The carbon and oxygen isotopes of planktonic foraminifera, and faunal assemblages of towing samples, £_13C of dissolved inorganic carbon, and £_18O of seawater collected from northern South China Sea (SCS) were analyzed in this study. Plankton tows were collected between December 2002 and December 2005 at water depth of 100m. In addition, fauna and sea water samples were sampled at different depths ranging between 50 and 300m at some stations. Generally, the faunal assemblages are dominated by Globigerinoides ruber, Globigerinoides sacculifer, Globigerinoides aequilateralis, Pulleniatina obliquiloculata, Neogloboquadrina dutertrei, and Globorotalia menardii. G. aequilateralis and G. menardii are dominated in warm months while G. ruber, G. sacculifer, and P. obliquiloculata are dominated in cold months. The relative abundances of G. sacculifer and G. aequilateralis obtained from towing samples in this study are significantly higher than those shown in underlying sediment traps and surface sediments, suggesting that the tests of these two taxa are prone to dissolution. In addition, the abundance of P. obliquiloculata which serves as an index taxon for the Kuroshio Current in Paleoceanography, is more abundant in the northern part than in the southern part of the SCS basin. Nevertheless, the £_13C and £_18O of G. sacculifer and P. obliquiloculata are significantly lighter than that in sediment traps and surface sediments, indicating some potential effects caused by the differential dissolution. Possible dwelling depths of P. obliquiloculata is estimated between 50 and 90m, whereas N. dutertrei is estimated between 20 and 80m according to Kim and O¡¦Neil (1997). The latter changes to 40~160m when the equation of Bouvier-Soumagnac and Duplessy (1985) is applied. Oxygen isotope compositions of G. sacculifer and G. ruber display a significant correlation with temperature (T) in the surface mixed layer. The slopes of £_18O/ T for these two species are similar to each other. The differences of £_18O (£G£_18O) between G. sacculifer and N. dutertrei, G. sacculifer and P. obliquiloculata, G. ruber and P. obliquiloculata are proved to be a good proxy indicator for reconstructing the upper water column based on the statistic relationship between £G£_18O and £GT (difference between mixed layer and 100m) in this study.

Στην παρούσα εργασία εξετάζονται οι συγκεντρώσεις των πλαγκτονικών τρηματοφόρων, όπως αυτές έχουν καταγραφεί σε δημοσιευμένες εργασίες και ανάλογες επιστημονικές βάσεις δεδομένων από την περιοχή της Μεσογείου για το χρονικό διάστημα των τελευταίων 18.000 χρόνων. Με σκοπό να εξεταστούν τυχόν χωρικές και χρονικές μετατοπίσεις των ελάχιστων και μέγιστων των συγκεντρώσεών τους και διαφοροποιήσεις τους σε σχέση με τις σημερινές. / In the present work the concentrations of planktonic foraminifera, as recorded in published papers and similar scientific databases from the Mediterranean region for the period of the last 18,000 years. To examine any spatial and temporal shifts of the minimum and maximum concentrations of these differences and their relationship to current.

The late Neogene represents an exceptionally dynamic period in Earth history during which the Northern Hemisphere has transitioned from a warmer, more equable climate to a cooler, more transient state characterized by waxing and waning continental ice sheets. While geographical distal, the tropical ocean has played a significant role in shaping the evolution of the climate system, as the opening and closing of low latitude (LL) ocean gateways and reorganization of oceanic and atmospheric circulation structure have helped shape the climate system into its present form. This study provides a reconstruction of sea surface temperature (SST), ocean circulation, and thermal structure of the LL eastern Pacific and North Atlantic based upon the compilation of proxy data derived from planktic foraminifer assemblages and geochemical techniques. This research begins with a paleoceanographic reconstruction of the eastern tropical Pacific (ETP) and subtropical Northwest Atlantic (NWA) during the early stages of uplift of the Central American Isthmus and associated shoaling of the Central American Seaway (CAS). In the subtropical NWA (DSDP 103 and ODP 1006), the 5.2 to 5.1 Ma interval is characterized by an increase in SST and sea surface salinity, indicating a strengthening of the Florida Current (FC) and Gulf Stream (GS). Sea surface temperature in the ETP Warm Pool (DSDP Site 84) remained relatively stable between 6.9 and 5.1 Ma, during which El Niño-like conditions persisted. A slight cooling is observed after this interval (with synchronous warming in the NWA), followed by the onset of major cooling at ~3.2 Ma, both of which are preceded by a shallowing of the thermocline. Stepwise cooling is attributed to enhanced Atlantic meridional overturn circulation (AMOC), which caused a shoaling of the main tropical thermocline, thereby strengthening the Walker Circulation and weakening the Pacific North Equatorial