Staphylococcus aureus is the leading cause of nosocomial infections in the US and is becoming increasingly difficult to treat due to the limited antibiotics available. Capsular polysaccharides (CP), a virulence factor produced by the bacterium, allows S. aureus to evade the uptake and killing by host neutrophils. It has been shown previously that CP serotype 5 retains more cell-associated CP while type 8 tends to release more CP into the supernatant. This research focused on whether this phenomenon is dependent upon the serotype-specific capHIJK genes that vary between the two serotypes. 6850, a methicillin- sensitive S. aureus (MSSA) serotype 8 strain, is a well characterized clinical isolate that was used in this study. This strain was subjected to two allelic replacement steps: the first step to replace the cap8HIJK genes with an ermB cassette, creating mutant 6850 (CP-); the second step to replace the ermB cassette with the cap5HIJK genes, which resulted in the creation of mutant 6850 (CP5). All 3 strains were characterized genotypically by PCR and phenotypically for growth rate, metabolic profile, and CP production. ELISA inhibition studies revealed that serotype 5 and the serotype 8 variants of S. aureus 6850 produced similar levels of cell-associated CP. These results suggest that cell wall anchoring of S. aureus CP5 and CP8 is not serotype specific, but instead is dependent on the genetic background of the bacterial strain. A better understanding of the anchoring mechanism may allow for development of alternative immunotherapeutics for S. aureus.

Interactions between non-starch polysaccharide (NSP) level, dietary lipid type, exogenous carbohydrase enzymes and irradiation were investigated. Ten treatment diets were fed to broilers in a performance and digestibility trial. Eight of the diets contained high levels of NSP, achieved by a high barley inclusion of 55% of the diet. Four of the treatments made use of non-irradiated barley, whereas the barley included in the other four diets was irradiated. By adding either 10% soya oil or yellow grease (fat) as the lipid source, sub groups were created which differed in fatty acid profile. Lastly, these treatments were further subdivided by supplementing one of the two diets from each subgroup with a commercially available combination of exogenous carbohydrase enzymes consisting of cellulases, xylanases and â - glucanases (Roxazyme G at 150 g/ton). The two control diets were based on maize (low NSP diets) with either soy oil or yellow grease. The high NSP diets had significantly lower (P<0.05) apparent metabolisable energy (AME) and lipid digestibility values than the low NSP diets. Lipid digestibility and AME values were also significantly lower (P<0.05) for diets containing yellow grease compared to soya oil. The birds that received yellow grease performed worse in terms of growth, feed intake and feed conversion ratio (FCR) than the oil-containing diets. These trends were evident throughout all treatments, although not always significant. The addition of carbohydrase to diets based on barley improved the dietary lipid digestibility and AME values. Significant improvements (P<0.05) in bird performance were noted for the barley diets with the yellow grease. Pre-irradiation of barley significantly increased (P<0.05) the AME value of diets, and improved lipid digestibility of the fat-containing treatment. The simultaneous combination of carbohydrase supplementation and barley irradiation proved to have an additive positive effect on feed quality and bird performance. For all treatments this combination improved the barley based diets to such an extent that it performed equally or significantly better (P<0.05) than its maize based counterpart. The irradiated barley-yellow grease based diets showed a more pronounced benefit with the addition of carbohydrase enzymes to the feed (P<0.05). / Dissertation (MSc(Agric))--University of Pretoria, 2008. / Animal and Wildlife Sciences / unrestricted

京都大学 / 新制・課程博士 / 博士(農学) / 甲第23519号 / 農博第2466号 / 新制||農||1086(附属図書館) / 学位論文||R3||N5350(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 和田 昌久, 教授 髙野 俊幸, 教授 河本 晴雄 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

No description available.

No description available.

No description available.

No description available.

