DYNAMICS of BACTERIAL CELL WALL
Team Leader : Marie-Pierre CHAPOT-CHARTIER
The cell wall of Gram-positive bacteria is a complex arrangement of different biopolymers: peptidoglycan (PG), polysaccharides (PS), teichoic acids and (glyco)proteins. It is a rigid structure to maintain cell shape and integrity but also a flexible and dynamic one to accommodate cell growth and division and to face changing environmental conditions. Therefore the functioning of bacterial cell wall is tightly linked to bacterial physiology. Besides, the components exposed at the bacterial surface determine important properties such as adhesion to surfaces or trigger complex responses such as the immune response in the host. Consequently, in complex ecosystems such as the human gastro-intestinal tract, the colonising potential of bacteria and their cross-talk with the host rely on their cell wall characteristics.
Although the nature and basic structure of the cell-wall components are known, numerous questions remain to construct an integral and dynamic model of the cell wall and to reach a comprehensive understanding of the role of its components. This makes the cell wall a very active field of research worldwide.
The following questions are the basis of our research work:
- What is the fine structure of the cell wall polymers and their structural diversity between strains and species?
- What is their location and which rules govern their assembling?
- What are the mechanisms which control synthesis and assembly of the cell wall polymers to guarantee cell integrity and at the same time allow growth and division?
- Which surface-exposed components of the cell wall interact with mammalian host at the level of the intestinal mucosa, considering particularly survival and persistence (colonisation), modulation of immune responses and commensal-pathogen transition?
In order to take into account the cell wall diversity, we have chosen to work on different models of Gram-positive bacteria: Lactococcus lactis, the model food lactic acid bacterium, probiotic Lactobacillus casei and Lactobacillus plantarum, and Streptococcus agalactiae (Group B streptococcus, GBS) an opportunist pathogen in neonates, an emerging pathogen in adults as well as a commensal bacterium. Better knowledge of the bacterial interactions with the host intestinal mucosa will allow developing L. lactis strains more efficient to deliver substances with health properties in a controlled way, to understand the probiotic properties of lactobacilli and the basis of commensalism in S. agalactiae.
Institut Micalis (UMR1319/INRA-AgroParisTech)
I.N.R.A., Domaine de Vilvert
78352 Jouy en Josas Cedex, France
Tel: 33 (0)1 34 65 22 68
Fax: 33 (0)1 34 65 20 65