220 



MANUAL OF DETERMINATIVE BACTERIOLOGY 



to wrinkled; may become yellowish, 

 brownish-yellow or chocolate brown. 



The organism fixes atmospheric nitro- 

 gen and gives off CO2, utilizing glucose 

 and sucrose. Other generally used car- 

 bon compounds are fructose, maltose, 

 mannitol, inulin, dextrin, galactose, 

 arabinose, starch, glycerol, ethyl alcohol, 

 acetate, butyrate, citrate, lactate, mal- 

 ate, propionate and succinate. 



Nitrate : Improves growth in amounts 

 less than 1 gm. per liter ; greater amounts 

 are toxic. 



Fixes nitrogen moderately actively. 



Chemical analysis : Four-day cultures 

 grown upon mannitol agar (Greene, 

 1935), when dried, are found to contain 

 less than 0.5 per cent of hemicelluloses, 

 less than 20 per cent of crude protein, 

 less than 5 per cent of ash, and more 

 than 30 per cent of lignin-like materials. 

 The nitrogen fraction contains less than 

 1 per cent of amide nitrogen, less than 1 

 per cent of humin nitrogen and about 1 

 per cent of basic nitrogen. 



Aerobic. 



Optimum temperature 25°C. to 28°C. 



Distinctive characters : Inability to 

 grow in peptone media, even in the 

 presence of glucose; frequent occur- 

 rence 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 agile Beijerinck. 

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

 From L. agilis, agile, quick. 



In studies on the chemical composition 

 of cells Greene (Soil Sci., 39, 1935, 327) 

 found Azotobacter vinelandii Lipman 

 (New Jersey Agr. Exp. Sta. Rept., 24, 

 1903, 238) to be very similar to Azoto- 

 bacter agile Beijerinck. Smith and Loh- 

 nis (Jour. Agr. Res., 23, 1923, 401) agree 

 and state furthermore that the two are 

 identical; they believe also that Azoto- 

 bacter vitreiim Lohnis and Westermann 

 (Cent. f. Bakt., II Abt., 22, 1908, 234) 

 is another synonym of Azotobacter agile. 



Smith (private communication) states 

 that Azotobacter vitreum is a very weak 

 growing, smooth strain of Azotobacter 

 agile. Kluyver and van Reenen (Arch. 

 Mikrobiol., 4, 1933, 299) feel that a dis- 

 tinction should be made between Azoto- 

 bacter agile and Azotobacter vinelandii. 

 In regard to the former, Kluyver and 

 van den Bout (Arch. Mikrobiol., 7, 1936, 

 263) suggest that it be further subdivided 

 into Azotobacter agile and Azotobacter 

 agile var. atypica, the latter referring to 

 an Azotobacter agile form that fails to 

 produce pigment. 



Rods: 4 to 6 microns in length, almost 

 spherical. Actively motile by means of 

 numerous peritrichous flagella (Hofer, 

 loc. oil). Some strains are reported to 

 be non-motile. Gram-negative. 



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. 



Mannitol agar slant: Grayish, trans- 

 lucent, 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, be- 

 coming yellowish-brown. 



In the presence of organic acids, a 

 greenish or reddish pigment is formed. 



The organism fixes atmospheric nitro- 

 gen actively, and gives off CO2. 



Aerobic. 



Chemical analysis : Four-day cultures 

 grown upon mannitol agar (Greene, 1935), 

 when dried, contain 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- 

 like materials. The nitrogen fraction 

 contains more than 1 per cent amide 

 nitrogen, more than 1 per cent humin 



