Director: Dr. Rut Carballido-López
The underlying question of our research is: how cells maintain a defined shape? What are the mechanisms to create and maintain for example a tube instead of a sphere or, why not, a star? Our aim is to understand the fundamental mechanisms controlling this important aspect of cellular development. For this, we are using a bacterial model, the gram-positive bacterium Bacillus subtilis, and we are focusing our efforts on key proteins of this process, the so-called bacterial cytoskeleton, with a particular emphasis on the “actin-like” MreB.
We are using a combination of genetics, genomics, transcriptomic, biochemistry, biophysic, microscopy, bioinformatic and modelization approaches. We are willing to tackle these fundamental questions through a clearly pluridisciplinary approach thanks to several collaborations in situ, but also in other European countries and in the USA.
The cytoskeleton is a key element of the bacterial shape through its control of the cell wall homeostasis, but it is also suspected to play a role in many other cellular processes. Thus, our objectives are to discover the role of the bacterial actin MreB in various fundamental processes like morphogenesis, cellular division, virulence, polarity, motility or secretion; to identify their underlying molecular mechanisms; to reveal the actors controlling the cell wall morphogenesis, together with its mechanical properties and its ultra-structure.
Several projects are currently ongoing:
MreBs: from function to actions
- MreB proteins are the bacterial homolog of eukaryotic actins. However their enzymatic properties are almost completely unknown and the parallel with actins seems less and less appropriate. We are currently undergoing a comprehensive biochemistry analysis of various MreB proteins to decipher their intimate mechanisms.
- A great deal of information was gathered from cytological studies, especially in the field of bacterial actin. Using advanced microscopy technics (such as TIRFM) we are revisiting the localization and behavior of fluorescently tagged MreBs. Recently, using TIRFM, we showed the unexpected dynamic of these proteins in 3 bacteria, and bring evidences for a cell-wall synthesizing machinery complex driven motion (Dominguez et al., 2011).
- MreBs seem to be part of multiprotein complexes involved in several cellular processes. In order to reveal new members of these complexes and the different pathways they are involved into, large scale genetic and biochemical screens for protein-protein interactions have been developed, revealing several promising leads.
Cell Wall morphogenesis: from MreB control to 3D structure
- The complexity of the processes influenced by MreBs and the large number of actors they involved, drive us to use a global systemic approach. Data are gathered using comprehensive “omics” approaches (tilling arrays…) and analyzed with dedicated computational tools, developed in collaboration.
- Cell wall synthesis is a highly complex process where genetic, mechanical and physical factors play an elusive but dynamic interplay. We challenge this problem by creating, in collaboration, a simplified dynamic model of the structure of the cell wall and its synthesis, in order to understand how physical constrains influence the shaping of the cells.
- We are determining the physicochemical properties of the bacterial cell surface by elucidating the structural organization and the chemical composition of the various constituents of the CW. For this, we are collaborating with several team in Europe and the US to 1- analyze the chemical composition, and 2- study by high resolution imaging the surface structure and physical properties of the cell envelop.
MreB proteins control acquisition and maintaining of the form of bacteria. Above, Bacillus subtilis, observed by SEM (Scanning Electron Microscopy). On the left-hand side of the picture are wild cell strands. To the right are mutant cells for the mbl gene (one of the three paralogue genes specifying MreB).
Main External Collaborations
- Dr. Roland Wedlich-Söldner, high-end high-resolution light microscopy (Max-Planck Institute of Biochemistry of Martinsried, Germany)
- Dr. Vincent Fromion, statistiques & modélisation mathématique(Unité MIG, INRA, Jouy-en-Josas)
- Dr. Paulo Tavares, bacteriophage SPP1 Infection (UMR CNRS 2472 INRA 1157, Gif-sur-Yvette)
- Dr. Dmitri Vezenov, scanning probe microscopy and magnetic tweezers (Department of Chemistry, Leihigh University, USA)
- Dr. Sergio Raposo Filipe, analysis of cell walls (ITQB of Lisbon, Portugal)
- Dr. Anne Galinier, MreB-associated proteins (LCB - CNRS UPR 9043, Marseille)
- Dr. Jan Maarten van Dijl, secretion systems (University of Groningen, Pays-Bas)
- Dr. Carlos São-José, phage receptor & secretion systems (University of Lisbon, Portugal)
- Dr. Pierre Nicolas, bioinformatique & statistiques (Université MIG, INRA, Jouy-en-Josas)
- Dr. Doug Weibel, microbial engineering (University of Wisconsin-Madison, USA)
- Dr. Adriano Henriques, control of shape by RodZ (ITQB of Lisbon, Portugal)
- Partenaires du projet TranSys
- Partenaires du projet BaSysBio