Mycoplasma

•Mycoplasmas are the smallest known prokaryotes without cell wall

•Due to lack of cell wall the cells are pleomorphic occuring in different shapes-sperical, ovoid and filamentous

•The plasticity of cells allows them to pass through bacteriological filters.

•The mycoplasmas were first studied by Nocard and Roux.

•Characters of Mycoplasmas

•These are common in animals (cattle, sheep, goats, dogs, rats, mice) and also humans. They are associated with rheumatic arthritis diseases, infections of mammary glands, respiratory tract and urinogenital system.

•Some members occur as saprobes in the soil, decaying organic matter and in the human oral cavity.

•Mycoplasma-like  organisms (MPLOs) cause plant diseases such as sandal spike, mulberry dwarf, grassy shoot of sugar cane and potato witches broom

•The cells are devoid of cell walls and consists of only a plamsmamembrane.They vary in size from  300 nm to about 0.2 micrometer in diameter.

•These are resistant to antibiotics like penicillin that act on cell walls but inhibited by tetracyclines and similar antibiotics that act on membrane pathways.

•Cells are highly pleomorphic, form varying with culture conditions.Under different conditions they appear as small coccoid bodies, ring forms and fine filaments, some of which are branched.

•Both DNA and RNA are present

•Cells are usually non motile, but some show  gliding movement in liquid surfaces.

•They are gram –ve .Most species require sterols and fatty acids inn their growth media for growth.

•Most species form colonies that have a characterstic of fried egg appearance.

•Mycoplasma hominis causes pleuroneumonia, inflammation of genitalis, non specific urethritis etc.,

•Mycoplasma pnuemoniae causes the disease primary a typical pneumonia, haemorrhagic laryngitis and vesicular inflammation of tympanum membrane.

•In plants they cause little leaf of brinjal, Bunchy top of papaya etc.,

•Mycoplasma mycoides causes pleuroneumonia in cattle.