Publications by authors named "Claire Valotteau"

16 Publications

  • Page 1 of 1

AFM Unravels the Unique Adhesion Properties of the Type IVc Pilus Nanomachine.

Nano Lett 2021 04 23;21(7):3075-3082. Epub 2021 Mar 23.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Croix du Sud, 4-5, bte, L7.07.07., B-1348 Louvain-la-Neuve, Belgium.

Bacterial pili are proteinaceous motorized nanomachines that play various functional roles including surface adherence, bacterial motion, and virulence. The surface-contact sensor type IVc (or Tad) pilus is widely distributed in both Gram-positive and Gram-negative bacteria. In , this nanofilament, though crucial for surface colonization, has never been thoroughly investigated at the molecular level. As assembles several surface appendages at specific stages of the cell cycle, we designed a fluorescence-based screen to selectively study single piliated cells and combined it with atomic force microscopy and genetic manipulation to quantify the nanoscale adhesion of the type IVc pilus to hydrophobic substrates. We demonstrate that this nanofilament exhibits high stickiness compared to the canonical type IVa/b pili, resulting mostly from multiple hydrophobic interactions along the fiber length, and that it features nanospring mechanical properties. Our findings may be helpful to better understand the structure-function relationship of bacterial pilus nanomachines.
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http://dx.doi.org/10.1021/acs.nanolett.1c00215DOI Listing
April 2021

Multiparametric Atomic Force Microscopy Identifies Multiple Structural and Physical Heterogeneities on the Surface of .

ACS Omega 2020 Aug 13;5(33):20953-20959. Epub 2020 Aug 13.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Croix du Sud, 4-5, bte L7.07.07, B-1348 Louvain-la-Neuve, Belgium.

A unique feature of the African trypanosome is the presence of an outer layer made of densely packed variable surface glycoproteins (VSGs), which enables the cells to survive in the bloodstream. Although the VSG coat is critical to pathogenesis, how exactly the glycoproteins are organized at the nanoscale is poorly understood. Here, we show that multiparametric atomic force microscopy is a powerful nanoimaging tool for the structural and mechanical characterization of trypanosomes, in a label-free manner and in buffer solution. Directly correlated images of the structure and elasticity of trypanosomes enable us to identify multiple nanoscale mechanical heterogeneities on the cell surface. On a ∼250 nm scale, regions of softer (Young's modulus ∼50 kPa) and stiffer (∼100 kPa) elasticity alternate, revealing variations of the VSG coat and underlying structures. Our nanoimaging experiments show that the cell surface is more heterogeneous than previously anticipated and offer promising prospects for the design of trypanocidal drugs targeting cell surface components.
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http://dx.doi.org/10.1021/acsomega.0c02416DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7450619PMC
August 2020

High-speed force spectroscopy: microsecond force measurements using ultrashort cantilevers.

Biophys Rev 2019 Oct 7;11(5):689-699. Epub 2019 Oct 7.

Aix-Marseille Univ, INSERM, CNRS, LAI, 13009, Marseille, France.

Complete understanding of the role of mechanical forces in biological processes requires knowledge of the mechanical properties of individual proteins and living cells. Moreover, the dynamic response of biological systems at the nano- and microscales span over several orders of magnitude in time, from sub-microseconds to several minutes. Thus, access to force measurements over a wide range of length and time scales is required. High-speed atomic force microscopy (HS-AFM) using ultrashort cantilevers has emerged as a tool to study the dynamics of biomolecules and cells at video rates. The adaptation of HS-AFM to perform high-speed force spectroscopy (HS-FS) allows probing protein unfolding and receptor/ligand unbinding up to the velocity of molecular dynamics (MD) simulations with sub-microsecond time resolution. Moreover, application of HS-FS on living cells allows probing the viscoelastic response at short time scales providing deep understanding of cytoskeleton dynamics. In this mini-review, we assess the principles and recent developments and applications of HS-FS using ultrashort cantilevers to probe molecular and cellular mechanics.
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http://dx.doi.org/10.1007/s12551-019-00585-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6815269PMC
October 2019

Staphylococcus aureus adhesion in endovascular infections is controlled by the ArlRS-MgrA signaling cascade.

PLoS Pathog 2019 05 22;15(5):e1007800. Epub 2019 May 22.

Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, United States of America.

Staphylococcus aureus is a leading cause of endovascular infections. This bacterial pathogen uses a diverse array of surface adhesins to clump in blood and adhere to vessel walls, leading to endothelial damage, development of intravascular vegetations and secondary infectious foci, and overall disease progression. In this work, we describe a novel strategy used by S. aureus to control adhesion and clumping through activity of the ArlRS two-component regulatory system, and its downstream effector MgrA. Utilizing a combination of in vitro cellular assays, and single-cell atomic force microscopy, we demonstrated that inactivation of this ArlRS-MgrA cascade inhibits S. aureus adhesion to a vast array of relevant host molecules (fibrinogen, fibronectin, von Willebrand factor, collagen), its clumping with fibrinogen, and its attachment to human endothelial cells and vascular structures. This impact on S. aureus adhesion was apparent in low shear environments, and in physiological levels of shear stress, as well as in vivo in mouse models. These effects were likely mediated by the de-repression of giant surface proteins Ebh, SraP, and SasG, caused by inactivation of the ArlRS-MgrA cascade. In our in vitro assays, these giant proteins collectively shielded the function of other surface adhesins and impaired their binding to cognate ligands. Finally, we demonstrated that the ArlRS-MgrA regulatory cascade is a druggable target through the identification of a small-molecule inhibitor of ArlRS signaling. Our findings suggest a novel approach for the pharmacological treatment and prevention of S. aureus endovascular infections through targeting the ArlRS-MgrA regulatory system.
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http://dx.doi.org/10.1371/journal.ppat.1007800DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6548404PMC
May 2019

Atomic Force Microscopy Demonstrates that Candida glabrata Uses Three Epa Proteins To Mediate Adhesion to Abiotic Surfaces.

mSphere 2019 05 1;4(3). Epub 2019 May 1.

Louvain Institute of Biomolecular Science and Technology, Université Catholique de Louvain, Louvain-la-Neuve, Belgium

The fungal pathogen can cause both mucosal and disseminated infections. Cell adhesion, a key step in colonization and infection, depends in primarily on the Epa family of cell adhesion proteins. While Epa proteins have been documented to mediate specific adhesion to host glycans, some of them also promote nonspecific adhesion to abiotic surfaces, though this is incompletely understood. Here we address this issue using a combination of genetics and single-cell force measurements. By quantifying the forces driving the attachment of single cells to hydrophobic and hydrophilic substrates, we show that cell adhesion is strongly increased by loss of Sir-mediated silencing. Using a series of mutant strains lacking specific genes, we demonstrate unexpectedly that three major Epa proteins, Epa1, Epa6, and Epa7, primarily contribute to both hydrophilic and hydrophobic interactions, suggesting a broad role for the Epa adhesins in mediating specific and nonspecific adherence and implicating Epa genes in biofilm formation on abiotic surfaces. cell wall proteins mediate the attachment of to abiotic surfaces through molecular interactions that are poorly understood. Here, we study the forces engaged in Epa-dependent adhesion using single-cell techniques. Fungal adhesion to hydrophilic and hydrophobic substrates involves mainly three Epa proteins, suggesting a broad role for the Epa adhesins in mediating adherence. These proteins might represent a potential target for the development of innovative antifungal drugs.
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http://dx.doi.org/10.1128/mSphere.00277-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6495341PMC
May 2019

Fluidic Force Microscopy Demonstrates That Homophilic Adhesion by Candida albicans Als Proteins Is Mediated by Amyloid Bonds between Cells.

Nano Lett 2019 06 30;19(6):3846-3853. Epub 2019 Apr 30.

Institute of Life Sciences , Université catholique de Louvain , Croix du Sud, 4-5, bte L7.07.06 , B-1348 Louvain-la-Neuve , Belgium.

