Mycoplasmas

           Mycoplasmas are the smallest (0.2-0.3mm) free-living microorganisms, therefore they can pass through bacterial filters, and one of the most pleomorphic, since they are devoid of cell walls. They occur as granules and filaments of various sizes. The granules may range from 100-1000 mm in size, with coccoid, balloon,disc, ring or star forms. The filaments are slender of varying lengths and show branching. Multiplication is by binary fission, budding or chain of beads produced. A distinctive feature seen in some species is a bulbons enlargement with a differentiated tip structure, by means of which the organisms get attached to suitable host cells carrying neuraminic acid receptors. They may be responsible for the hemadsorption shown by some species. They do not possess spores, flagella or fimbria. Some species exhibit a gliding motility. Mycoplasmas are Gram negative, but better stained by Giemsa stain. The cells are bounded by a soft trilaminar unit membrane containing sterols. Because of their plasticity, they can pass through filters and often mistaken for viruses.