REGULATING FACTORS IN BACTERIAL METABOLISM 671 



of a specific character or else that specific differences exist in 

 the way the glucose molecule is spht by these different forms 

 giving rise to different amounts of toxic substances. The inter- 

 esting fact remains that, under the same conditions, these closely 

 related forms manifest strikingly different powers of utihzation 

 of sugar. Such a difference exists between B. aerogenes and B. 

 coli, and Clark, taking advantage of this has devised a simple 

 method for differentiating the two under a given set of condi- 

 tions. The difference between B. aerogenes and B. coli is, per- 

 haps, more fundamental than that between the other members 

 of the group. Specific differences do exist, however, and experi- 

 ments are now well under way, which promise to furnish a basis 

 for separating certain of the other more closely related members 

 of this group. 



SUMMARY AND CONCLUSIONS 



A study of some of the factors involved in the regulation of 

 bacterial metabohsm was made. The effects of different con- 

 centrations of peptone on the utilization of glucose and amino- 

 acids, and of different concentrations of phosphate on the fer- 

 mentation of glucose were studied. The nature of the meta- 

 bolic changes waa measured by ammonia determinations by the 

 Folin method and by noting the change in the hydrogen ion 

 concentration by the Sorensen-Clark method. The results were, 

 briefly, as follows: 



1. The concentration of peptone is an appreciable factor, con- 

 trolhng the nutrition of bacteria. With a moderate amount of 

 glucose present the higher the concentration of peptone the 

 greater the amount of ammonia produced. The amount of 

 ammonia is in no case as great as in the sugar-free control, 

 indicating a distinct sparing effect. 



2. Primary phosphate acting as an acid-regulator plays a very 

 important part in the regulating of the carbohydrate utilization 

 by different bacteria of the colon-typhoid group. 



3. The different members of the colon-typhoid group mani- 

 fest specific differences in their power of completely utihzing 

 different amounts of sugar under a given set of conditions. 

 These differences may be utihzed for species differentiation. 



