284 



ORDER IV. EUBACTERIALES 



cent of amide nitrogen, less than 1 per cent 

 of humin nitrogen and about 1 per cent of 

 basic nitrogen. 



Aerobic. 



Optimum temperature, between 25° and 

 28° C. 



Distinctive characters: Inability to grow 

 in peptone media, even in the presence of 

 glucose; frequent occurrence of a dark brown 

 or black pigment. 



Source: Isolated from soil. 



Habitat : Occurs naturally in the majority 

 of neutral or alkaline field soils. 



2. Azotobacter agilis Beijerinck, 1901. 

 (Cent. f. Bakt., II Abt., 7, 1901, 577.) 



a'gi.lis. L. adj. agilis quick, agile. 



Rods, 4 to 6 microns in length, almost 

 spherical. Actively motile by means of 

 numerous, peritrichous flagella (Hofer, 

 Jour. Bact., 47, 1944, 415). Some strains 

 are reported to be non-motile. Gram-nega- 

 tive. 



Grows in absence of organic nitrogen. 



Gelatin: No liquefaction. 



Mannitol agar colonies: Circular, gray- 

 ish white, translucent with whitish center. 



Washed agar colonies : Show slight bluish 

 green fluorescence. The presence of a fluo- 

 rescent pigment is readily demonstrated 

 by placing cultures under ultraviolet light, 

 3600 A. Examination by paper chromotog- 

 raphy indicates that this pigment is not 

 fluorescin, the pigment found in fluorescent 

 pseudomonads (Johnstone, Jour. Bact., 

 69, 1955, 481). 



Mannitol agar slant: Grayish, translu- 

 cent, fluorescent. 



Plain agar slant : Yellowish white, smooth, 

 glistening, translucent with opaque center. 



Broth: Turbid, with sediment. 



Litmus milk: Becoming clear in 10 to 14 

 days. 



Potato: Yellowish white, slimy, becom- 

 ing yellowish brown. 



In the presence of organic acids, a green- 

 ish or reddish pigment is formed. 



The organism fixes atmospheric nitrogen 

 actively and gives off CO2 . 



Aerobic. 



Chemical analysis: Four-day cultures 

 grown upon mannitol agar, when dried, con- 



tain more than 4 per cent of hemicelluloses, 

 more than 45 per cent of crude protein, more 

 than 7 per cent of ash, and less than 4 per 

 cent of lignin-Iike materials. The nitrogen 

 fraction contains more than 1 per cent 

 amide nitrogen, more than 1 per cent humin 

 nitrogen, and 2 per cent or more of basic 

 nitrogen (Greene, Soil Sci., 39, 1935, 327). 



Optimum temperature, between 25° and 

 28° C. 



Distinctive characters: Lack of a brown 

 pigment; occasional fluorescence; growth 

 in peptone broth containing glucose. 



Comment: A non-chromogenic variety 

 of this species has been recognized by 

 Kluyver and van den Bout (Arch. f. Mi- 

 krobiol., 7, 1936,263). 



Source: Originally isolated from canal 

 water at Delft. 



Habitat: Occurs in water and soil. 



3. Azolobacter indicus Starkey and De, 

 1939. {Azotobacter iniicum (sic) Starkey and 

 De, Soil Sci., 47, 1939, 337.) 



in'di.cum. L. adj. indicus of India. 



Ellipsoidal rods, 0.5 to 1.2 by 1 7 to 2.7 

 microns when grown on nitrogen-free glu- 

 cose agar. One of the distinctive character- 

 istics is the presence of two large, round, 

 highly refractive bodies in the cells, one 

 usually at each end. Motile by means of 

 numerous peritrichous flagella (Hofer, Jour. 

 Bact., 47, 1944, 415). Gram-negative. 



The organism grows slowly but in time 

 produces large amounts of slime. Has high 

 acid tolerance, since it grows from pH 3 to 9. 



Sucrose or glucose agar plates: Colonies 

 are colorless, round, very much raised and 

 uniformly turbid, having much the appear- 

 ance of heavy starch paste. After two weeks, 

 a buff to light brown color develops. 



Mannitol agar slant: Grows very poorly. 



Peptone agar slant with 0.5 per cent glu- 

 cose: Limited grayish growth. 



Nutrient broth: No growth. 



Liquid media: Generallj^ turbid with 

 some sediment. 



Fixes atmospheric nitrogen readily with 

 either glucose or sucrose as source of energy. 



Aerobic. 



Optimum temperature, 30° C. 



