TAXONOMY: Bacteria -> Bacteroidetes/Chlorobi group -> Bacteroidetes -> Bacteroidia -> Bacteroidales -> Rikenellaceae -> Rikenella
Rods with pointed ends occurring singly, in pairs, or short chains. Short, filamentous, or swollen forms may occur in media with a high concentration of fermentable carbohydrate. Nonmotile. Nonsporeforming; strains do not survive 70°C for 10 min. Gram negative. Anaerobic. Growth enhanced by a fermentable carbohydrate (e.g., glucose). Optimum temperature ~37°C. Poor growth at 45°C and usually no growth below 25°C. Relatively few sugars are fermented, but glucose, lactose, mannose, and melibiose are fermented. Major end products of glucose fermentation are propionic and succinic acids, with moderate amounts of acetic acid, and trace amounts of alcohols. Glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and glutamate dehydrogenase are absent. Esculin is not hydrolyzed. Nitrate is not reduced. Nonhydroxylated and 3-hydroxylated long-chain fatty acids present. The fatty acids are primarily of the iso-methyl branched-chain types; moderate amounts of straight-chain saturated acids are also present. Menaquinones are produced. Isolated from fecal or cecal specimens from calves, chickens, and Japanese quails.