Counter Current. During the mid-Piacenzian warm period (MPWP; ~3.3-3.0 Ma), SST in the Panama Basin was ~0.8°C cooler than today, while the subtropical NWA was only ~1.1°C warmer. This corroborates evidence for reduced meridional SST gradients during the mid-Pliocene as well as the hypothesis that more vigorous ocean circulation--particularly in the NWA--was critical during this period. The timing of SST changes in the ETP and NWA (~5.1 Ma) suggest that the termination of permanent El Niño and enhanced AMOC did not contribute significantly to the onset of major Northern Hemisphere glaciation (NHG), as both of these events occur well before the beginning of the glacial cycles. However, these processes may have contributed to the development of the small ice sheets of the late Miocene and early Pliocene, but were most likely only preconditioning factors for the onset of major NHG. In contrast, changes in SST and relative thermocline position suggest that high latitude (HL) processes and global cooling may have influenced thermal structure in the ETP. The SST estimates provided indicate that even in its early stages, the shoaling of the CAS had significant implications for low-latitude ocean circulation and thermal structure, as well as for some of the most significant global climate events of the late Neogene, including the MPWP. During the MPWP, mean global surface temperatures were similar to those predicted for the next century (2-3˚ C warmer) while atmospheric CO2 concentrations, paleogeography, and paleobiology were similar to today. As such, the MPWP has been studied in detail as a potential (albeit imperfect) analog for future climate change and has provided a natural and unique test-bed for the integration of proxy data and general circulation models. Central to this research effort is the Pliocene Research, Interpretation, and Synoptic Mapping (PRISM) project, an iterative paleoenvironmental reconstruction of the MP focused on increasing our understanding of warm-period climate forcings, dynamics, and feedbacks by providing three-dimensional data sets for general circulation models. A mainstay of the PRISM project has been the development of a global sea surface temperature (SST) data set based primarily upon quantitative analyses of planktic foraminifer assemblages, supplemented with geochemical SST estimates wherever possible. In order to improve spatial coverage of the PRISM faunal and SST data sets in the LL North Atlantic, this study provides a description of the MP planktic foraminifer assemblage and multiproxy SST estimates from five Ocean Drilling Program sites (951, 958, 1006, 1062, and 1063) in the North Atlantic subtropical gyre (NASG), a region critical to Atlantic Ocean circulation and tropical heat advection. Assemblages from each core provide evidence for a temperature- and circulation-driven 5-10° northward displacement of MP faunal provinces, as well as regional shifts in planktic foraminifer populations linked to species ecology and interactions. General biogeographic trends also indicate that, relative to modern conditions, gyre circulation was stronger (particularly the Gulf Stream, North Atlantic Current, and North Equatorial Current) and meridionally broader. Overall, SST estimates suggest that surface waters in this region were not significantly warmer (1-2˚ C) than today and that mean annual SSTs along LL western boundary currents were indistinguishable from modern. Multiproxy SST data also provide evidence for enhanced northward transport of warm, salty, oligotrophic surface waters via a vigorous western boundary current system with warmer (cooler) cold-season (warm-season) temperatures. Collectively, this reconstruction of SST and ocean circulation provides support for a model of an enhanced Atlantic meridional overturn circulation (AMOC) system, with particularly vigorous LL western boundary currents and thus, more efficient northward heat transport. These trends therefore suggest that more vigorous thermohaline circulation, in conjunction with elevated atmospheric CO2 concentrations, played a significant role in shaping the global surface temperature distribution during the MPWP. A strengthening of the AMOC under warmer-than-modern conditions has significant implications for future climate change. The current generation of climate models suggests that HL warming and associated ice-sheet melting will induce a freshening of the North Atlantic and thus, to a reduction in the strength of the AMOC, thereby buffering surface temperature increases in the Northern Hemisphere. However, if after this transient period of climate system adjustment, Earth returns to a more Pliocene-like climate state the AMOC system may strengthen, thereby exacerbating the HL warmth caused by elevated atmospheric CO2 concentrations. Thus, through the reconstruction of warm-period SST and ocean circulation, this research provides insight into the potential operation of the LL North Atlantic and its associated impact on broad-scale Northern Hemisphere climate.

