Alexandrium fundyense NEU2011: Difference between revisions

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[[Image:cellstructure1.jpg|thumb|left|alt=Photo from Jane Lewis <i>Alexandrium fundyense</i>.|Cell structures of ''<i>Alexandrium fundyense</i>'' cells in log phase. C= chloroplasts. S= starch grains. Arrows= bacteria.  (9).]]
[[Image:cellstructure1.jpg|thumb|left|alt=Photo from Jane Lewis <i>Alexandrium fundyense</i>.|Cell structures of ''<i>Alexandrium fundyense</i>'' cells in log phase. C= chloroplasts. S= starch grains. Arrows= bacteria.  (9).]]
[[Image:a.fundyenselifecycle.jpg|thumb|center|alt=Photo from Oceanography <i>Alexandrium fundyense</i>.|Life cycle of ''<i>Alexandrium fundyense</i>''. Both asexual (binary fission) and sexual reproduction (gamete fusion) are shown(10).]]
[[Image:a.fundyenselifecycle.jpg|thumb|center|alt=Photo from Oceanography <i>Alexandrium fundyense</i>.|Life cycle of ''<i>Alexandrium fundyense</i>''. Both asexual (binary fission) and sexual reproduction (gamete fusion) are shown(10).]]
[[Image:cellstructure2.jpg|thumb|alt=Photo from Jane Lewis <i>Alexandrium fundyense</i>.|Cell structures of ''<i>Alexandrium fundyense</i>''. M= mitochondria. F= food vacuole. Arrows= bacteria(9).]]
[[Image:cellstructure2.jpg|thumb|right|alt=Photo from Jane Lewis <i>Alexandrium fundyense</i>.|Cell structures of ''<i>Alexandrium fundyense</i>''. M= mitochondria. F= food vacuole. Arrows= bacteria(9).]]


===<u>Metabolism</u>===
===<u>Metabolism</u>===

Revision as of 18:43, 31 March 2011

Drawing of Alexandrium fundyense.
Cartoon drawing of Alexandrium fundyense (1).




Classification

Photo by Jason Alexandrium fundyense.
Cluster of Alexandrium fundyense (7).

Eukaryota (Domain)

Protozoa (Kingdom)

Dinoflagellata (Phylum)

Dinophyceae (Class)

Peridiniphycidae (Subclass)

Gonyaulacales (Order)

Gonyaulacaceae (Family)

Alexandrium (Genus) (1)


Description and significance

Alexandrium fundyense is a photosynthetic marine dinoflagellate that lives in the upper water column (photic-zone) of coastal waters (2). It is a part of the Thecate group or “armored dinoflagellates”, meaning it has thecal plates made of cellulose) surrounding the cell like armor (2). Like all dinoflagellates it has two flagella. One is the transverse flagellum, which wraps around the cell in a groove in the thecal plates and provides propulsion and a spinning motion. The other is a longitudinal flagellum that extends from the posterior end of the cell and acts as a steering system (2). Alexandrium fundyense is a very significant microbe on the eastern seaboard as it causes yearly Red tide events when there are high nutrients and low grazing pressures in the coastal waters (3). These large coastal blooms of A. fundyense cause problems because they produce a neuromuscular toxin called a saxitoxin, which accumulates up the food chain and concentrates in the tissue of filter-feeding shellfish and fish. The consumption of these toxic shellfish by humans can lead to Paralytic Shellfish Poisoning (PSP), which can be fatal (3). It also leads to the shut down of coastal fishing in affected areas, which has large economic consequences for the fishing industry in those areas (3).

Genome Structure

SEM photo Alexandrium fundyense.
Alexandrium fundyense via SEM microscopy (8). The cingulum can clearly be seen around the cell.

The complete genome of Alexandrium fundyense has been sequenced (4) and it has been found that A. fundyense has highly redundant nuclear genes (5). DNA sequencing is the most frequently used and most reliable method for distinguishing different species of the Alexandrium genus. There is evidence of very little transcriptional regulation (5) and the mitochondrial mRNA is subject to editing (6).

