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The YFP Concentrator design

Introduction

One of the main result of Dubey and Ben-Yehuda papers proving the existence of nanotubes is the evidence of GFP diffusion from B.subtilis cells one to another. However the resulting fluorescence from this diffusion is quite weak supposedly due to the limited number of molecules passing through nanotubes. One alternative to get a better fluorescence signal with the same amount of fluorescent molecules is to concentrate them in foci. In order to do this we decided to use an already existing system based on a YFP:TetR fusion protein.

YFP:TetR is composed of Yellow Fluorescent Protein (YFP) and the Tetracycline Repressor Protein (TetR) that binds to the Tet operator sequence (TetO). Using the TetO array composed of a 10kb repeat of TetO sequences, we can concentrate YFP:TetR in several loci and increase the fluorescence sensitivity. The two different constructs, YFP:TetR and TetO Array, come from François-Xavier Barre, Andrew Wright and Dave Lane (Kinetics of plasmid segregation, Molecular Microbiology, 2004)

We use this design as a proof of the nanotube concept between B.Subtilis - B.Subtilis and B.Subtilis - E. Coli.

Making the YFP:tetR diffuse through the tube

In the emitter cell (B. Subtilis), we have inserted an expression system for the YFP:tetR. It contains the constitutive promoter pVeg, the RBS for B.subtilis and the YFP:tetR protein. Constitutively expressed YFP:tetR molecules will diffuse through the nanotube to the receiver cell.

In the receiver cell (B. Subtilis or E. Coli), there is the TetO array where diffused YFP:tetR will concentrate. The YFP is the monitor of the signal.

The principle of the design is summed up in the image below

Fig1: Schematics of the YFP concentration design

Model and experiments

To know more about what we have done on this system and in the experiments, we invite you to visit the corresponding diffusion modeling and experiment pages:

• Diffusion modelling
• Experiments