No description available.

Pseudomonas aeruginosa uses type IV pili (T4P) to colonize various materials and for surface-associated twitching motility. We previously identified five phylogenetically-distinct alleles of pi/A in P. aeruginosa, four of which occur in genetic cassettes with specific accessory genes (Kus et al., Microbiology 150:1315-1326, 2004). Each of the five pilin alleles, with and without its associated pilin accessory gene, was used to complement a group II PA01 pi/A mutant. Expression of group I or IV pi/A genes restored twitching motility to the same extent as the PA01 group II pilin. In contrast, complementation with group Ill or group V pi/A genes resulted in poor twitching that increased significantly when the cognate tfp Y or tfpZ accessory genes were cointroduced. The enhanced motility was linked to an increase in recoverable surface pili, and not to alterations in total pilin pools. Expression of the pilin genes, with or without accessory genes, in a PA01 pi/A-pi/T double mutant background resulted in expression of large amounts of surface pili, suggesting that the accessory proteins function to modulate pilin retraction dynamics. Reduction of twitching motility and surface piliation was also observed a tfpYknockout mutant of group Ill strain PA14, confirming that the accessory proteins enhance pilus assembly on the cell surface. The accessory proteins are specific for their cognate pilins; a PilAv-TfpY chimera produced few surface pili, resembling the phenotype of PA01 complemented with pi!Av alone. The linkage between specific pilin and accessory genes may be evolutionarily conserved because the accessory proteins antagonize pilus retraction, increasing pilus expression on the cell surface and thereby enhancing function. / Thesis / Master of Science (MSc)

No description available.

No description available.

The state of adhesion of bacteria to nanofiber-textured model surfaces is analyzed at single-cell level. The results reveal similarities between the effect of topography on bacteria-surface interactions and vesicle-surface interactions. The results are discussed in the context of controlling bacterial adhesion to surfaces using nanofibrous topographical features. / Master of Science

P. aerguinosa is a serious human bacterial pathogen. This thesis describes attempts to use structural biology to identify new starting points for drugs against P. aerguinosa .A number of fragment-based screening techniques were used in order to identify potential inhibitors to P. aerguinosa RmlA protein, the first enzyme in the L-Rhamnose pathway. A 500 “Rule of 3” Fragment Library (Maybridge) was investigated. The first approach was the application of Differential Scanning Fluorimetry (DSF) approach to detect ligands that bind and stabilize RmlA protein. The stabilisation of RmlA was determined by thermal unfolding in the presence of each of the 500 compounds. 21 of those compounds were found to increase the protein stability. The library was then screened by NMR spectroscopy for binding to RmlA. Two techniques were evaluated STD and WaterLOGSY. 106 compounds gave positive results in both NMR experiments. These hits were then tested by a simple STD competition binding with dTTP, a natural RmlA substrate, in order to identify those binding at the active or allosteric site. 21 out of the 106 compounds were observed to compete with dTTP. The results were compared to the results of the DSF screening. Compounds that tested positive in the dTTP competition binding STD experiment and in the DSF screening were tested for their ability to inhibit RmlA in a biological assay. A coupled enzyme assay was used to monitor RmlA activity. Only one compound, 3-pyridin-3-ylaniline, showed significant inhibition of the enzyme activity. The PA1645 protein from P. aerguinosa has been identified as essential. The protein was overexpressed, purified and crystallised. Data were collected at Diamond on beamline IO3 and phases were determined by S-SAD at a wavelength of 1.6Å. Final coordinates have been deposited in the protein data bank under entry code 2XU8. The structure has 3 molecules in the asymmetric unit. There is some ambiguity as to the validity of the proposed trimeric arrangement, with results from solution and crystal disagreeing. Fragment-based screening approach has been applied to RmlA protein, using the DSF technique, a number of ligand-based NMR experiments and a coupled enzyme biological assay. 3-pyridin-3-ylaniline was the only compound that showed significant inhibition of the enzyme activity. The structure of PA1645 from P. aerguinosa has been solved. This work will help to design new drugs to combat multi-drug resistant P. aerguinosa and MTB.

