Latest news

Caroline's paper on Listeria has been accepeted in PLoS Pathogens.
1 week 6 days ago

Here, you can find the proof version online.

 

Below, Listeria escaping the entry vacuole after growing for almost 10h inside it.

Our paper on the visualization of outer membrane proteins in Gram-positive and Gram-negative bacteria is out.
2 weeks 6 days ago

We demonstrated that the FAST reporter system can be generically used to label surface proteins both in Gram-Positive (E. coli) and Gram-negative (Listeria monocytogenes). Here is our paper. This work hase been done in collaboration with C. Beloin (Institut Pasteur), A. Lebreton (IBENS) and A. Gautier (Sorbonne University).

Postdoc position in quantitative cellular microbiology will be opened in 2021
32 weeks 2 days 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
32 weeks 2 days 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!
1 year 1 week 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 33 weeks 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