Evaluation du modèle Caenorhabditis elegans pour estimer la qualité d’une eau eau. Application à l’eau de la Dordogne sur la Communauté de Communes de Sumène-Artense

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Photokilling of Escherichia coli Using Hybrid Titania Nanoparticles Suspended in an Aqueous Liquid

International audienceIn this work, the photokilling of Escherichia coli using a " one-pot " synthesized suspension of anatase crystallized nanoparticles is evaluated. Preliminary to the biological tests concerning the antibacterial efficiency, the fabricated suspension , using a derived sol-gel process in soft chemistry condition, is characterized. Structural properties of the nano-particles are investigated using Electronic Transmission Microscopy (TEM) equipped with Selected Area Electron Dif-fraction (SAED) probe and X-ray diffraction. The inorganic solid content was evaluated by Thermogravimetric Analysis (TGA). Photodegradation of Acid Orange 7 in aqueous solution was used as a probe to assess the photocatalytic activity of the elaborated suspension under UV irradiation. The photokilling of Escherichia coli in presence of hybrid TiO 2 nanoparticles suspended in aqueous liquid under UV irradiation is evaluated. Such TiO 2 nanoparticles suspension shows a strong bactericidal activity with the total destruction of bacteria after only one hour

Environmental Toxicity and Antimicrobial Efficiency of Titanium Dioxide Nanoparticles in Suspension

International audienceThe aim of this work was to evaluate the photokilling efficiency of synthesized titanium dioxide nanoparticles in suspension. Two strains of Escherichia coli, Lactobacillus casei rhamnosus and Staphylococcus aureus were used as probes to test the photokilling activities of the nanoparticles. The toxicity effects of TiO 2 nanoparticles on the environment were determined by a standard test using gram-negative bioluminescent bacteria Vibrio fischeri. The antimicrobial activity of these nanoparticles (NPs) was then investigated versus NPs concentration, UV irradiation time and mi-cro-organism strains. We evaluated the LC50 values of the nanoparticles suspension by counting the Colony-Forming Units. Results highlighted the differences in bacteria sensitivity facing photo-killing treatment induced by the irradiation of anatase TiO 2 nanoparticles suspension. At the concentration of 1 g·L −1 TiO 2 , tested bacteria were killed after 30 minutes of photo-treatment. Using different TiO 2 concentrations, the Staphylococcus aureus gram-positive/catalase-positive bacteria were more resistant than gram-negative/catalase-positive ones or gram-positive/catalase-negative bacteria. An effect of UV irradiation was evaluated by the quantification of hydrogen peroxide generated by the photolysis of water molecules in presence of the nanoparticles with or without the most resistant bacterium (S. aureus). After 30 minutes with UV irradiation in these two conditions , the concentration of hydrogen peroxide was 35 µM in presence of 1.2 g·L −1 TiO 2 suspension. This result suggested that the resistance mechanism of S. aureus was not due to an extracelullar H 2 O 2 enzymatic degradation

La surface de trayon des vaches laitières : un réservoir de biodiversité ?

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Characterization and comparison of antioxidant activities of almond and hazelnutbased beverages and their fermented forms by a consortium of lactic bacteria

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Caenorhabditis elegans, un modèle utilisé pour le criblage de microbiotes fromagers à effet santé

International audienceCaenorhabditis elegans, un modèle utilisé pour le criblage de microbiotes fromagers à effet sant

Design and synthesis of original fluorescent probes for use in microscopy on a model organism : Caenorhabditis elegans

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Etude des propriétés biologiques de fractions de fromage à l’aide d’un modèle in vivo innovant.

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Caractérisation in vivo des mécanismes probiotiques de Lactobacillus rhamnosus Lcr35®

National audienceLa levure Candida albicans est un pathogène opportuniste retrouvée dans la flore commensale de 80% de la population. Elle est l’agent d’un grand nombre d’infections digestives et gynécologiques appelées candidoses. La prise d’antifongique, bien qu’efficace, peut entrainer une dysbiose favorable à une récidive ultérieure. Lactobacillus rhamnosus Lcr35® est un probiotique dont les propriétés antimicrobiennes, notamment anti-C. albicans, ont été démontrées à la fois in vitro et lors d’essais cliniques. Cependant, les mécanismes moléculaires expliquant ces propriétés n’ont pas encore été décrits. L’objectif de ma thèse est d’identifier ces mécanismes en utilisant un modèle in vivo physiologiquement proche de l’Homme, le ver Caenorhabditis elegans.Ce nématode modèle sera présenté suivi des différentes stratégies expérimentales mises en œuvre : (i) l’étude du temps de vie en présence du probiotique ou du pathogène, (ii) l’étude des effets préventifs et curatifs du probiotique vis-à-vis d’une infection fongique puis (iii) des études omiques (transcriptomique et métabolomique).Les premiers résultats ont mis en évidence que Lcr35® induit un effet positif sur la durée de vie de C. elegans à l’inverse de C. albicans qui induit un effet négatif. De plus, un effet protecteur du probiotique vis-à-vis d’une infection à C. albicans est observé. En effet, en présence de Lcr35®, le nématode résiste à l’infection et voit son temps de vie augmenter. En perspective, une étude transcriptomique de la réponse globale du ver à l’administration du probiotique et/ou du pathogène est envisagée dans le but d’identifier les mécanismes moléculaires responsables des effets observés

A clustering-based survival comparison procedure designed to study the Caenorhabditis elegans Model

Abstract Caenorhabditis elegans holds significant importance in current research, serving as a pivotal model organism that has greatly advanced the understanding of fundamental biological processes such as development, cellular biology, and neurobiology, helping to promote major advances in various fields of science. In this context, the survival of the nematode under various conditions is commonly investigated, employing a statistical survival analysis typically based on hypothesis testing, providing valuable insights into the factors influencing its longevity and its response to varying environmental factors. The extensive reliance on hypothesis testing is acknowledged as a concern in the scientific analysis process, emphasizing the need for a comprehensive evaluation of alternative statistical approaches to ensure rigorous and unbiased interpretation of research findings. In this paper, we propose an alternative method to hypothesis testing for evaluating differences in nematode survival. Our approach relies on a clustering technique that takes into account the complete structure of survival curves, enabling a more comprehensive assessment of survival dynamics. The proposed methodology helps to identify complex effects on nematode survival and enables us to derive the probability that a treatment induces a specific effect. To highlight the application and benefits of the proposed methodology, it is applied to two different datasets, one simple and one more complex