NH.-N 



2.0 

 2.0 

 3 6 

 3.2 

 7.5 

 5.9 

 4.5 



that, under sterile conditions, the fungi bring about a much greater 

 evolution of C0 2 than bacteria, the action of the pure cultures of fungi 

 approaching that of the complex mixture of organisms found in a soil 

 suspension. The amount of ammonia liberated by the fungi, particu- 

 larly by the rapidly growing forms (Asp. niger), was negligible in com- 

 parison with that liberated by the bacteria. In 12 days Trichoderma 

 and Asp. niger liberated, from 1 per cent alfalfa, about 21 per cent of 

 the carbon as C0 2 and a mere trace of the nitrogen as ammonia. 

 Bac. subtilis liberated, in 8 days, from 2 per cent alfalfa, only 8.9 

 per cent of the carbon as C0 2 , but 10.4 per cent of the nitrogen was 



12 Neller, J. R. Studies on the correlation between the production of carbon 

 dioxide and the accumulation of ammonia by soil organisms. Soil Soi., 5: 225- 

 241. 1918. 



