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RunellaRANK: GenusTAXONOMY: Bacteria -> Bacteroidetes/Chlorobi group -> Bacteroidetes -> Cytophagia -> Cytophagales -> Cytophagaceae -> Runella OVERVIEW: Rigid straight to curved rods, the degree of curvature varying among cells within a culture. In one species (Runella slithyformis), the cells range from nearly straight to crescent-shaped, but the ends of a cell may overlap, producing a ring-like structure with an outside diameter of 2.0–3.0 µm; in addition, filaments up to 14 µm long may also be produced, and on rare occasions, a coil of two to three turns may be produced. In other species, the cells are either long and filamentous or straight to slightly bent rods instead of crescent-shaped or ring-like as found with Runella slithyformis. Gram-stain-negative. Nonmotile. Resting stages are not known. Aerobic. Runella slithyformis has a strictly respiratory metabolism with oxygen as the terminal electron acceptor and produces acid oxidatively from a few carbohydrates, whereas Runella zeae can ferment sugars. Optimum temperature, 20–35°C. Colonies contain a pale pink or salmon-colored water-insoluble pigment. Catalase is either positive or weakly positive. The oxidase reaction differs among species. Chemo-organotrophic. In those species so far tested, the major quinone is MK-7. Isolated from freshwater (Runella slithyformis), activated sludge (Runella limosa and Runella defluvii), and the stems of Zea mays (Runella zeae).DNA G+C content (mol%): 40–49.Type species: Runella slithyformis |