Mosquitoes are responsible of spreading illnesses such as dengue, malaria and Japanese encephalitis. However, current methods of using chemical pesticides are non-specific in target. Adding further to the problem, over 90 percent of insecticides spread goes to waste as they fail to kill the targets and are subsequently absorbed by the environment instead. Continuation of this kind of practice may trigger ecological and environmental crisis in the future, therefore, a new approach is needed. To rid mosquitoes in an efficient and environmental-friendly way, we have come up with the Mosquito Intelligent Terminator.

The Mosquito Intelligent Terminator is a strain of E. coli that secretes crystal proteins, targetting the wrigglers, larvae of mosquitoes. These crystal proteins from Bacillus thuringiensis are toxic to certain types of mosquitoes only, addressing the problem of specificity. Next, in order to make an environmentally friendly insecticide our design also incorporates a genetic circuit controlling the expression level of cry protein and the population size of E. coli, thus a surplus will never exist as population is self-maintained in this system.

In summary, the Mosquito Intelligent Terminator is designed and optimized to be an ecological and environmental friendly mosquito pesticide.

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Crystal proteins, abbreviated cry proteins, are coded by the cry genes from Bacillus thuringiensis. Each kind of cry protein is highly specific and has different insecticidal toxin to different species of insects.

In our project, we cloned the cry gene from B. thuringiensis subsp. Israelensis HD522. It synthesizes an irregularly shaped parasporal crystal that is highly toxic to certain dipteran larvae, such as Aedes, Culex and Anopheles larvae. Bti parasporal crystalline inclusions contain four major polypeptides with molecular masses of 135, 125, 68 and 28 kDa, referred to as CryIVB, CryIVA, CryIVD, and CytA, respectively, according to the classification designed by Höfte and Whiteley (1989), and belonging to groups Cry4A, Cry4B, Cry11A, and Cyt1A of the new proposed classification (D Dean, personal communication).

Upon ingestion by susceptible insect larvae, the crystal inclusions are solubilized in the alkaline condition of midgut, and the crystal proteins are proteolytically processed by gut proteases into the activated toxin. The toxins activated by gut proteases bind to specific binding sites on the brush border membranes of insect midgut epithelial cells. The conformational change in the toxin molecules triggers the insertion of their pore-forming domain into the membrane. Finally, colloid-osmotic swelling and lysis of the cell result in the death of the larvae.

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We plan to spread mosquito intelligent terminator in areas where both wrigglers and E. coli thrive, such as areas with still water. By doing so, the E. coli will work as the "terminator" to the mosquito population. This technology is not limited to mosquito's only, with more than one hundred crystal proteins found and characterized, we can create different kinds of E. coli carrying different cry genes to broaden the pesticidal range.

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