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Project Description

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Research Problem

The Chesapeake Bay is Maryland’s most important natural landmark, housing a diverse ecosystem of plants, animals, and microbes. The Bay is also an economic boon to the state, as it is a major source of seafood as well as a popular tourist destination along the eastern seaboard. Over time, however, the Bay has been beset by environmental problems, which have steadily decreased water quality and economic output. For instance, the local oyster population in the bay has dropped to less than twenty percent of its original numbers (“Gem of”, 2008). Since oysters serve as natural water filters, this oyster deficiency has exacerbated the recent decrease in water clarity as well as the increase in chemical pollutant levels, both severe concerns for the Chesapeake Bay.

What is Causing this Decline?

A major biological reason for this decline has been the spread of an oyster pathogen called Perkinsus marinus, a unicellular protist also known as “Dermo” (Espinosa, Winnicki, & Allam, 2013). Dermo has been shown to infest oysters by entering their hemocyte cells, a type of immune cell, via induced phagocytosis. When inside the hemocyte, the parasite is capable of resisting the reactive oxygen species generated by the oyster immune system. This leads to proliferation inside the oyster hemocyte, eventually lysing the host cell and releasing more Dermo to restart the cycle (Allam et. al., 2013). This process leads to massive tissue damage and the eventual death of the oyster.

Our Research Interests

The mechanism of the initial induced phagocytosis involves binding between Dermo surface carbohydrate residues and CvGal1, a carbohydrate binding receptor used for food and pathogen recognition that is found on oyster hemocytes. This receptor traps the parasite and initiates phagocytosis (Tasumi & Vasta, 2007). Our initial goal is to create a recombinant E. coli expressing CvGal1 that would be an effective real-time biosensor for Dermo presence.

Our Research Plan

Binding of Dermo to this receptor would be coupled with the overexpression by E. coli of green fluorescent protein, thus creating a visual marker for the parasite. This would be generally accomplished via genetic cloning and bacterial transformation.

Although laboratory methods for Dermo detection using PCR exist, they are currently not capable of detecting the disease in real time. In the time needed to conduct a laboratory test, Dermo could have easily spread to many more oysters or have moved to a new location. This biosensor would help to accurately pinpoint Dermo location and infestation levels in water and oysters in real time. If we can pinpoint the location of Dermo, as elucidated in this research proposal, then we can ultimately develop a biosensor that can react to Dermo with targeted destruction.

Our Goals

The long term goal of our research team is to create a bacterial biosensor that not only detects Dermo but initiates its own “defense” response. Preliminary ideas for a response involve the release of antiprotozoal agents or inhibitors of ascorbate peroxidase—one of Dermo’s enzymes used to resist reactive oxygen species (Schott, Pecher, Okafor, & Vasta, 2003). While the health of the Chesapeake Bay oysters largely influences the Bay’s ecosystem, the detrimental effects of Dermo extends to all eastern oysters—the most harvested species of oyster in aquaculture. Our aims reach further than the task of protecting the Chesapeake Bay, we propose a mechanism that would protect all oyster populations along the eastern shore and in oyster farms worldwide from Dermo. This project is expected to last over several years and will be continued by future generations of undergraduate researchers.

Along with our research, we will also conduct various community outreach efforts to spread awareness on the current state of the Chesapeake Bay, as well as ways individuals can help and maintain our greatest natural resource. This will involve the team traveling to schools and community centers throughout the state. We also have a committee dedicated to creating an educational computer game that teaches others about the issues that the Chesapeake Bay currently faces. It is our team’s hope that our research results to be presented at the iGEM jamboree will ultimately have a profound and positive impact on the health of the Chesapeake Bay and oyster populations worldwide.

References

References

Allam, B., Carden, W. E., Ward, J. E., Ralph, G., Winnicki, S., & Espinosa, E. P. (2013). Early

host-pathogen interactions in marine bivalves: Evidence that the alveolate parasite

Perkinsus marinus infects through the oyster mantle during rejection of pseudofeces.

Journal of Invertebrate Pathology , 113(1), 26-34.

Espinosa, E. P., Winnicki, S., & Allam, B. (2013). Early host–pathogen interactions in a marine

bivalve: Crassostrea virginica pallial mucus modulates Perkinsus marinus growth and

virulence. Diseases of Aquatic Organisms, 104(3), 237-247.

"Gem of the Ocean; Oysters." The Economist (US) 20 Dec. 2008: n. pag. Print.

Schott, E. J., Pecher, W. T., Okafor, F., & Vasta, G. R. (2003). The protistan parasite Perkinsus

marinus is resistant to selected reactive oxygen species. Experimental Parasitology,

105 (3-4), 232-240.

Tasumi, S., & Vasta, G. (2007). A galectin of unique domain organization from hemocytes of

the Eastern oyster (Crassostrea virginica) is a receptor for the protistan parasite Perkinsus marinus. Journal of Immunology, 179(5), 3086-98.

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2. Project Details
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