Feb. 24, 1923 
Stimulating the Growth of Azotobacter 
669 
Table II .—Effect of aeration upon nitrogen fixation in culture ig 
i 
1 day. 
2 days. 
3 days. 
Gm. 
dex¬ 
trose. 
Mgm. 
N. 
Reaction. 
Gm. 
dex¬ 
trose. 
Mgm. 
N. 
Reaction. 
Gm. 
dextrose. 
Mgm. 
N. 
Reaction. 
Aerated. 
0.67 
.848 
5 -60 
0 
Alkalin.. 
.. .do. 
0.06 
.60 
10. 20 
4* So 
Alkalin.. 
. ..do. 
0 
Trace. 
12. so 
11. 26 
Alkalin. 
Do. 
Nonaerated. 
4 days. 
S days. 
6 days. 
Gm. 
dex¬ 
trose. 
Mgm. 
N. 
Reaction. 
Gm. 
dex¬ 
trose. 
Mgm. 
N. 
Reaction. 
Gm. 
dex¬ 
trose. 
Mgm. 
N. 
Reaction. 
Aerated. 
0 
12.90 
12. 06 
Alkalin.. 
0 
10.80 
Alkalin.. 
0 
10.80 
Alkalin. 
Nonaerated. 
0 
...do.... 
0 
10.80 
.. .do. 
0 
10.80 
Do. 
The effect of the forced aeration is noticed in the first three days of 
incubation by both the nitrogen fixed and the dextrose fermented. The 
amount of nitrogen finally fixed in the shallow culture flask was practi¬ 
cally as great as in the aerated culture. This would naturally be expected, 
however, as such cultures offered a maximum surface exposure. How¬ 
ever, nitrogen fixation and dextrose consumption was more prompt in the 
aerated cultures. 
The daily reaction of the cultures was alkaline, with possibly one ex¬ 
ception which was questionable. This was the nonaerated culture on the 
fourth day of incubation. The P H for the cultures reported alkaline 
averaged between 7.0 and 7.4. 
EFFECT OF AERATION UPON DEXTROSE FERMENTATION 
The ability of Azotobacter to fix nitrogen is dependent upon the energy 
derived from carbohydrate fermentation. The effect of aeration upon 
dextrose fermentation and the corresponding nitrogen fixation is demon¬ 
strated by the data in Table III. 
Table III .—Effect of aeration upon dextrose fermentation and nitrogen fixation 
Aerated cultures. 
Culture. 
1 day. 
2 days. 
3 days. 
4 days. 
5 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. 
232 H. 
0. 54 
. 61 
1-3 
4.6 
0. 26 
.09 
4-3 
4.6 
o- 07 
.04 
6.1 
0.04 
•03 
5-6 
7. 2 
a 04 
.03 
0*03 
•03 
8.4 
7.2 
Average. 
• 57 
2.9 
• 17 
4.4 
•05 
6. 1 
• °35 
6.4 
• 03s 
•03 
7.8 
26551 - 23 -- 7 
