FAMILY AZOTOBACTERIACEAE 



219 



FAMILY III. AZOTOBACTERIACEAE BERGEY, BREED AND MURRAY.* 



(Preprint, Manual, 5th ed., October, 1938, v and 71.) 



Cells without endospores. Relatively large rods or even cocci, sometimes almost 

 yeast-like in appearance. The type of flagellation in this genus has been definitely 

 established as peritrichous. Gram-negative. Obligate aerobes, usually growing in 

 a film on the surface of the culture medium. Capable of fixing atmospheric nitrogen 

 when provided with carbohydrate or other energ\^ source. Grow best on media 

 deficient in nitrogen. Soil and water bacteria. 



There is a single genus. 



Genus I. Azotobacter Beijeririck. 



(Beijerinck, Cent. f. Bakt., II Abt., 7, 1901, 567; Azotomonas Orla-Jensen, Cent. f. 

 Bakt., II Abt., 24, 1909, 444.) 



The definition is identical with that of the family. From Gr. azous, not living. 

 French, azote, nitrogen; Gr. bakiron, rod, stick. 

 The type species is Azotobacter chroococcu?7i Beijerinck. 



1. Azotobacter chroococcum Beijer- 

 inck. (Cent. f. Bakt., II Abt., 7, 1901, 

 567 and 9, 1902, 3; Bacillus azotobacter 

 Lohnis and Hanzawa, Cent. f. Bakt., II 

 Abt., 4^, 1914, 1; Bacillus chroococcus 

 Buchanan, General Syst. Bact., Balti- 

 more, 1925, 194.) From Gr. chroa, color; 

 coccos, grain; M. L. sphere. 



According to Lohnis and Smith (Jour. 

 Agr. Res., 23, 1923, 401) Azotobacter 

 beijerinckii Lipman (New Jersey Agr. 

 Exp. Sta. Rept., 25, 1904, 247), Azoto- 

 bacter woodstownii Lipman (ibid.), Azoto- 

 bacter smyrnii Lipman and Burgess (Cent, 

 f. Bakt., II Abt., U, 1915, 504) and Azoto- 

 bacter hilgardii Lipman (Science, 29, 

 1909, 941) are identical with Azotobacter 

 chroococcum. Greene (Soil Sci., 39, 

 1935, 327) studied Azotobacter chroococ- 

 cum and Azotobacter beijerinckii by 

 chemical analyses and found the chemical 

 composition of the cells to be practically 

 identical, but different from that of 

 Azotobacter vinelandii and Azotobacter 

 agile. Smith (private communication) 

 feels that Azotobacter beijerinckii is a 

 non-pigmented rough strain of Azoto- 

 bacter chroococcum. 



Grows in absence of organic nitrogen- 

 Rods : 2.0 to 3.0 by 3.0 to 6.0 microns, 

 occurring in pairs and packets and oc- 

 casionally in chains. The cells show 

 three or four refractile granules. The 

 organisms are surrounded hj a slimy 

 membrane of variable thickness, usually 

 becoming brownish in older cultures, due 

 possibly to the conversion of tyrosine to 

 melanin. The coloring matter is insolu- 

 ble in water, alcohol, ether and chloro- 

 form. Motile bj' means of numerous 

 peritrichous flagella (Hofer, Jour. Bact., 

 47, 1944, 415.) Gram-negative. 



Gelatin colonies: Very small, circular, 

 yellow, granular, later becoming yel- 

 lowish-brown. 



Gelatin stab: Only slight growth in 

 the stab. No liquefaction. 



Mannitol agar stab : Gray, may become 

 brownish. 



Nutrient broth: No growth even in 

 the presence of glucose ; peptone utilized 

 with difficulty. 



Litmus milk : Becoming clearer in 10 

 to 14 days. 

 Potato: Glossy, barely visible, slimy 



* Revised by Dr. A. W. Hofer, New York State Experiment Station, Geneva, 

 New York, June, 1938; further revision by Dr. A. W. Hofer, July, 1943. 



