Nitrogen Metabolism of Bacteria 23 



That the presence of glucose might decrease the peptone-splitting 

 power of the cultures by preventing, to some extent, the reproduction 

 of the organisms is contrary to experience, and would furthermore 

 make the identical ammonia curves difficult to explain. 



The decrease during the first 24-48 hours in the amount of free ^ 

 ammonia which was originally present in the culture medium is noticed 

 in the case of all the organisms studied. This decrease seems to take 

 place to practically the same extent in the cultures containing glucose. 

 It is undoubtedly true that in such cultures the most rapid multiplica- 

 tion of the organisms takes place during the first 24-48 hours. It is 

 therefore probable that this ammonia is utilized for the synthesis of 

 bacterial protein. That ammonium salts are so utilized by certain 

 micro-organisms when these salts are their only source of nitrogen 

 is a well-established fact. But that such micro-organisms as those 

 investigated should utilize ammonia in the presence of other forms of 

 nitrogen seems at first a little surprising. A glance at the curves repre- 

 senting the concentrations of ammonia in the glucose-containing culture 

 will show, however, that this compound is continuously utilized by the 

 bacteria in question. Frequent decreases in concentration take place 

 with all but the strongly proteolytic organism, B. subtilis. That the 

 same decreases are not observed in the cultures not containing glucose 

 is probably due to the greater proteolysis in the latter rather than to an 

 increased assimilation of ammonia in the presence of the sugar. It is 

 safe to assume that in no case does the ammonia found represent the 

 entire amount formed by the organisms in the course of metabolism. 



Also, an initial lowering of the amino-acid concentrations is 

 observed in most of the cultures. This lowering is generally greater in 

 the glucose-containing cultures, a fact which is doubtless explained by 

 the decreased proteolytic activity in the latter. 



In the cultures of B. subtilis and Sp. metchnikovii there is a ten- 

 dency toward accumulation of amino-acids, both in the presence and in 

 the absence of glucose. In the case of B. subtilis this accumulation 

 takes place after the first 24 hours at about an equal rate in both 

 cultures until the 7th day is reached. After this the culture not con- 

 taining the sugar shows a decrease while the one containing the sugar 

 continues to show an increase at about the same rate. The maximal 

 concentration of amino-acid in the case of the latter is not passed at 

 the end of the experiment on the 18th day. 



The ammonia curves of this organism are roughly parallel to the 

 amino-acid curves. The sum of the amino-acid nitrogen and ammonia 



