Trichodesmium (McMahon)

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Kingdom: Bacteria Domain: Phylum: Cyanobacteria Class: Order: Oscillatorialis Family: Genus: Trichodesmium


Trichodesmium thiebautii [1F]

Trichodesmium is a filamentous genus of cyanobacteria found in the open ocean. They can grow in solitude but are often found in filamentous colonies (called trichomes) that are a few millimeters in length. Trichodesmium form huge blooms in the open ocean that can extend for hundreds of kilometers. It thrives in nutrient-poor environments and is known for aerobically fixing atmospheric nitrogen.

This species was first described off the coast of Australia by Captain Cook in the 18th century. It is most related genetically to other marine cyanobacteria, including Synechococcus, Crocosphaera, and Anabaena. The species that has been completely sequenced, Trichodesmium erythraeum, has 7750108 base pairs and a 34% G-C content. It is available in pure culture (although it is difficult to grow) and is a photoautotroph (nitrogen fixing, photosynthetic bacteria).

Ecology and Significance

Trichodesmium is the main contributor of new nitrogen to the euphotic zone of marine waters, adding up to 30 mg/m2/day of ammonium to the ocean. It is widespread in tropical and subtropical oceans and is also a contributor of CO2 fixation through photosynthesis. It is often found in nutrient-poor (oligotrophic) environments near the surface and is often visible from above the water as huge, filamentous colonies. Blooms often occur in the summer in warm areas with low nitrogen.

Trichocesmium, like other cyanobacteria, produces neurotoxins that can be harmful to animals such as fish and oysters in the ocean such as fish at high enough levels. They have also been known to cause illness to humans both directly through contact and indirectly through consumption of animals laced with Trichodesmium neurotoxin. These large, harmful blooms are expected to increase in the future as nutrient (phosphorus) loading and global warming from human activity create a more optimal environment for cyanobacteria.

Genome Structure



[1] Golyshin, Peter N. “Genome Sequence Completed of Alcanivorax borkumensis, a Hydrocarbon-degrading Bacterium That Plays a Global Role in Oil Removal from Marine Systems.” 3 (2003): 215-20. Print.



[1] [2F] [2] [3F] [3] [4F] [4] [5F] [Original Figure. Author: Pawan Dhaliwal] [6F] 

[7F] [5]


Page authored by Rebecca LeBeau, student of Prof. Katherine Mcmahon at University of Wisconsin - Madison.