Postal Address :
Croix du Sud, 4-5
E-mail : Yves Dufrêne
Tel. +32 10 47 36 00
Secretariat +32 10 47 35 88
Carnoy Bldg (SC12)
Floor 04, room C455
Postdoc positions are available !
Microbiology at the nanoscale
Our goal is to push the limits of force nanoscopy beyond state-of-the-art to establish this nanotechnology as an innovative platform in biofilm research. By developing new tools, we wish to understand how pathogens use their surface molecules to guide cell adhesion and trigger infections, and to develop anti-adhesion strategies for treating biofilm-infections.
"Knowledge is limited. Imagination encircles the world.” ― A. Einstein
June 4, 2020
Fast chemical force microscopy reveals hydrophobic nanodomains on mycobacteria
In a new study published in Nanoscale Horizons, we show that fast quantitative imaging (QI) AFM combined with hydrophobic tips is a powerful tool to quantitatively map hydrophobic properties of bacterial pathogens, at high spatiotemporal resolution (∼10 min for 128 × 128 pixels images). We focus on Mycobacterium abscessus, a multidrug-resistant bacterial pathogen causing severe lung infections in cystic fibrosis patients. We discover that the transition from a smooth to a rough colony morphology, caused by the loss of cell envelope associated glycopeptidolipids (GPLs), leads to a dramatic change in surface hydrophobicity, smooth bacteria displaying unusual nanodomains with varying degrees of hydrophobicity. These results show that GPLs modulate the nanoscale distribution of hydrophobicity of M. abscessus, which is critical for regulating bacterial adhesion and aggregation, as well as virulence and pathogenicity. This study demonstrates the power of QI-AFM as a nanoimaging tool for probing the hydrophobic properties of cell surfaces in relation to function, at high speed and spatial resolution.
April 14, 2020
Mechanobiology: what makes bacterial pathogens so stiff?
Bacteria are surrounded by mechanically rigid cell envelopes, which play important roles in controlling cellular processes like growth, division, adhesion as well as resistance to drugs and environmental stresses. In the prototypical pathogen Escherichia coli, it has long been believed that peptidoglycan was the only biopolymer that conveys mechanical strength to the cell envelope. However, in a study published in Nature Communications, the teams of Yves Dufrêne and Jean-François Collet (WELBIO investigator) at the UCLouvain have identified the key roles of the lipoprotein Lpp in defining the E. coli cell envelope mechanics, using state-of-the-art nanoimaging techniques combined with genetic manipulation. They discovered that Lpp has a dual function, by covalently connecting peptidoglycan to the outermost cellular membrane and by precisely tuning the size of the periplasmic space. The researchers also found that Lpp-dependent cell mechanics has a major impact on antibiotic sensitivity, functional mutations in the protein increasing drastically the efficacy of vancomycin. This study, funded by the Excellence of Science (EOS), WELBIO and ERC fundings, demonstrates the power of coupling nanotechnology and molecular biology methods for understanding the molecular details behind bacterial stiffness, and for linking cellular mechanics to function, a grand challenge in current mechanobiology. The results show promise for the design of innovative antibacterial drugs targeting the molecular machineries that stabilize the cell envelope.
See the Nature Microbiology blog for more details.
See Daily Science
September 18, 2019
How strong is the fibrinogen bridge between staphylococcal surface protein ClfA and endothelial cell integrin aVb3 ?
Binding of the Staphylococcus aureus surface protein clumping factor A (ClfA) to endothelial cell integrin aVb3 plays a crucial role during sepsis, by causing endothelial cell apoptosis and loss of barrier integrity. ClfA uses the blood plasma protein fibrinogen (Fg) to bind to aVb3, but how this is achieved at the molecular level is not known. In a Nano Lett paper we demonstrate that the ClfA-Fg-aVb3 ternary complex is extremely stable, being able to sustain forces (∼800 pN) that are much stronger than those of classical bonds between integrins and the Arg-Gly-Asp (RGD) tripeptide sequence (∼100 pN). Our experiments favor a binding mechanism involving the extraordinary elasticity of Fg. In the absence of mechanical stress, RGD sequences in the Aa chains mediate weak binding to aVb3, whereas under high mechanical stress, exposure of cryptic Aa chain RGD sequences leads to extremely strong binding to the integrin.
May 26, 2019
Owing to David and the team we hosted ISPM 2019 which was a real success !
