Permanent stage
A permanent stage describes the formation of spores or cysts , usually to survive periods of drought. Such stages are often formed by unicellular organisms, but some multicellular organisms ( Metazoa ) also develop permanent stages.
On the one hand, the formation of endospores can take place, a form of persistence that is formed within an organism or cell, which distinguishes them from exospores . It protects the organism against dehydration, sound vibrations, UV radiation, chemical influences and heat.
An exospore (or ectospore) is a form of spore that is usually used to multiply bacteria or fungi and, unlike endospores, has no spore shell . Because of its low water content and the almost completely stopped metabolism , it is usually even more resistant to dehydration, sound vibrations, UV radiation, chemical influences and heat. Some exospores even show a certain tolerance to ionizing radiation .
Intact spores can survive for decades (according to some sources even centuries) without losing any significant functionality.
Another form of persistence is the cyst. Various lower plants and animals form capsule-like shells when living conditions are unfavorable. These very robust forms of rest can survive for several years, only to revert to normal life when the conditions are better.
Perennial eggs serve as a permanent stage for many lower cancers.
swell
- Brock, Mikrobiologie, Spektrum Akademischer Verlag, Heidelberg & Berlin, 2nd corrected edition 2003.
Individual evidence
- ^ Winfried Lampert, Ulrich Sommer: Limnoökologie . Georg Thieme Verlag, 1999, p. 66-67, 208, 318 .