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SELMAN A. WAKSMAN 



mately equal number of spores of A. niger and incubated at 28°C. 

 At the end of twenty-four hours a flask from each set was taken 

 out for the determination of ammonia and amino nitrogen; this 

 was repeated at regular intervals of twenty-four hours. The 

 data obtained are presented in table 4. 



The relation between the utilization of amino nitrogen by A. 

 niger and the formation of ammonia is revealed in the above 

 table. Asparagine contains half of its nitrogen in the form of 

 amino nitrogen, as determined by the method of Van Slyke. The 



TABLE 4 



The utilization of asparagine nitrogen and accumulation of ammonia by A . niger 

 Milligrams of NH2-N and NH3-N per 100 cc. of solution 



amount of sugar in all the media was 3 per cent. Where the 

 amount of asparagine was small, only traces of ammonia were 

 found and no autolysis was noticeable at the end of the experi- 

 ment. The more nitrogen the medium contained, the heavier 

 was the weight of the mycelium and the more autolysis it under- 

 went after the optimum growth has been completed. After the 

 organism made its optimum growth, the ammonia began to 

 accumulate in the medium very rapidly. With the high con- 

 centration of nitrogen in the medium, the sugar became the limit- 

 ing factor, and the rapid accumulation of ammonia was either 

 due to the autolysis of the organism or to the breaking up of the 



