Interactions peau/microbiote cutané : étude du microbiote cutané cultivable et influence de produits cosmétiques sur la virulence bactérienne. Apports de la technique de spectrométrie de masse MALDI-TOF

ROUEN-BU Sciences (764512102) / SudocSudocFranceF

Natural Variation of Hazelnut Allergenicity: Is There Any Potential for Selecting Hypoallergenic Varieties?

International audienceHazelnuts (Corylus avellanaL.) have an important role in human nutrition and health. However, they are a common cause of food allergy. Due to hazelnut varietal diversity, variety-dependent differences in the IgE-binding properties may be suspected, which could allow therapeutic strategies based on the use of hypoallergenic varieties to induce desensitization. In a proteogenomic approach, we aimed to evaluate the allergenic potential of a genetically diverse set of hazelnuts (n = 13 varieties). Minor differences were found at the level of genes encoding important allergens, namely Cor a 8, Cor a 9, and Cor a 14. Nevertheless, IgE-reactivity was similar for all varieties using sera from seven allergic individuals. The predominant IgE-reactive proteins were Cor a 9 (100%) and Cor a 1.04 (60%), with the former being the most frequently identified by a two-dimensional gel electrophoresis (2-DE)-based proteomic approach. Therefore, it seems that the conventional exclusion diet will hold its ground for the time being

Virulence of the <it>Pseudomonas fluorescens</it> clinical strain MFN1032 towards <it>Dictyostelium discoideum</it> and macrophages in relation with type III secretion system

<p>Abstract</p> <p>Background</p> <p><it>Pseudomonas fluorescens</it> biovar I MFN1032 is a clinical isolate able to grow at 37°C. This strain displays secretion-mediated hemolytic activity involving phospholipase C and cyclolipopeptides, and a cell-associated hemolytic activity distinct from the secreted hemolytic activity. Cell-associated hemolysis is independent of biosurfactant production and remains in a <it>gacA</it> mutant. Disruption of the hrpU-like operon (the basal part of type III secretion system from rhizospheric strains) suppresses this activity. We hypothesized that this phenotype could reflect evolution of an ancestral mechanism involved in the survival of this species in its natural niche. In this study, we evaluated the hrpU-like operon’s contribution to other virulence mechanisms using a panel of <it>Pseudomonas</it> strains from various sources.</p> <p>Results</p> <p>We found that MFN1032 inhibited the growth of the amoebae <it>Dictyostelium discoideum</it> and that this inhibition involved the hrpU-like operon and was absent in a <it>gacA</it> mutant. MFN1032 was capable of causing macrophage lysis, if the hrpU-like operon was intact, and this cytotoxicity remained in a <it>gacA</it> mutant. Cell-associated hemolytic activity and macrophage necrosis were found in other <it>P. fluorescens</it> clinical isolates, but not in biocontrol <it>P. fluorescens</it> strains harbouring hrpU-like operon. The growth of <it>Dictyostelium discoideum</it> was inhibited to a different extent by <it>P. fluorescens</it> strains without correlation between this inhibition and hrpU-like operon sequences.</p> <p>Conclusions</p> <p>In <it>P. fluorescens</it> MFN1032, the basal part of type III secretion system plays a role in <it>D. discoideum</it> growth inhibition and macrophage necrosis. The inhibition of <it>D. discoideum</it> growth is dependent on the GacS/GacA system, while cell-associated hemolytic activity and macrophage lysis are not. Virulence against eukaryotic cells based on the hrpU-like operon may be more than just a stochastic evolution of a conserved system dedicated to survival in competition with natural predators such as amoebae. It may also mean that there are some important modifications of other type III secretion system components, which remain unknown. Cell-associated hemolysis might be a good indicator of the virulence of <it>Pseudomonas fluorescens</it> strain.</p

Comparative Secretome Analyses of Human and Zoonotic Staphylococcus aureus Isolates CC8, CC22, and CC398

The spread of methicillin-resistant Staphylococcus aureus (MRSA) in the community, hospitals and in livestock is mediated by highly diverse virulence factors that include secreted toxins, superantigens, enzymes and surface-associated adhesins allowing host adaptation and colonization. Here, we combined proteogenomics, secretome and phenotype analyses to compare the secreted virulence factors in selected S. aureus isolates of the dominant human- and livestock-associated genetic lineages CC8, CC22, and CC398. The proteogenomic comparison revealed 2181 core genes and 1306 accessory genes in 18 S. aureus isolates reflecting the high genome diversity. Using secretome analysis, we identified 869 secreted proteins with 538 commons in eight isolates of CC8, CC22, and CC398. These include 64 predicted extracellular and 37 cell surface proteins that account for 82.4% of total secretome abundance. Among the top 10 most abundantly secreted virulence factors are the major autolysins (Atl, IsaA, Sle1, SAUPAN006375000), lipases and lipoteichoic acid hydrolases (Lip, Geh, LtaS), cytolytic toxins (Hla, Hlb, PSMβ1) and proteases (SspB). The CC398 isolates showed lower secretion of cell wall proteins, but higher secretion of α- and β-hemolysins (Hla, Hlb) which correlated with an increased Agr activity and strong hemolysis. CC398 strains were further characterized by lower biofilm formation and staphyloxanthin levels because of decreased SigB activity. Overall, comparative secretome analyses revealed CC8- or CC22-specific enterotoxin and Spl protease secretion as well as Agr- and SigB-controlled differences in exotoxin and surface protein secretion between human-specific and zoonotic lineages of S. aureus.Peer Reviewe

