266 
Journal of Agricultural Research 
Vol. XXIV, No. 3 
reported as 6.63 per cent moisture, 4.16 per cent ash, and 12.92 per cent 
protein. This protein he considers similar to other plant proteins. 
While the exact method of cultivation is not reported by all investi¬ 
gators, it appears in general that the nitrogen content of Azotobacter will 
vary according to the method of cultivation. The nitrogen of the growth 
scraped off Ashby agar media is reported much lower than in the residue 
filtered from the liquid cultures. 
The composition of seven cultures of Azotobacter cultivated on 
dextrose-Ashby agar was determined in this laboratory. The growth 
at the end of two to four days incubation at 30° C. was scraped off the 
surface of the agar, air dried, and analyzed for the total nitrogen and 
moisture content. The results are given in Table I. 
Tabi^K I .—Nitrogen content of Azotobacter cells grown on Ashby agar 
Culture No. 
Total 
nitrogen. 
Moisture. 
Per cent. 
3-48 
3. 78 
3 - 78 
3-09 
3 - 74 
4*55 
3 - 74 
Per cent. 
9. 12 
8.55 
10. 00 
6. 89 
8.10 
4.69 
9.48 
6 A. 
cr B. 
I B.. 
Averse. 
3 - 73 
8.12 
The percentage of total nitrogen noted in the seven cultures was 
uniform, averaging 3.73 per cent for all cultures and ranging from 3.48 
per cent to 4.55 per cent. If this nitrogen were calculated as protein, 
the average protein content of the cultures would be 23.31 per cent. 
An analysis of a composite sample of these cultures gave the following 
results: Moisture 8.58 per cent; total nitrogen 3.55 per cent; albuminoid 
nitrogen 1.89 per cent; ash 12.99 cent; phosphorus 0.57 per cent; and 
potassium 1.43 per cent. These figures indicate that only 53.1 per cent 
of the total nitrogen is protein. This gives a protein content of 11.81 
per cent instead of 23.31 per cent, as calculated from the total nitrogen. 
The chemical composition of the growth obtained from liquid cultures 
was determined for comparison. Culture No. 232 was aerated from two 
to four days at 30° C. in the dextrose-Ashby medium. The growth of 
cells was obtained by centrifuging in a Sharpies laboratory supercentri¬ 
fuge. A composite sample taken from the growth of several culture 
flasks was used for analysis. The composition was: Moisture 2.67 per 
cent; total nitrogen 5.15 per cent; albuminoid nitrogen 4.89 per cent; 
ash 4.62 per cent; phosphorus 0.24 per cent; and potassium 1.2 per cent. 
A comparison of this analysis with that obtained from the growth on 
Ashby agar reveals considerable difference. In the first place, a higher 
total nitrogen content is observed in the growth from the liquid culture. 
The most marked effect, however, is the high albuminoid content of the 
liquid culture, it being 94.9 per cent of the total nitrogen. This gives a 
protein content of 30.56 per cent, as compared with 11.81 per cent for 
the growth obtained from Ashby agar. The liquid culture produced a 
growth with a lower ash content than did the culture on agar. 
