Nitrogen Metabolism of Bacteria 9 



culture of B. proteus. Tests for this compound in the cultures of B. pyocyaneus 

 were all negative. Folin's" method was employed for the determination of 

 creatinin. 



Table 1 gives the analytical data for this test. The figures represent 

 the total amount in milligrams of the substance mentioned at the head 

 of the column, that is present in 100 c.c. of the culture fluid on the 

 corresponding day. The third column under each organism gives the 

 ratio between the amounts of amino-acid nitrogen and ammonia 

 nitrogen present on each day of the test. Chart 1 represents the same 

 results in the form of curves. 



The data show very marked differences between the two organ- 

 isms in their action on peptone solutions. In the culture of B. proteus 

 we notice for the first 2 days a decrease in the amino-acid already 

 present in the medium, followed by a rise in concentration on the 

 3rd, 4th and 5th days. Thereafter the concentration rises and falls 

 without any tendency to get very far from a mean value of about 50 

 mgm. per 100 c.c. The ammonia nitrogen also decreases for the first 2 

 days, but thereafter rises rapidly until the end of the experiment, reach- 

 ing the concentration of nearly 70 mgm. per 100 c.c. The ratio between 

 the two forms of nitrogen decreases rapidly throughout the test. 



The culture of B. pyocyaneus likewise shows an initial decrease in 

 its amino-acid nitrogen, followed by fluctuations up and down until 

 the 6th day, after which there occurs a gradual rise in concentration 

 until the end of the experiment on the 10th day. The free ammonia 

 also suffers a decrease in this culture in the first 24 hours. Thereafter 

 there is a general tendency toward a slow increase of this substance, 

 but in two instances, on the 4th and 7th days, a decrease occurs. The 

 ratio, amino-acid nitrogen to ammonia nitrogen, falls in this case also, 

 but the decline is much slower than in the case of B. proteus, and the 

 ratio does not, in the time of the experiment, reach nearly so low a 

 value. These differences are made plainer by the curves. The amino- 

 acid curve of B. pyocyaneus tends to rise rapidly. The free ammonia 

 curve of B. proteus rises very rapidly; that of B. pyocyaneus is much 

 more gradual. 



It is interesting to note that both cultures show an initial decrease 

 in both their amino-acid nitrogen and their ammonia nitrogen, indicat- 

 ing that, for purposes of growth and reproduction, these organisms 

 select the simpler forms of nitrogen in preference to the more complex 

 peptone and proteose molecules. This seems to be in accord with the 



"» Jour. Biol. Chetn., 1914, 17, p. 469. 



