Nostocales
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Nostocales are a taxonomic order within the class of the Cyanophyceae . The cells always form single-row threads ( filaments ) from one behind the other, never transverse, round or cylindrical cells. The cell threads are always unbranched and surrounded by cylindrical jelly shells . The filaments often form large-area associations up to several centimeters in length.
Almost all genera form larger permanent cells ( hormogonies ) surrounded by thickened cell walls , which also differ from vegetative cells in their oval shape and stored granules made of cyanophycean starch or polyphosphate or polypeptides . In contrast to the filamentous order of the Oscillatoriales, there are no mobile hormogonies.
Many genera form heterocysts for nitrogen fixation , which are distributed at regular intervals over the cell threads. Weak light or a lack of phosphate trigger the formation of spores (akinetes). These large, elongated, oval cells are often close to the heterocysts and can survive decades of drought, cold and lack of food.
The order includes 17 families with around 1430 species. The best known are the genera occurring in freshwater such as Nostoc (family Nostocaceae ) as well as the genus Nodularia (family Aphanizomenonaceae) and the genus Anabena (family Nostocaceae) and the Aphanizomenon flos aquae (family Aphanizomenonaceae), which are found in saltwater, both in Occurs in both fresh and brackish water.
literature
- JLSlonczewski, JWFoster: Mikrobiologie 2nd edition, 2012, Springer Verlag Berlin, Heidelberg, ISBN 978-3-8274-2909-4
- Guiry, MD & Guiry, GM 2017. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. Nostocales ; accessed on September 6, 2017.
