Physical Properties of HumanMycoplasmaSpecies

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Abstract
Studies were made of the comparative morphology and stability of five Mycoplasma species of human origin (M. hominis type-1, M. salivarium, M. fermentans, M. pneumoniae, M. pharyngis). Broth-cultivated organisms were examined by electron microscopy to determine their relative appearance after uniform processing, including fixation-drying with formaldehyde vapor. M. pneumoniae was characterized by the occurrence of 250- to 300 -m[mu] spheres in clusters, and M. pharyngis by the appearance of filaments 120 m[mu] by 1.5 to 8 [mu]; the remaining species revealed a variety of structures, including spheres, rings, and short filaments. To complement these findings, the effect of physical stresses on viability of the mycoplasma was measured by exposing the organisms to heat (in saline), osmotic variations (in sucrose), and sonic oscillation and repetitive freeze-thawing (in culture medium). M. pneumoniae was most resistant to heat, vibration, and freeze-thawing; M. pharyngis was most sensitive to heat and vibration, but was least affected by osmotic changes. The remaining organisms assumed intermediate positions. The type-related variations in relative morphology and stability suggest differing physical attributes of the mycoplasmas studied, supporting taxonomic differentiation of the five species based on metabolic and immunological criteria.