264 A SYMPOSIUM ON RESPIRATORY ENZYMES 



earlier studies (3). It is of interest to examine such cultures for re- 

 spiratory activity. My associate. Dr. R. H. Burris, has determined the 

 Q02 values of a 12-hour culture of Azotobacter agilis on a number of 

 substrates; his findings were as follows: endogenous, 28; glucose, 

 29; lactate, 129; arabinose, 29; acetate, 1109; ethyl alcohol, 1240. 

 When a 48-hour culture was used, these values were greatly reduced. 



More recently Mr. Joe Wilson in our laboratory has made similar 

 observations with Azotobacter vinelandii. In most of these studies a 

 24-hour culture was diluted, and the oxygen uptake measured im- 

 mediately for a period of 60 minutes. The substrate was sucrose, the 

 temperature 30° C, the pH 7.0. Air was used as the gas phase so 

 that opportunity for growth existed, but no detectable fixation of 

 nitrogen occurred during this short experimental period. To avoid 

 the error attached to estimation of dry weight, he calculated the 

 rate of respiration on the basis of cell nitrogen (4). Since these cells 

 of Azotobacter contain about 10 per cent nitrogen, such Q02 (N) 

 values are on the average about 10 times as great as the Qoo based on 

 dry weight. Under these conditions the values of the Q02 (N) ranged 

 from 25,000 to 30,000. 



These data emphasize the extremely high rate of respiration of 

 difiFerent species of Azotobacter and suggest that this organism may 

 well provide an excellent source for the preparation and isolation of 

 different enzyme systems concerned with tlie transfer of hydrogen 

 from substrate to molecular oxygen. With this in mind we are in- 

 vestigating methods for growing Azotobacter on a scale considerably 

 greater than any previously attempted. In a pilot plant designed for 

 yeast production we have succeeded in producing several pounds of 

 moist azotobacter cells during a growth period of 24 to 30 hours. 



REFERENCES 



1. Meyerhof, O., and Burk, D., Z. physik. Chem., 139A, 117 (1928). 



2. Meyerhof, O., and Schulz, W., Biochem. Z., 250, 35 (1930). 



3. Wilson, J. B., and Wilson, P. W., Jour. Bact., 42, 141 (1941). 



4. Burris, R. H., and Wilson, P. W., Proc. Soc. Exp. Biol. Med., 45, 721 ( 1940). 



REACTIONS IN CELL-FREE ENZYME SYSTEMS 

 COMPARED WITH THOSE IN THE INTACT CELL 

 F. F. NoRD, Fordham University: 



In interpreting the results of investigations of bacterial metabolism 

 a few principles should be mentioned which, in addition to the very 

 recent use of tracers, appear to have been applied in approaching 



