The family Azotobacteraceae contains aerobic diazotrophs with two Genera, Azomonas and Azotobacter, distinguished by the ability to form cysts. The family is also characterized by variable cell shape, the classic shape being ovoid while many are pleomorphic. With an adequate supply of Mo the Azotobacteraceae are able to fix at least 10 mg of molecular nitrogen per gram of carbohydrate consumed under aerobic conditions. Like most Pseudomonadacea, the Azotobacteraceae are able to utilize a wide variety of carbon sources, including sucrose ⁴. Recent analysis of the unannotated genome of Azotobacter vinelandii has shown that this bacterium is most appropriately grouped in the family Pseudomonadaceae. The original familial distinction was based on the ability to fix nitrogen, but a few Pseudomonadaceae have been found to fix nitrogen as well ¹. The relation is not surprising given the ability of many Azotobacteraceae to fluoresce due to the production of Pyoverdine, a nonribosomal peptide siderophore typical of many Pseudomonadaceae ²,³.
References:
Note 1: Rediers H, Vanderleyden J, De Mot R. 2004. Azotobacter vinelandii: a Pseudomonas in disguise? Microbiology. 150Pt 5):1117-9. Species A. vinladii Azotobacter are usually motile, oval, or spherical bacteria, form thick-walled cysts, and may produce large quantities of capsular slime. ... A cyst is a closed sac having a distinct membrane and developing abnormally in a cavity or structure of the body. ... Genera Azotobacter group Cellvibrio Pseudomonas The Pseudomonadaceae are a family of bacteria, including Pseudomonas, Cellvibrio, together with the Azotobacter group. ... Nonribosomal peptides (NRP) are secondary metabolites, usually produced by microorganisms like bacteria and fungi. ... A Siderophore (greek for iron carrier) is an iron chelating compound secreted by microorganisms. ...

Note 2: Meyer JM. 2000. Pyoverdines: pigments, siderophores and potential taxonomic markers of fluorescent Pseudomonas species. Arch Microbiol. 174(3):135-42.

Note 3: Schwarzer D, Finking R, Marahiel MA. 2003. Nonribosomal peptides: from genes to products. Nat Prod Rep. 20(3):275-87.

Note 4: Tchan Y. Azotobacter. Tchan Y, and New P. Azomonas. Krieg NR, Holt JG (eds.) Bergey’s Manual of Systematic Bacteriology, Volume 1. 1984. Williams and Wilkins. Baltimore, MD 219-234