Gram-negative rod, 1.5 μm long by 0.5 μm wide. When the microorganism is grown in mannitol medium, one polar flagellum is observed by transmission electron microscopy and the species is motile although it is immotile in citrate medium. Strict aerobe; positive for esculin hydrolysis, β-galactosidase activity, and oxidase activity but negative for indole formation, glucose fermentation, arginine dihydrolase activity, and gelatinase activity. From the assimilation tests, able to utilize D-glucose, L-arabinose, D-mannose, D-mannitol, N-acetyl-D-glucosamine, maltose, L-malic acid, dextrin, D-arabitol, D-fructose, L-fucose, D-galactose, gentiobiose, α-D-glucose, m-inositol, α-D-lactose, lactulose, D-melibiose, β-methyl-D-glucoside, D-psiscose, D-raffinose, L-rhamnose, D-sorbitol, sucrose, trehalose, turanose, methyl pyruvate, mono-methyl succinate, D,L-lactic acid, L-aspartic acid, L-glutamic acid, L-ornithine, L-proline, L-pyroglutamic acid, urocanic acid, inosine, uridine, glycerol, glucose-1-phosphate, and glucose-6-phosphate. Optimal growth occurs at 30°C on mannitol, at neutral pH (7 or 8) and at low % NaCl. The strain can oxidize arsenite but does not appear to grow chemolithoautotrophically. Phylogenetically the species is 97.0% identical to Blastobacter aggregatus and 97.7% identical to Agrobacterium tumefaciens. Based on DNA-DNA hybridizations, AOL15 is 30 to 31% identical to Blastobacter aggregatus and 10 to 15% identical to Agrobacterium tumefaciens, which confirms that it is a new species. Bacterium isolated from the surface of the aquatic macrophyte Potamogeton pectinatus in Hot Creek, California. The strain type is AOL15—deposited in the American Type Culture Collection (ATCC BAA-24).