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AquaspirillumRANK: GenusTAXONOMY: cellular organisms -> Bacteria -> Proteobacteria -> Betaproteobacteria -> Neisseriales -> Chromobacteriaceae -> Aquaspirillum OVERVIEW: Rigid, helical cells, 0.2–1.4 µm in diameter; however, one species is vibrioid and one species contains straight-to-curved rods. A polar membrane underlies the cytoplasmic membrane at the cell poles in all species so far examined for this characteristic by electron microscopy. Intracellular poly-β-hydroxybutyrate is formed, except in two species. Some species form thin-walled coccoid bodies, which predominate in cultures of three to four weeks. Gram negative. Motile by polar flagella, generally bipolar tufts; one species is monotrichous, others have a single flagellum at one or at each pole. Aerobic to microaerophilic, having a respiratory type of metabolism with oxygen as the terminal electron acceptor; a few species can grow anaerobically with nitrate. The optimal growth temperature for most species is 30–32°C. Chemoorganotrophic; however, one species is a facultative hydrogen autotroph. Oxidase positive. Usually catalase and phosphatase positive. Indole and sulfatase negative. Casein, starch, and hippurate are not hydrolyzed. No growth occurs in the presence of 3% NaCl. A few species can denitrify. Nitrogenase activity occurs in some species, but only under microaerobic conditions. Carbohydrates are not usually metabolized, but a few species can attack a limited variety. Amino acids or the salts of organic acids serve as carbon sources. Vitamins are not usually required. Usually occur in stagnant, freshwater environments.The mol% G + C of the DNA is: 49–66.Type species: Aquaspirillum serpens |