RANK: Genus

TAXONOMY: cellular organisms -> Bacteria -> Proteobacteria -> Gammaproteobacteria -> Cardiobacteriales -> Cardiobacteriaceae -> Dichelobacter


Large straight or slightly curved rods, 3–6 × 1.0–1.7 μm, with rounded ends. Freshly isolated cells often have terminal swellings, this feature is less pronounced after subculture. Gram negative but with a tendency to resist decolorization. Organisms stained with Loeffler methylene blue have prominent polychromatic granules toward the poles and at intermediate sites within the cells. Grows slowly only under strictly anaerobic conditions but is not rapidly killed by exposure to oxygen. The cells have large numbers of thin polar fimbriae or pili that vary in number according to changes in colony morphology. The pili belong to the type IV or N-methylphenylalanine family; consequently, the cells exhibit the twitching motility and spreading of colonies that is characteristic of cells with type IV pili. The organism also produces extracellular serine proteases that are relatively heat stable. Ammonia is produced from arginine, asparagine, serine, and threonine. Positive for ornithine decarboxylase, phosphatase (weak), H2S production, selenite reduction, and proteolytic activity on gelatin, casein, and albumin. Negative for acid or gas production from carbohydrates; ammonia production from phenylalanine, cysteine, citrulline, and ornithine; starch hydrolysis; esculin hydrolysis; indole production; nitrate reduction; growth in 0.1% bile; hemolysis; arginine decarboxylase; catalase; oxidase; urease; DNase; coagulase; lipase; lecithinase; and hyaluronidase. The genus contains a single species, Dichelobacter nodosus. Further details on the properties of the genus are available elsewhere (Beveridge, 1941, Cato et al., 1979, Holdeman et al., 1984a, Skerman, 1989; Dewhirst et al., 1990).The mol% G + C of the DNA is: 45.Type species: Dichelobacter nodosus