Publications by authors named "Marion Mathelié-Guinlet"

21 Publications

  • Page 1 of 1

AFM force-clamp spectroscopy captures the nanomechanics of the Tad pilus retraction.

Nanoscale Horiz 2021 Jun;6(6):489-496

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

Motorization of bacterial pili is key to generate traction forces to achieve cellular function. The Tad (or Type IVc) pilus from Caulobacter crescentus is a widespread motorized nanomachine crucial for bacterial survival, evolution and virulence. An unusual bifunctional ATPase motor drives Tad pilus retraction, which helps the bacteria to land on target surfaces. Here, we use a novel platform combining a fluorescence-based screening of piliated bacteria and atomic force microscopy (AFM) force-clamp spectroscopy, to monitor over time (30 s) the nanomechanics and dynamics of the Tad nanofilament retraction under a high constant tension (300 pN). We observe striking transient variations of force and height originating from two phenomena: active pilus retraction and passive hydrophobic interactions between the pilus and the hydrophobic substrate. That the Tad pilus is able to retract under high tensile loading - at a velocity of ∼150 nm s-1 - indicates that this nanomachine is stronger than previously anticipated. Our findings show that pilus retraction and hydrophobic interactions work together to mediate bacterial cell landing and surface adhesion. The motorized pilus retraction actively triggers the cell to approach the substrate. At short distances, passive hydrophobic interactions accelerate the approach phenomenon and promote strong cell-substrate adhesion. This mechanism could provide a strategy to save ATP-based energy by the retraction ATPase. Our force-clamp AFM methodology offers promise to decipher the physics of bacterial nanomotors with high sensitivity and temporal resolution.
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http://dx.doi.org/10.1039/d1nh00158bDOI Listing
June 2021

Staphylococcus aureus vWF-binding protein triggers a strong interaction between clumping factor A and host vWF.

Commun Biol 2021 Apr 12;4(1):453. Epub 2021 Apr 12.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium.

The Staphylococcus aureus cell wall-anchored adhesin ClfA binds to the very large blood circulating protein, von Willebrand factor (vWF) via vWF-binding protein (vWbp), a secreted protein that does not bind the cell wall covalently. Here we perform force spectroscopy studies on living bacteria to unravel the molecular mechanism of this interaction. We discover that the presence of all three binding partners leads to very high binding forces (2000 pN), largely outperforming other known ternary complexes involving adhesins. Strikingly, our experiments indicate that a direct interaction involving features of the dock, lock and latch mechanism must occur between ClfA and vWF to sustain the extreme tensile strength of the ternary complex. Our results support a previously undescribed mechanism whereby vWbp activates a direct, ultra-strong interaction between ClfA and vWF. This intriguing interaction represents a potential target for therapeutic interventions, including synthetic peptides inhibiting the ultra-strong interactions between ClfA and its ligands.
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http://dx.doi.org/10.1038/s42003-021-01986-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8041789PMC
April 2021

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

AFM in cellular and molecular microbiology.

Cell Microbiol 2021 Mar 12:e13324. Epub 2021 Mar 12.

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

The unique capabilities of the atomic force microscope (AFM), including super-resolution imaging, piconewton force-sensitivity, nanomanipulation and ability to work under physiological conditions, have offered exciting avenues for cellular and molecular biology research. AFM imaging has helped unravel the fine architectures of microbial cell envelopes at the nanoscale, and how these are altered by antimicrobial treatment. Nanomechanical measurements have shed new light on the elasticity, tensile strength and turgor pressure of single cells. Single-molecule and single-cell force spectroscopy experiments have revealed the forces and dynamics of receptor-ligand interactions, the nanoscale distribution of receptors on the cell surface and the elasticity and adhesiveness of bacterial pili. Importantly, recent force spectroscopy studies have demonstrated that extremely stable bonds are formed between bacterial adhesins and their cognate ligands, originating from a catch bond behaviour allowing the pathogen to reinforce adhesion under shear or tensile stress. Here, we survey how the versatility of AFM has enabled addressing crucial questions in microbiology, with emphasis on bacterial pathogens.
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http://dx.doi.org/10.1111/cmi.13324DOI Listing
March 2021

Adhesion of to During Co-Infection Promotes Bacterial Dissemination Through the Host Immune Response.

Front Cell Infect Microbiol 2020 2;10:624839. Epub 2021 Feb 2.

Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, Department of Biology, KU Leuven, Leuven, Belgium.

