PROTEOLYTIC ACTIVITIES OF SOIL MICROORGANISMS 485 



that the peptone is broken down, a part of the decomposition 

 products being utilized by the growing organism, while ammonia, 

 also perhaps other nitrogenous substances, are left in the medium 

 as waste products of the metabohsm of the organism. The daily 

 fluctuations in the content of dtoino nitrogen show that the 

 splitting of the peptone may go hand in hand with the utilization 

 of the amino nitrogen formed and its further splitting into 

 ammonia and other products. The accumulation of the am- 

 monia proceeds along entirely different lines than that of the 

 amino nitrogen: while the latter gradually declines, the amount 

 of the former gradually rises, giving at the end of 19 days as much 

 as 50 per cent of the total nitrogen in the form of ammonia. The 

 lack of accumulation of amino nitrogen can be explained by the 

 fact that the organism used in this experiment grows very 

 rapidly and probably uses all the amino nitrogen as soon as it is 

 spht off the protein molecule, or converts it into ammonia. In 

 the case of certain other organisms, as is seen in table 2, the 

 amino nitrogen accumulates in the mediimi, either due to the 

 slow development of the organisms or to their inability to convert 

 amino nitrogen rapidly into ammonia. The accumulation of 

 ammonia is gradually increasing from day to day, the velocity 

 of the reaction depending entirely on the sugar content of the 



medium. . . 



Miyake (1916), using the results obtained by other investi- 

 gators on bacterial activities, has shown that the processes of 

 ammonification and nitrification are autocatalytic chemical 

 reactions. To apply this theory to the results obtained m table 

 3 and also to show more clearly the difference m velocity of 

 ammonia accumulation due to the presence or absence of sugar 

 the curves of autocatalysis were computed for the quantities o 

 ammonia obtained. The tables of Dr. T. B. Robertson (1915) 

 were used for this work, the constants having been determined 

 from all of the observations by the method of least squares. 



The curves presented in figure 1 and figure 2 are the theoretical 

 curves obtained, while the observed quantities are given as dots. 

 In figure 1 we can readily see that the amount of ammonia ac- 

 cumulated by A. niger from peptone in the presence of available 



