Team:Grenoble/Project/Main Results


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iGEM Grenoble 2012


Main results

This part will present the pre-regional Jamboree main results.

Simple amplification loop

In a first place, biologists and modellers worked on a simple amplification loop.

The modellers proved that a simple amplification loop could not work. There is no state where GFP is not expressed.

Why an AND gate ?

The team thought that an AND gate could be our solution. It could add a biological noise filter and resolve the problem of the continuous expression of GFP.

Modelling results confirmed that built system will work.

Biological results

Biological AND gate test.

As you can see the paraBAD works as expected. We began the construction of the amplification loop (paraBAD_gfp_cyaA).

Issues encountered

We have not yet constructed that part. We had some problem with the ligation procedure. Another explanation could be that our bacteria are transformed with the right construction leading to an over-expression of Adenylate cyclase which is lethal: this can be attributed to the fact that overproduction of cAMP is lethal to Escherichia coli possibly due to an accumulation of methylglyoxal [1][2].

And after?

In the future weeks (according to ours results) we will try to make the culture of our transformed bacteria in a medium complemented with glucose and acetate.
As we have had issues constructing paraBAD-gfp-cyaA using the standard restriction/ligation procedure, we are going to try another approach. We want to insert it on pSB3C5 using the Gibson Assembly procedure (we have the brick but we are failing the insertion).
Once this construction is achieved, we will transform BW25113 ΔcyaA E. Coli strain to test the designed amplification feed-forward loop using the same protocol as for the AND gate.

We also plan to test our engineered membrane receptor (TapZ) in BW25113 ΔEnvZ E. Coli strain. To test it, we are going to use an mCherry reporter under the promotion of pOmpC.
A possible track would be to add another regulation system on the adenylate cyclase production with the riboswitch RsmA/rsmY.
In order to estimate the functionality of our new riboswitch, we are planning to transform one strain of BW25113 with plac-fha1-mcherry (on a low-copy plasmid) and in a second strain the previous construct plus plac-RBS-rsmA (medium-copy plasmid). In a last strain we will add the third partner (plac-rsmY on a high-copy plasmid) to estimate its inhibition release action. To characterize this we will use flow cytometry experiments.