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Team:Minnesota/ProjectTimeBomb
From 2008.igem.org
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Overall project
The process of in situ Bioremediation would be aided through the use of microorganisms that undergo synchronized cell death. Bioremediation relies on microorganisms' enzymatic pathways to break down hazard chemicals in the environment. However, in order to protect the environment from the release of a foreign population of microorganisms, most contaminants have to be excavated or pumped off-site (ex situ) before the proper microogranisms can be applied. The transport of contaminants makes ex situ bioremediation just as expensive as the burn or bury methods of waste removal. Although if the remediating microorganisms were engineered to clean up until the contaminant was removed, and then collectively die, their impact on native populations could be reduced significantly. To achieve synchronized apoptosis after a set number of generations we first had be able to link cell divisions to a predictable buildup of toxin. This required that the a promoter regulated by cell cycle state would have to be cloned out of E. coli.
The protein DnaA is required for cell replication and the cell cycle dependent repression of mioC. Replication of the bacterial chromosome is triggered through the highly conserved binding of DnaA proteins to a region called the oriC. There are several binding sites for DnaA within, upstream, and downstream of the oriC region which induce replication during mitosis. (1) However, four of these DnaA binding sites are also found in the promoter of the gene mioC. (2) (3) In this case, the binding of DnaA has been found to repress the promoter of mioC during mitosis. (3)
Project Detail
First Proof of Concept: Linking Cell Division To a Reporter
The cell cycle dependent expression of the mioC promoter should accurately count cell division when linked to a reporter. The insertion of mioC into a plasmid upstream from a tetracycline repressor (tetR) will allow for tetR mediated repression of the tetracycline promoter in the bottom construct (Figure 1). Therefore, the expression of GFP from the bottom construct should only occur during cell division. To visualize each cell division a short pulse of GFP, confered by the LVA tag, was thought a preferable means to reduce background noise. The initial synchronization of cell division (1st generation cells) will be done by alternating media conditions.
Second Proof of Concept: Incorporation of Antitoxin (MazE) and Antitoxin (MazF) into a Feedback Loop
