Trichodesmium

Trichodesmium

Taxobox
color = lightgrey
name = "Trichodesmium"
regnum = Bacteria
divisio = Cyanobacteria
ordo = Oscillatoriales
genus = "Trichodesmium"
subdivision_ranks = Species
subdivision = "T. contortum" "T. erythraeum" "T. hildebrandtii" "T. tenue" "T. thiebautii" "Trichodesmium", also called sea sawdust, is a genus of filamentous cyanobacteria. They are found in nutrient poor tropical and subtropical ocean waters (particularly around Australia, where they were first described by Captain Cook). "Trichodesmium" fixes atmospheric nitrogen into ammonium, usable also for other organisms. While far from the only nitrogen fixing bacteria, they are among the most important of the marine varieties, and are being extensively studied for their role in nutrient cycling in the ocean. Unlike other nitrogen fixing bacteria, "Trichodesmium" does not have heterocysts, nor any other specialised cells for this task. Furthermore, nitrogen fixation peaks at mid-day, i.e. occurs during the same time as photosynthesis. Inhibitor studies even revealed that photosystem II activity is essential for nitrogen fixation in this organism. All this may seem contradictory at first glance, because the enzyme responsible for nitrogen fixation, nitrogenase, is irreversibly inhibited by oxygen. However, "Trichodesmium" utilises photosynthesis for nitrogen fixation by carrying out the Mehler reaction, during which the oxygen produced by PSII is reduced again after PSI. This regulation of photosynthesis for nitrogen fixation involves rapidly reversible coupling of their light-harvesting antenna, the phycobilisomes, with PSI and PSII. "Trichodesmium" forms blooms and provides substrate for many small oceanic organisms (bacteria, diatoms, dinoflagellates, protozoa, and copepods).

References

Kana TM (1993) Rapid oxygen cycling in "Trichodesmium thiebautii". Limnol Oceanogr 38: 18-24

Berman-Frank I, Lundgren P, Chen Yi-B, Küpper H, Kolber Z, Bergman B, Falkowski P (2001) Segregation of nitrogen fixation and oxygenic photosynthesis in the marine cyanobacterium "Trichodesmium". Science 294, 1534-1537

Küpper H, Ferimazova N, Šetlík I, Berman-Frank I (2004) Traffic lights in "Trichodesmium": regulation of photosynthesis for nitrogen fixation studied by chlorophyll fluorescence kinetic microscopy. Plant Physiology 135(4), 2120-2133

External links

* [http://charles-darwin.classic-literature.co.uk/the-voyage-of-the-beagle/ebook-page-08.asp Charles Darwin's description of sailing through a "Trichodesmium" bloom]

* [http://research.myfwc.com/features/view_article.asp?id=22896 Trichodesmium in Florida — 2004] , Florida Fish and Wildlife Conservation Commission [http://research.myfwc.com/ Fish and Wildlife Research Institute]


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  • trichodesmium — trich·o·des·mi·um …   English syllables

  • trichodesmium — /trɪkoʊˈdɛzmiəm/ (say trikoh dezmeeuhm) noun a nitrogen fixing bacterium occurring in the ocean in large colonies causing brown blooms; sea sawdust. {Greek trichoma hair + desmos bond, from the resemblance of the colonies to matted hair} …  

  • genus Trichodesmium — noun a genus of blue green algae • Hypernyms: ↑bacteria genus • Member Holonyms: ↑Oscillatoriaceae, ↑family Oscillatoriaceae • Member Meronyms: ↑trichodesmium …   Useful english dictionary

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