Nitrogen Metabolism of Bacteria 



13 



B. proteus gives very similar curves for ammonia and amino-acid, 

 as it did in the 2% peptone solution, the ammonia values being high 

 and the amino-acid values comparatively low, but showing, however, 

 a tendency toward a maximum about the 6th day. On account of 

 the ability of this organism to produce creatinin from peptone, the 

 values for this compound cannot be taken to indicate the extent to 

 which the extractives are utilized. 



B. coli shows somewhat high ammonia values ; in view of the com- 

 parative volumes of the cultures, they are enormously higher than the 

 values on corresponding days shown by this organism in pure peptone 

 solutions (see Table 4). 



TABLE 2 



The Production of Amino-acid and Ammonia by Bacteria in Meat-Extract 

 Peptone Solutions 



As none of the organisms used in the described tests reached the 

 limits of its chemical activity in the time of the experiment, it was 

 thought worth while to repeat the experiment, continuing it over a 

 longer period. Furthermore, as it was thought possible that the 

 removal of samples with a pipet every 24 hours might introduce errors 

 by disturbing the culture or through failure to take account of slight 

 differences that might exist in the concentration of the substances 

 determined in different layers of the solution, the following rather 

 tedious method was used: 



A 2% peptone solution containing 0.5% NaCl was made up and placed in 

 40-c.c. portions in small Erlenmeyer flasks. These, after sterilization in the 

 autoclave, were all placed in the incubator at Zl C. Each day 2 flasks were 

 inoculated with 1 loopful of a 24-hour peptone culture of B. proteus and B. 

 pyocyaneus, respectively. In this way separate cultures were obtained ranging 

 in age from 1 to 28 days, all of which had been inoculated with approximately 



