Cyst (biology)

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Cyst sac in Triops longicaudatus

A cyst ( ancient Greek κύστις kýstis , German 'bladder' ), Germanized cyst , is the permanent form of certain single-celled organisms , plants and animals that form under unfavorable living conditions such as drought or lack of nutrients. They can also be used for reproduction and spread. Protozoa in particular, which live in dry waters, have the ability to form cysts, or encysts.

The cysts of certain bacteria , e.g. B. Azotobacter , arise through transformation of the living cell and have a thickened cell wall . Several cells can also be surrounded by a solid cover, as is the case with the myxobacteria or the tadpole shrimp known as Triops . Cyst-forming protists usually excrete a covering that protects against the influences of the environment. Polyhydroxybutyric acid (PHB) is often stored in the cyst as a storage substance .

Cysts withstand dryness, mechanical stress and radiation, but not extreme heat.

See also


  • Lexicon of Biology. 4th volume, Spektrum Akademischer Verlag, Heidelberg, 2000 ISBN 3-8274-0329-4