Acetobacter diazotrophicus (di.a.zo.troʹphi.cus.Gr. prefix di, two, double; N.L.n. azotum, nitrogen; Gr.adj. trophikos, nursing, tending or feeding; M.L. masc. adj. diazotrophicus, one that feeds on dinitrogen). Cells are straight rods with rounded ends, about 0.7 to 0.9 by ±2 gm. Long involution forms occur in unshaken rich liquid media. Motile by lateral or peritrichous flagella (Fig. 2). Produces brown water-soluble pigments on GYC medium. Dark brown colonies are formed on potato agar supplemented with 10% sucrose, and dark orange colonies are formed on a nitrogen-poor medium containing bromothymol blue (1). Forms 2-ketogluconic acid and 2,5-diketogluconic acid from glucose. These organisms are microaerobic dinitrogen fixers which grow on N2 as a sole nitrogen source in semisolid media and after initial growth with starter nitrogen in liquid media; they grow well in liquid media with combined nitrogen sources. Nitrate is not reduced, and N2 fixation occurs at high nitrate concentrations (10 mM). The optimum growth temperature is around 30°C, and the optimum pH is 5.5. Does not grow at pH 7.0, but does grow and fix N2 at pH values below 3.0. H2S is not formed from L-cysteine, except by some strains when they are grown in a medium containing sucrose instead of glucose. Grows well in mineral media containing NH4+. Growth is poor on organic acids, but acetate and lactate are oxidized to CO2 and water. High concentrations (10%) of sucrose are the best carbon source for growth, but glucose, fructose, and galactose are also used. Growth and N2 fixation occur with 30% glucose or 30% sucrose. Ethanol (1%), mannitol, and glycerol are also used as carbon sources. The major cellular fatty acid is C18;1 acid. The ubiquinone type is Q10. Other features are listed in Table 2. The average guanine-plus-cytosine content of the DNA ranges from 61 to 63 mol% (as determined by the thermal denaturation method). The habitat is roots and stems of sugarcane.

lives in the roots and stems of sugarcane

The type strain is strain LMG 7603 (= Döbereiner PA 5 = ATCC 49037).