CHE.496/2009/Schedule/Oral presentations of part design/Group 3
Group 3
- Members:
Parts
- Part 1
- Description
A genetic oscillator would be designed that would utilize negative feedback and the quorum sensing mechanism to simultaneously express a gene at a certain time, based on the presence of an inducer. This type of oscillator is driven mainly by two elements: the concentration of a repressor protein and the dynamics of an activator protein forming an inactive complex with the repressor. Either protein would serve as an inducer, so that quorum sensing would be used to sync the output of the bacteria. Since simultaneous activation is threshold based, the period of oscillation could be used to account for the synthesis of the activator and repressor proteins. Eventually, the concentrations would reach a certain threshold and simultaneous gene expression would occur.
- Sources & References
http://ieeexplore.ieee.org/iel5/4290605/4290606/04290624.pdf?arnumber=4290624 http://www.pnas.org/content/99/9/5988.full
- Part 2
- Description
A band pass filter would be constructed that utilizes feedback to regulate the expression of a gene based on input concentrations. An inducer would be used that codes for two genes, and the product of one of these genes would act to suppress the expression of the other gene. The suppressed gene would act on a reporter gene (like GFP) so that expression of this gene would be observed. Once a certain level of expression was reached, based on the concentration of the input inducer, the output would be sufficiently visible, but as the concentration of the input inducer increased, eventually the negative feedback by the suppressor gene would overwhelm the signaling gene and decrease the output. So, it would take a certain level of inducer for any output to be observed, and eventually the negative feedback would suppress the output at a certain (higher) inducer level, so that a band pass filter would be achieved.
- Source & References
Genetic parts to program bacteria link
- Part 3
- Part 4
Part 5
Purpose
To enable qualitative detection of an antibody by E coli. This would be useful for detecting a disease based on antibodies present in a sample.
Description
Competitive binding by an antigen would be used with the quorum sensing mechanism and florescent protein expression to devise a disease detection system. In quorum sensing, transcription of a group of bacteria can be turned on simultaneously when a threshold level of inducer is reached. Bacteria will not recognize their own inducers, so the presence of inducers that induce gene expression must come from other bacteria. Ideally, the GFP promoter would be modified to contain tet operator elements, allowing repression by TetR. Presence of an antibody would promote the expression of the SSK1 transcription factor, which would suppress the TetR repressor, thus activating the GFP operon and promoting expression of GFP. The presence of this inducer would promote other bacteria to express GFP. The antibody would need to be detected, possibly by using a tag protein.
Source & References
- Cell-to-cell signalling in Escherichia coli and Salmonella enterica. Ahmer BM. Mol Microbiol. 2004 May;52(4):933-45. Review.
- Hense BA, Kuttler C, Müller J, Rothballer M, Hartmann A and Kreft JU (2007). "Does efficiency sensing unify diffusion and quorum sensing?". Nature Reviews Microbiology 5: 230–239.
- http://2008.igem.org/Team:University_of_Ottawa/Project (modifing GFP for repression by TetR)
