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RahnellaRANK: GenusTAXONOMY: cellular organisms -> Bacteria -> Proteobacteria -> Gammaproteobacteria -> Enterobacteriales -> Enterobacteriaceae -> Rahnella OVERVIEW: Straight rods 0.5–0.7 × 2–3 μm, conforming to the general definition of the family Enterobacteriaceae. Gram negative, motile by peritrichous flagella when grown at 25°C. Facultatively anaerobic. Chemoorganotrophic. Psychrotolerant, growing at 4°C. d-Glucose is fermented with the production of acid and, for the majority of strains, gas. Nitrate is reduced to nitrite. Oxidase negative, catalase positive. Negative for lysine and ornithine decarboxylases and for arginine dihydrolase. Most strains are (weakly) positive for phenylalanine deaminase (after 48 h), methyl red, and Voges–Proskauer reaction. Acids are produced from various carbohydrates, including l-arabinose, cellobiose, lactose, maltose, mannose, l-rhamnose, raffinose, d-xylose, and salicin. Sequence analyses of the 16S rDNA of four Rahnella strains clearly placed the genus within the Gammaproteobacteria in the family Enterobacteriaceae. Highest 16S rDNA sequence similarity to Yersinia enterocolitica ATCC 9610T (97.7%). By omitting the hypervariable regions VI and V5 (corresponding to E. coli base positions 147–1490; Brosius et al., 1978), Hafnia alvei ATCC 13337T showed the highest sequence similarity (96.63%) to R. aquatilis ATCC 33071T. Most often isolated from fresh water, but also found in the intestine of snails and various other environmental habitats, including soils and the rhizosphere. Can occasionally be isolated from foods or human clinical specimens, including wound infections, bacteremias, feces from patients with acute gastroenteritis, and septicemia, especially from immunocompromised patients. The genus currently includes three genomospecies (R. aquatilis [Rahnella genomospecies 1], Rahnella genomospecies 2, and Rahnella genomospecies 3), which cannot be phenotypically differentiated. The mol% G + C of the DNA is: 51–56. Type species: Rahnella aquatilis
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