Hospital Acquired Infections and equipment contamination are some of the biggest issues faced by the healthcare industry worldwide. These infections generally range from mild to life threatening human infections which lead to increased costs and prolonged hospitalization time. The primary factor which caused these issues were biofilm forming bacteria which are able to withstand medications and defend themselves from various cleaning procedures. Another aspect which make these bacteria troublesome is that they are able to hide inside the biofilm, thus evading a lot of diagnostic tests. The methods used to detect these biofilms are unfortunately toxic to cells and cannot be used in vivo. Though there is enough data on the formation of biofilm on abiotic surfaces, the data present on the biophysical properties, structural organizations within the biofilm or their viscoelastic properties is very limited. In this master’s degree project, a dynamic monitoring platform is made for 2 different strains of the Salmonella Enteritidis bacteria where their structural and biophysical properties was investigated. Each strain lacks either curli or cellulose which are major components responsible for proper biofilm formation so performing these experiments on them gave us important information on how their properties get affected over time. Bacterial growth monitoring for all the strains were performed by measuring the absorbance every hour over a period of 5h and it was observed that all the strains had a very similar growth pattern until the end of the 4th hour after which they showed very mild differences. The next set of experiments involved using an eQCM to monitor the formation of biofilm on the surface of a quartz chip over 48h. There were differences observed in the biofilm formation pattern and mass deposition which provided clues as to how the biofilm formation and their viscoelastic properties are affected due to the mutations. This led to finding further clues regarding which aspect of biofilm formation is targeted by a specific mutant.

Biofilms have the potential to form on various abiotic surfaces and have been found to be more resistant to environmental stressors. Therefore, there is a need to investigate the biofilm forming ability and characteristics of Salmonella strains isolated from poultry meat. These studies characterized the biofilm forming capabilities of 5 Salmonella strains on abiotic surfaces, and investigated changes in gene expression that are associated with Salmonella biofilm formation in 3 Salmonella strains. Salmonella biofilms were cultivated on stainless steel, concrete, rubber, and polyethylene under static and shear stress conditions. Biofilm matrix density was determined using a modified crystal violet assay, and attached cells were enumerated by direct plating on tryptic soy agar plates. Additionally, biofilm development was verified using scanning electron microscopy. Extracellular matrix density was affected by a surface-incubation condition interaction, in which the OD600 was higher on stainless steel under shear stress, as compared to static incubation (P < 0.001). On polyethylene, the OD600 was higher under static incubation (P < 0.001). The number of attached cells was highest on polyethylene under shear stress, irrespective of strain (6.4 log/coupon; P < 0.001). The study tracked changes in the expression of the biofilm-associated genes csgD, bapA, bcsA, adrA, and luxS. The gene expression levels in 24 h planktonic cells, 4-day old biofilms, and 5-day old biofilms were compared to those in 12 h planktonic cells and normalized to 16S RNA. Three different Salmonella serovars were used in this study: Salmonella Typhimurium, Reading, and Kentucky. Upregulation of csgD, bcsA, adrA, and luxS at 24 h was observed exclusively in Salmonella Reading (P = 0.028). In 4-day old biofilms, downregulation of all 5 genes was detected (P < 0.001). However, in 5-day old biofilms, the expression of bapA, bcsA, adrA, and luxS increased across all tested Salmonella serovars. These findings highlight the variations in gene expression across different Salmonella serovars, emphasizing the need to remove and prevent Salmonella attachment on food contact surfaces. Through further investigation, it may be possible to establish environmental stress thresholds for biofilm formation and optimize intervention strategies to mitigate Salmonella attachment and persistence on industrial materials.

