T-mycoplasmas: a study of the morphology, ultrastructure and mode of division of some human strains.

The morphology of 10 strains of T-mycoplasma was studied in wet preparations of viable cells by darkfield, phase-contrast and interference microscopy, and in fixed preparations by various techniques of electron microscopy. Mycoplasma-like artefacts in the horse-serum component of the medium were eliminated by filtration. All 10 strains were similar. Individual cells were spherical, 0-25-1-0 mum in size, with a bounding trilaminar membrane, 10 nm thick and containing 7-5-12-5-nm particles, and a layer of pilus-like projections, 5-8 nm long, on the outer surface. A possible capsular matrix was observed only by the pseudoreplica technique. The cells contained 12-15-nm ribosomes, nuclear fibroids 7-5-9 nm wide, and vacuoles. During replication, the cell elongated slightly and the ribsomes migrated to the ends of the cell leaving a ribosome-free area into which the bounding membrane invaginated to form a bud. The bud eventually separated by completion of the process of invagination; a cross-septum did not form. Usually only a single bud developed but sometimes two appeared simultaneously.