How cell surface molecules are spatially organized and how they interact with their environment are key questions in current cell biology and microbiology, which today are still largely unsolved owing to the lack of high-resolution probing techniques. The Dufrêne lab studies the molecular surface architecture, properties and interactions of living cells - particularly bacteria and yeasts - using atomic force microscopy (AFM) techniques. The strategy involves developing advanced AFM methods (cell preparation and tip functionalization, high-resolution imaging of live cells, single-molecule force spectroscopy and recognition imaging) and combining these nanotools with fluorescence, genetics and cell biology approaches to address the cell surface.
Recent breakthroughs include:
(i) deciphering the supramolecular architecture of microbial cell walls, and their remodelling during cell growth or incubation with drugs (direct observation of Staphylococcus aureus peptidoglycan digestion by lysostaphin, nanoscale study of the interactions between mycobacteria and antimycobacterial drugs, imaging the nanoscale organization of peptidoglycan in living Lactococcus lactis);
(ii) unravelling the spatial arrangement of chemical properties on living microbes (direct measurement of hydrophobic forces on cell surfaces using AFM; high-resolution cell surface dynamics of germinating Aspergillus fumigatus conidia);
(iii) understanding the molecular elasticity of cell wall polysaccharides and proteins, in relation with function (conformational analysis of single polysaccharide molecules on live Lactobacillus rhamnosus GG bacteria, unfolding cell adhesion proteins on living Candida albicans cells, mechanical behavior of Saccharomyces cerevisiae sensors);
(iv) studying the spatial distribution of cell surface receptors and their stress-induced reorganization (clustering of cell adhesion proteins and yeast sensors).
Our experiments contribute to the growth of the emerging field of microbial nanoscopy, which should have an important impact on nanomedicine, for understanding microbe-drug and microbe-host interactions and for developing new anti-microbial strategies.