Anabaena

Anabaena sp.

Anabaena is a genus of filamentous cyanobacteria or " blue-green algae ."

Features

Anabaena forms unbranched, einzellreihige threads of blue-green, gray-green to yellow- green color. The individual cells are spherical to cylindrical. At the cell boundaries, the threads are always constricted to a string of pearls. The threads may be surrounded by a jelly.

The growth is by cell division within the thread. Reproduction is asexually by fragmentation of the filaments. Unfavorable periods are survived as permanent stages, as elongated oval akinetes.

In the thread often are colorless, thick-walled, slightly larger cells, the heterocysts. Heterocysts these are able to fix nitrogen from the air and reduce it to ammonium.

Occurrence

Most species live in fresh water, a few also occur in sea water. The species live in the plankton at the base ( benthic ) and to water plants in small and large, nutrient- rich waters. Also in acidic bog waters they occur. You can ascend and descend by forming and dismantling of gas vacuoles in the water.

Ecology

Different Anabaena species form symbioses with other plants, for example with the Algenfarn ( Azolla ), and supply them with nitrogen compounds.

Some species can form neurotoxins: anatoxin (1 - ( 8 -amino- cyclooct -1-enyl ) ethanone ), can trigger the cattle dying.

Some species of Anabaena are used in rice fields as an effective natural fertilizer.

Genetics

A DNA sequencing project was carried out in 1999, in which the complete genome has been mapped from Anabaena variabilis, which is 7.2 million base pairs long. The study continued its focus on the heterocysts.

Species

There are around 100 known species. The most common central European species are:

  • Anabaena circinalis standing in the plankton waters can produce water flowers.
  • Anabaena flos -aquae in ponds and lakes, forming water blooms in the form of greasy slime layers on the water surface.
  • Anabaena spiroides, common in lakes and ponds.
  • Anabaena cylindrica, on aquatic plants and bottom of ponds and lakes.
  • Anabaena sphaerica, in pools, ponds, bog waters.

Documents

  • K.-H. Linne von Berg, K. Hoef -Emden, B. Marin, M. Melkonian: The Cosmos algae leader. The main freshwater algae under the microscope. Kosmos, Stuttgart 2004. ISBN 3-440-09719-6
  • H. Streble, D. Krauter: The Life in the Water. Microflora and microfauna of fresh water. Kosmos, Stuttgart, 2006. ISBN 978-3-440-10807-9
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