Three strains of cyanobacteria (Anabaena PCC7120, A. variabilis and Nostoc commune), all belonging to the family Nostocaceae, were found to be capable of modulating the production and chemical composition of extracellular polysaccharides (EPS) in response to carbon and nitrogen availability as well as pH. While the carbohydrate compositions of the glycans produced by the different organisms were indicative of their recent evolutionary divergence, there were measurable differences that were dependent upon growth conditions. The EPS resulting from biofilm growth conditions was reduced in glucuronic acid levels in both Anabaena variabilis ATCC 29413 and Anabaena PCC 7120. Under planktonic conditions, the glycan from A. variabilis contained glucuronic acid when grown in nitrate-free BG-11₀ medium whereas A. PCC 7120 produced similar levels in standard BG-11 medium. This suggests that phylogeneticallyrelated cyanobacteria respond very differently to changes in their local environment. The pH of BG-11 cultures increased to 9-10 for all three strains of cyanobacteria. The increase resulted in an increase in the amount of dissolved inorganic carbon available in the medium, creating an imbalance in the carbon-nitrogen ratio, with the complete consumption of 17.65 mmol L⁻¹ nitrates raising the pH to near 10 in BG-11 medium. While increased carbon availability has been shown to induce capsulated morphologies in strains of cyanobacteria, only Nostoc commune DRH-1 exhibited this behavior, and only when grown in BG-11 medium. Carbon and nitrogen availability as well as pH modulate the monosaccharide composition of the glycan generated by cyanobacteria investigated. The different characteristics of the glycans produced can affect the survivability of the organisms and the community structure of cyanobacterial biofilms and microbial mats found in nature. As cyanobacteria are ubiquitous organism both now and in the past, they play a pivotal role in the biological and geological processes of the Earth, controlling the availability and cycling of carbon and nitrogen both actively and passively. / Master of Science in Life Sciences

Les virus influenza provoquent chaque année la grippe saisonnière qui peut toucher 5 à 15 % de la population. Les médicaments antiviraux sont un moyen important complémentaire à la vaccination pour le traitement et la prévention de la grippe. Actuellement, deux classes d’antiviraux ont été approuvées, l'une pour inhiber l'étape de décapsidation (l’inhibiteur du canal ionique M2), et l'autre pour empêcher la libération de néo-virions (l’inhibiteur de la neuraminidase). Cependant, de plus en plus de virus sont nativement résistants aux inhibiteurs de la protéine M2. Des virus résistants aux inhibiteurs de la neuraminidase ont également circulé durant les hivers 2008 – 2009. Le développement de nouveaux médicaments afin de substituer ou de compléter ces inhibiteurs est donc crucial dans la lutte contre les virus de la grippe. L’accent mis ces dernières années sur l’activité biologique des sucres (oligosaccharides/polysaccharides) montre une voie pour l’étude de l’activité antivirale d’une des plus importantes biosources. Dans le but d'évaluer le potentiel antigrippal des molécules dérivées de sucres, nous avons effectué un criblage à partir d'une bibliothèque de 245 composés de polysaccharides et d'oligosaccharides, dont la plupart proviennent d’algues et de végétaux supérieurs. Plusieurs molécules actives réparties dans différentes familles de sucres ont été mises en évidence. Parmi les candidats d'intérêt, l’oligosaccharide sulfaté 152, appartenant à la famille des arabinogalactanes de l'espèce Codium fragile, a présenté une activité inhibitrice vis-à-vis des deux virus influenza de type A et de type B in vitro. Le mécanisme d’action de cet oligosaccharide a été caractérisé. Il montre que les deux glycoprotéines de surface, l’hémagglutinine et la neuraminidase, sont les cibles virales de cette molécule / The annual seasonal flu caused by influenza viruses can affect 5 to 15 % of the population. In addition to vaccination, the use of antiviral drugs in the treatment and prevention allows the control of influenza virus infection. So far, two classes of antiviral drugs have been approved for influenza treatment, one to inhibit the uncoating step (M2 inhibitors), and the other to prevent the release of progeny virions (NA inhibitors). However, the emergence and circulation of M2 inhibitor resistant viruses at high frequencies have restricted the use of these inhibitors. Neuraminidase inhibitor resistance among circulating influenza viruses has emerged since the 2008 – 2009 season. The development of new classes of antiviral agents is crucial in the fight against influenza virus. In recent years, many molecules belonging to a large group of compounds known as carbohydrates (oligosaccharides/polysaccharides) have been revealed essential for various biological activities. The establishment of carbohydrate-based antiviral agents is, therefore, a highly promising strategy. In order to evaluate the potentially anti-influenza molecules derived from carbohydrates, we have performed a screening from a library of 245 polysaccharides and oligosaccharides. These compounds were extracted mainly from plants and algae. Several active molecules of different families have been identified. Among them, the sulphated oligosaccharide 152, belonging to the family of arabinogalactane, was found to be highly active toward both influenza virus A and B in vitro. This oligosaccharide was purified from the green algal species Codium fragile. The study of the 152 mechanism suggests that this oligosaccharide can cooperatively inhibit both viral HA binding activity and NA catalytic activity

