Feb. io, 1923 
Life History of Azotobacter 
421 
The characteristic pink growth on potato reminded the senior author 
that some strains of Bacterium lactis viscosum, tested by him in 1904 for 
nitrogen fixation, had presented a very similar appearance (23). One of 
these cultures was still available, as was another strain of the same 
organism, isolated in 1909 from slimy milk. When tested, both strains 
behaved exactly alike and appeared very similar to the white fungoid 
growth of Azotobacter. Cell morphology, colony formation, the char¬ 
acteristic growth in milk and on potato were the same in both cases, 
and it was on account of these observations that with the fungoid Azoto¬ 
bacter strains frequently repeated tests in milk were made which, as was 
mentioned above, caused indeed a transformation to slime-producing 
rods, which proved to be identical with Bacterium lactis viscosum. 
5. —SMAIX NON S FOR U DATING RODS 
White and yellow nonsporulating rods were observed with all four 
types of Azotobacter; but their morphological and cultural behavior 
allowed a clear separation, those dervied from Azotobacter chroococcum and 
A . Beijerinckii being sharply differentiated from those of A . agile and 
A . vitreum. 
The white slime-producing small rod form of Azotobacter chroococcum 
and A . Beijerinckii exhibited all marks of Bacterium lactis viscosum 
(18 , p. 316; 23 , p. 587, 590). A transfer from Adametz’s original culture, 
which was received recently from Krai’s Museum, differed considerably 
from the older descriptions, including that published by Adametz (j). 
The rods were of very irregular size and shape, motile by peritrichous 
flagella; they produced gas from mannite and various sugars, but milk 
was still made slimy. They also gave a yellow dwarfed strain, and a 
yellow as well as an orange fungoid growth identical to that of A. chroococ¬ 
cum. Furthermore, large globular and oval cells were formed quite 
readily which resembled typical Azotobacter cells very closely (fig. 48 
on PI. 4 and fig. 57 on PI. 5). That Bacterium lactis viscosum is able to 
fix nitrogen was shown before by the senior author (23). 
The yellow nonsporulating rods developed from Azotobacter chroococ¬ 
cum and A. Beijerinckii were practically counterparts to the white rods, 
as well as to the yellow strains branched off from Bacterium coli , Bact. 
typhosum , etc. (18 f p. 382; 25, p. 57). On the other hand, they are 
directly related to the dwarfed yellow growth, as well as to the yellow 
fungoid type, from which they were developed and into which they could 
be transformed. Some strains were motile by polar flagella, others were 
immotile; all were Gram-negative. They liquefied beef gelatine to a 
varying degree, grew on beef agar as a slimy, bright yellow layer, made 
milk alkaline and digested it partially, and produced on potato a thick, 
greenish yellow to bright yellow to yellow-brownish slimy growth. The 
general character of the smallest rods, developed from the dwarfed growth, 
was sometimes very similar to that of Bacterium turcosum (Zimm.) 
Lehm. et Neum., while the larger motile or immotile yellow rods resem¬ 
bled more those strains described as Bacterium ochraceum and Bacterium 
fulvum (Zimm.) Lehm. et Neum, 
The white rods observed with Azotobacter agile amd A. vitreum either 
produced fluorescence or left the color of the substrate unchanged In 
both cases, however, morphology, flagellation, reproductive organs, col¬ 
ony formation, and growth on the various media were those of a Bacterium 
fluorescens which did not liquefy gelatine or only weakly (Bacterium 
