The yeast Saccharomyces cerevisiae has a remarkable ability to adapt its lifestyle to fluctuating or hostile environmental conditions. This adaptation most often involves morphological changes such as pseudofilaments, biofilm formation, or cell aggregation in the form of flocs. A prerequisite for these phenotypic changes is the ability to self-adhere and to adhere to abiotic surfaces. This ability is conferred by specialized surface proteins called flocculins, which are encoded by the FLO genes family in this yeast species. This mini-review focuses on the flocculin encoded by FLO11, which differs significantly from other flocculins in domain sequence and mode of genetic and epigenetic regulation, giving it an impressive plasticity that enables yeast cells to swiftly adapt to hostile environments or into new ecological niches. Furthermore, the common features of Flo11p with those of adhesins from pathogenic yeasts make FLO11 a good model to study the molecular mechanism underlying cell adhesion and biofilm formation, which are part of the initial step leading to fungal infections.

It is generally accepted that microbes play a critical role in maintaining gut barrier function, making them ideal to target in order to mitigate the effects of intestinal diseases such as inflammatory bowel disease with specialist supplementations such as probiotic or postbiotic preparations. In this study, specific strains of Lactobacillus helvictus both live and inactivated and Lactobacillus plantarum inactivated were fed to zebrafish at an inclusion level of 6 × 10⁶ cells/g in order to assess the effects on gut barrier function and protection. Taken together, our results indicate that dietary administration of pro- or postbiotics strengthens the gut barrier function and innate immunity of healthy zebrafish in a strain-specific and process-dependent way. With some differences in the response intensity, the three treatments led to increased intestinal villi length and proportion of IELs, reinforcement of the GC population and up-regulated expression of biomarkers of AMP production and tight junction zona-occludin 2a (zo-2a). In addition, LPPost had an impact on the adaptive immune response, and we hypothesized that it conferred the potential to drive Th17/ILC3 immunity, as suggested by its effect on the gene expression of il22, of different AMPs, and the expression of zo2a. Moreover, LPPost showed the potential to drive Th1/ILC1-like immunity, with a higher percentage of CD8⁺ cells and higher ifnγ gene expression. In summary, the use of inactivated Lactobacilli species in this study represented a promising strategy for improving barrier function and regulating the immune fate of the intestinal mucosa in a strain-specific way.

Cell wall synthesis and protein glycosylation require the import of nucleotide diphosphate–sugar conjugates into the Golgi that must be counterbalanced by phosphate (Pi) export. Numerous Golgi nucleotide-sugar transporters have been characterized, but transporters mediating Golgi Pi export remain poorly understood. We used plant and yeast genetics to characterize the role of 2 Arabidopsis (Arabidopsis thaliana) proteins possessing an EXS domain, namely ERD1A and ERD1B, in Golgi Pi homeostasis. ERD1A and ERD1B localized in cis-Golgi and were broadly expressed in vegetative and reproductive tissues. We identified ERD1 putative orthologs in algae, bryophytes, and vascular plants. Expressing ERD1A and ERD1B in yeast complemented the erd1 mutant phenotype of cellular Pi loss via exocytosis associated with reduced Golgi Pi export. The Arabidopsis erd1a mutant had a similar phenotype of apoplastic Pi loss dependent on exocytosis. ERD1A overexpression in Nicotiana benthamiana and Arabidopsis led to partial mislocalization of ERD1A to the plasma membrane and specific Pi export to the apoplastic space. Arabidopsis erd1a had defects in cell wall biosynthesis, which were associated with reduced shoot development, hypocotyl growth, cell wall extensibility, root elongation, pollen germination, pollen tube elongation, and fertility. We identified ERD1 proteins as Golgi Pi exporters that are essential for optimal plant growth and fertility.

• Functionalisation of AFM dendritips with conA, WGA and anti-β-1,3/β-1, 6-glucan antibodies. • Cell wall polysaccharides were immobilized on epoxy-activated glass slides. • Specific binding of immobilized polysaccharides to functionalized dendritips. • Functionalized dendritips used as a new tool to probe yeast cell surface.

Combinaison d’approches biochimique, moléculaire et biophysique afin d’étudier l’impact de la souche et du procédé industriel sur la composition et l’architecture moléculaire de la paroi cellulaire de la levure: L’intérêt pour la paroi de la levure s’est accru récemment par l’explosion des activités de bioraffineries augmentant la production de biomasse, et par le besoin de valoriser cette biomasse dans d’autres débouchés comme en nutrition animale et en œnologie pour leurs propriétés probiotiques et de sorption. Le but de cette thèse était de combiner des approches biochimiques, biophysiques et les puces à ADN afin d'étudier les relations entre ces paramètres ainsi que de mettre en évidence l'impact des souches, des conditions de croissance et des procédés sur la composition et les propriétés biophysiques de la paroi cellulaire. Une méthode acido-enzymatique a été développée pour quantifier spécifiquement chacun des quatre composants de la paroi cellulaire de la levure, à savoir les mannanes, la chitine, les β-1,3-glucanes et les β-1,6-glucanes. Cette méthode a été validée sur des souches mutantes et a permis d’évaluer les effets de divers stress. Ultérieurement, l'utilisation de la microscopie à force atomique (AFM) a permis l'étude des mêmes souches et de quatre souches utilisées dans la fermentation industrielle. Ils ont démontré des propriétés nanomécaniques et adhésives distinctes, en raison de différences dans la composition et la structure de la paroi cellulaire. Dans la dernière partie, les effets du procédé d’autolyse et du séchage à lit fluidisé sont présentés. Ce procédé industriel ne modifie pas la composition de la paroi cellulaire, mais induit une modification de la topographie et des propriétés de surface de la cellule. En outre, en utilisant l'AFM nous avons imagés sur S. cerevisiae des patchs hautement adhésifs formant des nanodomaines à la surface de la cellule.