Difference between revisions of "Part:BBa K546546"

Revision as of 20:53, 17 September 2011

The Synchroscillator: A Tunable Synchronized Oscillatory System

--Still under construction--

This BioBrick device yields an oscillating pattern of GFP (with an LVA Tag) expression, in the way described below. It contains two differing hybrid promoters that allows for stabilization of the oscillation.

Usage and Biology

The Tunable Syncrhonized Oscillatory System (Synchroscillator) consists mainly of one negative feedback loop, i.e. a biological process that downregulates itself, one positive feedback loop, i.e. a biological process that induces itself, and the reporter protein Green Fluorescent Protein (GFP). Both feedback loops are regulated by hybrid promoters that can decrease the transcription rates upon presence of the Tet Repressor Protein (TetR) or lac repressor (LacI) DNA-binding protein.

The positive feedback loop is created by the quorum sensing (QS) molecule, or autoinducer: 3OC6HSL. This autoinducer is able to diffuse through a colony of bacteria (and was found in a Vibrio species that uses it to react to its cell density in a culture). 3OC6HSL is produced by the enzyme encoded by the luxI gene. Most important of this is that 3OC6HSL is able to increase the transcription rate of the luxI gene, in the whole colony. It does so, by binding to the hybrid 3OC6HSL-LacI promoter if LacI is absent.

Interacting with the positive feedback loop is the negative feedback loop. Also this feedback loop is caused by presence of the QS molecule. That is, 3OC6HSL binds a (hybrid) promoter as a complex with the constitutively expressed LuxR protein. This complex raises the transcription rate of the autoinducer inactivation enzyme A (aiiA) gene and therefore the concentration AiiA. As its gene name suggests, the AiiA is capable of inactivating the 3OC6HSL autoinducer. The promoter in front of the aiiA gene is a hybrid promoter and can also be repressed by the Tet Repressor Protein (TetR). In conclusion, the QS autoinducer is both formed and degraded by the BioBrick system and both processes can be set by LacI and TetR initially.

If the concentration rise and drop of 3OC6HSL occured with the same rate by both the positive and negative feedback loops, the concentration of the QS molecule would remain constant. However, under the right circumstances an oscillation could be created. When the autoinducer concentration rises before it finally initiates the negative feedback loop the GFP signal, that depends on the autoinducer concentration, would first increase and remain constant. However, the the production and degradation rate of 3OC6HSL are not the same. AiiA inactivates 3OC6HSL more quickly than it's formed. After the concentration of the autoinducer has dropped so much that aiiA no longer is expressed the concentration will still be be lowered until too much AiiA is deteriorated, which is a natural process inside the cell. The positive feedback loop will increase the autoinducer production rate again and start the next cycle.

More about this BioBrick device? Another [http://2011.igem.org/Team:Wageningen_UR/Project/IntroductionProj1 description] and the [http://2011.igem.org/Team:Wageningen_UR/Project/ModelingProj1#Mathematical_model_of_the_construct modeling] of are placed on the Wiki page of the project it was made in.

Sequence and Features