8 H. J. Sears 



Creatinin is attacked slowly by bacteria'" as is creatin also. Nawiasky showed 

 that the latter was decomposed by B. proteus only to the extent of 8.64%. 

 Only 3.69% of the amount attacked was accounted for by the ammonia pro- 

 duced. He assumed that methylguanidin was formed. 



THE PRODUCTION BY BACTERIA OF AMINO-ACID AND AMMONIA 



FROM PEPTONE 



That ammonia is the chief end product of the nitrogen metaboHsm 

 of bacteria seems to have been well established. That the ammonia- 

 production by an organism growing on a protein or peptone medium 

 is always a measure of the organism's proteolytic activity cannot, from 

 this fact, be assumed to be true. It is quite conceivable that, because 

 of the differences in the rate of the decomposition of the primary 

 products of proteolysis, this criterion might lead us astray. We might, 

 for instance, have an accumulation of amino-acids in the medium and 

 a very slight production of ammonia, or, on the other hand, a decom- 

 position of the amino-acids as fast as formed with a consequently 

 high concentration of ammonia. It would give a better idea, therefore, 

 of the rate and extent of protein-decomposition if data were secured 

 on the concentrations of both amino-acid and ammonia. The new 

 method originated by Van Slyke^^ for determining amino-acid nitrogen 

 now makes the procuring of such data possible. The analytical 

 results of the examination of a large number of cultures with respect 

 to their change day by day in amino-acid and ammonia content are 

 given in the following pages by means of tables. Some are shown also 

 in the form of curves. 



The free ammonia was determined by Folin's aeration method, in which 

 Ca(0H)2 is used to set the ammonia free from its salts. After the ammonia 

 had been completely removed, the sample was filtered off from the excess 

 calcium hydroxid and a determination of the amino-acid was made by Van 

 Slyke's micro method. The Kjeldahl-Gunning- Arnold method was used for 

 total-nitrogen determinations. 



The first organisms investigated were the strongly putrefactive facultative 

 anaerobes, B. proteus-vulgaris and B. pyocyaneus. The medium used was a 

 solution containing 2% peptone and 0.5% NaCl. Five hundred cubic centi- 

 meters of this solution were placed in each of two 1000-c.c. flasks. After ster- 

 ilization in the autoclave at 15 pounds' extra pressure, they were inoculated and 

 placed in an incubator at Z7 C. By means of a sterile pipet a sample was with- 

 drawn from each immediately after inoculation, and at intervals of 24 hours 

 thereafter for 11 days. These samples were analysed at once for free ammonia 

 and amino-acids. Creatinin was also determined in the samples from the 



'« Ackermann: Ztschr. Biol., 1913, 62, p. 208; 63, p. 78. 

 " Jour. Biol. Chem., 1913, 16, p. 161. 