Pseudomonas fluorescens, a forgotten member of the human cutaneous microflora in interaction with skin communication and defense peptides

International audienc

Impact of Uriage thermal water on the physiology of skin bacteria

International audienc

Pseudomonas fluorescens, a forgotten member of the human cutaneous microflora in interaction with skin communication and defense peptides

International audienc

Effect of GABA, a Bacterial Metabolite, on Pseudomonas fluorescens Surface Properties and Cytotoxicity

Abstract: Different bacterial species and, particularly Pseudomonas fluorescens, can produce gamma-aminobutyric acid (GABA) and express GABA-binding proteins. In this study, we investigated the effect of GABA on the virulence and biofilm formation activity of different strains of P. fluorescens. Exposure of a psychotropic strain of P. fluorescens (MF37) to GABA (10 −5 M) increased its necrotic-like activity on eukaryotic (glial) cells, but reduced its apoptotic effect. Conversely, muscimol and bicuculline, the selective agonist and antagonist of eukaryote GABAA receptors, respectively, were ineffective. P. fluorescens MF37 did not produce biosurfactants, and its caseinase, esterase, amylase, hemolytic activity or pyoverdine productions were unchanged. In contrast, the effect of GABA was associated to rearrangements of the lipopolysaccharide (LPS) structure, particularly in the lipid A region. The surface hydrophobicity of MF37 was marginally modified, and GABA reduced its biofilm formation activity on PVC, but not on glass, although the initial adhesion was increased. Five other P. fluorescens strains were studied

Bacteriophages as Antimicrobial Agents? Proteomic Insights on Three Novel Lytic Bacteriophages Infecting ESBL-Producing Escherichia coli

International audienceWith the emergence of multiresistant bacteria, the use of bacteriophages is gaining renewed interest as potential antimicrobial agents. The aim of this study was to analyze the structure of three lytic bacteriophages infecting Escherichia coli (SD1, SD2, and SD3) using a gel-based proteomics approach and the cellular response of this bacterium to phage SD1 infection at the proteome level. The combination of the results of 1-DE and 2-DE followed by mass spectrometry led to the identification of 3, 14, and 9 structure proteins for SD1, SD2, and SD3 phages, respectively. Different protein profiles with common proteins were noticed. We also analyzed phageinduced effects by comparing samples from infected cells to those of noninfected cells. We verified important changes in E. coli proteins expression during phage SD1 infection, where there was an overexpression of proteins involved in stress response. Our results indicated that viral infection caused bacterial oxidative stress and bacterial cells response to stress was orchestrated by antioxidant defense mechanisms. This article makes an empirical scientific contribution toward the concept of bacteriophages as potential antimicrobial agents. With converging ecological threats in the 21st century, novel approaches to address the innovation gaps in antimicrobial development are more essential than ever. Further research on bacteriophages is called for in this broader context of planetary health and integrative biology

Cytoskeletal components can turn wall-less spherical bacteria into kinking helices

International audienceBacterial cell shape is generally determined through an interplay between the peptidoglycan cell wall and cytoplasmic filaments made of polymerized MreB. Indeed, some bacteria (e.g., Mycoplasma ) that lack both a cell wall and mreB genes consist of non-motile cells that are spherical or pleomorphic. However, other members of the same class Mollicutes (e.g., Spiroplasma , also lacking a cell wall) display a helical cell shape and kink-based motility, which is thought to rely on the presence of five MreB isoforms and a specific fibril protein. Here, we show that heterologous expression of Spiroplasma fibril and MreB proteins confers helical shape and kinking ability to Mycoplasma capricolum cells. Isoform MreB5 is sufficient to confer helicity and kink propagation to mycoplasma cells. Cryoelectron microscopy confirms the association of cytoplasmic MreB filaments with the plasma membrane, suggesting a direct effect on membrane curvature. However, in our experiments, the heterologous expression of MreBs and fibril did not result in efficient motility in culture broth, indicating that additional, unknown Spiroplasma components are required for swimming