The fungal pathogen Candida albicans frequently forms drug-resistant biofilms in hospital settings and in chronic disease patients. Cell adhesion and biofilm formation involve a family of cell surface Als (agglutinin-like sequence) proteins. It is now well documented that amyloid-like clusters of laterally arranged Als proteins activate cell-cell adhesion under mechanical stress, but whether amyloid-like bonds form between aggregating cells is not known. To address this issue, we measure the forces driving Als5-mediated intercellular adhesion using an innovative fluidic force microscopy platform. Strong cell-cell adhesion is dependent on expression of amyloid-forming Als5 at high cell surface density and is inhibited by a short antiamyloid peptide. Furthermore, there is greatly attenuated binding between cells expressing amyloid-forming Als5 and cells with a nonamyloid form of Als5. Thus, homophilic bonding between Als5 proteins on adhering cells is the major mode of fungal aggregation, rather than protein-ligand interactions. These 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.
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http://dx.doi.org/10.1021/acs.nanolett.9b01010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6638552PMC
June 2019

Localized incorporation of outer membrane components in the pathogen .

EMBO J 2019 03 11;38(5). Epub 2019 Jan 11.

Research Unit in Biology of Microorganisms (URBM), Narilis University of Namur (UNamur), Namur, Belgium

The zoonotic pathogen is part of the Rhizobiales, which are alpha-proteobacteria displaying unipolar growth. Here, we show that this bacterium exhibits heterogeneity in its outer membrane composition, with clusters of rough lipopolysaccharide co-localizing with the essential outer membrane porin Omp2b, which is proposed to allow facilitated diffusion of solutes through the porin. We also show that the major outer membrane protein Omp25 and peptidoglycan are incorporated at the new pole and the division site, the expected growth sites. Interestingly, lipopolysaccharide is also inserted at the same growth sites. The absence of long-range diffusion of main components of the outer membrane could explain the apparent immobility of the Omp2b clusters, as well as unipolar and mid-cell localizations of newly incorporated outer membrane proteins and lipopolysaccharide. Unipolar growth and limited mobility of surface structures also suggest that new surface variants could arise in a few generations without the need of diluting pre-existing surface antigens.
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http://dx.doi.org/10.15252/embj.2018100323DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6396147PMC
March 2019

Bacterial Sexuality at the Nanoscale.

Nano Lett 2018 09 31;18(9):5821-5826. Epub 2018 Aug 31.

Louvain Institute of Biomolecular Science and Technology , Université catholique de Louvain , Croix du Sud, 4-5 , B-1348 Louvain-la-Neuve , Belgium.

Understanding the basic mechanisms of bacterial sexuality is an important topic in current microbiology and biotechnology. While classical methods used to study gene transfer provide information on whole cell populations, nanotechnologies offer new opportunities for analyzing the behavior of individual mating partners. We introduce an innovative atomic force microscopy (AFM) 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. We demonstrate that the adhesion forces between single donor and recipient cells are very strong (∼2 nN). Using a mutant plasmid, we find that these high forces are mediated by a pXO16 aggregation locus that contains two large surface protein genes. Notably, we also show that AFM can be used to mechanically induce plasmid transfer between single partners, revealing that transfer is very fast (<15 min) and triggers major cell surface changes in transconjugant cells. We anticipate that the single-cell technology developed here will 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. Also, the method could be useful in nanomedicine for the design of antiadhesion compounds capable of preventing intimate cell-cell contacts, therefore providing a means to control the resistance and virulence of bacterial pathogens.
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http://dx.doi.org/10.1021/acs.nanolett.8b02463DOI Listing
September 2018

Force-Induced Strengthening of the Interaction between Clumping Factor B and Loricrin.

mBio 2017 Dec 5;8(6). Epub 2017 Dec 5.

Institute of Life Sciences, Université Catholique de Louvain, Louvain-la-Neuve, Belgium