Cell structure and metabolism

Cell Structure

A. fundyense have a longitudinal flagella protruding from the sulcus on the ventral surface. Transverse flagella wrap around the cell along the cingulum, producing a propelling force and giving the cell a whirling motion characteristic of most dinoflagellates (11). Despite these flagella, the species has weak mobility and thus lives in the upper water column as plankton (2). The cell walls are divided into thick cellulose plates bound together by sutures, which are collectively called theca, and give the dinoflagellate an “armored” appearance (11). The usual cellular organelles such as smooth and rough endoplasmic reticulum, Golgi apparatus, mitochondria and food vacuoles are intact. Unique features include the dinokaryon, in which the chromosomes are condensed inside the nucleus, which is considered an advanced structure (12). Bacteria are closely associated with dinoflagellates during most phases of life, including both vegetative phases and sexual reproduction. Bacteria can be found both on the membrane surfaces as well as within the cell itself (9). A. fundyense reproduces by both asexual and sexual reproduction. First, cysts are produced that become swimming cells that germinate and divide under suitable conditions. When conditions become less favorable, the cells stop growing in order to form gametes which then combine to form zygotes and eventually cysts (10). The accumulation of these swimming cells in marine environments is what causes shellfish toxicity in seafood.

Photo from Jane Lewis Alexandrium fundyense.
Cell structures of Alexandrium fundyense cells in log phase. C= chloroplasts. S= starch grains. Arrows= bacteria. (9).
Photo from Oceanography Alexandrium fundyense.
Life cycle of Alexandrium fundyense. Both asexual (binary fission) and sexual reproduction (gamete fusion) are shown(10).
Photo from Jane Lewis Alexandrium fundyense.
Cell structures of Alexandrium fundyense. M= mitochondria. F= food vacuole. Arrows= bacteria(9).

Metabolism

As an autotroph, specifically a photosynthetic organism, A. fundyense uses light as its main energy source to create food. This species is classified as a phytoplankton and contains chloroplasts. Dinoflagellate chloroplasts each have three membranes, furthering the idea that these chloroplasts are products of endosymbiosis of engulfed algae (12). In the early stages of growth, cells produce a neuromuscular toxin called saxitoxin (STX) that is responsible for paralytic shellfish poisoning (2).

Ecology

Pathology

Current Research

Summery of Keafer et al. 2009. Toxic Alexandrium fundyense blooms in the Nauset Marsh system on Cape Cod Massachusetts (13)

Keafer et al. (13) studied the bloom dynamics in the Nauset Marsh system on Cape Cod, MA, USA which experiences blooms of the dinoflagellate Alexandrium fundyense every spring. This study started in 2008 when the researchers looked at the concentration of cysts within the sediments of 73 sites in the marsh. In the following spring they took weekly water samples from inside the marsh and looked at the concentration of A. fundyense in the water over the course of the bloom. Peaks in algal concentrations were seen in sites with the highest cyst concentrations and the bloom in the Nauset Marsh peaked before the offshore Gulf of Maine bloom had started. They also saw the bloom was worst (highest cell concentrations) in areas of the marsh with minimal flushing (Salt and Mill pond) while the bloom was somewhat alleviated in areas of high flushing (the central marsh and inlet). This indicates that within the Nauset Marsh, especially in areas with low levels of flushing the bloom is self sustaining and is not driven by the large offshore blooms. This is an ongoing project that will look further at the different dynamics that affect the annual blooms in the Nauset Marsh.