Nesta tese, organizada em capítulos, são apresentados diferentes estudos sobre processos que afetam a história de vida, o potencial de dispersão, as preferências do assentamento larval e o recrutamento efetivo do coral invasor Tubastraea coccinea. No primeiro capítulo, demonstra-se que plânulas produzidas por T. coccinea são capazes de sofrer metamorfose e agregar-se em grupos de até oito pólipos ainda na coluna d´água, sem que ocorra previamente assentamento larval. Nesta seção, foi avaliada também a sobrevivência de propágulos para testar se diferentes níveis de agregação possibilitam uma extensão do período planctônico e, portanto, um aumento do potencial de dispersão. Os resultados obtidos mostram que pólipos natantes sobrevivem mais que plânulas, provavelmente por serem capazes de se alimentar e, assim, suprir a alta demanda energética associada à natação e à procura de um substrato favorável para o assentamento. Grupos de dois ou mais pólipos sobrevivem mais que pólipos solitários. Porém, a mortalidade não diferiu entre agrupamentos pequenos (2-3 pólipos) e grandes (4-8 pólipos), o que sugere que existe um limite para o tamanho ótimo dessas colônias pelágicas. A maioria dos grupos de pólipos que se mantém nadando na coluna d´água (80%) permanece viva após seis meses, o que sugere que a capacidade de sofrer metamorfose no ambiente pelágico e formar colônias de pólipos planctônicos é uma característica chave na história de vida da espécie, incrementando o potencial de dispersão, a conectividade entre populações e a capacidade de colonização de novos ambientes. No segundo capítulo, é caracterizada primeiramente a distribuição espacial de colônias adultas e pólipos fundadores do coral T. coccinea sobre substratos rochosos com diferentes orientações. Para isso, foi avaliada a consistência desses padrões para duas escalas espaciais, uma pequena (de dezenas de metros) e outra intermediária (de unidades de quilômetros). Posteriormente, estudaram-se as preferências durante o assentamento larval e os padrões de recrutamento sobre superfícies com diferentes orientações através de experimentos de campo e laboratório. O objetivo principal desta secção foi determinar se os padrões de distribuição de recrutas e colônias adultas podem ser explicados por processos que ocorrem durante etapas larvais ou pós-larvais iniciais. Os resultados indicam que tanto a flutuabilidade das larvas quanto o comportamento ativo de natação, não relacionado com condições de luminosidade, são fatores que determinam claramente o padrão de distribuição do coral. Como parte desse padrão, observou-se que a densidade de recrutas juvenis é maior em substratos orientados para baixo, sendo quase nula nas superfícies orientadas para cima. Com exceção da quase ausência de indivíduos sobre áreas orientadas para cima, existem diferenças substanciais entre a distribuição de recrutas e adultos para as demais orientações, principalmente para superfícies verticais. Essas diferenças podem estar relacionadas com o escoamento costeiro, o qual é intenso na região de estudo e pode causar depósito excessivo de sedimentos sobre superfícies positivas, inibindo o desenvolvimento de colônias deste coral. Por outro lado, interações competitivas com outras espécies de corais azooxantelados poderiam ser a causa da diminuição da abundância de T. coccinea em substratos negativos. No terceiro e último capítulo desta tese avaliou-se o potencial de interação de Tubastraea coccinea com espécies representativas de uma comunidade bentônica do litoral norte do Estado de São Paulo, recentemente invadida. Amostragens no campo, visando estimar a densidade de recrutas juvenis de T. coccinea sobre diferentes tipos de manchas formadas por organismos incrustantes, foram usadas para obter uma primeira inferência sobre o potencial de facilitação, ou inibição, do recrutamento. Os cnidários Carijoa riisei, Parazoanthus sp e Obelia dichotoma afetaram negativamente o recrutamento do coral sol, enquanto que algas incrustantes coralináceas facilitaram o recrutamento e podem facilitar a colonização do coral. O papel da mediação alelopática foi avaliado a partir de experimentos de laboratório, nos quais foram medidas diferentes componentes do assentamento larval em função da exposição das larvas a extratos brutos de várias espécies acompanhantes. Os testes mostraram a ocorrência geral de alelopatias negativas, as quais em alguns casos levaram apenas à inibição do assentamento, mas em outros à rápida mortalidade das larvas, sugerindo a ação de metabólitos tóxicos. Adicionalmente, foram realizados estudos comparativos de comunidades com a presença, ou ausência, do coral invasor, considerando fatores relevantes para a sua ocorrência, como a orientação do substrato. As comunidades invadidas por T. coccinea tendem a apresentar maior riqueza e equitatividade. A invasão no local de estudo é relativamente recente, pelo que os resultados encontrados devem estar mais relacionados a diferenças na susceptibilidade dessas comunidades à invasão, do que a eventuais efeitos das colônias do coral sol desenvolvidas nas mesmas. Se for assim, o estabelecimento do coral sol no litoral do Estado de São Paulo poderá implicar em uma perda significativa da diversidade biológica de substratos consolidados rasos. Os dados obtidos nesse estudo, abordando aspectos relevantes da vida