Nitrogen Metabolism of Bacteria 27 



The data for B-. cloacae and for B. faecalis-alkaligenes indicate that 

 these two organisms are comparable with respect to their activity in 

 the gelatin medium. The amino-acid concentrations are low in both 

 cases. B. cloacae, however, forms comparatively large amounts of free 

 ammonia, the rate of formation being slightly higher in the sugar- 

 free culture. The amino-acid figures do not differ greatly in the two 

 cultures of this organism. Considering the well-known utilization of 

 glucose by B. cloacae, it is surprising that its protein-sparing action is 

 so little marked in this case. B. faecalis-alkaligenes lives up to its repu- 

 tation in these cultures, also, in showing no decrease in its ammonia- 

 production in the presence of glucose. 



The two sets of cultures of B. pyocyaneus, the one grown under 

 aerobic, the other under anaerobic conditions, furnish an instructive 

 comparative study in the biochemistry of micro-organisms. The sur- 

 prising fact in these data is that so little difference is shown between 

 the two sets. On the whole the greater chemical activity seems to be 

 shown in the cultures grown without the exclusion of oxygen. This 

 difference is apparent, however, only during the first half of the period 

 of the experiment. The effect of glucose is greater in the aerobic 

 than in the anaerobic cultures. As multiplication appeared to be much 

 slower in the latter, it is very likely that the differences which do 

 exist are to be ascribed to differences in the numbers of organisms 

 rather than to actual differences in the course or extent of chemical 

 change due to the presence or absence of oxygen. Likewise, the 

 apparently lowered protein-sparing effect of glucose in the anaerobic 

 cultures is probably due to a difference between the numbers of organ- 

 isms, for there was an unquestionably heavier growth in the anaerobic 

 culture containing the sugar than in the sugar-free culture grown 

 under the same conditions. 



The cultures of B. welchii show this effect of glucose very plainly. 

 The enormously greater chemical activity of this organism when grown 

 with glucose can only be attributed to greatly increased multiplication 

 in the presence of glucose. The appearance of the cultures fully sub- 

 stantiates this conclusion. 



It will be observed from the data that the proteolytic activity of B. 

 welchii when grown under favorable conditions is considerable. As 

 will be pointed out later, the nitrogen determined in the form of 

 amino-acid and ammonia cannot be assumed to represent nearly all the 

 nitrogen which is removed from its combinations in the protein mole- 

 cule to form simpler compounds. When we consider, therefore, that 



