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Experiments of the YFP concentrator design

This system is an improvement of the original experiment with the GFP. To see the fluorescence better, we decided to concentrate the YFP fluorescent molecules fused to TetR on the TetO array to make them more visible in the cell. We have been kindly given the plasmids containing the YFP:TetR construct and the TetO array by D. Lane. We biobricked the YFP:TetR construct and the TetO array so that they can be used by the synthetic biology community. The results are presented here in detail.

Design overview

YFP:TetR/TetO array system

More information on the design here.

Parts and biobrick system construction

YFP:TetR construction

Cloning plan of YFP:TetR construction

TetO array construction

Cloning plan of TetO array construction

Results

For this design our results are the following:

• We successfully biobricked both the YFP:TetR (BBa_K606025) and the TetO Array (BBa_K606026) constructs
• We characterized the YFP:TetR fusion protein expression both in E.coli and B.subtilis
• We characterized the TetO array expression both in E.coli and B.subtilis

Testing the YFP:tetR and tetO array strains from D. Lane

In the article [1], E. coli strains are growing at 20°C to avoid protein aggregation. But nanotubes between B. subtilis have only been observed at 37°C. We tested different possibilities: at 37°C or 30°C and different concentrations of arabinose (0% - 0,1% -0,2%) to deal with protein aggregation.

YFP:TetR / TetO array : 37°C

YFP:TetR / TetO array inducted with no arabinose in E. Coli from Dave Lane plasmids.

YFP:TetR / TetO array inducted with 0,2% arabinose in E. Coli from Dave Lane plasmids.

YFP:TetR / TetO array : 30°C

YFP:TetR / TetO array inducted with no arabinose in E. Coli from Dave Lane plasmids.

YFP:TetR / TetO array inducted with 0,2% arabinose in E. Coli from Dave Lane plasmids.

With both YFP:TetR and TetO array plasmids, we can see few spots of fluorescence with 0,2% arabinose. Because there are in the cell extremity, we can suppose that it is concentrated fluorescence in TetO arrays. Nevertheless the protein aggregation is obvious when there is only YFP:tetR at 30°C and 37°C in E. coli.

More pictures and information on the notebook here.

Characterization: Biobricked TetO Array

Microscopy of double transformed pFX234 / Biobricked TetO Array in E. Coli

To characterize this part properly, we took pictures of different strains containing TetO alone; YFP:TetR; or both TetO and YFP:TetR. In each case we made a control where the promoter was not induced with arabinose in E. coli (double transformated with pFX234 and TetO Array).

TetO array only: 37°C

tetO / TetO array inducted with no arabinose on E. Coli .

tetO / TetO array inducted with 0,2% arabinose on E. Coli .

YFP:TetR only: 37°C

YFP:TetR / YFP:TetR inducted with no arabinose on E. Coli .

YFP:TetR / YFP:TetR inducted with 0,2% arabinose on E. Coli .

YFP:TetR + TetO array: 37°C

YFP:TetR-TetO/ full construct inducted with no arabinose on E. Coli .

YFP:TetR-TetO / full construct inducted with 0,2% arabinose on E. Coli .

YFP:TetR and YFP:TetR + TetO array: 37°C - Zoom and comparison

YFP:TetR inducted with 0,2% arabinose on E. Coli .

YFP:TetR-TetO / full construct inducted with 0,2% arabinose on E. Coli .

The pictures of TetO alone show no YFP activity, which was expected because there is no YFP sequence in these plasmids.
The TetR-YFP construct which (emitter part) occasionally shows gross aggregated YFP.
After observing the cells carrying both the TetO and YFP:TetR constructs, we can obviously distinguish glowing dots in some cells. They reflect the behavior we expected. Indeed, appearance of dots (red arrow) shows that the receiver (TetO array) actually links tightly to the YFP:TetR fusion protein!

Microscopy of ibpA mCherry double transformated in E. Coli

We wanted to be able to distinguish precisely the fusion protein aggregated from the YFP:TetR biding to TetO array. We transformated ibpA mCherry cells (expressing a mcherry in a agregation chaperon protein, with courtesy of Anne-Sophie Coquel, Inserm U1001) with pFX234 YFP:TetR and biobricked TetO Array plasmids to differenciate TetO array foci from YFP:TetR aggregates.

• Case of YFP:TetR over-expression by arabinose induction

Microscopy shows overlap for most foci and mCherry agregation but there is some foci that is alone.
Hopefully we don't expect to get high concentrations of YFP:TetR in receiver cells so aggregates will not happen in them.

• Case of YFP:TetR low expression by arabinose induction

Microscopy shows that most of aggregates are gone and we have more not-overlaping foci.
We could manage to get less aggregation if we deal with the arabinose induction.

To be continued...

Next step is to biobrick the YFP:TetR fusion protein so we can finish the cloning plan and put the system in B. subtilis. Hopefully we can improve our GFP diffusion experiments and have a better characterisation of nanotubes !