La recherche de nouvelles molécules pour combattre Pseudomonas.aeruginosa est d'une grande importance. L'utilisation des antibiotiques a spectre large a grandement accru la résistance de P.aeruginosa aux antibiotiques. Malgré cette situation, aucune nouvelle drogue active sur P.aeruginosa n'a été introduite en pratique clinique durant les 2 dernières décennies. Le monoxyde de carbone (CO) pourrait agir comme un inhibiteur efficace de la chaîne respiratoire de P.aeruginosa mais l'utilisation pratique de ce gaz comme molécule antibactérienne est gênée par sa toxicité et les difficultés de manipulation. Une avancée fondamentale récente dans le domaine de la recherche sur le CO a été la découverte des « carbon monoxide releasing molecules » (CO-RMs), qui servent de transporteur et délivre des quantités contrôlées de CO aux systèmes biologiques.Nous montrons ici que les CO-RMs possèdent des propriétés antibactériennes contre P.aeruginosa. Cet effet antibactérien des CO-RMs à lieu à des concentrations non toxiques pour les cellules eucaryotes et passe par une interaction du CO libérer par le transporteur avec la chaîne respiratoire bactérienne. Nous présentons des résultats in vivo montrant que les CO-RMs diminuent l'inoculum bactérien et augmentent la survie des souris après une bactériémie à P.aeruginosa. La comparaison de 4 CO-RMs ayant différente structures chimiques suggère que la précence d'un métal de transition joue un rôle important dans l'activité antibactérienne des CO-RMs. Une autre découverte importante présentée dans ce travail est l'inhibition de l'activité antibactérienne de certain CO-RMs par les molécules contenant des résidus thiols. Cette découverte limite la possibilité d'utiliser les CO-RMs concernés comme des agents anti-infectieux.En considérant les résultats présentés dans ce travail, l'inhibition de la chaîne respiratoire pourrait être considérée comme un nouveau mécanisme prometteur pour la recherche de nouveaux agents pharmaceutique pour combattre les infections à P.aeruginosa. / The search of new molecules to fight Pseudomonas.aeruginosa is of paramount importance. The use of broad spectrum antibiotics has greatly increased the antibiotic resistance of P.aeruginosa. In spite of this situation, no new drug against P.aeruginosa has been successfully introduced into the clinic in the past 2 decades. Carbon monoxide (CO) could act as an effective inhibitor of the respiratory chain in P. aeruginosa but the practical use of this gas as an antibacterial molecule is hampered by its toxicity and difficulty to manipulate. A recent fundamental development in the field of CO research has been the discovery of carbon monoxide-releasing molecules (CO-RMs), which serve as carriers for the delivery of controlled amounts of CO in biological systems.Here, we show that CO-RMs possesse bactericidal properties against P.aeruginosa. This antimicrobial effect of CO-RMs occurs at non toxic concentrations for eukaryotic cells and is mediated by an interaction of CO liberated by the carrier with bacterial respiratory chain. We present in vivo results showing that CO-RMs decrease bacterial inoculum and increase survival in mice following P.aeruginosa bacteraemia. A comparison of 4 CO-RMs with different chemical structures suggests that the presence of a transition metal center plays an important role in the antibacterial activity of CO-RMs. Another important finding presented in this work is the inhibition of the antibacterial activity of some CO-RMs by thiol containing molecules. This finding could deserve the possibility to use concerning CO-RMs as anti-infective agent.Considering results presented in this work, inhibition of respiratory chain could be considered as a promising new mechanism for the research in new pharmaceutical agent to fight P.aeruginosa infections.

Les composés polyaromatiques polysoufrés représentent une classe de molécules peu étudiées, malgré leurs propriétés intéressantes. La présence du soufre influence les propriétés redox, photophysiques et de complexation. Nous avons préparé une série de ces composés par des réactions de substitution nucléophile aromatique. Ceux-ci peuvent être fonctionnalisés par des unités polyaromatiques, tels que l’anthracène ou le pyrène, ou par des glycosides. Leurs propriétés de luminescence ont été étudiées en particulier sous l’angle de l’émission induite par l’agrégation, où les composés deviennent émissifs lorsqu’ils sont immobilisés en phase solide ou fortement refroidis. Ils permettent également de stabiliser des nanoparticules de fer/platine, où une forte densité d’atomes de soufre divalent joue un rôle important en nanosciences. Les dérivés glycosylés ont été testés chez différentes lectines comme ConA, PAIL, PAIIL et Bc2lA, les trois dernières étant impliquées dans les infections bactériennes chez les patients atteints de mucoviscidose. Les études comprennent les propriétés photophysiques, de réticulation et des mesures d’affinité par des méthodes biophysiques (SPR, ITC et HIA). Ceci a ammené à la production de nouveaux biocapteurs ou sondes luminescentes basés sur des interactions sélectives lectine-sucre dans l’éventualité future de dispositifs de diagnostics et de détection à partir d’expression de lectines (ex. cancer, infections bactériennes, etc.).Une autre classe de composés polyaromatiques a été étudiée, les hélicènes. Ces molécules hélicoïdales chirales sont retrouvées sous deux formes énantiomériques, selon le pas d’hélice. Nous présentons ici une nouvelle méthode de synthèse des hélicènes par une voie organométallique de réactions d’annulation et d’insertions C-H. Une étude poussée des conditions réactionnelles a été réalisée. Nous avons préparé des hélicènes fonctionnalisés. Les dérivés bromés et cyanés du [5]-hélicène ont été déposés sur la surface de Suzuki, afin d’étudier par nc-AFM les propriétés de structuration de ces produits sur une surface isolante. Le [5]-hélicène a aussi été fonctionnalisé par des unités mannosylés, dans les mêmes perspectives que pour les astérisques soufrés glycosylés. Ces hélicènes glycosylés sont les premiers de la sorte décrit dans la littérature. Ils ont présenté des propriétés convenables vers des sondes luminescentes chirales et d’autres biocapteurs, qui sont basés sur les interactions lectine-sucre. / Polysulfurated polyaromatic compounds represent a class of molecules that are not extensively studied, despite their interesting properties. The presence of sulfur affects their redox, photophysical and complexation properties. We prepared a series of these compounds by using some aromatic nucleophilic substitutions. They can be further functionalized by some polyaromatic units, such as anthracene or pyrene, or by some glycosides.Their luminescence properties have been especially studied for their agregation induced emission properties, where the emission of the compounds is turned on when they are immobilized in solid phase or strongly cooled. These compounds can also be used to stabilize iron/platinum nanoparticles, where a high density of divalent sulfur atoms play an important role in nanosciences. Glycosylated derivatives have been tested with different lectins like ConA, PAIL, PAIIL and Bc2lA, the last three being involved in bacterial infections found in patient suffering from cystic fibrosis. Studies include photophysical and reticulation properties, and also affinitiy assays by using biophysical methods (SPR, ITC, and HIA). It provided some novel biosensors or luminescent sensors based on some selective lectin-carbohydrate interactions, in the event of future diagnostic devices and biological detection originating from lectins expressions (ex. cancer, bacterial infection, etc.).Another class of polyaromatic compounds has been studied, the helicenes,. Those chiral helical molecules can be found under two enantiomeric forms, according to the sense of the helical pitch.We herein present a new synthetic method of helicenes based on an organometallic route for some annulation reactions and C-H insertions. An exhaustive study of reaction conditions has been performed. We have prepared some functionnalized helicenes. Brominated and cyanated [5]-helicene derivatives have been deposited on a Suzuki surface, in order to study their structuration properties by nc-AFM on a non conductive surface. [5]-helicene was further functionnalized with some mannosylated units, with the same perspectives as for the glycosylated sulfurated asterisks. Those glycosylated helicenes are the first of their kind described in the literature. They provided some adequate properties toward new chiral and luminescent sensors, as well as other biosensors, which are based on lectin-carbohydrate interactions.

Pseudomonas aeruginosa (PA) représente un véritable problème de santé publique étant l'une des principales causes d'infections nosocomiales et de mortalité chez les patients atteints de fibrose cystique. Cette bactérie provoque des pathologies respiratoires chroniques qui persistent malgré une thérapie antibiotique agressive à cause de l'émergence de souches résistantes et de la formation du biofilm. Une stratégie prometteuse consiste à inhiber les facteurs de virulence de PA tels que PA-IL qui est une lectine soluble impliquée dans la reconnaissance des résidus galactose et qui semble jouer un rôle dans l'adhésion de la bactérie au glycocalyx autour de la cellule hôte ainsi que dans le développement du biofilm. Alors que les interactions lectine-carbohydrate sont caractérisées par une spécificité élevée, l'affinité entre les lectines et les saccharides simples est faible et une présentation multivalente des unités saccharidiques est généralement requise pour atteindre une interaction significative d'un point de vue physiologique. Ce manuscrit décrit la synthèse de glycooligonucléotides dont l'affinité envers PA-IL a été étudiées par DNA Direct Immobilisation microarray. Les blocs de construction saccharidiques ont été assemblés sur des échafaudages phosphorylés en utilisant une combinaison de synthèse en phase solide d'ADN et « click chemistry » (cycloaddition 1,3-dipolaire azide/alcyne). Grâce à la technologie glycoarray, les glycomimétiques ont été analysés à une échelle nanomolaire. Les résultats expérimentaux ont permis d'établir des relations structure-activités précises. En outre, des études des docking ont confirmé les résultats expérimentaux. La synthèse des candidats les plus affins envers PA-IL a été conduite sans l'étiquette d'ADN et à plus grande échelle pour vérifier par des analyses biologiques leurs propriétés anti-adhésives ou inhibitrices du biofilm. / Pseudomonas aeruginosa (PA) is a major public health issue due to its impact on nosocomial infections as well as its impact on cystic fibrosis patient mortality. It often leads to chronic respiratory infection despite aggressive antibiotic therapy due to the emergence of resistant strains and to the formation of biofilm. A promising approach is to inhibit the virulence factors of PA such as PA-IL which is a soluble lectin implicated in the recognition of galactose residues that seems to be involved in the adhesion of the bacterium to the glycocalyx surrounding host's cells as well as in the biofilm development.If carbohydrate-lectin interactions proceed with high specificity, the affinity between lectins and simple saccharides is low and a multivalent display of saccharidic units is generally required to attain physiologically significant association. This manuscript reports the synthesis of high affinity glycooligonucleotides toward PA-IL for its inhibition and their bindings properties were studied on a DNA direct immobilisation microarray. Glycoside building blocks were assembled on phosphorylated scaffolds using a combination of DNA solid phase synthesis and microwave assisted « click chemistry » (copper (I) catalyzed 1,3-dipolar cycloaddition). Thanks to glycoarray technology the glycomimetics were studied at the nanomole scale. The experimental results have been used to assess structure binding relationships. In addition, docking studies have confirmed ours experimental results. The synthesis of the best hits as anti-biofilm or anti-adhesive molecules have been synthesized at upper scale without their DNA tag for biological studies as anti-adhesive compounds and biofilm inhibitors of PA.

Os biofilmes constituem uma forma de crescimento que permite a maior sobrevivência e resistência de microrganismos a agentes de controle como antibióticos e desinfetantes. Apesar da grande disponibilidade de agentes antimicrobianos no mercado, há escassez de produtos específicos e efetivos na erradicação/inibição de biofilmes. Existe atualmente grande interesse na seleção de moléculas capazes de inibir o crescimento dos biofilmes ou removê-los quando já estabelecidos. Doenças como fibrose cística (P. aeruginosa) e cárie dentária (S. mutans), são patologias intrinsecamente ligadas à formação de biofilmes. O principal objetivo deste trabalho foi avaliar o potencial de chalconas sintéticas e derivados no controle e erradicação de biofilmes. As chalconas foram testadas quanto à capacidade de inibir a formação de biofilme e de remover biofilmes pré-estabelecidos. Os biofilmes de P. aeruginosa foram inibidos pela presença da molécula (E)-1-(3-hidroxinaftalen-2-il)-3-fenilprop-2-em-1-ona (11), mostrando redução de 48,8% na biomassa e 60,2% na viabilidade. A redução máxima na biomassa atingiu 70,9%. Já para o tratamento de biofilmes pré-estabelecidos, a molécula (1E,4E)-1,5-difenilpenta-1,4-dien-3-ona (10) mostrou redução de 53,5% na biomassa do biofilme de P. aeruginosa. Na formação do biofilme de S. mutans, a presença da molécula (1E, 4E)-1,5-bis(4-bromofenil)penta-1,4-dien-3-ona (15) reduziu a biomassa em 67,4%. Em concentrações elevadas essa redução chegou a 95,1%. Em biofilmes pré-estabelecidos de S. mutans, o tratamento com a molécula (2E,4E)-1,5-difenilpenta-2,4-dien-1-ona (12) reduziu a biomassa celular em 62,7%, e a viabilidade celular em 58,4%. Já a molécula (E)-3-(2-hidroxifenil)-1-fenilprop-2-en-1-ona (21), quando utilizada no tratamento de biofilmes pré-estabelecidos, mostrou redução de 26,4% na biomassa e 91,6% na viabilidade de S. mutans; além de evidenciar danos à estrutura celular do microrganismo. Todas as moléculas supracitadas promoveram redução na espessura dos biofilmes. Os antibióticos ampicilina e polimixina foram menos eficientes na remoção de biofilmes comparativamente às moléculas testadas. As moléculas não apresentaram CIM frente às bactérias, entretanto, afetaram a viabilidade celular. O tratamento da superfície de poliestireno com as chalconas não impediu a adesão das bactérias, e resultou na redução da hidrofobicidade do material. A superfície celular de S. mutans apresentou predomínio de cargas negativas e forte caráter hidrofóbico enquanto que P. aeruginosa apresentou baixa hidrofobicidade além de caráter básico. Os resultados evidenciam a potencialidade do uso das chalconas e seus derivados para o controle e erradicação de biofilmes Streptococcus mutans e Pseudomonas aeruginosa. / Biofilms constitute a growth mode which allows greatest survival and resistance of microorganisms to antibiotics and disinfectants. Despite the wide availability of antimicrobial agents in the market, there are few specific and effective products to the eradication / inhibition of biofilms. Thus, there is a great interest in the search of molecules able to inhibit biofilms or remove them once established. Diseases such as cystic fibrosis (P. aeruginosa) and dental caries (S. mutans), are intrinsically linked to the formation of biofilms. The aim of this study was to evaluate the potential of chalcones and their synthetic derivatives to the control and eradication of biofilms. The chalcones were tested for the ability to inhibit biofilm formation and also to remove pre-established biofilms. Biofilms of P. aeruginosa was inhibited by the presence of the molecule (E) -1- (3-hydroxynaphthalen-2-yl) -3-phenylprop-2-en-1-one (11) showing reduction of 48.8% biomass and 60.2% viability. The maximum reduction in biomass reached 70.9%. For the treatment of pre-established biofilms, the molecule (1E, 4E) -1,5-difenilpenta-1,4-dien-3-one (10) showed a 53.5% reduction in biomass of P. aeruginosa biofilm. Biofilms of S. mutans, growing in the the presence of the molecule (1E, 4E) -1,5-bis (4-bromophenyl) penta-1,4-dien-3-one (15) showed a biomass reduction of 67.4 %. At higher concentrations this reduction reached 95.1%. In pre-established biofilms of S. mutans, treatment with the molecule (2E, 4E) -1,5-difenilpenta-2,4-dien-1-one (12) reduced cell biomass in 62.7%, and cell viability by 58.4%. The molecule (E) -3- (2-hydroxyphenyl) -1-phenylprop-2-en-1-one (21), when used in the treatment of pre-established biofilms, showed 26.4% reduction in biomass and 91.6% in the viability of S. mutans; furthermore, the chalcone 21 caused damage to the cellular structure of the microorganism. All the aforementioned molecules promoted a reduction in the thickness of biofilms. The antibiotics polymyxin and ampicillin were less efficient on removing biofilms comparatively to the chalcones. The molecules affected cell viability however, no MIC was observed under the range of concentrations evaluated. The treatment of the polystyrene surface with chalcones did not prevent bacterial adhesion moreover, hydrophobicity of the material was reduced. S. mutans cell surface showed a predominance of negative charges and strong hydrophobic character while P. aeruginosa showed low hydrophobicity and basic character. The results demonstrate that synthetic chalcones and derivatives are potential candidates to the control and eradication of Streptococcus mutans and Pseudomonas aeruginosa biofilms.