Two mollicutes (strains F7 [T = type strain] and F28) isolated from floral surfaces of plants growing in Morocco and France were capable of sustained growth in serum-free (or cholesterol-free) mycoplasma broth media. The two isolates were found to be genomically and serologically related. Morphologic examination of the organisms by electron and dark-field microscopic techniques showed that each strain consists of small, nonhelical, nonmotile, pleomorphic coccoid cells surrounded by a single cytoplasmic membrane. No evidence of cell walls was observed. Growth in serum-free or cholesterol-free medium was sustained only when the medium contained a Tween 80 fatty acid mixture (0.01 or 0.04%). The organisms grew rapidly in most conventional mycoplasma culture medium formulations containing horse or fetal bovine serum or a bovine serum fraction and under either aerobic or anaerobic environments. The optimum temperature for growth was 28°C, but multiplication occurred over a temperature range from 20 to 35°C. Both strains catabolized glucose and mannose, but did not hydrolyze arbutin, arginine, or urea. The molecular mass of the genome of strain F7 was determined to be about 886 megadaltons, while the base composition (guanine-plus-cytosine content) of the DNA was found to be 30.0 mol%. The two isolates were serologically unrelated to type strains of the 11 previously described species and to 10 other unclassified sterol-nonrequiring mollicutes cultivated from various animal, plant, or insect sources. Strain F7 (= ATCC 49495) is the type strain of sp. nov.


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