Interspecies interactions greatly influence the virulence, drug tolerance and ultimately the outcome of polymicrobial biofilm infections. A synergistic interaction is observed between the fungus and the bacterium . These species are both normal commensals of most healthy humans and co-exist in several niches of the host. However, under certain circumstances, they can cause hospital-acquired infections with high morbidity and mortality rates. Using a mouse model of oral co-infection, we previously showed that an oral infection with predisposes to a secondary systemic infection with . Here, we unraveled this intriguing mechanism of bacterial dissemination. Using static and dynamic adhesion assays in combination with single-cell force spectroscopy, we identified Als1 and Als3 adhesins as the molecular players involved in the interaction with and in subsequent bacterial dissemination. Remarkably, we identified the host immune response as a key element required for bacterial dissemination. We found that the level of immunosuppression of the host plays a critical yet paradoxical role in this process. In addition, secretion of candidalysin, the peptide responsible for immune activation and cell damage, is required for colonization and subsequent bacterial dissemination. The physical interaction with enhances bacterial uptake by phagocytic immune cells, thereby enabling an opportunity to disseminate.
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http://dx.doi.org/10.3389/fcimb.2020.624839DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7884861PMC
February 2021

Single-cell fluidic force microscopy reveals stress-dependent molecular interactions in yeast mating.

Commun Biol 2021 01 4;4(1):33. Epub 2021 Jan 4.

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

Sexual agglutinins of the budding yeast Saccharomyces cerevisiae are proteins mediating cell aggregation during mating. Complementary agglutinins expressed by cells of opposite mating types "a" and "α" bind together to promote agglutination and facilitate fusion of haploid cells. By means of an innovative single-cell manipulation assay combining fluidic force microscopy with force spectroscopy, we unravel the strength of single specific bonds between a- and α-agglutinins (~100 pN) which require pheromone induction. Prolonged cell-cell contact strongly increases adhesion between mating cells, likely resulting from an increased expression of agglutinins. In addition, we highlight the critical role of disulfide bonds of the a-agglutinin and of histidine residue H of α-agglutinin. Most interestingly, we find that mechanical tension enhances the interaction strength, pointing to a model where physical stress induces conformational changes in the agglutinins, from a weak-binding folded state, to a strong-binding extended state. Our single-cell technology shows promises for understanding and controlling the complex mechanism of yeast sexuality.
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http://dx.doi.org/10.1038/s42003-020-01498-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7782832PMC
January 2021

binds to the N-terminal region of corneodesmosin to adhere to the stratum corneum in atopic dermatitis.

Proc Natl Acad Sci U S A 2021 01;118(1)

Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin 2, Ireland;

colonizes the skin of the majority of patients with atopic dermatitis (AD), and its presence increases disease severity. Adhesion of to corneocytes in the stratum corneum is a key initial event in colonization, but the bacterial and host factors contributing to this process have not been defined. Here, we show that interacts with the host protein corneodesmosin. Corneodesmosin is aberrantly displayed on the tips of villus-like projections that occur on the surface of AD corneocytes as a result of low levels of skin humectants known as natural moisturizing factor (NMF). An mutant deficient in fibronectin binding protein B (FnBPB) and clumping factor B (ClfB) did not bind to corneodesmosin in vitro. Using surface plasmon resonance, we found that FnBPB and ClfB proteins bound with similar affinities. The binding site was localized to the N-terminal glycine-serine-rich region of corneodesmosin. Atomic force microscopy showed that the N-terminal region was present on corneocytes containing low levels of NMF and that blocking it with an antibody inhibited binding of individual cells to corneocytes. Finally, we found that mutants deficient in FnBPB or ClfB have a reduced ability to adhere to low-NMF corneocytes from patients. In summary, we show that FnBPB and ClfB interact with the accessible N-terminal region of corneodesmosin on AD corneocytes, allowing to take advantage of the aberrant display of corneodesmosin that accompanies low NMF in AD. This interaction facilitates the characteristic strong binding of to AD corneocytes.
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http://dx.doi.org/10.1073/pnas.2014444118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7817190PMC
January 2021

Stress-Induced Catch-Bonds to Enhance Bacterial Adhesion.

Trends Microbiol 2021 Apr 19;29(4):286-288. Epub 2020 Dec 19.

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

Physical forces have a profound influence on bacterial cell physiology and disease. A striking example is the formation of catch-bonds that reinforce under mechanical stress. While mannose-binding by the Escherichia coli FimH adhesin has long been the only thoroughly studied microbial catch-bond, it has recently become clear that proteins from other species, such as staphylococci, are also engaged in such stress-dependent interactions.
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http://dx.doi.org/10.1016/j.tim.2020.11.009DOI Listing
April 2021

Single-Molecule Analysis Demonstrates Stress-Enhanced Binding between Surface Protein IsdB and Host Cell Integrins.