pelágica e bentônica de T. coccinea, constituem um acervo de informação que poderá subsidiar planos de controle e monitoramento da espécie invasora, contribuindo ao estabelecimento de critérios de gestão de áreas de conservação. / In this thesis, organized in chapters, we present studies on the processes affecting the life history, dispersal potential, larval settlement preferences, and effective recruitment of the invasive coral Tubastraea coccinea. In the first chapter we report, for the first time, that larvae produced by the sun coral may metamorphose and aggregate in the water column without previous settling on any substrate. We then compared the survival of different types of propagules to test whether alternative development pathways allow longer pelagic life, and thus higher dispersal potential. Our results show that single-polyps live longer than planulae, probably because they can feed and sustain minimal metabolic activity. Clustered polyps live longer than solitary polyps, as expected if per capita polyp mortality rates are similar between these categories. However, mortality rate did not differ between small (2-3 polyps) and large (4-8 polyps) clusters, indicating that, in overall conditions, polyp performance attain a maximum at intermediate aggregations, setting an eventual adaptive upper limit to cluster size. In our experiment, over 80% of swimming colonies remained alive for a period exceeding six months. We conclude that pelagic metamorphosis and cluster formation may be an important mechanism allowing connectivity among populations and the colonization of new habitats. Moreover, founder individuals resulting from pelagic polyp aggregation can generate greater genetic variability in benthic developing colonies. In the second chapter, we first characterized spatial distributions of adult colonies and single-polyp recruits of the invasive azooxanthellate coral Tubastraea coccinea over substrates of different orientation, and evaluated their consistency at both small (several tens of meters) and intermediate (a few km) spatial scales. We then assessed, through field and laboratory experiments, larval preferences and relative settlement and recruitment rates on surfaces with different orientations to determine whether processes taking place during the larval and early post-larval stages could help explain the distribution patterns of recruits and adult colonies. Results suggest that larval passive buoyancy and active larval behavior, unrelated to light conditions, determine a clear settlement distribution pattern, in which the density of settlers is highest at undersurfaces and almost nil at upward facing horizontal substrates. Except for an almost absence of settlers, recruits and adult individuals on upward facing horizontal habitat, there is substantial mismatch between the distribution of settlers and that of recruits and adult colonies. The latter were also common in vertical substrates in the field. We speculate that coastal runoff at the study area and subsequent sedimentation may inhibit coral development on flat upward facing habitat, and that competitive interference and pre-emptive interactions with native azooxanthellate corals could constrain abundance of T. coccinea in underface horizontal habitat. In the third and final chapter of this thesis, the interactions of representative species of the benthic community of the north shore of São Paulo state with the exotic coral, recently introduced at the study site, were evaluated. Field surveys of the density of juvenile recruits of T. coccinea on different types of patches formed by fouling organisms allowed us to detect the effect of competitor species that inhibit coral recruitment. The Cnidarians Carijoa riisei, Parazoanthus sp and Obelia dichotoma negatively affected the juvenile recruitment of the sun coral. Conversely, it was observed that the recruitment of this scleractinian is considerably greater on several other species (chiefly fouling coralline algae), which act as facilitators and promote coral colonization. The role of allelopathic interactions mediating larval settlement was investigated through a settlement experiment using extracts of different companion species. Results indicated a general negative allelopathic response, either limited to settlement inhibition or leading acute mortality, the latter suggesting toxic effects. We also conducted comparative studies of communities with and without the invasive coral, considering other factors that could influence coral occurrence, such as substratum orientation. Species richness and evenness were general higher in invaded communities. The sun coral invasion is relatively recent in the study area and, therefore, these results are probably related to differences in the susceptibility of these assemblages to be invaded, rather than eventual effects of established colonies on them. If this is so, the establishment of T. coccinea in São Paulo state may lead to a significant loss of biological diversity in shallow rocky habitat. Our data give a full account of relevant aspects of the pelagic and benthic life of this invasive coral, and constitute a collection with no precedence that may subsidize plans of control and monitoring of this invasive species, contributing to the establishment of criteria used in the management of conservation areas.

