Latest news

Postdoc position in quantitative cellular microbiology will be opened in 2021
4 hours 9 min ago

Bacterial communities colonize and attach to solid surfaces thanks to adhesive molecules exposed on the bacterial outer envelope. While a substantial number of molecular actors involved in bacterial adhesion have been characterized, their dynamics and their coordination on the bacterial envelope remain out of sight because the secretion machineries interfere with the fluorescence of standard probes. Recently, we showed thanks to mechanical assays that adhesive molecules were enriched at the old pole of bacteria. From this polar localization at single cell level, it results that microcolonies composed of rod-shaped bacteria develop into dense aggregates rather than into chains where bacteria would be highly exposed to their environment. This organization at the level of the community has a large impact in terms of biofilm tolerance to antibiotics and causes major health concerns by generating nosocomial diseases. In this project, we propose to use a new generation of fluorescent reporters, in order to measure the spatial dynamics of adhesive proteins exposed on the cell envelope of E. coli. By comparing physical modeling and experiments, we will aim at understanding the microscopic mechanisms that are responsible for adhesion polarity at the single cell level and how antibiotics could perturb this polarity and thus the structure of bacterial communities.

 

We are looking specifically for physicists with a training in optics, image analysis and numerical simulations (we will not respond to candidates, who do not fit these requirements). Motivated candidates should contact Nicolas Desprat (nicolas.desprat@phys.ens.fr).

"Fluorescent secreted bacterial effectors reveal an intravacuolar replication compartment for Listeria monocytogenes" on BioRxiv
4 hours 16 min ago

In collaboration with the lab of Alice Lebreton (IBENS), we uploaded the paper of Caroline Peron-Cane on BioRxiv.

Abstract:

Imaging the dynamics of secreted virulence factors in real time is impaired by the paucity of appropriate fluorescent tools. Here, we demonstrated that the fluorogenic reporter FAST can be used to tag secreted proteins, and thereby monitored infection dynamics among a population of epithelial cells exposed to the human pathogen Listeria monocytogenes (Lm). By tracking individual FAST-labelled vacuoles after internalisation of Lm into host cells, we unveiled the heterogeneity of residence time inside entry vacuoles. Although half of the bacterial population escaped rapidly as previously described, a significant fraction remained entrapped several hours in Long Residence Vacuoles (LRVs), independently of the secretion of the membrane-destabilizing pore-forming toxin listeriolysin O (LLO). We imaged LLO-FAST in LRVs during infection, and also showed that LLO enabled Lm to proliferate inside these compartments. Unexpectedly, Lm growth in LRVs was as fast as in the cytosol. LRVs thus constitute an alternative replication niche in epithelial cells that might promote the colonization of host tissues.

Finally our book came out!
21 weeks 8 hours ago

It took years but our book on single DNA experiments finally came out in 2018! More than 10 years...Available in all book stores.

Evolution of cell shape uploaded on bioRxiv
2 years 1 week ago

Cell shape is a fundamental property in bacterial kingdom. MreB is a protein that determines rod-like shape, and its deletion is generally lethal. Here, we deleted the mreB homolog from rod-shaped bacterium Pseudomonas fluorescens SBW25 and found that ΔmreB cells are viable, spherical cells with a 20% reduction in competitive fitness and high variability in cell size. We show that cell death, correlated with increased levels of elongation asymmetry between sister cells, accounts for the large fitness reduction. After a thousand generations in rich media, the fitness of evolved ΔmreB lines was restored to ancestral levels and cells regained symmetry and ancestral size, while maintaining spherical shape. Using population sequencing, we identified pbp1A, coding for a protein involved in cell wall synthesis, as the primary target for compensatory mutations of the ΔmreB genotype. Our findings suggest that reducing elongasome associated PBPs aids in the production of symmetric cells when MreB is absent.

Preprint on BiorXiv

Job opening at Depixus
2 years 6 weeks ago

Depixus is operating in one of the most dynamic and exciting areas of bioscience today. We are seeking highly talented individuals to join our teams based in both Paris, France and Cambridge, UK.

Technical excellence is very important but you will also need to be innovative, enterprising, and enjoy working within a close-knit team. The development of our technology requires scientists and engineers from a wide range of disciplines.

We accept resumes at all times; if you think you could help us then we would love to hear from you! For more information please contact: jobs@depixus.com. Positions that are currently open are listed below.

New post-doc positions
4 years 21 weeks ago

We are looking for biophysicists to study development and cancer in zebrafish using the optogenetic tools developed in the team. Experience in molecular/cell biology and microscopy are required. Basic programming skills (for image acquisition and analysis) are appreciated.  Candidates should submit their CV + publications and 3 letters of recommendation from kown researchers in the field to: david@lps.ens.fr