Nano Lett 2020 12 25;20(12):8919-8925. Epub 2020 Nov 25.

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

Binding of surface proteins to endothelial cell integrins plays essential roles in host cell adhesion and invasion, eventually leading to life-threatening diseases. The staphylococcal protein IsdB binds to β3-containing integrins through a mechanism that has never been thoroughly investigated. Here, we identify and characterize at the nanoscale a previously undescribed stress-dependent adhesion between IsdB and integrin αβ. The strength of single IsdB-αβ interactions is moderate (∼100 pN) under low stress, but it increases dramatically under high stress (∼1000-2000 pN) to exceed the forces traditionally reported for the binding between integrins and Arg-Gly-Asp (RGD) sequences. We suggest a mechanism where high mechanical stress induces conformational changes in the integrin from a low-affinity, weak binding state to a high-affinity, strong binding state. This single-molecule study highlights that direct adhesin-integrin interactions represent potential targets to fight staphylococcal infections.
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http://dx.doi.org/10.1021/acs.nanolett.0c04015DOI Listing
December 2020

Force-clamp spectroscopy identifies a catch bond mechanism in a Gram-positive pathogen.

Nat Commun 2020 10 27;11(1):5431. Epub 2020 Oct 27.

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

Physical forces have profound effects on cellular behavior, physiology, and disease. Perhaps the most intruiguing and fascinating example is the formation of catch-bonds that strengthen cellular adhesion under shear stresses. Today mannose-binding by the Escherichia coli FimH adhesin remains one of the rare microbial catch-bond thoroughly characterized at the molecular level. Here we provide a quantitative demonstration of a catch-bond in living Gram-positive pathogens using force-clamp spectroscopy. We show that the dock, lock, and latch interaction between staphylococcal surface protein SpsD and fibrinogen is strong, and exhibits an unusual catch-slip transition. The bond lifetime first grows with force, but ultimately decreases to behave as a slip bond beyond a critical force (~1 nN) that is orders of magnitude higher than for previously investigated complexes. This catch-bond, never reported for a staphylococcal adhesin, provides the pathogen with a mechanism to tightly control its adhesive function during colonization and infection.
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http://dx.doi.org/10.1038/s41467-020-19216-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7591895PMC
October 2020

The Molecular Complex between Staphylococcal Adhesin SpsD and Fibronectin Sustains Mechanical Forces in the Nanonewton Range.

mBio 2020 07 7;11(4). Epub 2020 Jul 7.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium

The bacterial pathogen is involved in canine otitis externa and pyoderma as well as in surgical wound and urinary tract infections. Invasion of canine epithelial cells is promoted by fibronectin (Fn)-binding proteins SpsD and SpsL through molecular interactions that are currently unknown. By means of single-molecule experiments, we discover that both adhesins have distinct molecular mechanisms for binding to Fn. We show that the SpsD-Fn interaction has a strength equivalent to that of a covalent bond (∼1.5 to 1.8 nN), which is an order of magnitude stronger than the binding force of classical receptor-ligand complexes. We suggest that this extreme mechanostability originates from the β-sheet organization of a tandem β-zipper. Upon binding to FnI modules, the intrinsically disordered binding sequences of SpsD would shift into an ordered structure by forming additional β-strands along triple peptide β-sheets in the Fn molecule. Dynamic force measurements reveal an unexpected behavior, i.e., that strong bonds are activated by mechanical tension as observed with catch bonds. By contrast, the SpsL-Fn interaction involves multiple weak bonds (∼0.2 nN) that rupture sequentially under force. Together with the recently described dock, lock, and latch complex, the ultrastrong interaction unraveled here is among the strongest noncovalent biological interaction measured to date. Our findings may find applications for the identification of inhibitory compounds to treat infections triggered by pathogens engaged in tandem β-zipper interactions. Binding of surface proteins SpsD and SpsL to fibronectin (Fn) plays a critical role in the invasion of canine epithelial cells. Here, we discover that both adhesins have different mechanisms for binding to Fn. The force required to separate SpsD from Fn is extremely strong, consistent with the unusual β-sheet organization of a high-affinity tandem β-zipper. By contrast, unbinding of the SpsL-Fn complex involves the sequential rupture of single weak bonds. Our findings may be of biological relevance as SpsD and SpsL are likely to play complementary roles during invasion. While the SpsD β-zipper supports strong bacterial adhesion and triggers invasion, the weak SpsL interaction would favor fast detachment, enabling the pathogen to colonize new sites.
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http://dx.doi.org/10.1128/mBio.00371-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7343985PMC
July 2020

Nanomechanics of the molecular complex between staphylococcal adhesin SpsD and elastin.

