Powder puff spiroplasma: a new epiphytic mycoplasma [isolated from healthy flowers of Calliandra haematocephala]

A spiroplasma (strain PPS1) isolated from healthy flowers of Calliandra haematocephala in Florida has been found to be a member of a serogroup of the Spiroplasmataceae. It is distinct from Spiroplasma citri and from other described spiroplasmas as determined by growth inhibition, fluorescent antibody, and ELISA serological tests. PPS1 was also distinguished from S. citri and several other spiroplasmas by the guanine + cytosine content of its DNA. PPS1 requires sterol for growth, is inhibited by digitonin, grows at 20-30°C, and does not hydrolyze arginine or urea. The ready isolation of this and similar organisms from surfaces of healthy plants emphasizes that caution should be exercised in attempts to isolate cell wall-less prokaryotes from the interior of diseased plants. Although some strains of spiroplasmas are known as insect pathogens in nature, the ecological role(s) of the flower-inhabiting spiroplasmas has yet to be fully determined.