Bacterial pathogens that colonize host surfaces are subjected to physical stresses such as fluid flow and cell surface contacts. How bacteria respond to such mechanical cues is an important yet poorly understood issue. uses a repertoire of surface proteins to resist shear stress during the colonization of host tissues, but whether their adhesive functions can be modulated by physical forces is not known. Here, we show that the interaction of clumping factor B (ClfB) with the squamous epithelial cell envelope protein loricrin is enhanced by mechanical force. We find that ClfB mediates adhesion to loricrin through weak and strong molecular interactions both in a laboratory strain and in a clinical isolate. Strong forces (~1,500 pN), among the strongest measured for a receptor-ligand bond, are consistent with a high-affinity "dock, lock, and latch" binding mechanism involving dynamic conformational changes in the adhesin. Notably, we demonstrate that the strength of the ClfB-loricrin bond increases as mechanical force is applied. These findings favor a two-state model whereby bacterial adhesion to loricrin is enhanced through force-induced conformational changes in the ClfB molecule, from a weakly binding folded state to a strongly binding extended state. This force-sensitive mechanism may provide with a means to finely tune its adhesive properties during the colonization of host surfaces, helping cells to attach firmly under high shear stress and to detach and spread under low shear stress. colonizes the human skin and the nose and can cause various disorders, including superficial skin lesions and invasive infections. During nasal colonization, the surface protein clumping factor B (ClfB) binds to the squamous epithelial cell envelope protein loricrin, but the molecular interactions involved are poorly understood. Here, we unravel the molecular mechanism guiding the ClfB-loricrin interaction. We show that the ClfB-loricrin bond is remarkably strong, consistent with a high-affinity "dock, lock, and latch" binding mechanism. We discover that the ClfB-loricrin interaction is enhanced under tensile loading, thus providing evidence that the function of an surface protein can be activated by physical stress.
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http://dx.doi.org/10.1128/mBio.01748-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5717387PMC
December 2017

Nucleation and growth of a bacterial functional amyloid at single-fiber resolution.

Nat Chem Biol 2017 Aug 19;13(8):902-908. Epub 2017 Jun 19.

Structural Biology Brussels, Vrije Universiteit Brussel, Brussels, Belgium.

Curli are functional amyloids produced by proteobacteria like Escherichia coli as part of the extracellular matrix that holds cells together into biofilms. The molecular events that occur during curli nucleation and fiber extension remain largely unknown. Combining observations from curli amyloidogenesis in bulk solutions with real-time in situ nanoscopic imaging at the single-fiber level, we show that curli display polar growth, and we detect two kinetic regimes of fiber elongation. Single fibers exhibit stop-and-go dynamics characterized by bursts of steady-state growth alternated with periods of stagnation. At high subunit concentrations, fibers show constant, unperturbed burst growth. Curli follow a one-step nucleation process in which monomers contemporaneously fold and oligomerize into minimal fiber units that have growth characteristics identical to those of the mature fibrils. Kinetic data and interaction studies of curli fibrillation in the presence of the natural inhibitor CsgC show that the inhibitor binds curli fibers and predominantly acts at the level of fiber elongation.
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http://dx.doi.org/10.1038/nchembio.2413DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5580806PMC
August 2017

Antibacterial properties of sophorolipid-modified gold surfaces against Gram positive and Gram negative pathogens.

Colloids Surf B Biointerfaces 2017 Sep 2;157:325-334. Epub 2017 Jun 2.

Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Réactivité de Surface, UMR 7197, 4 place Jussieu, 75005 Paris, France. Electronic address:

Sophorolipids are bioderived glycolipids displaying interesting antimicrobial properties. We show that they can be used to develop biocidal monolayers against Listeria ivanovii, a Gram-positive bacterium. The present work points out the dependence between the surface density and the antibacterial activity of grafted sophorolipids. It also emphasizes the broad spectrum of activity of these coatings, demonstrating their potential against both Gram-positive strains (Enteroccocus faecalis, Staphylococcus epidermidis, Streptococcus pyogenes) and Gram-negative strains (Escherichia coli, Pseudomonas aeruginosa and Salmonella typhymurium). After exposure to sophorolipids grafted onto gold, all these bacterial strains show a significant reduction in viability resulting from membrane damage as evidenced by fluorescent labelling and SEM-FEG analysis.
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http://dx.doi.org/10.1016/j.colsurfb.2017.05.072DOI Listing
September 2017

Single-Cell and Single-Molecule Analysis Unravels the Multifunctionality of the Staphylococcus aureus Collagen-Binding Protein Cna.

ACS Nano 2017 02 2;11(2):2160-2170. Epub 2017 Feb 2.

Institute of Life Sciences, Université Catholique de Louvain , Croix du Sud, 4-5, bte L7.07.06, Louvain-la-Neuve B-1348, Belgium.

