Nitrogen Metabolism of Bacteria 35 



A few strongly proteolytic organisms are exceptions to the rule in 

 that their cultures show steadily increasing concentrations of amino- 

 acid. Among these are B. pyocyaneus, B. subtilis, Sp. cholerae, and 

 Sp. metchnikovii. 



Most species, when grown in peptone or peptone gelatin media, 

 show an inclination to utilize the simpler compounds of nitrogen before 

 attacking the protein or peptone. 



Most species also show evidences of a continuous utilization of 

 ammonium salts in small amounts. 



The general phenomenon of the protein-sparing effect of glucose 

 is evident in most cultures not only from their concentrations of free- 

 ammonia, but also from their concentrations of amino-acid, and, in 

 fact, may be disclosed by the latter when the former fails to give evi- 

 dence of it, as is true in the case of B. faecalis-alkaligenes and B. dysen- 

 teriae, Shiga. 



Practically the same characteristics of ammonia- and amino-acid- 

 production are shown by the organisms on peptone solutions containing 

 5% gelatin as on pure peptone solutions, except that the concentra- 

 tions in the former media are much greater in the case of those organ- 

 isms having a gelatin-liquefying power. 



The ammonia and amino-acid curves of B. pyocyaneus grown 

 aerobically do not differ materially from those of the same organism 

 grown anaerobically. 



B. welchii, when grown under favorable conditions, shows very 

 strong proteolytic activity. 



The free ammonia and amino-acid curves of most micro-organ- 

 isms give evidence of the existence in their cultures of large amounts 

 of nitrogenous products intermediary between amino-acid and 

 ammonia. 



Urea and uric acid are not found in peptone cultures of bacteria, 

 probably because of the ease with which these substances are decom- 

 posed by most species. 



No method could be found for the detection and determination of 

 allantoin which was applicable to peptone cultures or to cultures con- 

 taining asparagin. 



A few species of bacteria are capable of producing creatin and 

 creatinin in sugar-free peptone cultures. Many more are capable of 

 producing these substances in peptone media containing glucose, the 

 probable reason for this effect of the sugar being its sparing action for 

 the two compounds in question. 



