Nitrogen Metabolism of Bacteria 17 



An examination of the tables, or a glance at the curves, shows at 

 once that, as would be expected, the peptolytic activity of B. subtilis is 

 much greater than that of any of the rest, Sp. metchnikovii being the 

 only one in this group which shows a comparable production of amino- 

 acid or of ammonia. It is unfortunate that, as the result of a con- 

 tamination on the 7th day, the examination of the only other organism 

 having a gelatin-liquefying power, namely. Staphylococcus pyogenes, 

 could not be carried out over the full period. The data obtained, how- 

 ever, indicate that in its chemical activity it is to be compared with the 

 nonliquefying member of the group rather than with those mentioned. 



The effect of glucose on the nitrogen metabolism of the cultures is 

 apparent in both the amino-acid and the free-ammonia curves. In all 

 cases, except those of B. faecalis-alkaligenes and B. dysenteriae, there 

 is an unquestionably lower ammonia-production in the cultures con- 

 taining glucose. The cultures of B. dysenteriae, when the slightly dif- 

 ferent conditions which may exist in the two flasks are taken into 

 account, may be said to give practically identical ammonia curves. The 

 same is probably true of B. faecalis-alkaligenes, altho it is interesting to 

 note that, in this case, the curve of the glucose-containing culture is 

 consistently above that of the one containing no glucose. 



If it is assumed that neither of the organisms just mentioned is 

 capable of utilizing glucose, it becomes difficult to explain the lower 

 concentrations of amino-acids in the cultures containing this carbo- 

 hydrate. There seem to be but two possible explanations of this fact. 

 Either the glucose shows a protein-sparing action in that it decreases 

 the peptone-decomposition by the organisms, or it acts in a manner that 

 must be considered the direct opposite of this. That is, it brings about 

 a more rapid breaking-down into simpler compounds of nitrogen of the 

 amino-acids resulting from the splitting of the peptone. In this case 

 it is necessary to assume that the breaking down of the amino-acids 

 is not carried on to the free-ammonia stage or else that this stage is 

 passed and free nitrogen or the oxids of nitrogen are formed. 



The latter theory is so entirely in disagreement with all the well- 

 known biologic reactions of glucose that it may safely be put out of 

 consideration at once. If we accept then as an explanation of the facts 

 the theory of decreased nitrogen metabolism, we have two instances 

 of this phenomenon which are not indicated b)' the production of free 

 ammonia. 



