Réponses des plantes invasives [i]Ludwigia grandiflora[/i] et [i]Ludwigia peploides[/i] sous conditions de stress hydrique et salin

absen

Réponses des plantes invasives [i]Ludwigia grandiflora[/i] et [i]Ludwigia peploides[/i] sous conditions de stress hydrique et salin

absen

Does plasticity of the aquatic invasive plant, L. grandiflora, to terrestrial environment involve an epigenetic component?

International audienc

Value of the Galleria mellonella model for exploring the Staphylococcus aureus extracellular vesicles impact on host-pathogen interactions

International audienceIntroduction and objectivesExtracellular vesicles (EVs) are nanometric particles secreted from the membrane into the surrounding environment. They play a crucial role in intercellular communication through their ability to transport bioactive molecules. Various functions have been attributed to EVs produced by Staphylococcus aureus: biofilm formation, cytotoxicity, immunomodulation... These functions suggest their involvement in host-pathogen interactions and pathogenesis. However, in vivo data remain scarce to date. The aim of this work was to test the larval Galleria mellonella model to assess the impact of EVs in vivo.Materials and methodsDerivated HG003 reference strain-EVs were purified by steric exclusion chromatography. Different quantities of EVs were injected into the larval circulatory system to determine the minimum lethal dose. Impact of EVs, alive bacteria and PBS buffer was compared at different times after injection, both on aspects of mortality, macroscopy/microscopy, and expression of factors of larval innate immunity (e.g., opsonins, anti-microbial peptides...) by RT-qPCR from 2 distinct environments, (i) hemolymph (HL; larval circulatory system) and (ii) fat body (FB). All experiments were performed in triplicate.Results, discussion and conclusionPreliminary data showed that only a significant quantity of EVs (1010 EVs) were responsible for early larval mortality. Microscopy data allowed us to visualize S. aureus bacteria as well as clusters of EVs, each condition exhibiting a specific immune response and cellular remodeling. The larval immune response proved to be specific to the condition tested (bacteria vs. EVs), and depended on post-infection time and localization (HL vs. FB). Compared to bacteria, EVs induced an early activation of the majority of tested-innate factors in the HL, whereas a rather late activation in the FB. In addition, certain immune players were specifically induced by EVs. The G. mellonella model therefore appears suitable for assessing the contribution of S. aureus EVs to pathogenesis

Hypomethylation of the aquatic invasive plant, Ludwigia grandiflora subsp. hexapetala mimics the adaptive transition into the terrestrial morphotype

International audienceOngoing global changes affect ecosystems and open up new opportunities for biological invasion. The ability of invasive species to rapidly adapt to new environments represents a relevant model for studying short‐term adaptation mechanisms. The aquatic invasive plant, Ludwigia grandiflora subsp. hexapetala, is classified as harmful in European rivers. In French wet meadows, this species has shown a rapid transition from aquatic to terrestrial environments with emergence of two distinct morphotypes in 5 years. To understand the heritable mechanisms involved in adjustment to such a new environment, we investigate both genetic and epigenetic as possible sources of flexibility involved in this fast terrestrial transition. We found a low overall genetic differentiation between the two morphotypes arguing against the possibility that terrestrial morphotype emerged from a new adaptive genetic capacity. Artificial hypomethylation was induced on both morphotypes to assess the epigenetic hypothesis. We analyzed global DNA methylation, morphological changes, phytohormones and metabolite profiles of both morphotype responses in both aquatic and terrestrial conditions in shoot and root tissues. Hypomethylation significantly affected morphological variables, phytohormone levels and the amount of some metabolites. The effects of hypomethylation depended on morphotypes, conditions and plant tissues, which highlighted differences among the morphotypes and their plasticity. Using a correlative integrative approach, we showed that hypomethylation of the aquatic morphotype mimicked the characteristics of the terrestrial morphotype. Our data suggest that DNA methylation rather than a new adaptive genetic capacity is playing a key role in L. grandiflora subsp. hexapetala plasticity during its rapid aquatic to terrestrial transition

Fat matters: Fermented whole milk potentiates the anti-colitis effect of Propionibacterium freudenreichii

International audienceInflammatory bowel diseases (IBD) constitute a growing concern in western countries. They coincide with gut microbiota dysbiosis, including a loss of immunomodulatory bacteria. Accordingly, probiotic products containing selected immunomodulatory bacterial strains mitigate IBD. Selected strains of Propionibacterium freudenreichii display promising modulatory properties and prevent colitis in animal models. Dairy matrices protect propionibacteria immunomodulatory surface antigens during digestive transit. However, the functional role of the dairy matrix components in such fermented dairy products remains unknown. In the present workthis study, P. freudenreichii CIRM-BIA129, a probiotic strain known for its anti-inflammatory properties, was used to ferment whole milk, skim milk or skim milk ultrafiltrate. The preventive potential of fermented products was tested in DSS-induced mice colitis, in comparison with their unfermented counterparts. P. freudenreichii-fermented milk prevented colitis. Dairy fat in the fermented product potentiated the anti-colitis effects of the probiotic. This work opens new perspectives for developing immunomodulatory functional fermented foods