Chemical composition and ultrastructure of Mycoplasma hominis

Abstract

Mycoplasma hominis belongs to the family Mycoplasmataceae, which includes the smallest free-living organisms known to exist. Despite the small size of the organism, its chemical composition and cell structure are almost as complex as in other bacteria. The cytoplasm contains typical 70S bacterial ribosomes and a circular double-stranded DNA molecule. Both of these structures have been well characterized. Like other mycoplasmas, M. hominis lacks a cell wall. The cytoplasmic membrane is the outer boundary of the cell. The membrane lipid and protein composition of M. hominis has been established. The presence of various high-molecular-weight proteins at the extracellular side of the membrane in different strains is probably important in terms of the immunogenic heterogeneity of M. hominis. Furthermore, sugar-containing structures at the outside of the membrane may be important in the interaction between M. hominis and the mucosal surfaces of its human hosts. However, the information available on the cell structure of M. hominis is still inadequate for an exact definition of the relation between host and parasite.