The collagen-binding protein Cna is a prototype cell surface protein from Staphylococcus aureus which fulfils important physiological functions during pathogenesis. While it is established that Cna binds to collagen (Cn) via the high-affinity collagen hug mechanism, whether this protein is engaged in other ligand-binding mechanisms is poorly understood. Here, we use atomic force microscopy to demonstrate that Cna mediates attachment to two structurally and functionally different host proteins, i.e., the complement system protein C1q and the extracellular matrix protein laminin (Lam), through binding mechanisms that differ from the collagen hug. We show that single Cna-C1q and Cna-Lam bonds are much weaker than the high-affinity Cna-Cn bond and that their formation does not require the B-region of Cna. At the whole cell level, we find that bacterial adhesion to C1q-substrates involves only one (or two) molecular bond(s), while adhesion to Lam is mediated by multiple bonds, thus suggesting that multivalent or cooperative interactions may enhance the strength of adhesion. Both C1q and Lam interactions can be efficiently blocked by monoclonal antibodies directed against the minimal Cn-binding domain of Cna. These results show that Cna is a multifunctional protein capable of binding to multiple host ligands through mechanisms that differ from the classical collagen hug.
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http://dx.doi.org/10.1021/acsnano.6b08404DOI Listing
February 2017

Mechanical Strength and Inhibition of the Staphylococcus aureus Collagen-Binding Protein Cna.

mBio 2016 10 25;7(5). Epub 2016 Oct 25.

Institute of Life Sciences, Université catholique de Louvain, Louvain-la-Neuve, Belgium

The bacterial pathogen Staphylococcus aureus expresses a variety of cell surface adhesion proteins that bind to host extracellular matrix proteins. Among these, the collagen (Cn)-binding protein Cna plays important roles in bacterium-host adherence and in immune evasion. While it is well established that the A region of Cna mediates ligand binding, whether the repetitive B region has a dedicated function is not known. Here, we report the direct measurement of the mechanical strength of Cna-Cn bonds on living bacteria, and we quantify the antiadhesion activity of monoclonal antibodies (MAbs) targeting this interaction. We demonstrate that the strength of Cna-Cn bonds in vivo is very strong (~1.2 nN), consistent with the high-affinity "collagen hug" mechanism. The B region is required for strong ligand binding and has been found to function as a spring capable of sustaining high forces. This previously undescribed mechanical response of the B region is of biological significance as it provides a means to project the A region away from the bacterial surface and to maintain bacterial adhesion under conditions of high forces. We further quantified the antiadhesion activity of MAbs raised against the A region of Cna directly on living bacteria without the need for labeling or purification. Some MAbs are more efficient in blocking single-cell adhesion, suggesting that they act as competitive inhibitors that bind Cna residues directly involved in ligand binding. This report highlights the role of protein mechanics in activating the function of staphylococcal adhesion proteins and emphasizes the potential of antibodies to prevent staphylococcal adhesion and biofilm formation.

Importance: Cna is a collagen (Cn)-binding protein from Staphylococcus aureus that is involved in pathogenesis. Currently, we know little about the functional role of the repetitive B region of the protein. Here, we unravel the mechanical strength of Cna in living bacteria. We show that single Cna-Cn bonds are very strong, reflecting high-affinity binding by the collagen hug mechanism. We discovered that the B region behaves as a nanospring capable of sustaining high forces. This unanticipated mechanical response, not previously described for any staphylococcal adhesin, favors a model in which the B region has a mechanical function that is essential for strong ligand binding. Finally, we assess the antiadhesion activity of monoclonal antibodies against Cna, suggesting that they could be used to inhibit S. aureus adhesion.
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http://dx.doi.org/10.1128/mBio.01529-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5080380PMC
October 2016

Forces guiding staphylococcal adhesion.

J Struct Biol 2017 01 17;197(1):65-69. Epub 2015 Dec 17.