Neste trabalho, investigou-se o crescimento e as interações de microorganismos, anaeróbios, em batelada com células planctônicas e em reatores diferenciais com biofilme, sob condições termofílicas (55ºC). Foram utilizadas técnicas clássicas para caracterizar os microorganismos anaeróbios estritos e biologia molecular (FISH), com sondas fluorescentes específicas, para caraterizar e quantificar os microrganismos pertencentes ao domínios Archea e Bacteria. Foram realizadas experimentos com meios de cultivo contendo acetato de sódio e propionato de sódio, na presença de sulfato de sódio. Os resultados do FISH mostraram, para os ensaios em batelada com acetato e sulfato, o predomínio de organismos pertencentes ao Domínio Archea (ARC915+MB1174) representados pelo gênero Methanosarcina sp. e bacilos fluorescentes. No biofilme, para a mesma condição, houve predomínio de células do Domínio Bacteria (EUB338) e relacionadas com a oxidação do acetato. Para a condição de cultivo com lactato e sulfato, as células bacterianas semelhantes a Desulfotomaculum sp. predominaram nos reatores em batelada e diferenciais, justificando a elevada porcentagem de células do Domínio Bacteria. Os resultados do NMP mostraram uma maior concentração de anaeróbios totais na condição lactato e sulfato (\'10 POT.11\' - \'10 POT.12\'). Para as arqueas metanogênicas essa concentração foi eveidenciada para a condição de cultivo com acetato e sulfato (\'10 POT.4\'). Os resultados desse trabalho sugeriram que em reatores em batelada, na condição de cultivo com acetato e sulfato, ocorreu equilíbrio entre metanogênese, oxidação de acetato e sulfatogênese, enquanto no biofilme, foram favorecidos os dois primeiros tipos de metabolismo. A condição lactato mais sulfato favoreceu a sulfetogênese em ambos os reatores. No reator diferencial, alimentado com proprionato e sulfato ocorreu fermentação com crescimento sintrófico entre oxidadoras de proprionato, metanogênicas e redutoras de sulfato hidrogenotróficas. / In this work, were investigated the growth and interactions of anaerobic microorganisms, in batch and differential reactors with planktonic cells and biofilm, respectively, in thermophilic conditions (55°C). Classic and molecular biology methods (FISH) were utilized to characterize strict anaerobes, with specific fluorescence probes, to characterize the Archaea and Bacteria Domain cells. Experiments with sodium acetate, s01ium lactate and sodium propionate plus sodium sulfate were realized. To the acetate and sulfate batch assays the results of FISH showed the predominance of Archaea Domain cells (ARC915+MB1174), represented by genera Methanosarcina sp. and fluorescents rods. Under the same conditions the biofilm results showed predominance of Bacteria Domain cells (EUB338) and those related to the acetate oxidation. In lactate plus sulfate condition the bacteria cells, as Desulfotomaculum sp., predominated in batch and differential reactors, justifying the high percentage of Bacteria Domain cells. The MPN results showed a high concentration of total anaerobes under lactate plus sulfate condition (\'10 POT.11\' - \'10 POT.12\'). For methanogenic arquea this concentration was obtained in the acetate plus sulfate condition (\'10 POT.4\'). These results suggest a process equilibrium may have occurred among methanogenesis, acetate oxidation and sulfidogenesis in batch reactors under acetate plus sulfate conditions. However, methanogenesis and acetate oxidation metabolisms predominated in the biofilm. Sulfidogenesis was easier in both reactors, under lactate plus sulfate conditions. In the differential reactors with propionate plus sulfate, the fermentation was in syntrophic co-culture among propionate oxidizing bacteria, methanogenic and hydrogenotrophic sulfate reducing bacteria.

