400 NATHAN BERMAN AND LEO F. RETTGER 



sugar present, these organisms may produce enough acid in 

 twenty-four hours to prevent further metaboHsm. The presence 

 of a buffer, Hke dipotassium phosphate, tends to prevent such 

 inhibition, | 



Kendall and Walker's conception that the presence of glucose 

 delays the production of the proteolytic enzyme can not be 

 accepted. A bacterial proteolytic enzyme, as a rule, is not 

 produced within the first twenty-four hours, but requires a 

 longer period before it makes its appearance in detectable quan- 

 tities. Previous to enzyme formation some anabolism must 

 take place, unless some enzyme has been transferred in the 

 process of inoculation. In the tests in which the buffer reagent 

 was employed the proteolytic enzyme appeared as soon in the 

 sugar media as in the plain bouillon. 



A positive indol test does not necessarily indicate that the 

 sugar has been entirely fermented. Homer's explanation that 

 the presence of glucose in a medium prevents indol formation 

 because it forms a chemical combination with the tryptophan 

 is therefore based on a false assumption. 



The present investigation has shown conclusively that fer- 

 mentable sugars in moderate amounts'do not affect the nitrogen 

 metabolism of bacteria, providing experimental conditions are 

 favorably maintained, or in other words, under conditions of 

 favorable environment. The common belief in a so-called 

 ''sparing action" of sugars in a protein medium is untenable, 

 in the light of these experiments. According to this idea pro- 

 tein nitrogen is left unattacked, and thus spared from all par- 

 ticipation in the metabolism. There is a true sparing action, 

 however, in the sense that the nitrogen is utilized merely for 

 growth, and that the sugar furnishes the energy. For example, 

 the more luxuriant growth of the organisms here used in the 

 glucose media containing the buffer as compared with plain 

 peptone broth, may be explained on the basis that the nitrogen 

 was used for growth, and that the sugar furnished the necessary 

 energy supply. In plain peptone broth the nitrogenous food 

 material furnishes both the energy and the nitrogen for 

 necessary cell metabolism. 