Flow chart summarizing the effects of Alexandrium fundyense on the blue mussel, Mytilus edulis (14)
Graph showing the effects of Alexandrium fundyense consumption on disease in the blue mussel, Mytilus edulis (14)

Summery of Galimany et al. 2008. Experimental exposure of the blue mussel (Mytilus edulis, L.) to the toxic dinoflagellate Alexandrium fundyense (14)

Galimany et al. (14) investigated the effects of Alexandrium fundyense on the blue mussel (Mytulus edulis). They did this by exposing clusters of mussels to A. fundyense for up to 9 days and monitoring the growth rate, hemocyte levels, fecal pellet and pseudofeces content, and parasite levels of the mussels. They also performed mouse assays to determine the level of toxicity in the mussels. They looked at these different measures for mussel health on day 0, 3, 7 , and 9 during the treatment and days 12 and 15 during the recovery periods. All of the mouse assays were inconclusive showing that the level of saxitoxin in the mussels was not high enough to be detectable by the methods used to by resource managers in the field and would not cause harmful symptoms in humans. There were still marked effects of A. fundyense on the mussels themselves. Mussels exposed to A. fundyense were shown to have a decreased growth rate and lower hemocyte levels. They found that mussels exposed to A. fundyense showed lower levels of hemocytes in their tissue while showing higher levels in their feces and pseudofeces. After 9 days of exposure to A. fundyense mussels showed higher levels of parasite infection generally by trematodes which are thought to have opportunistically taken advantage of the mussel's compromised immune system. After the removal of the A. fundyense all mussels recovered completely from the effects after 6 days.

Cool Fact

References

(1) Alexandrium fundyense Balech (1996-2001). Retrieved 20 February 2011 from Algaebase official site http://www.algaebase.org/search/species/detail/?species_id=40289.

(2) http://www.eol.org/pages/910093

(3) Bruce A. Keafer, James H. Churchill, Dennis J. McGillicuddy, Donald M. Anderson. 2005. Bloom development and transport of toxic Alexandrium fundyense populations within a coastal plume in the Gulf of Maine. Deep-Sea Research Part II. 52: 2674-2697

(4) http://www.boldsystems.org/views/taxbrowser.php?taxid=317138 Accessed 2/20/2011

(5) Erdner, D. L. and D. M. Anderson. 2006. Global transcriptional profiling of the toxic dinoflagellate Alexandrium fundyense using Massively Parallel Signature Sequencing. BMC genomics 7:88

(6) Zhang, H. and S. Lin. 2005. Mitochondrial cytochrome b mRNA editing in dinoflagellates: possible ecological and evolutionary associations? Journal of Eukaryotic Microbiology 52:538-545.

(7) Courtesy of Jason Selwyn.

(8) Mooney-Seus, Maggie. 2009. National Oceanographic and Atmospheric Administration (NOAA). NOAA Approves State Spending Plan for Federal Red Tide Disaster Aid. Accessed 22 February 2011. http://www.nefsc.noaa.gov/press_release/2009/MediaAdv/MA0905/Alexandrium%20spp.jpg.

(9) Lewis, Jane, Gay Kennaway, Susana Franca and Esla Alverca. Bacterium-dinoflagellate interactions: investigative microscopy of Alexandrium spp. (Gonyaulacales, Dinophyceae). 2001. Phycologia. 40(3): 280-285.

(10) L. C. Backer and D. J. McGillicuddy. Harmful Algal Blooms: at the interface between coastal oceanography and human health. 2006. Oceanography. 19(2): 94–106.

(11) MacRae, Andrew. “Dinoflagellates” Palynology. University of Calgary: Department of Geology and Geophysics. <http://www.geo.ucalgary.ca/~macrae/palynology/dinoflagellates/dinoflagellates.html>.

(12) Dinoflagellate. New World Encyclopedia. 23 August 2008. <http://www.newworldencyclopedia.org/entry/Dinoflagellate>.

(13) Keafer, B. A., B. G. Crespo, K. Norton, J. Selwyn, M. Richlen, D. Farber, H. Lind, M. Hickey, T. O'Neil, and D. M. Anderson. 2009. Toxic Alexandrium fundyense blooms in the Nauset Marsh system on Cape Cod Massachusetts. Fifth Symposium on Harmful Algae in the U.S., Ocean Shores, Washington.

(14) Galimany, E., I. Sunila, H. Hégaret, M. Ramón, and G. H. Wikfors. 2008. Experimental exposure of the blue mussel (Mytilus edulis, L.) to the toxic dinoflagellate Alexandrium fundyense: Histopathology, immune responses, and recovery. Harmful algae 7:702-711.