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MethylococcalesRANK: OrderTAXONOMY: cellular organisms -> Bacteria -> Proteobacteria -> Gammaproteobacteria -> Methylococcales OVERVIEW: Cells appear as cocci or rods, 0.8–1.5 × 1.0–1.5 µm. Usually occur singly or in pairs. Form a polysaccharide-containing cyst-like resting stage that is desiccation sensitive. Poly-β-hydroxybutyrate granules present. Gram negative. If motile, cells are propelled by single polar flagellum. Catalase and oxidase positive. Strictly aerobic respiratory metabolism with oxygen as the electron acceptor. Obligate utilizers of methane and methanol for carbon and energy. Contain a partially functional Benson–Calvin cycle (phosphoribulokinase and ribulose-1,5-diphosphate carboxylase activity present); however, incorporation of CO2 for cellular carbon occurs only in the presence of methane. Fix atmospheric nitrogen via an oxygen-sensitive nitrogenase. Thermotolerant or moderately thermophilic with optimal growth between 40–60°C. Major fatty acids include C16:0 and C16:1 ω7c. 18-Methyleneubiquinone-8 (MQ-8) is the predominant lipoquinone. Isolated from sediments of freshwater lakes and rivers, wetland muds, activated sludge, and wastewater. Belongs to the Gammaproteobacteria as part of the Order Methylococcales, Family Methylococcaceae. The mol % G + C of the DNA is: 59–65 (Tm). Type species: Methylococcus capsulatus
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