Karenia brevis
A Microbial Biorealm page on the genus Karenia brevis
Classification
Higher order taxa
cellular organisms; Eukaryota; Alveolata; Dinophyceae; Gymnodiniales; Gymnodiniaceae; Karenia
Species
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NCBI: Taxonomy |
Karenia brevis
Description and significance
Karenia brevis is an aquatic marine dinoflagellate in the phylum Protozoa and super group Alveolates. This Protist is of microscopic proportion usually between 20 and 40 μm in size. These unicellular, flagellated, photosynthetic organisms have cellulose plates (theca) that surround the cell. The plates are secreted by Alveoli (membrane bound vesicles just below the cell membrane) hence their super group name and create the outer boundary for the cell. Located on the cellulose plates are two grooves called the transverse and longitudinal groove. K. brevis has two flagella and these grooves are where the flagellum are attached. One flagellum raps around the body of the cell in the transverse groove, while the other extends from the body of the cell on the longitudinal groove. Using their flagella for locomotion they are able to have some source of propelling movement in the water column.
These dinoflagellates are usually found in abundant masses near coastal waters in warmer conditions. Though they are found in several other places in the vast ocean water, this area is of particular concern. K. brevis has an active involvement in harmful algal or “red tides” off the coasts of Florida and California. This is a problem due to the potent neurotoxins called brevetoxin’s that these cells create, and when there is an abundance or bloom of these organisms’ resources become limited. There is more competition for space and sunlight, as these organisms die from lack of resources they release their neurotoxins. The neutoxin’s cause all sorts of environmental and economic problems such as massive fish kills, fisheries crashing, paralytic shellfish poisoning, etc. This is a dangerous time for humans to eat seafood and can cause some major health problems and diseases.
Genome structure
K. brevis has a large haploid genore consisting of about 1 x 10 ^11 bp. It consists of permanently condensed chromatin which lacks nucleosomes. The condensed chromosomes have a characteristic banding pattern with stacked disks that form a continuous left-handed twist along the longitudinal axis. The disks end in less tightly packed loops of DNA that contain actively transcribed DNA. The K. brevis genome has not yet been sequenced due to its large size.
Cell structure and metabolism
Interesting features of cell structure; how it gains energy; what important molecules it produces.
Ecology
Karenia brevis is a dinoflagellate which is found in the Gulf of Mexico, along the coasts of Texas, Louisiana, Florida, and North Carolina. They are photosynthetic and perform much of the area's primary production. Because they require light, they cannot live at depths below 200 feet. Karenia brevis has a temperature range between 4 and 33 degrees Celsius. However, their optimal range is 22-28 degrees Celsius. In addition, this organism can live in a salinity of between 25-45 ppt. While they are not symbiotic organisms, they do provide a great deal of oxygen to the environment with one estimate stating they perform around 20% of the primary production in the West Florida Shelf during blooms or red tides. While researchers are unsure of the conditions necessary for these red tides, several hypotheses revolve around the species' requirements for metals.
Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Current Research
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Cool Factor
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References
http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi
http://www.cdc.gov/nceh/hsb/hab/default.htm
Van Dolah, F.M., et al., The Florida red tide dinoflagellate Karenia brevis: New insights into cellular and molecular processes underlying bloom dynamics. Harmful Algae (2009), doi:10.1016/j.hal.2008.11.004 http://m.plankt.oxfordjournals.org/content/29/3/301.full
Edited by student of Iris Keren