Université catholique de Louvain, Institute of Life Sciences, Croix du Sud 4-5, bte L7.07.06, B-1348 Louvain-la-Neuve, Belgium; Walloon Excellence in Life Sciences and Biotechnology (WELBIO), Belgium. Electronic address:

Staphylococcus epidermidis and Staphylococcus aureus are two important nosocomial pathogens that form biofilms on indwelling medical devices. Biofilm infections are difficult to fight as cells within the biofilm show increased resistance to antibiotics. Our understanding of the molecular interactions driving bacterial adhesion, the first stage of biofilm formation, has long been hampered by the paucity of appropriate force-measuring techniques. In this minireview, we discuss how atomic force microscopy techniques have enabled to shed light on the molecular forces at play during staphylococcal adhesion. Specific highlights include the study of the binding mechanisms of adhesion molecules by means of single-molecule force spectroscopy, the measurement of the forces involved in whole cell interactions using single-cell force spectroscopy, and the probing of the nanobiophysical properties of living bacteria via multiparametric imaging. Collectively, these findings emphasize the notion that force and function are tightly connected in staphylococcal adhesion.
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http://dx.doi.org/10.1016/j.jsb.2015.12.009DOI Listing
January 2017

Structure of Bolaamphiphile Sophorolipid Micelles Characterized with SAXS, SANS, and MD Simulations.

J Phys Chem B 2015 Oct 2;119(41):13113-33. Epub 2015 Oct 2.

Sorbonne Universités , UPMC Univ Paris 06, CNRS, Collège de France, UMR 7574, Chimie de la Matière Condensée de Paris, F-75005 Paris, France.

The micellar structure of sophorolipids, a glycolipid bolaamphiphile, is analyzed using a combination of small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS), and molecular dynamics (MD) simulations. Numerical modeling of SAXS curves shows that micellar morphology in the noncharged system (pH< 5) is made of prolate ellipsoids of revolution with core-shell morphology. Opposed to most surfactant systems, the hydrophilic shell has a nonhomogeneous distribution of matter: the shell thickness in the axial direction of the ellipsoid is found to be practically zero, while it measures about 12 Å at its cross-section, thus forming a "coffee bean"-like shape. The use of a contrast-matching SANS experiment shows that the hydrophobic component of sophorolipids is actually distributed in a narrow spheroidal region in the micellar core. These data seem to indicate a complex distribution of sophorolipids within the micelle, divided into at least three domains: a pure hydrophobic core, a hydrophilic shell, and a region of less defined composition in the axial direction of the ellipsoid. To account for these results, we make the hypothesis that sophorolipid molecules acquire various configurations within the micelle including bent and linear, crossing the micellar core. These results are confirmed by MD simulations which do show the presence of multiple sophorolipid configurations when passing from spherical to ellipsoidal aggregates. Finally, we also used Rb(+) and Sr(2+) counterions in combination with anomalous SAXS experiments to probe the distribution of the COO(-) group of sophorolipids upon small pH increase (5 < pH < 7), where repulsive intermicellar interactions become important. The poor ASAXS signal shows that the COO(-) groups are rather diffused in the broad hydrophilic shell rather than at the outer micellar/water interface.
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http://dx.doi.org/10.1021/acs.jpcb.5b05374DOI Listing
October 2015

Biocidal Properties of a Glycosylated Surface: Sophorolipids on Au(111).

ACS Appl Mater Interfaces 2015 Aug 6;7(32):18086-95. Epub 2015 Aug 6.

†Sorbonne Universités, UPMC Univ Paris 06, CNRS, Collège de France, Laboratoire de Chimie de la Matière Condensée de Paris, UMR 7574, 11 Place Marcelin Berthelot, 75005 Paris, France.

Classical antibacterial surfaces usually involve antiadhesive and/or biocidal strategies. Glycosylated surfaces are usually used to prevent biofilm formation via antiadhesive mechanisms. We report here the first example of a glycosylated surface with biocidal properties created by the covalent grafting of sophorolipids (a sophorose unit linked by a glycosidic bond to an oleic acid) through a self-assembled monolayer (SAM) of short aminothiols on gold (111) surfaces. The biocidal effect of such surfaces on Gram+ bacteria was assessed by a wide combination of techniques including microscopy observations, fluorescent staining, and bacterial growth tests. About 50% of the bacteria are killed via alteration of the cell envelope. In addition, the roles of the sophorose unit and aliphatic chain configuration are highlighted by the lack of activity of substrates modified, respectively, with sophorose-free oleic acid and sophorolipid-derivative having a saturated aliphatic chain. This system demonstrates thus the direct implication of a carbohydrate in the destabilization and disruption of the bacterial cell envelope.
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http://dx.doi.org/10.1021/acsami.5b05090DOI Listing
August 2015