Lorsqu'un biofilm se développe dans des conditions statiques, deux populations, sessiles et planctoniques, coexistent et peuvent échanger des cellules. Cependant, l'immigration de cellules planctoniques dans un biofilm n'a, jusqu'à présent, fait l'objet que de peu d'études dans le cas d'un biofilm monoespèce. Chez B. cereus, un pathogène alimentaire, notre équipe a récemment montré que des bactéries planctoniques mobiles peuvent pénétrer en profondeur à l'intérieur d'un biofilm formé en immersion. L'objectif du présent travail était, en partant de ces données, de déterminer le rôle du recrutement dans le développement du biofilm formé en interface air-liquide, et de caractériser ce processus d’un point de vue physiologique et moléculaire. Nous avons montré que la population planctonique est massivement recrutée par le biofilm, mais que, dans nos conditions expérimentales, ce recrutement ne contribue que de façon marginale à la croissance du biofilm. Nous avons mis au point deux dispositifs expérimentaux (en interface air-liquide et en immersion) permettant de quantifier le recrutement, ce qui nous a permis de cribler une banque de mutants, obtenue par mutagenèse aléatoire, pour sélectionner des clones inaptes à être recrutés. Le criblage de 1700 clones a abouti à la sélection d'un gène: Bthur002_62720. La délétion de ce gène par échange allélique affecte fortement la capacité du mutant à être recruté, et la complémentation rétablit le phénotype sauvage. Ce gène code pour une protéine probablement localisée dans l'enveloppe bactérienne. Il est porté par un plasmide, pCT8513, et pourrait être un élément mobile dont l'acquisition augmenterait fortement la capacité de la bactérie réceptrice à être recrutée par un biofilm. Enfin, nous avons mis en évidence le rôle du locus eps dans le recrutement des cellules planctoniques par un biofilm formé en interface air-liquide. Ce locus est homologue du locus epsA-O de Bacillus subtilis, requis chez cette espèce pour la production des exopolysaccharides de la matrice du biofilm. Chez B. cereus, nous avons montré que le locus eps est impliqué dans la formation d’une gaine d’exopolysaccharides faiblement liée à la paroi bactérienne. Cette couche d'exopolysaccharides contribue, avec d'autres exopolysaccharides d'origine inconnue, à la formation de la matrice du biofilm, et joue un rôle important dans l'adhésion de la bactérie sur des surfaces inertes et vivantes. En favorisant l'adhésion de la bactérie sur des surfaces vivantes, le locus eps pourrait faciliter son intégration dans le biofilm. Il pourrait également être impliqué dans le pouvoir pathogène de la bactérie. / When biofilm is developing in static conditions, cell exchanges between sessile and planktonic coexisting population can emerge. Up to now, very few are known about the implication of planktonic cells integration in monospecies biofilm development. in B. cereus, a foodborne pathogen, our team have shown that motility is a key factor for biofilm development and for the deep penetration of motile planktonic bacteria inside a biofilm formed in immersed condition. Based on these data, the purpose of the present work was to determine the role of recruitment in the development of biofilm in air-liquid interface and to characterize this phenomenon physiologically and in a molecular aspect. We showed that a massive planktonic population is integrated in the developing biofilm, however, in our experimental conditions this recruitment contributes only marginally to the biofilm growth. We have developed two recruitment systems (in air-liquid interface and in immersion condition), to quantify recruitment, which has allowed us to screen a library of mutants obtained by random mutagenesis in order to select clones unable to be recruited by a preformed biofilm. Screening of 1700 clones resulted in the selection of a gene: Bthur002_62720. The deletion of this gene by allelic exchange strongly affects the ability of the mutant to be recruited, and complementation restored the wild type phenotype. This gene encodes a protein probably localized in the bacterial envelope. It is carried by a plasmid, pCT8513, and could be a mobile element whose acquisition would greatly increase the ability of the recipient bacterium to be recruited by a biofilm. Finally, we have highlighted the role of the eps locus in the recruitment of planktonic cells in a biofilm formed at air-liquid interface. This locus is homologous to Bacillus subtilis epsA-O locus, required in this species for the production of exopolysaccharides of the biofilm matrix. In B. cereus, we have shown that the eps locus is involved in the formation of an exopolysaccharides sheath weakly bound to the bacterial cell wall. This exopolysaccharides layer contributes with other exopolysaccharides of unknown origin, to the formation of the biofilm matrix, and plays an important role in the adhesion of bacteria on inanimate and living surfaces.By promoting bacterial adhesion on living surfaces; the eps locus could help bacteria integration into the biofilm. It could also be involved in the pathogenicity of bacteria.

