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SpirillumRANK: GenusTAXONOMY: cellular organisms -> Bacteria -> Proteobacteria -> Betaproteobacteria -> Nitrosomonadales -> Spirillaceae -> Spirillum OVERVIEW: Rigid, helical cells, 1.4–1.7 × 14–60 μm. A polar membrane underlies the cytoplasmic membrane at the cell poles and is visible in ultrathin sections. Intracellular poly-β-hydroxybutyrate granules are formed. Coccoid bodies are not formed. Gram negative. Motile by large bipolar tufts of flagella having a long wavelength and about one helical turn; these are composed of approximately 75 flagella and are easily visible by dark-field or phase-contrast microscopy. Microaerophilic in ordinary liquid media, but can grow aerobically in special media or with certain supplements. Colonies on solid media can be obtained only under special conditions. Have a strictly respiratory type of metabolism with oxygen as the terminal electron acceptor. Growth does not occur anaerobically with nitrate. Optimal temperature, 30°C. Oxidase and phosphatase positive. Catalase negative. Indole and sulfatase negative. Casein, starch, esculin, gelatin, DNA, and RNA are not hydrolyzed. Inhibited by extremely low levels of hydrogen peroxide in the culture medium. NaCl levels above 0.02% are inhibitory. Phosphate levels greater than 0.01 M are inhibitory. Carbohydrates are not catabolized. The salts of certain organic acids are used as carbon sources; succinate is used especially well. Vitamins are not required. Occur in stagnant, freshwater environments.The mol% G + C of the DNA is: 38 or 36.Type species: Spirillum volutans |