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Anabaena

(Genus)

Overview

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Anabaena is a of filamentous cyanobacteria, or blue-green algae, found as plankton. It is known for its nitrogen fixing abilities, and they form symbiotic relationships with certain plants, such as the mosquito fern. They are one of four genera of cyanobacteria that produce neurotoxins, which are harmful to local wildlife, as well as farm animals and pets.

A DNA sequencing project was undertaken in 1999, which mapped the complete genome of Anabaena, which is 7.2 million base pairs long. The study focused on heterocysts, which convert nitrogen into ammonia. Certain species of Anabaena have been used on rice paddy fields, proving to be an effective natural fertilizer.

Species

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Nitrogen Fixation By anabaena

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Under nitrogen-limiting conditions, vegetative cells differentiate into heterocysts at semi-regular intervals alongthe filaments. Heterocysts are cells that are terminally specialized for nitrogen fixation. The interior of these cells is microoxic as a result of increased respiration, inactivation of O2-producing photosystem (PS) II, and formation of a thickened envelope outside of the cell wall. Nitrogenase, sequestered within these cells, transforms dinitrogen into ammonium at the expense of ATP and reductant—both generated by carbohydrate metabolism, a process that is supplemented, in the light, by the activity of PS I. Carbohydrate, probably in the form of sucrose, is synthesized in vegetative cells and moves into heterocysts. In return, nitrogen fixed in heterocysts moves into the vegetative cells, at least in part in the form of amino acids.[1]

Taxonomy

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The Genus Anabaena is further organized into finer groupings including:

References

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  1. ^ Herrero A and Flores E (editor). (2008). The Cyanobacteria: Molecular Biology, Genomics and Evolution, 1st ed., Caister Academic Press. ISBN 978-1-904455-15-8 . 

Sources

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Last Revised: November 20, 2008