Nanoscale 2020 Jul 24;12(26):13996-14003. Epub 2020 Jun 24.

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

Staphylococcus pseudintermedius surface protein SpsD binds to extracellular matrix proteins to invade canine epithelial cells. Using single-molecule experiments, we show that SpsD engages in two modes of interaction with elastin that are tightly controlled by physical stress. Binding is weak (∼100 pN) at low tensile force (i.e. loading rate), but is dramatically enhanced (up to ∼1500 pN) by mechanical tension. Consistent with a "dock, lock, and latch" (DLL) mechanism, this force represents among the highest mechanical strengths known for a non-covalent biological interaction. The transition from weak to strong binding correlates with an increase in molecular stiffness but, surprisingly, with a decrease in molecular extension. This unanticipated mechanical behavior indicates that the adhesin is engaged in two distinct interaction mechanisms. Our results emphasize the crucial role of protein nanomechanics in the adhesion of staphylococci, and illustrate their wide diversity of force-dependent ligand-binding activities. These single-molecule mechanical experiments may contribute to the development of antiadhesion approaches to treat infections caused by S. pseudintermedius and other bacterial pathogens engaged in DLL interactions.
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http://dx.doi.org/10.1039/d0nr02745fDOI Listing
July 2020

Bacterial Cell Mechanics Beyond Peptidoglycan.

Trends Microbiol 2020 09 25;28(9):706-708. Epub 2020 May 25.

Institute of Life Sciences, UCLouvain, Croix du Sud, 4-5, bte L7.07.07, B-1348 Louvain-la-Neuve, Belgium; Walloon Excellence in Life sciences and Biotechnology (WELBIO), Wavre, Belgium. Electronic address:

The bacterial cell envelope plays essential roles in controlling cell shape, division, pathogenicity, and resistance against external stresses. In Escherichia coli, peptidoglycan (PG) has long been thought to be the primary component that conveys mechanical strength to the envelope. But a recent publication demonstrates the key contribution of the lipoprotein Lpp in defining the stiffness of the cell envelope and its sensitivity to drugs.
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http://dx.doi.org/10.1016/j.tim.2020.04.013DOI Listing
September 2020

Lipoprotein Lpp regulates the mechanical properties of the E. coli cell envelope.

Nat Commun 2020 04 14;11(1):1789. Epub 2020 Apr 14.

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

The mechanical properties of the cell envelope in Gram-negative bacteria are controlled by the peptidoglycan, the outer membrane, and the proteins interacting with both layers. In Escherichia coli, the lipoprotein Lpp provides the only covalent crosslink between the outer membrane and the peptidoglycan. Here, we use single-cell atomic force microscopy and genetically engineered strains to study the contribution of Lpp to cell envelope mechanics. We show that Lpp contributes to cell envelope stiffness in two ways: by covalently connecting the outer membrane to the peptidoglycan, and by controlling the width of the periplasmic space. Furthermore, mutations affecting Lpp function substantially increase bacterial susceptibility to the antibiotic vancomycin, indicating that Lpp-dependent effects can affect antibacterial drug efficacy.
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http://dx.doi.org/10.1038/s41467-020-15489-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7156740PMC
April 2020

How Microbes Use Force To Control Adhesion.

J Bacteriol 2020 05 27;202(12). Epub 2020 May 27.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium

Microbial adhesion and biofilm formation are usually studied using molecular and cellular biology assays, optical and electron microscopy, or laminar flow chamber experiments. Today, atomic force microscopy (AFM) represents a valuable addition to these approaches, enabling the measurement of forces involved in microbial adhesion at the single-molecule level. In this minireview, we discuss recent discoveries made applying state-of-the-art AFM techniques to microbial specimens in order to understand the strength and dynamics of adhesive interactions. These studies shed new light on the molecular mechanisms of adhesion and demonstrate an intimate relationship between force and function in microbial adhesins.
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http://dx.doi.org/10.1128/JB.00125-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7253613PMC
May 2020

Entropic Bristles Tune the Seeding Efficiency of Prion-Nucleating Fragments.

