Description of the thesis topic

R-bodies are molecular pistons produced by endosymbiotic bacteria that can grow in a fraction of a second from 500 nm self-winding ribbons to 20 micron needles capable of perforating biological membranes. Their extension is triggered by a pH variation without chemical energy consumption, via a mechanism that remains poorly understood. We propose here to study the dynamics and mechanism of the R-body extension-retraction cycle, combining biological, imaging, force measurement and modeling approaches. R-bodies will be produced in bacteria, purified and immobilized inside microfluidic chambers allowing on-demand medium exchange. We will evaluate the influence of medium viscosity on R-body extension dynamics and the force generated during retraction, using optical tweezers. We will build a numerical model of the R-body using the measured parameters. This work will enable us to understand the extension-retraction mechanism of R-bodies, opening up new avenues for the development of organic micro-actuators.

Work Context

This thesis will be funded by the HiFunMat interdisciplinary thematic institute. The PhD student will join the Biointerface group at the Institut des Sciences des Matériaux de Mulhouse (IS2M) under the supervision of Laurent Pieuchot, CNRS research fellow and head of the group. The group comprises 15 people, including 6 permanent researchers and engineers. Igor Kulic and Tatiana Schmatko, researchers in the MCube group at the Institut Charles Sadron, will co-supervise the physical experimentation and modeling part of the project. IS2M has a staff of around 180, including 60 permanent researchers with skills in chemistry, physics and biology. Mulhouse is located in Alsace, in eastern France, on the borders of Germany (Freiburg im Breisgau) and Switzerland (Basel), with direct access to Paris (less than 3 hours by TGV) and an international airport (Euroairport, 20 km).

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.

Constraints and risks

No risk identified.