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Objectives: The main aim of our work was to get one step closer to the in vivo conditions. We started from a multispecies static biofilm model containing five different bacteria, implementing specific enhancements. Our second goal was to improve the analysis of such biofilms regarding collection and identification. Material and Methods: We started from a multispecies static model with five oral strains growing on hydroxyapatite discs to improve it on multiple points. We modified culture conditions and added two more strains. We also changed bacteria collection, which evolved from manually scrapping the discs surface to the combination of ultrasonic and mechanical harvesting. In a further another step, we developed a dynamic model implementing the above changes with a continuous supply of medium flow and waste disposal. Different methods have been evaluated to monitor the presence of all the species within the biofilms, and to quantify them: gram staining, PCR, MALDI-TOF-MS, qPCR. Results: The modifications brought to our static model confirmed its reproducibility. Even if improvements need to be made, our dynamic model of oral biofilm is already a good alternative to more sophisticated and expensive models. Conclusions: This new oral biofilm model represents the premises of another way to study the environmental variations effects on bacterial development, its larger application will result in a better understanding of oral health significant factors.

Vineyards and wineries are ecological habitats that house a diverse community of yeast and bacteria. Grapes and cellars are two sources of S. cerevisiae strains involved in the winemaking process, but the relationship between both S. cerevisiae populations is still poorly understood. Indeed strains in vineyards samples are rarely the same as those isolated from vats. In order to better apprehend this issue, 1374 S. cerevisiae isolates were collected from 193 samples of Merlot grapes obtained across 5 Bordeaux regions and from 11 spontaneously fermenting must of 7 cellars. We obtained 402 different genotypes using 17 microsatellite markers. A first analysis of genotypes indicated that approximately ¼thof isolates presented more than 75% of similarity with commercial yeast starters, suggesting that they escaped from the cellar environment, but presented variations higher that could be detected from the analysis of their industrial batch production. The resulting S. cerevisiae populations of 302 grapes-associated and 225 cellar-associated unique profiles revealed a global low differentiation (Fst=0.036), but with differences from sites to sites. To limit potential geographic or sampling effects, a subset of 72 individuals were selected among the vineyard and cellar isolates, representing 5 cellars and the vines located in their immediate environment. Again a low differentiation was noticed (Fst= 0.03 +/- 0.001). The geneflow between vines and cellars was inferred, using a likelihood approach implemented in the software MIGRATE. Inferences showed that cellar and grape metapopulations present similar theoretical sizes and are connected by asymmetric geneflow: almost 4 times higher in the direction "grapes-to-cellar" than for "cellar-to-grapes" (number of migrants per generation 191 [166 -226] versus 55 [25 - 83], respectively). This reveals that vines and cellars are two compartments of the same ecosystem, which has deep ecological significance.

Oenococcus oeni is the most common species of lactic acid bacteria associated with malolactic fermentation in wine. Here, we report the genome sequence of the lytic phage OE33PA (vB_OeS_OE33PA)., Oenococcus oeni is the most common species of lactic acid bacteria associated with malolactic fermentation in wine. Here, we report the genome sequence of the lytic phage OE33PA (vB_OeS_OE33PA). It has a morphotype similar to that of members of the Siphoviridae family, a linear 39,866-bp double-stranded genome with cohesive ends, and 57 predicted open reading frames.

Research on the origin and the side effects of chitosan stabilizing properties in wine. Applied Natural Products : From Discoveries To Innovations

International audience; Oenococcus oeni is the lactic acid bacterium that most commonly drives malolactic fermentation (MLF) in wine. Though the importance of MLF in terms of wine microbial stability and sensory improvement is well established, it remains a winemaking step not so easy to control. O. oeni displays many adaptation tools to resist the harsh wine conditions which explain its natural dominance at this stage of winemaking. Previous findings showed that capsular polysaccharides and endogenous produced dextran increased the survival rate and the conservation time of malolactic starters. In this paper, we showed that exopolysaccharides specific production rates were increased in the presence of single stressors relevant to wine (pH, ethanol). The transcription of the associated genes was investigated in distinct O. oeni strains. The conditions in which eps genes and EPS synthesis were most stimulated were then evaluated for the production of freeze dried malolactic starters, for acclimation procedures and for MLF efficiency. Sensory analysis tests on the resulting wines were finally performed.

Oenococcus oeni is the lactic acid bacterium that most commonly drives malolactic fermentation (MLF) in wine. Though the importance of MLF in terms of wine microbial stability and sensory improvement is well established, it remains a winemaking step not so easy to control. O. oeni displays many adaptation tools to resist the harsh wine conditions which explain its natural dominance at this stage of winemaking. Previous findings showed that capsular polysaccharides and endogenous produced dextran increased the survival rate and the conservation time of malolactic starters. In this paper, we showed that exopolysaccharides specific production rates were increased in the presence of single stressors relevant to wine (pH, ethanol). The transcription of the associated genes was investigated in distinct O. oeni strains. The conditions in which eps genes and EPS synthesis were most stimulated were then evaluated for the production of freeze dried malolactic starters, for acclimation procedures and for MLF efficiency. Sensory analysis tests on the resulting wines were finally performed.

Comparison of the Spearman correlation matrices; vintage 2011 (circle = ρ

International audience; Hanseniaspora uvarum is one of the most abundant yeast species found on grapes and in grape must, at least before the onset of alcoholic fermentation (AF) which is usually performed by Saccharomyces species. The aim of this study was to characterize the genetic and phenotypic variability within the H. uvarum species. One hundred and fifteen strains isolated from winemaking environments in different geographical origins were analyzed using 11 microsatellite markers and a subset of 47 strains were analyzed by AFLP. H. uvarum isolates clustered mainly on the basis of their geographical localization as revealed by microsatellites. In addition, a strong clustering based on year of isolation was evidenced, indicating that the genetic diversity of H. uvarum isolates was related to both spatial and temporal variations. Conversely, clustering analysis based on AFLP data provided a different picture with groups showing no particular characteristics, but provided higher strain discrimination. This result indicated that AFLP approaches are inadequate to establish the genetic relationship between individuals, but allowed good strain discrimination. At the phenotypic level, several extracellular enzymatic activities of enological relevance (pectinase, chitinase, protease, β-glucosidase) were measured but showed low diversity. The impact of environmental factors of enological interest (temperature, anaerobia, and copper addition) on growth was also assessed and showed poor variation. Altogether, this work provided both new analytical tool (microsatellites) and new insights into the genetic and phenotypic diversity of H. uvarum, a yeast species that has previously been identified as a potential candidate for co-inoculation in grape must, but whose intraspecific variability had never been fully assessed.

Comparison of the Spearman correlation matrices; vintage 2013 (circle = ρ

National audience

National audience