Cell Rep 2020 02;30(8):2834-2845.e3

VIB Center for Brain and Disease Research, 3000 Leuven, Belgium; Switch Laboratory, Department of Cellular and Molecular Medicine, KULeuven, 3000 Leuven, Belgium. Electronic address:

Prions of lower eukaryotes are self-templating protein aggregates with cores formed by parallel in-register beta strands. Short aggregation-prone glutamine (Q)- and asparagine (N)-rich regions embedded in longer disordered domains have been proposed to act as nucleation sites that initiate refolding of soluble prion proteins into highly ordered fibrils, termed amyloid. We demonstrate that a short Q/N-rich peptide corresponding to a proposed nucleation site in the prototype Saccharomyces cerevisiae prion protein Sup35 is sufficient to induce infectious cytosolic prions in mouse neuroblastoma cells ectopically expressing the soluble Sup35 NM prion domain. Embedding this nucleating core in a non-native N-rich sequence that does not form amyloid but acts as an entropic bristle quadruples seeding efficiency. Our data suggest that large disordered sequences flanking an aggregation core in prion proteins act as not only solubilizers of the monomeric protein but also breakers of the formed amyloid fibrils, enhancing infectivity of the prion seeds.
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http://dx.doi.org/10.1016/j.celrep.2020.01.098DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7043027PMC
February 2020

What makes bacterial pathogens so sticky?

Mol Microbiol 2020 04 16;113(4):683-690. Epub 2020 Jan 16.

Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium.

Pathogenic bacteria use a variety of cell surface adhesins to promote binding to host tissues and protein-coated biomaterials, as well as cell-cell aggregation. These cellular interactions represent the first essential step that leads to host colonization and infection. Atomic force microscopy (AFM) has greatly contributed to increase our understanding of the specific interactions at play during microbial adhesion, down to the single-molecule level. A key asset of AFM is that adhesive interactions are studied under mechanical force, which is highly relevant as surface-attached pathogens are often exposed to physical stresses in the human body. These studies have identified sophisticated binding mechanisms in adhesins, which represent promising new targets for antiadhesion therapy.
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http://dx.doi.org/10.1111/mmi.14448DOI Listing
April 2020

Detrimental impact of silica nanoparticles on the nanomechanical properties of Escherichia coli, studied by AFM.

J Colloid Interface Sci 2018 Nov 29;529:53-64. Epub 2018 May 29.

Univ. Bordeaux, CNRS, LOMA, UMR5798, 351 cours de la Libération, 33400 Talence, France. Electronic address:

Despite great innovative and technological promises, nanoparticles (NPs) can ultimately exert an antibacterial activity by affecting the cell envelope integrity. This envelope, by conferring the cell its rigidity and protection, is intimately related to the mechanical behavior of the bacterial surface. Depending on their size, surface chemistry, shape, NPs can induce damages to the cell morphology and structure among others, and are therefore expected to alter the overall mechanical properties of bacteria. Although Atomic Force Microscopy (AFM) stands as a powerful tool to study biological systems, with high resolution and in near physiological environment, it has rarely been applied to investigate at the same time both morphological and mechanical degradations of bacteria upon NPs treatment. Consequently, this study aims at quantifying the impact of the silica NPs (SiO-NPs) on the mechanical properties of E. coli cells after their exposure, and relating it to their toxic activity under a critical diameter. Cell elasticity was calculated by fitting the force curves with the Hertz model, and was correlated with the morphological study. SiO-NPs of 100 nm diameter did not trigger any significant change in the Young modulus of E. coli, in agreement with the bacterial intact morphology and membrane structure. On the opposite, the 4 nm diameter SiO-NPs did induce a significant decrease in E. coli Young modulus, mainly associated with the disorganization of lipopolysaccharides in the outer membrane and the permeation of the underlying peptidoglycan layer. The subsequent toxic behavior of these NPs is finally confirmed by the presence of membrane residues, due to cell lysis, exhibiting typical adhesion features.
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http://dx.doi.org/10.1016/j.jcis.2018.05.098DOI Listing
November 2018

Probing the threshold of membrane damage and cytotoxicity effects induced by silica nanoparticles in Escherichia coli bacteria.

Adv Colloid Interface Sci 2017 Jul 28;245:81-91. Epub 2017 Apr 28.

