Date : 21/7/2010

Internship proposal for : Master 2

Laboratory

Laboratoire de Physique Statistique (ENS)
UMR 8550 CNRS, University Paris 7
24 rue Lhomond 75005 Paris
Director : Eric Perez
Website : http://pimprenelle.lps.ens.fr/biolps/
Main discipline : Molecular biologySystems Biology

Supervisor

Nicolas Desprat
email : This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
phone : +33 144323496

Subjects / Tools-Methodologies

1 : siderophore/Cooperation is ubiquitous in living systems ranging from cooperative genes and cooperative cells in metazoan tissues, to cooperative behaviors structuring animal societies. At each scale, cooperation seems to be essential for achieving higher levels of organization. Yet, while the product of cooperation confers a gain of fitness to its recipient, it imputes a cost to the producer. From the individual perspective, defecting is a more advantageous strategy. The secretion of siderophores by Pseudomonas aeruginosa, which enables those bacteria to retrieve iron from the surrounding medium, is an archetype of such a social dilemma. Producers pay a metabolic cost for their production, whereas non-producers can benefit from the diffusing pool of siderophores in the extracellular medium. We developed tools allowing to describe the dynamics of cell-to-cell variability in monoclonal populations growing under a microscope. We propose to investigate the interplay between iron regulation pathway and phenotypic variability using mutants and fluorescent reporters. In parallel, we are implementing a laser ablation procedure that enables to selectively regulate the number of phenotypes.
2 : microscopy, image analysis, laser ablation/
3 : The ABCD Lab consists mainly of physicists working in tight collaboration with biologists and chemists. Our strong experimental background enabled the development of new reliable tools to study different problematics in biology. Today, the activities of the lab encompass approximately all scales of description in biology : single molecule micromanipulation, study of replication fork rescue in single bacterium, cell fate addressing during development of zebrafish and phenotypic variability in bacterial population. 1. Single molecule micromanipulations are devoted to the study of DNA and DNA-protein interactions based on a magnetic tweezers system. The lab is currently working at : ñ an in-vitro reconstitution of the replication fork ñ a new sequencing method of single DNA molecules ñ the action of diverse helicases, topoisomerases and translocases on DNA 2. At the cell level, the lab is interested in how in-vivo replication forks can restart after controlled arrest. This project involves single molecule fluorescence and microfluidics. 3. The part of the lab dedicated to developmental biology uses a 2-photon set-up to influence cell lineage in the course of embryo development by using photo-activable molecules which can rapidly triggered in a single cell at a given time. 4. At the population level, the lab is focusing on the role of phenotypic variability for iron regulation in Pseudomonas aeruginosa population. The technics developed for this purpose are essentially : microscopy, image analysis, microfluidics and laser ablation. We are also trying to implement a long term evolution experiment of Escherichia coli in a temperature gradient./