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Axis 3

The environmental bacterial cell


Bacteria are incredibly efficient at colonizing various ecological niches, in soils, oceans or even mammalian hosts, developing numerous adaptive strategies to colonize their environment by secreting macromolecules, secondary metabolites, adhering and/or moving in their biotope. Due to the complexity of their cell envelope, bacteria have evolved sophisticated machineries. LCB teams study all aspects of these machineries from structure-function relationships, to dynamic regulations in cells and evolution.  In particular, we study mechanisms which involve the secretion of macromolecules to adapt bacteria to their niche, Fe-S dependent secondary metabolites and sophisticated systems  to capture and degrade nutrients in the extracellular environment, for example cellulose and surrounding plant cell wall associated polysaccharides.  Bacteria also interact with their environment via Type-IV filamentous nanomachines, which allow polymerization of retractile fibers across the cell envelope. Remarkably and depending on their types these systems allow secretion, adhesion and even motility in pathogenic, but also in soil bacteria. Motility is a particularly fascinating process, allowing the coordinated movement of thousands of bacterial cells, for example in Myxococcus xanthus which uses this process to predate over other microorganisms. Other bacteria swim along the earth’s magnetic field using intracellular magnets and sometimes thousands of flagella operating coordinately at the surface of multicellular assemblies. Last, bacteria themselves are subject to pathogens and in particular viruses called bacteriophages. We study how phages manipulate their host cells to their benefit, but also how phage genes can be co-opted in bacterial genomes and allow the emergence of new phenotypic traits, an important engine for evolution.
Keywords: adaptation, flagella, secretion, pili, pathogenesis, bacteriophages