Ce travail avait pour principal objectif la synthèse de nouveaux systèmes amphiphiles à base de polysaccharides neutres (guar, hydroxyéthyl guar) ou chargés (acide hyaluronique), par greffage de groupements hydrophobes le long de la chaîne polysaccharidique. La stratégie de synthèse proposée pour ces dérivés amphiphiles repose sur des réactions d'éthérification en milieu basique des polysaccharides à partir d'éthers de glycidyle (époxydes) hydrophobes commerciaux (hexadécyl éther de glycidyle, phényl éther de glycidyle) et non commerciaux (Brij 56 époxyde, OP10 époxyde). Des dérivés de type Brij56® ont été sélectionnés en raison de leur structure chimique particulière, présentant un bloc oligo(éthylène glycol) (OEG) associé à une chaîne alkyle hydrophobe, susceptibles de conduire en milieu aqueux à des propriétés différentes par rapport à des dérivés alkylés classiques du fait de l'hydrophile du bloc OEG. Plusieurs conditions de greffage ont été testées et appliquées également à un dérivé de la cellulose disponible commercialement (hydroxyéthyl cellulose) afin de comparer l'efficacité des réactions en fonction de la nature du polysaccharide. L'analyse du comportement en milieu aqueux des polysaccharides hydrophobiquement modifiés par des mesures de viscosité met en évidence soit des augmentations de viscosité, soit des diminutions. Des analyses plus approfondies combinant la diffusion de la lumière et la spectroscopie de fluorescence en utilisant des sondes hydrophobes ont montré que de telles diminutions pouvaient être expliquées dans certains cas (acide hyaluronique) par la formation de particules de taille nanométrique. / The main aim of this work was the synthesis of new amphiphilic systems from neutral polysaccharides (guar, hydroxyethyl guar) or charged polysaccharides (hyaluronic acid), based on the grafting of hydrophobic groups along the polysaccharide backbone. The synthetic strategy proposed for these derivatives relies on etherification reactions of the polysaccharides in alkaline media from commercial hydrophobic alkyl glycidyl ethers (epoxides) (glycidyl hexadecyl ether, phenyl glycidyl ether) or non commercial glycidyl ethers (Brij 56 epoxide, OP10 epoxide). Derivatives of Brij 56 have been selected due to their peculiar chemical structure consisting of an oligo(ethylene glycol) (OEG) block associated to a hydrophobic alkyl chain, expected to lead to different properties in aqueous media compared to classical alkylated derivatives as a result of the hydrophilic character of the OEG block. Several grafting conditions have been tested and also applied to a commercially available cellulose derivative (hydroxyethyl cellulose) in order to compare the efficiency of reactions as a function of the nature of the polysaccharide. The analysis of the behavior in aqueous media of hydrophobically modified polysaccharides by viscosity measurements demonstrated either increases of viscosity or decreases. Deeper investigations combining dynamic light scattering and fluorescence spectroscopy showed that such viscosity decreases was related to some cases (hyaluronic acid) to the formation of nanosized particles.