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SpirochaetaRANK: GenusTAXONOMY: cellular organisms -> Bacteria -> Spirochaetes -> Spirochaetia -> Spirochaetales -> Spirochaetaceae -> Spirochaeta OVERVIEW: Flexible helical cells 0.2–0.75 μm in diameter and 5–250 μm in length. All species have two periplasmic flagella per cell except Spirochaeta plicatilis, which has many periplasmic flagella. Under unfavorable conditions, spherical cells or structures 0.5–2.0 µm (occasionally up to 10 µm) in diameter are formed. Cells translocate when suspended in liquids and crawl or creep when in contact with solid surfaces. Obligately anaerobic or facultatively anaerobic. Under aerobic growth conditions the facultatively anaerobic species usually produce carotenoid pigments that give a yellow, yellow-orange, or red coloration to colonies or cells in liquid media. Thermophilic species are known. Optimum temperature range, 25–68°C. Chemo-organotrophic, using a variety of carbohydrates as carbon and energy sources. The main products of anaerobic carbohydrate metabolism are ethanol, acetate, CO2, and H2. Under aerobic conditions, facultatively anaerobic species oxidize carbohydrates yielding primarily CO2 and acetate. Indigenous to aquatic freshwater and marine environments such as the sediments, mud and water of ponds, marshes, swamps, lakes, rivers, and hot springs. Occur commonly in H2S-containing environments. Free-living. None reported to be pathogenic.DNA G+C content (mol%): 50–65 (Bd), 45–66 (Tm), 50–58.5 (HPLC).Type species: Spirochaeta plicatilis |