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2016-09-16T12:36:44Z No. of bitstreams: 1 Guilherme Krahl_.pdf: 3540605 bytes, checksum: f897aa64ffa767d4eab27ec750818120 (MD5) / Made available in DSpace on 2016-09-16T12:36:44Z (GMT). No. of bitstreams: 1 Guilherme Krahl_.pdf: 3540605 bytes, checksum: f897aa64ffa767d4eab27ec750818120 (MD5) Previous issue date: 2016-07-29 / UNISINOS - Universidade do Vale do Rio dos Sinos / O Paleoceno caracteriza-se por um intervalo que sucede o evento de extinção em massa do K/Pg, o qual afetou diversos grupos fósseis. Seu estudo, portanto, revela não apenas padrões sequenciais de radiação evolutiva como processos relacionados à complexa recuperação dos ecossistemas marinhos. Devido a suas características ecológicas os foraminíferos planctônicos são uma importante ferramenta paleoceanográfica para a compreensão da evolução físico-química dos sistemas pelágicos, bem como da evolução do grupo ao longo do Paleoceno. Neste contexto, este trabalho objetiva a caracterização bioestratigráfica e paleoecologica com base em foraminíferos planctônicos paleógenos do testemunho DSDP Site 356 (Leg 39), localizado no Atlântico Sul ocidental. / The Paleocene is characterized by an interval that succeeds the K-Pg mass extinction event which affected several fossil groups. In its study reveals not only a sequential pattern of evolutionary radiation but also processes related to the complex recovery of marine ecosystems. Due to their ecological characteristics the planktonic foraminifera are an important paleoceanographic tool for the understanding of the physicochemical evolution of marine pelagic systems as well as the evolution of the group along the Paleocene. In this context, this paper aims to conduct a biostratigraphic and paleoecological analysis based on Paleogene planktonic foraminifera assemblages (Danian/Seladriano) from the DSDP Site 356 (Leg 39) drilled in the western South Atlantic.

The "Mystery Interval" (17.5-14.5 ka) is an unusual time period of abrupt global climate change during the late glacial between Heinrich event 1 and the Bølling-Allerød warm period (~17.5-14.5 ka). This period was characterized by extreme cooling in the North Atlantic region, warming in Antarctica, the rise of atmospheric greenhouse gases, and a variety of hydrologic changes around the globe, all of which may have stemmed from Heinrich event 1 and the possible collapse of the Atlantic?s meridional overturning circulation. A distinctive and unique gray clay layer was deposited in Cariaco Basin, Venezuela, within this time period, which has no apparent counterpart in the basin?s sediment record for at least the last full glacial-interglacial cycle. One hypothesis for the origin of the gray layer is that the initial pulse of deglacial sea level rise over the shallow Unare Platform, south of the basin, caused remobilization and rapid emplacement of previously deposited shelf sediments. However, analysis of the timing and extent of sea level rise as well as evidence from radiocarbon ages and a comparison of the organic content of gray layer sediments and known turbidites in the basin does not support this hypothesis. The alternative hypothesis, that the gray layer is related to increased fluvial discharge from local rivers as a result of elevated regional rainfall, is supported by a number of lines of evidence. The bulk sediment elemental content measured by scanning X-ray fluorescence (XRF) (this study) and clay mineralogy (Yu, 1996) support input of local river sediments. Coccolith abundances (Mertens et al., 2009), sea surface salinity (SSS) estimates and foraminiferal Ba/Ca analysis (this study) are also consistent with freshening of surface waters caused by elevated river runoff. This implies increased rainfall in the region which is corroborated by elemental and mineralogical ratios that point to increased precipitation and chemical weathering. Average terrigenous grain size and terrigenous fluxes are also in line with modern rainy season data. Despite prior suggestions that the Cariaco Basin region should be dry due to a southward-shifted Inter-tropical Convergence Zone (ITCZ) during cool periods in the North Atlantic, such as the Mystery Interval, data presented in this thesis suggest elevated rainfall and fluvial input related to deposition of the gray layer. Multiple lines of proxy evidence indicate that Cariaco Basin may have been characterized by a drier climate in the first part of the Mystery Interval but then shifted to a wetter climate in the second part, after ~16.5 ka, which might resolve this apparent conflict. The change to wetter conditions is most likely due to a northward shift in the position of the ITCZ, possibly due to warming tropical North Atlantic sea surface temperatures (SSTs) and/or extreme North Atlantic seasonality. Comparison of the Cariaco Basin climate records to climate observations from around the globe reveal a similar shift in climatic conditions around the same time, suggesting that the Mystery Interval may actually have been a two-phase event. Although many of the climatic observations from around the world can be explained by a shift from a southerly position of the ITCZ within the first part of the Mystery Interval to a more northerly position during the later part of the interval, many regions are not directly affected by the ITCZ and other complicating factors may play a role in the rapid climate changes observed globally.