April 30, 2019
Fluidic force microscopy captures amyloid bonds between yeast cells
Congrats to Jérôme et al., including P. Lipke (New York Brooklyn College), for measuring the forces driving Als5-mediated intercellular adhesion in Candida albicans, using an innovative fluidic force microscopy platform (Nano Lett). The results point to a model whereby amyloid-like β-sheet interactions play a dual role in cell-cell adhesion, that is, in formation of adhesin nanoclusters ( cis-interactions) and in homophilic bonding between amyloid sequences on opposing cells ( trans-interactions). Because potential amyloid-forming sequences are found in many microbial adhesins, we speculate that this novel mechanism of amyloid-based homophilic adhesion might be widespread and could represent an interesting target for treating biofilm-associated infections. This new methodology is also discussed in Trends Microbiol. (2019, 27(9):728-730).
April 30, 2019
Staphylococcus aureus protein A binding to von Willebrand factor is activated by force
Protein A (SpA) binds to von Willebrand factor (vWF) under flow, but the molecular basis of this stress-dependent interaction has not yet been elucidated. Congrats to Felipe and our collaborators at the University of Pavia who have shown that the SpA-vWF interaction is regulated by a new force-dependent mechanism. This study published in mBio highlights the role of mechanoregulation in controlling the adhesion of S. aureus and shows promise for the design of small inhibitors capable of blocking colonization under high shear stress.
November 1, 2018
Atomic force microscopy-based mechanobiology
Mechanobiology describes how biological systems respond to mechanical stimuli. In a Nature Reviews Physics review paper, together with several experts in the field, the nBio team survey the basic principles, advantages and limitations of applying and combining atomic force microscopy-based modalities with complementary techniques to characterize the morphology, mechanical properties and functional response of complex biological systems to mechanical cues.
September 12, 2018
Bacterial sexuality at the nanoscale
With the Mahillon team we introduce an innovative atomic force microscopy platform to study and mechanically control DNA transfer between single bacteria, focusing on the large conjugative pXO16 plasmid of the Gram-positive bacterium Bacillus thuringiensis, a study published in Nano Lett. This technology may enable researchers to mechanically control gene transfer among a wide range of Gram-positive and Gram-negative bacterial species and to understand the molecular forces involved.
August 14, 2018
Staphylococcus aureus and eczema: a nanoscale view
Bacterium-skin interactions play important roles in skin disorders, yet their molecular details are poorly understood. In a paper published in mBio, we and our collaborators in Ireland decipher the molecular forces at play during adhesion of Staphylococcus aureus to skin corneocytes in the clinically important context of atopic dermatitis, also known as eczema. We identify a unique relationship between the level of natural moisturizing factor in the skin and the strength of bacterium-corneocyte adhesion. Bacterial adhesion is primarily mediated by the surface protein clumping factor B and is enhanced by physical stress, highlighting the role of protein mechanobiology in skin colonization. Similar to a catch bond behavior, this mechanism represents a promising target for the development of novel antistaphylococcal agents.
May 7, 2018
Mechanobiology: Staphylococcus aureus under tension !
Staphylococcus aureus is an important bacterial pathogen which is a leading cause of biofilm-associated infections on indwelling medical devices. Biofilms are currently estimated to be involved in more than 65 % of hospital-acquired infections. There is evidence that bacterial adhesion and biofilm formation are favored under high physical stress, but how this is achieved at the molecular level is not known. In a study published in PNAS, our team, together with the Trinity College Dublin, has elucidated the mechanism by which S. aureus responds to mechanical tension. We focused on the bacterial surface protein ClfA, and on its interaction with fibrinogen, a blood protein that rapidly covers implanted medical devices. Using atomic force microscopy, we showed that ClfA behaves as a force-sensitive molecular switch that potentiates staphylococcal adhesion under mechanical stress. The adhesion of ClfA is weak at low tensile force, but is dramatically enhanced by mechanical tension, as observed with catch bonds. Strong bonds are inhibited by a peptide mimicking Fg, which offers prospects for the development of antiadhesion therapeutics. These findings are of biological significance because they explain at the molecular level the ability of ClfA to promote bacterial attachment under high physiological shear stress. This study emphasizes the role of mechanobiology in staphylococcal biofilms, a topic that we also discusses in a recent perspective article in Science.
For more details, see https://uclouvain.be/fr/sciencetoday/actualites/le-stress-du-staphylocoque-dore.html
April 24, 2018
New ACS Nano paper: Mechanical forces guiding Staphylococcus aureus cellular invasion
Invasion of mammalian cells by S. aureus involves fibronectin-dependent bridging between FnBPs on the bacterial surface and α5β1 integrins in the host cell membrane, but the fundamental forces involved are poorly understood. With our colleagues from the University of Pavia, we have used state of the art single-cell and single-molecule experiments to quantify the molecular forces engaged in this three component interaction, revealing that the fibronectin bridge between FnBPs and the α5β1 integrin is mechanically strong.
March 30, 2018.
New perspective article in Science: Force matters in hospital-acquired infections
Building up on an outstanding paper by Gaub et al. we discuss how extremely strong forces help staphylococci to colonize biomaterials and infect humans.