24 H.' J. Sears 



nitrogen in the non-glucose-containing culture on the 7th day is nearly 

 the same as the sum of these two substances in the glucose-containing 

 culture on the 18th day, and is approximately equal to 3/5 of the total 

 nitrogen of the culture medium. Of all the cultures tested, that of 

 Sp. metchnikovii shows the greatest reduction of proteolytic activity 

 due to the presence of glucose. - In the sugar-containing culture of this 

 organism the concentration of ammonia is uniformly low while in that 

 free of sugar it reaches a value of 50.5 mgm., or about 17% of the 

 total nitrogen of the medium. The amino-acid content of this culture 

 attains the value of 113.2 mgm., or about 37% of the total nitrogen 

 content. Taking into account, as will be pointed out later, the presence 

 of other simple compounds of nitrogen, we can say that this organism 

 in the absence of sugar is capable of decomposing almost completely 

 a 2% solution of peptone. By the same reasoning B. subtilis may be 

 said to be capable of this even in the presence of 1% of glucose. 



THE PRODUCTION OF AMINO-ACID AND AMMONIA BY BACTERIA IN MEDIA 



CONTAINING GELATIN 



The medium used in these tests was a 1% peptone solution containing 0.5% 

 of NaCl to which was added 5% of pure gelatin. The medium was cleared 

 by means of egg white, made neutral to phenolphthalein, and filtered until clear. 

 To one half of the solution so prepared 1% of glucose was added. Both por- 

 tions were then placed in 300-c.c. flasks, 200 c.c. to each. Calcium carbonate 

 was added to the samples containing the carbohydrate. All the flasks were 

 sterilized under IS pounds' extra pressure for 10 minutes. They were then all 

 inoculated at the same time and placed together in the same incubator at 27 C. 



All the organisms used were capable of liquefying gelatin except B. faecalis- 

 alkaligenes and B. cloacae. The strict anaerobe, B. aerogenes-capsulatus, and 

 the facultative anaerobe, B. pyocyaneus, were grown under anaerobic conditions 

 by keeping the surface of the medium covered with a thick layer of sterilized 

 paraffin oil. Samples were removed at definite intervals by means of sterile 

 pipets. These samples were heated in steam at 100 C. for one-half hour and 

 at once subjected to analysis. 



Tables 13 to 16 inclusive give the analytical results. The total 

 nitrogen of the sterile medium was 828.6 mgm. per 100 c.c. B. subtilis 

 shows much the same characteristics in its action on gelatin as on the 

 peptone solution. It produces both amino-acid and free ammonia much 

 more rapidly at first in the absence of glucose, but the rate of the 

 production of these substances in the presence of the sugar increases 

 in the later stages until, at the end of the 5th week, the concentration 

 of ammonia nitrogen is actually greater in this culture than in the 

 culture containing no glucose and the concentration of the amino-acid 

 nitrogen is nearly equal to that in the culture not containing glucose. 



