Dissemination and survival of commercial wine yeast in the vineyard: a large-scale, three years study

The use of commercial wine yeast strains as starters has been extensively generalised over the past two decades. In this study, a large-scale sampling plan was devised over a period of three years in six different vineyards to evaluate the dynamics and survival of industrial yeast strains in the vineyard. A total of 198 grape samples were collected at various distances from the wineries, before and after harvest, and yeast strains isolated after spontaneous fermentation were subsequently identified by molecular methods. Among 3780 yeast strains identified, 296 isolates had a genetic profile identical to that of commercial yeast strains. For a large majority (94%), these strains were recovered at very close proximity to the winery (10-200m). Commercial strains were mostly found in the post harvest samples, reflecting immediate dissemination. Analysis of population variations from year to year indicated that permanent implantation of commercial strains in the vineyard did not occur, but instead that these strains were subject to natural fluctuations of periodical appearance/disappearance like autochthonous strains. Our data show that dissemination of commercial yeast in the vineyard is restricted to short distances and limited periods of times and is largely favoured by the presence of water runoff.ENOSAFE (Nº 762, Programa AGRO, medida 8.1) and the grant nº 657 C2 from the cooperation agreement between the Portuguese Institute for International Scientific and Technological Cooperation (ICCTI) and the French Embassy in Lisbon and the Marie Curie Fellowship of the European Community programme of Quality of Life under Contract QLK4-CT-2001-51873

Evaluation of an Antimicrobial L-Amino Acid Oxidase and Peptide Derivatives from Bothropoides mattogrosensis Pitviper Venom

Healthcare-associated infections (HAIs) are causes of mortality and morbidity worldwide. The prevalence of bacterial resistance to common antibiotics has increased in recent years, highlighting the need to develop novel alternatives for controlling these pathogens. Pitviper venoms are composed of a multifaceted mixture of peptides, proteins and inorganic components. L-amino oxidase (LAO) is a multifunctional enzyme that is able to develop different activities including antibacterial activity. In this study a novel LAO from Bothrops mattogrosensis (BmLAO) was isolated and biochemically characterized. Partial enzyme sequence showed full identity to Bothrops pauloensis LAO. Moreover, LAO here isolated showed remarkable antibacterial activity against Gram-positive and -negative bacteria, clearly suggesting a secondary protective function. Otherwise, no cytotoxic activities against macrophages and erythrocytes were observed. Finally, some LAO fragments (BmLAO-f1, BmLAO-f2 and BmLAO-f3) were synthesized and further evaluated, also showing enhanced antimicrobial activity. Peptide fragments, which are the key residues involved in antimicrobial activity, were also structurally studied by using theoretical models. The fragments reported here may be promising candidates in the rational design of new antibiotics that could be used to control resistant microorganisms

Exploring the chemistry of uncultivated bacterial symbionts: Antitumor polyketides of the pederin family

Symbiotic bacteria have long been proposed as being responsible for the production of numerous natural products isolated from invertebrate animals. However, systematic studies of invertebrate-symbiont associations are usually associated with serious te

