670 
Vol. XXIII, No. 8 
Journal of Agricultural Research 
Table III .—Effect of aeration upon dextrose fermentation and nitrogen fixation —Con. 
Nonaerated cultures. 
Culture. 
1 day. 
2 days. 
3 days. 
4 days. 
S days. 
6 days. 
Gm. 
dex¬ 
trose. 
Mgm. 
N. 
Gm. 
dex¬ 
trose. 
Mgm. 
N. 
Gm. 
dex¬ 
trose. 
Mgm. 
N. 
Gm. 
dex¬ 
trose. 
Mgm. 
N. 
Gm. 
dex¬ 
trose. 
Mgm. 
N. 
Gm. 
dex¬ 
trose. 
Mgm. 
N. 
12 BE. 
1 
0. 7 
0.8 
a 7 
0. 8 
0. 7 
0. 8 
0. 7 
0. 8 
0. 7 
0. 8 
0. 7 
33a H... . 
1 
0 
.8 
0 
.8 
•7 
• 7 
.6 
• 7 
.6 
Average. 
1 
• 35 
.8 
• 35 
.8 
• 7 ! 
• 75 
• 7 
• 75 
■65 
■ 751 
• 65 
Flasks containing 250 cc. of media were inoculated and incubated under 
aerating and nonaerating conditions. An aerated and nonaerated culture 
flask was analyzed each day for six days. The daily increase of nitrogen 
fixed as well as the daily consumption of dextrose in the aerated and 
nonaerated cultures is shown. 
The marked effect of aeration upon Azotobacter is again indicated by 
these figures. In the aerated cultures the consumption of dextrose is 
very rapid. An average of 95 per cent of the original amount of dextrose 
disappeared within three days. Such is not the case in the nonaerated 
cultures. The average of the two cultures indicates that only 20 per cent 
of the dextrose was consumed within six days in the absence of aeration. 
The comparative effect of aeration and nonaeration upon azofication 
and dextrose consumption is more clearly illustrated in figure 1 by the 
curves made from these data. 
The striking effect of aeration is thus plainly evident, both in the 
nitrogen fixed and in the dextrose consumed. A close relationship is 
evident between the dextrose fermentation and azofication. 
RATE OF NITROGEN FIXATION AND DEXTROSE FERMENTATION 
Observation was made upon the comparative rate of nitrogen fixation 
and dextrose consumption in aerated cultures. 
Allen (8) contributes data from one experiment and concludes that 
the results show that the rate of carbohydrate (dextrose) consumption 
by Azotobacter does not proceed in a manner similar to the rate of increase 
in cell numbers. Some of his cultures were agitated by mechanical means. 
This agitation appeared to hasten dextrose consumption as compared 
with those cultures which were not agitated. 
The results obtained from six cultures of Azotobacter are shown in 
Table IV. The organisms were inoculated into a bottle holding 1,500 
cc. of 1 per cent dextrose medium. The cultures were aerated two, four, 
six, and eight days. Total nitrogen and sugar determinations were 
made at the end of these periods by removing aseptically 150 cc. of the 
culture from the bottle. Curves plotted from the average of these results 
in figure 2, demonstrate a correlation between the rate of nitrogen 
fixation and dextrose fermentation. In general the results are similar 
to those indicated in figure 1. 
The data representing the general average of the figures in the table 
are recapitulated in Table V. It will be noticed that the rate of azofica¬ 
tion per gram of dextrose for each period of two days, is practically the 
same, namely, 6.90, 9.37, 8.34, and 9.74 gm. of nitrogen. 
