I am interested in the organisation and dynamics of bacterial chromosomes and the proteins involved in this process, especially the Nucleoid-Associated-Proteins (NAPs). Using a variety of tools (biochemistry, biophysics, genetics and microscopy), I am trying to understand the binding of proteins such as MatP, Fis, H-NS, and their effect on the structure of the chromosome in E. coli. To do this, I have been combining a biophysical method, the Tethered Particle Motion (TPM) set-up, with short-time microscopy, which allows to generate physical properties of chromosomal loci (MSD, Diffusion Coefficient…) by analysing the motion of foci in the cell in different conditions or mutants.
Example of a TPM set-up to study MatP
a. A bead is attached to a single DNA molecule (*). When a protein binds (here, MatP binds matS sites), this induces a conformational change (**) or a loop (***), which reduces the apparent length of the DNA, and therefore the Brownian motion of the bead.
b. Example of a trace for a bead linked to a DNA containing 2 matS. Several, short looping events can be observed, indicating the dynamics of the loop formation.
In collaboration with Dr. Catherine Tardin (IPBS).
Example of chromosomal loci movement
A loci near the origin of replication has been tagged with a parS sequence, so that we can observe a focus formed by the fixation of ParB-GFP. We are then using Matlab scripts to extract the trajectories of each focus, and their properties.
In collaboration with Prof. Pietro Cicuta, Cambridge University.
Our last paper is being advertised on the CNRS webpage
Post-replicative pairing of sister ter regions in Escherichia coli involves multiple activities of MatP
Crozat E, Tardin E, Salhi M, Rousseau P, Lablaine A, Bertoni T, Holcman D, Sclavi B, Cicuta P, Cornet F
Nature communications 30 July 2020