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Updated: Feb 14


  • The mycoplasmas are the simplest self-replicating prokaryotes.

  • Mycoplasma is considered as the smallest known cell of about 0.1 micron (µm) in diameter.

  • First discovered by Pasteur in 1843, as a causal agent of pleuropneu­monia of cattle and called PPLO.

  • Later, in 1898 Nocard and Roux, successful obtained pure culture of these microorganisms in media.

  • Mycoplasmas are commonly found in soil, hot spring, sewage water and also in humans, plants and animals.


  • On the basis of their nutritional require­ment.

  • 1. Mycoplasma: They need cholesterol for their growth.

  • 2. Acholeplasma: They do not need choles­terol for their growth but will incorporate it into the membrane if it gets in the medium.

  • 3. Thermoplasma: They do not require cholesterol for their growth.


  • The mycoplasma cell contains a plasma membrane, ribosomes, RNA, proteins and ds circular DNA molecule.

  • The cell is devoid of cell wall, highly pleomorphic and thus are called joker of microbiology.

  • Taxonomically, the lack of a cell wall is used to separate mycoplasmas from other bacteria.

  • They may be ring-like, granular, coccoid, pear-shaped, fila­mentous, etc.

  • The colonies of mycoplasma have a characteristic round form with a thickened centre and a delicate periphery like a fried egg.

  • They reproduce by vegetative means i.e., by binary fission and budding.


  • Mycoplasmas are widespread in nature as parasites of humans, mammals, reptiles, fish, arthropods, and plants.

  • Plant Diseases:

  • Little leaf disease of brinjal,

  • Bunchy top of papaya,

  • Big bud of tomato,

  • § Witches broom of legumes,

  • § Yellow dwarf of tobacco,

  • § Strip disease of sugarcane,

  • § Clover dwarf,

  • § Cotton virescence.

  • Human diseases:

  • § Pleuropneumonia is caused by Mycoplasma hominis

  • § Primary a typical pneumonia is caused by Mycoplasma pneumonia

  • § Mycoplasma hominis and Mycoplasma fermentants cause infertility in man.

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