Univ. Bordeaux, CNRS, LOMA, UMR 5798, 351 cours de la Libération, 33400 Talence, France; Cellule de transfert NanoPhyNov, ADERA, LOMA, 351 cours de la Libération, 33400 Talence, France. Electronic address:

The engineering of nanomaterials, because of their specific properties, is increasingly being developed for commercial purposes over the past decades, to enhance diagnosis, cosmetics properties as well as sensing efficiency. However, the understanding of their fate and thus their interactions at the cellular level with bio-organisms remains elusive. Here, we investigate the size- and charge-dependence of the damages induced by silica nanoparticles (SiO-NPs) on Gram-negative Escherichia coli bacteria. We show and quantify the existence of a NPs size threshold discriminating toxic and inert SiO-NPs with a critical particle diameter (Φ) in the range 50nm-80nm. This particular threshold is identified at both the micrometer scale via viability tests through Colony Forming Units (CFU) counting, and the nanometer scale via atomic force microscopy (AFM). At this nanometer scale, AFM emphasizes the interaction between the cell membrane and SiO-NPs from both topographic and mechanical points of view. For SiO-NPs with Φ>Φ no change in E. coli morphology nor its outer membrane (OM) organization is observed unless the NPs are positively charged in which case reorganization and disruption of the OM are detected. Conversely, when Φ<Φ, E. coli exhibit unusual spherical shapes, partial collapse, even lysis, and OM reorganization.
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http://dx.doi.org/10.1016/j.cis.2017.04.012DOI Listing
July 2017

Influence of oxidized lipids on palmitoyl-oleoyl-phosphatidylcholine organization, contribution of Langmuir monolayers and Langmuir-Blodgett films.

Chem Phys Lipids 2016 10 12;200:74-82. Epub 2016 Jul 12.

Laboratoire Ondes et Matière d'Aquitaine (LOMA), UMR CNRS 5798, Université de Bordeaux, 351 cours de la libération, 33405 Talence Cedex, France. Electronic address:

In this work, we studied the interaction of two oxidized lipids, PoxnoPC and PazePC, with POPC phospholipid. Mean molecular areas obtained from (π-A) isotherms of mixed PoxnoPC-POPC and PazePC-POPC monolayers revealed different behaviors of these two oxidized lipids: the presence of PoxnoPC in the monolayers induces their expansion, mean molecular areas being higher than those expected in the case of ideal mixtures. PazePC-POPC behave on the whole ideally. This difference can be explained by a different conformation of oxidized lipids. Moreover the carboxylic function of PazePC is protonated under our experimental conditions, as shown by (π-A) isotherms of PazePC at different pH values. Both oxidized lipids induce also an increase of the monolayer elasticity, PoxnoPC being slightly more efficient than PazePC. These monolayers were transferred from the air-water interface onto mica supports for a study by AFM. AFM images are on the whole homogenous, suggesting the presence of only one lipid phase in both cases. However, in the case of PazePC-POPC monolayers, AFM images show also the presence of areas thicker of 7nm to 10nm than the surrounding lipid phase, probably due to the local formation of multilayer systems induced by compression.
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http://dx.doi.org/10.1016/j.chemphyslip.2016.07.001DOI Listing
October 2016

Morphological and nanostructural surface changes in Escherichia coli over time, monitored by atomic force microscopy.

Colloids Surf B Biointerfaces 2016 May 6;141:355-364. Epub 2016 Feb 6.

Université de Bordeaux, LOMA, CNRS UMR 5798, 351 Cours de la Libération, 33405 Talence, France. Electronic address:

The present study aims at evaluating intrinsic changes in Escherichia coli (E. coli) surface over time, by Atomic Force Microscopy (AFM). For that purpose, bacteria were immobilized on mica or on mica previously functionalized by the deposition of a polyelectrolyte multilayer cushion. AFM images reveal that E. coli population goes through different stages. Firstly, after a week, the number of healthy bacteria decreases resulting in a release of cellular components which likely become, in turn, a nutrition source for increasing the healthy population after around two weeks. Finally, after one month, most of the bacteria is dead. Our study shows a transition of a healthy rod-shaped bacterium to a dead collapsed one. Most importantly, along with the morphological evolution of bacteria, are the structure changes and the mechanical properties of their outer membrane, emphasized by AFM phase images with very high resolution. Indeed, the surface of healthy bacteria is characterized by a phase separation pattern, thereafter mentioned as "ripples". Bacterial ageing goes along with the loss of this organized structure, turning into circular areas with irregular boundaries. These changes are likely caused by a re-organization, due to external stress, of mainly lipopolysaccharides (LPS) present in the outer membrane of E. coli.
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http://dx.doi.org/10.1016/j.colsurfb.2016.02.006DOI Listing
May 2016