Nitrogen Metabolism of Bacteria 



15 



The amino-acid figures are comparable with those of Table 1. B. proteus 

 gives a fluctuating, but consistently low value, while B. pyocyaneus gives a 

 relatively high value, which shows a tendency to increase with the age of the 

 culture. The ratios, when the volumes concerned are taken into account, show 

 practically the same characteristics as those in Table 1. 



An experiment similar to the foregoing was carried out also on the three 

 organisms, B. coli-communis, B. typhosus, and Sp. cholerae. The technic was 

 identical with that described in the case of B. proteus and B. pyocyaneus. 

 Table 4 gives the data on this experiment. 



TABLE 4 

 The Production of Amino-acid and Ammonia by Bacteria in a Peptone Solution 



Little comment is necessary on these figures. The irregularity in the rate 

 of ammonia-production which was mentioned in connection with Table 3 is 

 found here also. It will be observed, however, that the figures representing 

 the concentrations of amino-acid nitrogen deviate very little in the case of 

 B. coli and B. typhosus from those found with uninoculated medium. In the 

 culture of Sp. cholerae there is a decided increase of amino-acid nitrogen with 

 the age of the culture. As would be expected, the ammonia-production by this 

 organism is relatively high also. 



With the same technic as that just described, cultures were examined of 

 B. proteus-vulgaris on a 1% peptone solution containing 10 gm. of Liebig's meat 

 extract per liter. In addition to amino-acid nitrogen and ammonia, both creatin 

 and creatinin were determined in this case. Table 5, which gives the analytical 

 data for the test, shows that on this medium also there is a very great irregu- 

 larity in the production of ammonia. It is impossible to estimate from these 

 data at what age cessation of chemical activity occurs. The creatinin values 

 would indicate that this compound is continuously decomposed throughout the 

 entire period of 37 days. The fluctuating values for creatin are undoubtedly 

 due, in part, to the different degrees to which this substance is decomposed in 

 sterilization. 



It is evident from these examples that this method of procedure 

 is unsuited to the quantitative study of the pcptolytic activity of micro- 

 organisms. Succeeding experiments were carried on, therefore, with 



