METABOLISM OF MICROBES 95 



It is apparent that fungi assimilate much less nitrogen per unit of 

 carbon, but, as has been mentioned above, they use much more of 

 the total carbon contained in the material during the decomposition 

 process. 



The following calculations show what would happen as the 

 fungi decompose such substances as cellulose, straw, alfalfa, and 

 dried blood. For the sake of simplicity, it is assumed that all of 

 the organic material is decomposed. This is not absolutely the 

 case, but the errors introduced by this assumption will not greatly 

 modify the results which are calculated. 



Cellulose contains 45 per cent carbon. In 100 pounds of cellu- 

 lose there are 45 pounds of carbon, 35 per cent of which is assimi- 

 lated, as assumed previously. 



45 X 0.35 = 15.75 pounds of carbon assimilated. 



For every ten parts of carbon there is one part of nitrogen assimi- 

 lated, or 10 per cent as much nitrogen as carbon assimilated. 



15.75 X 0.10 = 1.575 pounds of nitrogen assimilated. 



Since there is no nitrogen in cellulose, there would be a deficit of 

 nitrogen, which would have to be added to the medium in which 

 the decomposition was taking place. 



Some straws contain about 37 per cent of carbon and 0.5 per 

 cent of nitrogen. In 100 pounds of straw there would be 37 

 pounds of carbon and 0.5 pound of nitrogen. The following figures 

 indicate the result of its decomposition: 



37 X 0.35 = 12.95 pounds of carbon assimilated. 

 12.95 X 0.10 = 1.295 pounds of nitrogen assimilated. 



Since there was 0.5 pound of nitrogen in the straw originally, if this 

 was all used by the fungi, 1.295 — 0.50 = 0.795 pound of nitrogen 

 would appear as a deficit which would have to be supplied to the 

 fungi in order that decomposition of the straw take place. 



Alfalfa may be assumed to contain 40 per cent of carbon and 3 

 per cent of nitrogen. In 100 pounds there would be 40 pounds of 

 carbon and 3 pounds of nitrogen. 



40 X 0.35 = 14.00 pounds of carbon assimilated. 

 14.00 X 0.10 = 1.40 pounds of nitrogen assimilated. 



1.40 — 3.00 = —1.60 pounds of nitrogen, meaning that there 



