668 



I. J. KLIGLER 



not occur in the same medium when 0.5 per cent phosphate is 

 present. Another interesting point is that the final hydrogen 

 ion concentration is higher when no phosphate is present; the 

 primary phosphate obviously tends to keep down the concen- 

 tration of the hydrogen ions. 



TABLE III 



The effects of different amounts of peptone, with and without phosphate, on the 



utilization of the carbohydrate and peptone, as indicated by the 



hydrogen ion concentration 



COMPOSITION OF THE MEDIA 



Phosphate . 



Glucose 



Peptone 



Days. 



0.0% 

 0.5% 

 5% 



0.0% 

 0.5% 

 1.0% 



0.0% 

 0.5% 



1.5% 



0.5% 

 0.5% 

 0.5% 



0.5% 

 0.5% 

 1.0% 



0.5% 

 0.5% 



1.5% 



Cultures 



B. coli* 



B. paracoli. . . 

 B. cloacae. . . 

 B. aerogenes. 

 B. typhi 



4.6 



5.2 

 4.6 

 4.8 



4.8 

 4.8 

 5.6 

 4.6 

 4.6 



4.6 



5.6 

 4.8 

 4.6 



4.6 



4.8 

 6.6 

 5.0 

 4.7 



4.8 

 6.4 

 4.8 

 4.6 



4.6 

 4.6 



6.8 

 5.6 

 4.8 



4 



5.0 



6.5 



6.6 



5.0 



5.1 

 5.2 

 6.8 

 6.6 

 5.1 



5.4 

 5.2 

 6.6 

 6.4 



4.8 



6.6 

 5.2 

 7.0 

 6.8 

 5.0 



6.0 

 5.3 

 6.8 



6.6 

 5.0 

 7.2 



* This strain of B. coli gave these results constantly. Observations in con- 

 nection with other experiments indicate that not all strains behave in this man- 

 ner. It is quite likely that there are two types of B. coli (corresponding to the 

 B. communior and B. communis respectively), which may be differentiated in 

 this way. 



(2) Effect of different concentrations of phosphate on the metabo- 

 lism of bacteria. The results of the experiments recorded above 

 indicated that primary phosphate, acting apparently as an acid 

 regulator, played an important part in controlling the nutritive 

 processes of bacteria. In order to get more light on the nature 

 of this regulatory mechanism and its influence on the carbo- 

 hydrate and peptone utilization the following tests were per- 

 formed : 



Media were made containing a constant and optimum amount 

 of peptone (1 per cent), comparatively low concentrations of 



