Gram-negative sometimes Gram-variable; aerobic metabolism (O2 as the terminal electron acceptor); utilization of glycerol; no utilization of N-acetylglucosamine, D-mannitol, D-ribose, sucrose, and D-sorbitol; no acid formation from glucose or fructose; require no biotin for growth; optimum growth temperature: 37 °C; optimum pH: 6.0 - 8.7; formation of nonmotile cyst-like forms, or C-forms in the presence of O2 to protect the nitrogenase; oxidase- and urease-positive; assimilation and dissimilation of nitrate.