Films moléculaires nanostructures pour applications fonctionnelles

Cette thèse décrit l'étude de différentes méthodologies qui ont été utilisées pour contrôler l'assemblage de trois systèmes moléculaires sur des surfaces, afin de former des structures supramoléculaire hautement ordonnées à l'échelle nanoscopique et microscopique. Les structures de couches minces ont été préliminairement étudiées par microscopie à force atomique (AFM) à l'interface solide-air.La première partie de la thèse porte sur la technique de préparation de couches minces Langmuir-Blodgett (LB). Cette technique permet d'obtenir une croissance latérale de monocouche orientée sur un substrat de mica et ce, à partir de molécules amphiphiles possédant une queue hydrophobe simple ou double. Des monocouches ordonnées ont été réalisées suivant deux méthodes différentes. La première méthode consiste à exploiter le phénomène d'instabilité lié au transfert de molécules sur des substrats dans le procédé Langmuir-Blodgett (LB), ce qui permet de générer des canaux périodiques de taille nanométrique dans le cas de monocouche de dimyristoyl-phosphatidylcholine (DMPC) transférée sur un substrat de mica. La seconde méthode utilisée consiste à utiliser des molécules amphiphiles possédant de grosses têtes amphiphiles interagissant fortement entre elles. L'utilisation des molécules de palmitate de quercetine (QP) ont permis l'obtention de structures supramoléculaires de type fibre et ceci dans des domaines micrométriques. Les images AFM (mode tapping) de films mixtes montrent que les fibres adoptent une conformation courbée conduisant à de nouveaux types de domaines en forme de spirale. Les résultats obtenus ouvrent de nouvelles perspectives pour l'utilisation de films LB comme outil permettant d'organiser des monocouches a plusieurs composants avec un haut degré de précision. La seconde partie de la thèse est consacrée à l'autoassemblage, sur des surfaces, d'une nouvelle classe de système macromoléculaire, des polyrotaxanes conjugués entoures par des cyclodextrines, dans le but d'optimiser les performances des LEDs basés sur ces architectures complexes. En particulier la morphologie de surface des mélanges de poly(4,4'-diphenylenevinylene) PDV, soluble dans l'eau, et de leur forme "rotaxane" -CD-PDV, avec du poly(ethylene oxyde) PEO, déposés par spin coating a été étudié par AFM en mode tapping. Cette dernière technique a permis de révéler l'existence d'un processus de reconnaissance interfacial. Ce phénomène a été mis en évidence par l'absence de ségrégation de phase ainsi que par l'ordre structural induit par le choix du substrat. Ceci démontre la bonne miscibilité des deux constituants hydrophiles, comme le confirment les mesures de luminescence des films et des dispositifs intégrant ces systèmes. Par ailleurs, des analyses AFM effectuées sur films d' epousseur "submonolayer" de polyrotaxane à base de poly-para-phenylene ( -CD-PPP) seul ou mélangé avec du PEO, démontre que l'interaction entre les deux composants a lieu à l'échelle moléculaire. Au contraire, pour les mélanges de PEO avec des polymères conjugués solubles dans des solvants organique, comme le poly(9,9'-dioctylfluorene-alt-benzothiadiazole) F8BT ou des CD-polyrotaxanes à base de polyfluorene alkylé, on observe des structures de surface qui indique des séparations de phases.La dernière partie de la thèse traite de la création de nanojunctions d'hybrides organométalliques, qui sont les composants de base pour de futures applications dans le domaine de la nanoélectronique. Ce qui nécessite à la fois la synthèse de structures moléculaires auto assemblées (approche bottom-up) et la fabrication de nanogaps métalliques par des méthodes de lithographie (top-down). L'auto assemblage d'un gélifiant de faible poids moléculaire, le cyclohexane trisamide, en structure colonnaire via des liaisons hydrogènes a été étudié sur des films préparés par drop casting. Le but de cette étude était d'utiliser un champ électrique (DC) pour orienter les fibres entres deux nanoélectrodes. Le champ électrique a été appliqué entre deux électrodes en or fabriquées sur un wafer de silicone à l'aide d'un faisceau d'ions focalisé (FIB). Bien que les fibres tendent à former des superstructures, une faible proportion de ces architectures s'oriente convenablement lors de l'application du champ électrique.Les résultats décrit dans cette thèse montrent qu'il est important de pouvoir contrôler des interactions intramoléculaires ainsi qu'intermoléculaire, sans oublier les interactions spécifique au surfaces afin de pouvoir piloter l'autoassemblage sur des surfaces solides et ainsi créer des architectures nanométriques pré-programmées ayant des fonctions bien définies. De plus, il a été démontré qu'une approche supramoléculaire représente une voie possible vers la fabrication de prototypes de dispositifs pour l'électronique moléculaire avec des performances améliores.In this thesis different methodologies have been used to drive the assembly at surfaces of three different (macro)molecular systems towards highly ordered supramolecular nanoscopic and microscopic structures. The structures of the thin films have been studied at the solid-air interface making use primarily of Scanning Force Microscopy (SFM). The first part of the thesis was focused on the use of the Langmuir-Blodgett (LB) technique to grow laterally ordered monolayers on mica from amphiphilic molecules having either a double or a single hydrophobic tail. Ordered monolayers were produced using two different strategies. The former exploits instability phenomena connected to the LB transfer and allows the generation of periodic nanometric channels, in dimyristoyl-phosphatidylcholine (DMPC) monolayers transferred to mica. The latter strategy consists of assembling amphiphiles having large and strongly mutually interacting heads. In this case, quercetin palmitate (QP) molecules were used to build up micrometric domains of supramolecular fiber-like structures. In the mixed films, the nanoscopic fibers were observed by tapping mode SFM to adopt a curved conformation and wrap up, leading to novel spiral-like domains. The results obtained open new perspectives to the use of LB as a tool for nanopatterning (multicomponents) monolayers with a high degree of precision. The second part of the thesis was devoted to self-assembly at surfaces of a new class of supramolecular system, based on cyclodextrin-threaded conjugated polyrotaxanes, with the final aim of optimizing the performance of LEDs based on these complex architectures. In particular the surface morphology of blends of water soluble poly(4,4'-diphenylenevinylene), PDV and of the correspondent rotaxinated form -CD-PDV, with poly(ethylene oxide), PEO, grown by spin-coating was explored by non-contact SFM. The SFM analysis revealed the occurrence of an interfacial recognition process, which is evidenced by a structural order induced by the chosen substrate, and the absence of phase segregation. This provides evidence for a good miscibility of the two hydrophilic components, as supported by luminescence data from films and devices constituted by those systems. This was also proved by the SFM analysis on sub-monolayer thick films of poly-para-phenylene based polyrotaxane ( -CD-PPP) naked and blended with PEO, highlighting the interaction between the two components at single molecule level. Significant surface structures, indicative of phase separations, were instead observed when blending PEO with organic-solvent soluble conjugated polymers, such as poly(9,9'-dioctylfluorene-alt-benzothiadiazole) F8BT, and alkylated polyfluorene based CD-polyrotaxanes. The third part was addressed to the tailoring of hybrid organic-metallic nanojunctions, which are key components for future applications in the field of nanoelectronics. This required the combination of the self-assembly of molecular structures (bottom-up approach) with micro- and nano-fabrication for the production of metallic nanogaps with lithographic methods (top-down). The self-assembly behavior of a low molecular weight gelators, cyclohexane trisamide which self-associate into columnar structures through hydrogen bonding, was studied on films prepared by drop-casting. The goal was to use a DC electric field to place the well-defined ordered supramolecular arrangement in between two facing Au nanoelectrodes, supported on a silicon wafer, nanofabricated by means of Focused Ion Beam. Although the fibers tend to intercoil into super-structures, a weak propensity of these architectures to orient as a consequence of the applied electric field was found. The results described in this thesis reveal that it is of prime importance to achieve a full control over the interplay of intra-molecular as well as inter-molecular and interfacial interactions in order to drive the nanoconstruction at solid surfaces towards pre-programmed architectures with given properties. Moreover it is demonstrated that the supramolecular approach represents a successful route to fabricate prototype of molecular electronics devices with improved performance.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF