Im Rahmen dieser Doktorarbeit wurden die Hangkarbonate von zwei miozänen heterozoischen Karbonatsystemen näher untersucht: die Malta Inselgruppe (zentrales Mittelmeer) und das Marion Plateau (Nordost Australien, ODP Leg 194). Die Auswirkungen der mittelmiozänen Abkühlung (Mi3), die auf 13.6 Ma datiert wird und starken Einfluß auf die Sauerstoffisotopenkurve hatte, in den oben genannten Flachwassersystemen stellten das Ziel dieser Arbeit dar. Dieses Abkühlungsereignis beeinflußte außerdem sehr stark die ozeanographischen und klimatischen Muster, die im weiteren Verlauf zum modernen Eishausklima führten. So steht insbesondere die Vereisung von Ostantarktika mit diesem Ereignis in Verbindung. Diese Arbeit untersucht den Einfluß dieses Ereignisses auf Flachwassersysteme, um vorliegende Untersuchungen in Tiefwassersystemen zu ergänzen und so zum globalen Verständnis des miozänen Klimawechsels beizutragen.<br /> <br /> Die Profile auf der Maltainselgruppe wurden mit Hilfe von Kohlenstoff- und Sauerstoffisotopen Auswertungen im Gesamtgestein, Gesamtgesteinmineralogie, Tonmineralanalyse und organischer Geochemie untersucht. Durch einen Wechsel von karbonatischeren zu tonigeren Sedimenten beeinflußte das mittelmiozäne Abkühlungsereignis die Sedimentation in diesem Gebiet sehr stark. Weiterhin wurde beobachtet, daß jede Phase der antarktischen Vereisung, nicht nur das mittelmiozäne Hauptereignis, zu einem erhöhten terrigenen Eintrag in den Hangsedimenten der Maltainselgruppe führte. Akkumulationsraten zeigen, daß dieser erhöhte terrigene Eintrag den einzelnen Vereisungsperioden zusammenhängt und die karbonatischen Sedimente durch tonreiche Sedimente &ldquo;verunreinigt&rdquo; wurden. Das daraufhin entwickelte Modell erklärt diesen erhöhten terrigenen Eintrag mit einer nordwärtigen Verlagerung der innertropischen Konvergenzzone durch die Bildung von kalten, dichten Luftmassen, die zu verstärkten Niederschlägen in Nordafrika führten. Diese verstärkten Niederschläge (oder verstärkter afrikanischer Monsun) beeinflußten die kontinentale Verwitterung und den Eintrag, mit der Folge, daß verstärkt terrigene Sedimente im Bereich der Hangsedimente der Maltainselgruppe abgelagert wurden. Die tonreichen Intervalle weisen Ähnlichkeiten zu sapropelischen Ablagerungen auf, was mit Hilfe der Spektral analyse des Karbonatgehalts und der geochemischen Analyse des organischen Materials gezeigt wurde. <br /> <br /> Auf dem Marion Plateau wurden die Sauerstoff- und Kohlenstoffisotopenkurven anhand von Foraminiferen der Gattung Cibicidoides spp. rekonstruiert. Der Karbonatgehalt wurde mit Hilfe einer chemischen Methode (Coulometer) ermittelt. Genauso wie die Sedimente der Maltainselgruppe beeinflußte das mittelmiozäne Abkühlungsereignis (Mi3) auch die Sedimente auf dem Marion Plateau. So kam es bei 13,8 Ma, in etwa zur Zeit der Vereisung von Ostantarktika, zu einem Abfall der Karbonatakkumulationsraten. Weiterhin traten Änderungen in der Zusammensetzung der Sedimente auf, so nehmen neritische Karbonatfragmente ab, der planktische Foraminiferengehalt nimmt zu und es wurden verstärkt Quarz und Glaukonit abgelagert. Ein überraschendes Ergebnis ist die Tatsache, daß der große N12-N14 Meeresspiegelabfall um 11,5 Ma die Akkumulationsraten der Karbonate auf dem Hang nicht beeinflußte. Dieses Ergebnis ist umso erstaunlicher, da Karbonatplattformen normalerweise sehr sensitiv auf Meeresspiegeländerungen reagieren. Der Grund, warum sich die Karbonatakkumulationsraten schon um 13,6 Ma (Mi3) und nicht erst um 11,5 Ma (N12-N14) verringerten, liegt in der Tatsache, daß die ozeanischen Strömungen die Karbonatsedimentation auf dem Hang des Marion Plateau schon im Miozän kontrollierten. Das mittelmiozäne Ereignis (Mi3) erhöhte die Stärke diese Strömungen und als eine Ursache wurde die Karbonatakkumulation auf den Hängen reduziert. Die Amplitude des N12-N14 Meeresspiegelabfalls liegt bei 90 m unter der Berücksichtigung der Sauerstoffisotopendaten aus der Tiefsee und Berechnungen des Meeresspiegels anhand des &ldquo;coastal onlaps&rdquo;, die während Leg 194 gemacht wurden. Die Isotopendaten dieser Arbeit weisen hingegen auf einen verringerten Meeresspiegelabfall von 70 m hin.<br /> <br /> Als allgemeine Schlußfolgerung kann gesagt werden, daß der mittelmiozäne Klimaumschwung die Karbonatsysteme zumindest an den beiden untersuchten Lokalitäten beeinflußt hat. Allerdings waren die Auswirkungen sehr von den unterschiedlichen lokalen Gegebenheiten abhängig. Insbesondere wirkten sich die Anwesenheit einer Landmasse (Malta) und die Abwesenheit einer Barriere vor den Einflüssen des offenen Ozeans (Marion Plateau) stark auf die Ablagerung der Karbonate aus. / This study investigated the slope carbonates of two Miocene carbonate systems: the Maltese Islands (in the Central Mediterranean) and the Marion Plateau (Northeastern Australia, drilled during ODP Leg 194). The aim of the study was to trace the impact of the Miocene cooling steps (events Mi1-Mi6) in these carbonate systems, especially the Mi3 event, which took place around 13.6 Ma and deeply impacted the marine oxygen isotope record. This event also profoundly impacted oceanographic and climatic patterns, eventually leading to the establishment of the modern ice-house world. In particular, East Antarctica became ice covered at that period. The rational behind the present study was to investigate the impact that this event had on shallow water systems in order to complement the deep-sea record and hence acquire a more global perspective on Miocene climate change.<br /> <br /> The Maltese Islands were investigated for trends in bulk-rock carbon and oxygen isotopes, as well as bulk-rock mineralogy, clay minerals analysis and organic geochemisty. Results showed that the mid Miocene cooling event deeply impacted sedimentation at that location by changing sedimentation from carbonate to clay-rich sediments. Moreover, it was discovered that each phase of Antarctic glaciation, not just the major mid Miocene event, resulted in higher terrigenous input on Malta. Mass accumulation rates revealed that this was linked to increased runoff during periods when Antarctica was glaciated, and thus that the carbonate sediments were &ldquo;diluted&rdquo; by clay-rich sediments. The model subsequently developed to explain this implies feedback from Antarctic glaciations creating cold, dense air masses that push the ITCZ Northward, thus increasing precipitation on the North African subcontinent. Increased precipitation (or stronger African monsoon) accelerated continental weathering and runoff, thus bringing more terrigenous sediment to the paleo-location of the slope sediments of Malta. Spectral analysis of carbonate content and organic matter geochemical analysis furthermore suggest that the clay-rich intervals are similar to sapropelic deposits.<br /> <br /> On the Marion Plateau, trends in oxygen and carbon isotopes were obtained by measuring Cibicidoides spp foraminifers. Moreover, carbonate content was reconstructed using a chemical method (coulometer). Results show that the mid Miocene cooling step profoundly affected this system: a major drop in accumulation rates of carbonates occurs precisely at 13.8 Ma, around the time of the East Antarctic ice sheet formation. Moreover, sedimentation changes occurred at that time, carbonate fragments coming from neritic environments becoming less abundant, planktonic foraminifer content increasing and quartz and reworked glauconite being deposited. Conversely, a surprising result is that the major N12-N14 sea-level fall occurring around 11.5 Ma did not impact the accumulation of carbonates on the slope. This was unexpected since carbonate platform are very sensitive to sea-level changes. The model developed to explain that mass accumulation rates of carbonates diminished around 13.6 Ma (Mi3 Event) instead of 11.5 Ma (N12-N14 event), suggests that oceanic currents were controlling slope carbonate deposition on the Marion Plateau prior to the mid-Miocene, and that the mid Miocene event considerably increase their strength, hence reducing the amount of carbonate being deposited on slope sites. Moreover, by combining results from deep-sea oxygen isotopes with sea-level estimates based on coastal onlaps made during Leg 194, we constrain the amplitude of the N12-N14 sea-level fall to 90 meters. When integrating isotopic results from this study, this amplitude is lowered to 70 meters.<br /> <br /> A general conclusion of this work is that the mid Miocene climatic shift did impact carbonate systems, at least at the two locations studied. However, the nature of this response was highly dependant on the regional settings, in particular the presence of land mass (Malta) and the absence of a barrier to shelter from the effects of open ocean (Marion Plateau).

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The use of kaolinite for preparing functionalized materials for specialized applications is still a relatively niche research subject. This is in spite of its low cost, high availability, and the potential for covalently grafting organic functional groups to its inner and outer surfaces. These grafted compounds have been shown to be highly resistant to heat and solvents, making them very useful for certain applications, for example in polymer nanocomposite materials that require high thermal resistance during polymer processing. Solid state NMR has been shown to play an essential role in solving the structure of functionalized kaolinite materials, however the current knowledge base for these functionalized kaolinites is notably lacking for some nuclei such as 1H, 27Al and 17O. Research was undertaken to address these concerns by developing new synthetic strategies for preparing kaolinite based materials for use as nanocomposites and to examine commonly prepared modified kaolinite precursors materials by 1H and 27Al MAS NMR in an attempt to demonstrate their utility for characterizing kaolinite intercalated and grafted complexes. Solid state 1H NMR of a natural kaolinite, kGa-1b, identified two main proton signals attributed to inner and inner surface hydroxyl protons. The different affinity of these two types of hydroxyl groups towards exchange with deuterium was used to differentiate between the two. The 1H NMR spectra of a DMSO intercalated kaolinite, kDMSO, and a methanol grafted kaolinite, kmethoxy, were fitted with high accuracy using models consistent with the known structures of these materials. The 27Al MAS NMR spectra of a natural kaolinite, kGa-1b, a DMSO intercalated kaolinite, kDMSO, and a methanol grafted kaolinite, kmethoxy measured at 21.1T showed little difference between one another, while noticeable differences could be seen at 4.7T. 27Al MQMAS experiments found almost no difference between these materials in the multiple quantum dimension, suggesting the differences that were observed are a result of differences in quadrupolar parameters rather than chemical shifts. The 27Al NMR spectra of kGa-1b, kDMSO and kmethoxy were fitted with good accuracy using models consistent with known structures of these materials. Different Al(III) sites with CQ values varying by up to 0.6MHz were found. The 27Al NMR spectra of two different methanol grafted kaolinites were also compared and it was found that the intensities of the sites with lower values of CQ were dependent on the quantity of grafted aluminum sites. The interlayer space of kaolinite was functionalized with a block copolymer: poly(ethylene)-block-poly(ethylene glycol) using a kaolinite pre-intercalated with DMSO, kDMSO, and with a biodegradable polymer: poly(lactide) using a kaolinite pre-intercalated with urea, kurea, both by using melts of the polymer. The polymers were found to completely displace their precursors from the interlayer space giving a monolayer type arrangement of the polymer. Attempts were made to graft compounds containing polymerizable functional groups: 3-allyloxy-1,2-propanediol and ethylene glycol vinyl ether to kaolinite’s inner surfaces using a kaolinite pre-intercalated and grafted with methanol, kmethoxy, and a kaolinite pre-intercalated with DMSO, kDMSO, respectively. Both compounds were found to displace their precursors from the interlayer space, adopting a monolayer type arrangement. 13C and 29Si NMR results suggest 3-allyloxy-1,2-propanediol’s allyl group remains intact and partially keys into the clay mineral’s siloxane rings. Ethylene glycol vinyl ether was found to undergo intramolecular cyclization to form an acetal product, consuming its vinyl group in the process. This reaction was observed using an unmodified kaolinite, kGa-1b, suggesting that the clay mineral’s surfaces, both inner and outer, act as an acid catalyst.

Le développement de la multirésistance chez Escherichia coli est un problème important en médecine animale et humaine. En outre, l’émergence et la diffusion des déterminants de résistance aux céphalosporines à larges spectres de troisième génération (ESCs) parmi les isolats, incluant des céphalosporines essentielles en médecine humaine (ex. ceftriaxone et ceftiofur), est un problème majeur de santé publique. Cette thèse visait trois objectifs. D’abord étudier la dynamique de la résistance aux antimicrobiens (AMR) ainsi que la virulence et les profils génétiques de la AMR des E. coli isolées de porcs recevant une nourriture post-sevrage supplémentée avec de la chlortétracycline et de la pénicilline G, et, accessoirement, évaluer les effets d'additifs alimentaires sur cette dynamique en prenant pour exemple d'étude un minéral argileux, la clinoptilolite, étant donné son possible lien avec le gène blaCMY-2 qui confère la résistance au ceftiofur. L'objectif suivant était d'investiguer les mécanismes menant à une augmentation de la prévalence du gène blaCMY-2 chez les porcs qui reçoivent de la nourriture médicamentée et qui n'ont pas été exposés au ceftiofur Ici encore,nous avons examiné les effets d’un supplément alimentaire avec un minéral argileux sur ce phénomène. Enfin, notre dernier objectif était d’étudier, dans le temps, les génotypes des isolats cliniques d'E. coli résistant au ceftiofur, isolés de porcs malades au Québec à partir du moment où la résistance au ceftiofur a été rapportée, soit de 1997 jusqu'à 2012. Dans l'étude initiale, la prévalence de la résistance à 10 agents antimicrobiens, incluant le ceftiofur, s’accroît avec le temps chez les E.coli isolées de porcelets sevrés. Une augmentation tardive de la fréquence du gène blaCMY-2, encodant pour la résistance au ceftiofur, et la présence des gènes de virulence iucD et tsh a été observée chez les isolats. La nourriture supplémentée avec de la clinoptilolite a été associée à une augmentation rapide mais, par la suite, à une diminution de la fréquence des gènes blaCMY-2 dans les isolats. En parallèle, une augmentation tardive dans la fréquence des gènes blaCMY-2 et des gènes de virulence iucD et tsh a été observée dans les isolats des porcs contrôles, étant significativement plus élevé que dans les porcs ayant reçu l'additif au jour 28. La diversité, au sein des E. coli positives pour blaCMY-2 , a été observée au regard des profils AMR. Certaines lignées clonales d'E.coli sont devenues prédominantes avec le temps. La lignée clonale du phylotype A prédominait dans le groupe supplémenté, alors que les lignées clonales du phylotype B1, qui possèdent souvent le gène de virulence iucD associé aux ExPEC, prédominaient dans le groupe contrôle. Les plasmides d'incompatibilité (Inc) des groupes, I1, A/C, et ColE, porteurs de blaCMY-2, ont été observés dans les transformants. Parmi les souches cliniques d'E.coli ESC-résistantes, isolées de porcs malades au Québec de 1997 à 2012, blaCMY-2 était le gène codant pour une β-lactamase le plus fréquemment détecté; suivi par blaTEM et blaCTX-M,. De plus, les analyses clonales montrent une grande diversité génétique. Par contre, des isolats d'E. coli avec des profils PFGE identiques ont été retrouvés dans de multiples fermes la même année mais aussi dans des années différentes. La résistance à la gentamicine, kanamycine, chloramphenicol, et la fréquence de blaTEM et de IncA/C diminuent significativement au cour de la période étudiée, alors que la fréquence de IncI1 et de la multirésistance à sept catégories d'agents antimicrobiens augmente significativement avec le temps. L'émergence d'isolats d'E. coli positifs pour blaCTX-M, une β-lactamase à large spectre et produisant des ESBL, a été observée en 2011 et 2012 à partir de lignées clonales distinctes et chez de nombreuses fermes. Ces résultats, mis ensemble, apportent des précisions sur la dissémination de la résistance au ceftiofur dans les E. coli isolées de porcs. Au sein des échantillons prélevés chez les porcs sevrés recevant l'alimentation médicamentée sur une ferme, et pour laquelle une augmentation de la résistance au ceftiofur a été observée, les données révèlent que les souches d'E. coli positives pour blaCMY-2 et résistantes aux ESCs appartenaient à plusieurs lignées clonales différentes arborant divers profils AMR. Le gène blaCMY-2 se répand à la fois horizontalement et clonalement chez ces E. coli. L'ajout de clinoptilotite à la nourriture et le temps après le sevrage influencent la clonalité et la prévalence du gène blaCMY-2 dans les E. coli. Durant les 16 années d'étude, plusieurs lignées clonales différentes ont été observées parmi les souches d'E. coli résistantes au ceftiofur isolées de porc malades de fermes québécoises, bien qu’aucune lignée n'était persistante ou prédominante pendant l'étude. Les résultats suggèrent aussi que le gène blaCMY-2 s'est répandu à la fois horizontalement et clonalement au sein des fermes. De plus, blaCMY-2 est le gène majeur des β-lactamases chez ces isolats. À partir de 2011, nous rapportons l'émergence du gène blaCTX-M dans des lignées génétiques distinctes. / Development of multidrug resistance in Escherichia coli is an important problem in animal and human medicine. Further, emergence and spread of determinants for resistance to third generation extended-spectrum cephalosporins (ESCs) such as the critically important cephalosporins in human medicine (e.g. ceftriaxone and ceftiofur) among isolates is a public health concern. Thus, the objectives of the present thesis were (1) to study the dynamic of antimicrobial resistance (AMR) phenotypes as well as virulence and AMR gene profiles in E. coli from pigs receiving a feed medicated with chlortetracycline and penicillin G following weaning and to study the effect of feed supplementation with a clay mineral, clinoptilolite, on this dynamic; (2) To investigate the mechanisms leading to an increase in the prevalence of blaCMY-2 conferring resistance to ceftiofur in pigs receiving medicated feed but which had not received ceftiofur, and to examine the effect of feed supplementation with a clay mineral on this phenomenon; and (3) to investigate the temporal characterization of clinical isolates of ceftiofur-resistant E.coli from diseased pigs in Quebec, Canada from 1997, when ceftiofur resistance was first reported, to 2012. In the initial study, prevalence of resistance to 10 antimicrobial agents, including ceftiofur, increased over time in E.coli isolates from weaned pigs. A late increase in the frequency of blaCMY-2, the gene encoding resistance to ceftiofur, and the presence of virulence genes iucD and tsh were observed in the isolates. Feed supplementation with clinoptilolite was associated with an early increase but later decrease in the frequency of the blaCMY-2 gene in isolates. Concurrently, a later increase in the frequency of the blaCMY-2 and the virulence genes iucD and tsh was observed in the control pig isolates, being significantly greater than in the supplemented pigs at day 28. Diversity among the blaCMY-2-positive E. coli isolates with respect to AMR patterns was observed. Certain clonal lineages of E. coli became predominant with time. The clonal lineage of phylotype A predominated in the supplemented group, whereas the clonal lineages of phylotype B1 which often possessed the ExPEC-associated virulence gene iucD, predominated in the control group. The blaCMY-2-carrying plasmids of incompatibility (Inc) groups, I1, A/C, and ColE were observed in transformants. In ESC-resistant E.coli clinical isolates from diseased pigs in Quebec, from 1997 to 2012, blaCMY-2 was the most frequently detected β-lactamase gene, followed by blaTEM and blaCTX-M and clonal analysis showed high diversity. E. coli isolates with identical PFGE patterns were found in multiple farms in the same year and also in different years. Resistance to gentamicin, kanamycin, chloramphenicol, and the frequency of blaTEM and IncA/C significantly decreased over the study time, whereas the frequency of IncI1 and multidrug-resistance to seven antimicrobial categories significantly increased over time. Emergence of blaCTX-M-positive, extended-spectrum β-lactamase (ESBL)-producing E. coli isolates was observed in 2011 and 2012 from distinct clonal lineages and multiple farms. Taken together, this work gives some insight into the spread of ceftiofur resistance in E.coli isolates from pigs. Results reveal that in weaned pigs receiving medicated feed on one farm in which an increase in ceftiofur resistance was observed, the blaCMY-2-positive E.coli resistant to ESCs belonged to several different clonal lineages with diverse AMR patterns. The blaCMY-2 gene spread both horizontally and clonally in E. coli. Feed supplementation with clinoptilolite and time period after weaning influenced the clonality and the prevalence of blaCMY-2 gene in E. coli. In ceftiofur-resistant E.coli strains isolated from diseased pigs in farms throughout Quebec over a 16 year period, several different pathogenic clonal lineages were observed, although none was persistent or predominant over the study time. The results suggest that blaCMY-2 gene spreads both horizontally and clonally on and between farms. Furthermore, blaCMY-2 was the major β-lactamase gene in these isolates. From 2011, we report the emergence of blaCTX-M in distinct clonal lineages.