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SyntrophomonasRANK: GenusTAXONOMY: Bacteria -> Terrabacteria group -> Firmicutes -> Clostridia -> Clostridiales -> Syntrophomonadaceae -> Syntrophomonas OVERVIEW: Slightly helical rods, 0.5–1.0 by 2–7 µm, with slightly tapered rounded ends. Most cells occur singly or in pairs with helical chains of three or more. Multiplication is by binary fission. Cells possess 2–8 flagella (about 20 nm in diameter) that are inserted laterally in a linear fashion on the concave side of the cell, about 130 nm or more apart. Under most conditions, cells usually exhibit only sluggish twitching motility. Cells have an unusual multilayered cell wall that stains Gram-negative. Muramic and meso-diaminopimelic acids are present and the organism is susceptible to penicillin. Poly-β-hydroxybutyrate is present. Cells β-oxidize saturated fatty acids anaerobically with protons serving as the electron acceptors in co-cultures with a hydrogenotroph. Growth is much faster with Methanospirillum hungatei, which utilizes both H2 and formate, than with methanogens such as Methanobacterium bryantii that utilize only H2. In co-culture, cells produce acetate and H2 from butyrate and longer straight-chain, even-numbered-carbon fatty acids and acetate, propionate, and H2 from n-valerate and longer straight-chain, odd-numbered-carbon fatty acids. At least some strains produce acetate, isovalerate, and H2 from iso acids such as isoheptanoate and some strains produce acetate, propionate, and H2 from 2-methylbutyrate. It is possible, but has not yet been determined, that anteiso acids such as anteisooctanoate are degraded to acetate, anteisohexanoate, and H2. The strains studied so far can, with considerable difficulty, be adapted to grow slowly in axenic culture on crotonate, with acetate and butyrate as the products. Carbohydrates, proteinaceous materials, alcohols, and other organic compounds do not support growth. Common electron acceptors such as fumarate, malate, nitrate, oxygen, sulfate, sulfite, sulfur, and thiosulfate are not utilized with butyrate as the electron donor. Growth may be stimulated in co-cultures by factors in rumen fluid or mixtures of vitamins or both. Isolated as co-cultures from anaerobic ecosystems, such as aquatic sediments, sewage digester sludge, the rumen, and rice field mud, where organic matter is degraded, with CO2 and CH4 as major products. The temperature range for growth of co-cultures with Methanospirillum hungatei is in the broad mesophilic range, with an optimum of 30–37°C. Phylogenetically, as determined by 16S rRNA gene sequencing, the genus Syntrophomonas forms a deeply branched lineage in the bacteria related to the Firmicutes.DNA G+C content (mol%): 40–47.Type species: Syntrophomonas wolfei |