STUDIES ON AZOTOBACTER CHROOCOCCUM BEIJ. 365 



by the presence or absence of combined nitrogen in the solution. 

 These carbon relations are in reahty so closely connected with 

 the nitrogen relations that to treat them separately would make 

 the discussion abstract and unsound. 



The fact that the cells seem to attack the sugar with a respir- 

 atory quotient of C02:02 = db 1 is apparently misleading and 

 is not corroborated by a study of the sugar consumption. As 

 we have seen we are forced to admit a first phase in the sugar 

 metabohsm, a phase that could well be named one of prepara- 

 tion, one in fact in which the sugar is worked up and changed 

 into a compound or compounds of a non-reducing nature. From 

 the study of the gas exchanges, it appears that the presence of 

 nitrates aids in the better utihzation of the sugar. (Tables 

 7 and 11.) 



In this first stage, the ''ferment power" of the organism is 

 great and it is probably in this stage too, that the nitrates play 

 an important role; in fact it is at this stage that the nitrate 

 assimilation is at a maximum and evidence leads us to beheve 

 in a close relationship and interdependence of the two exalted 

 functions, high ''ferment power" and nitrate disappearance. 

 Our filtration experiments before inoculation give us a proof 

 of the paramount importance of nitrates in the process of sugar 

 utilization, and, although the interpretation to be given to these 

 facts is as yet unknown, evidence leads us to the behef that 

 nitrates perform an intermediary function in the sugar fermen- 

 tation and assimilation and it may well be that this preparation 

 stage is directly dependent upon the formation of sugar-nitrate 

 complexes analogous to the phosphate sugar complexes of 

 Harden and Young. 



In Allen's filtered solutions phosphates proved indispensable 

 probably on account of their necessity in the formation of com- 

 plexes of the hexose-phosphate type. The fact that nitrates 

 proved to behave in a like manner leads us to the belief that 

 Azotobacter cells may be capable of attacking complexes of the 

 hexose-phosphate tj^e as well as some homologues that involve 

 the nitrate radicle. 



