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AgrobacteriumRANK: GenusTAXONOMY: Bacteria -> Proteobacteria -> Alphaproteobacteria -> Rhizobiales -> Rhizobiaceae -> Rhizobium/Agrobacterium group -> Agrobacterium OVERVIEW: Rods 0.6–1.0 × 1.5–3.0 μm, occurring singly or in pairs. Nonsporeforming. Gram negative. Motile by 1–4 peritrichous flagella. Aerobic, possessing a strictly respiratory type of metabolism with oxygen as the terminal electron acceptor. Some strains are capable of anaerobic respiration in the presence of nitrate. Most strains are able to grow under reduced oxygen tensions in plant tissues. Optimal temperature for growth: 25–28°C. Colonies are usually convex, circular, smooth, nonpigmented to light beige. Growth on carbohydrate-containing media is usually accompanied by copious extracellular polysaccharide slime. Catalase positive. Usually oxidase positive and urease positive. Indole is not produced. Chemoorganotrophs, utilizing a wide range of carbohydrates, salts of organic acids, and amino acids as carbon sources, but not cellulose, starch, agar, or chitin. Produce an acid reaction in mineral salts media containing mannitol and other carbohydrates. Ammonium salts and nitrates can serve as nitrogen sources for strains of some species; others require amino acids and additional growth factors. 3-ketoglycosides are produced by the majority of strains belonging to A. tumefaciens. Strains of some species in this genus invade the crown, roots, and stems of a great variety of dicotyledonous and some gymnospermous plants via wounds, causing transformation of the plant cells into autonomously proliferating tumor cells. Oncogenicity is correlated with the presence of a large tumor-inducing plasmid. Habitat: soil. Oncogenic strains occur mainly in soils previously contaminated with diseased plant material. Some non-oncogenic Agrobacterium strains have been isolated from human clinical specimens. The mol% G + C of the DNA is: 57–63. Type species: Agrobacterium tumefaciens
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