Massenspektrometrie basierte Bioanalytik an Modellorganismen

The aim of this work was both the development and application of mass spectrometry (MS) based analytical methods for the investigation of biological research questions on model organisms. The primary focus was on the relative-quantitative proteome analysis by mass spectrometry. A secondary technological aspect of import was the separation of biomolecules by high-performance liquid chromatography (HPLC). The efficient fractionation and separation of complex peptide mixtures form enzymatic full-proteome digests is essential to facilitate a comprehensive mass spectrometric proteome analysis. The combination of HPLC and MS (LC-MS) was applied in the three projects of this thesis.Das Ziel dieser Arbeit war die Etablierung und Anwendung massenpektrometrischer Analysemethoden zur Untersuchung biologisch relevanter Fragestellungen an Modellorganismen. Im Vordergrund stand dabei die relativ-quantitative Proteomanalyse. Als sekundäre Technologie war die mehrdimensionaler Flüssigkeitschromatographie ein Schwerpunkt der Arbeit. Um eine möglichst umfassende massenspektrometrische Analyse komplexer, aus Vollproteom-Isolaten hergestellter Peptidlösungen zu gewährleisten, ist eine effiziente Fraktionierung und Auftrennung der Probe essentiell. Hochleistungsflüssigkeitschromatographie in Kombination mit Massenspektrometrie (LC-MS) wurde in den drei Teilprojekten dieser These angewandt

Remote Sensing of Arctic Vegetation: Relations between the NDVI, Spatial Resolution and Vegetation Cover on Boothia Peninsula, Nunavut

Arctic tundra environments are thought to be particularly sensitive to changes in climate, whereby alterations in ecosystem functioning are likely to be expressed through shifts in vegetation phenology, species composition, and net ecosystem productivity (NEP). Remote sensing has shown potential as a tool to quantify and monitor biophysical variables over space and through time. This study explores the relationship between the normalized difference vegetation index (NDVI) and percent-vegetation cover in a tundra environment, where variations in soil moisture, exposed soil, and gravel till have significant influence on spectral response, and hence, on the characterization of vegetation communities. IKONOS multispectral data (4 m spatial resolution) and Landsat 7 ETM+ data (30 m spatial resolution) were collected for a study area in the Lord Lindsay River watershed on Boothia Peninsula, Nunavut. In conjunction with image acquisition, percent cover data were collected for twelve 100 m × 100 m study plots to determine vegetation community composition. Strong correlations were found for NDVI values calculated with surface and satellite sensors, across the sample plots. In addition, results suggest that percent cover is highly correlated with the NDVI, thereby indicating strong potential for modeling percent cover variations over the region. These percent cover variations are closely related to moisture regime, particularly in areas of high moisture (e.g., water-tracks). These results are important given that improved mapping of Arctic vegetation and associated biophysical variables is needed to monitor environmental change.On croit que les environnements de la toundra arctique sont particulièrement sensibles aux changements climatiques, en ce sens que toute altération du fonctionnement de l’écosystème est susceptible d’être exprimée dans le réarrangement de la phénologie de la végétation, de la composition des espèces et de la productivité nette de l’écosystème (PNÉ). La télédétection s’avère un outil efficace de quantification et de surveillance des variables biophysiques dans le temps et dans l’espace. Cette étude explore la relation entre l’indice d’activité végétale et le pourcentage de couverture végétale en milieu de toundra, où les variations propres à l’humidité du sol, au sol exposé et au till de gravier ont une influence considérable sur la réponse spectrale et, par conséquent, sur la caractérisation des communautés végétales. Des données multispectrales IKONOS (résolution spatiale de 4 m) et des données ETM+ de Landsat 7 (résolution spatiale de 30 m) ont été recueillies pour une zone d’étude visée par la ligne de partage des eaux à la hauteur de la rivière Lord Lindsay, dans la péninsule de Boothia, au Nunavut. De concert avec l’acquisition d’images, les données relatives au pourcentage de couverture ont été recueillies pour douze terrains d’étude de 100 m sur 100 m dans le but de déterminer la composition de la communauté végétale. De fortes corrélations ont été dénotées dans le cas des valeurs de l’indice d’activité végétale calculées à l’aide de détecteurs de surface et de détecteurs satellisés et ce, à l’échelle des terrains ayant servi d’échantillon. Par ailleurs, les résultats laissent entendre que le pourcentage de couverture est hautement corrélé avec l’indice d’activité végétale, ce qui indique une forte possibilité de modélisation des variations de pourcentage de couverture dans la région. Ces variations du pourcentage de couverture sont étroitement liées au régime d’humidité, particulièrement dans les régions où l’humidité est élevée (comme les traces d’eau). Ces résultats revêtent de l’importance étant donné qu’il y a lieu d’améliorer le mappage de la végétation arctique et les variables biophysiques connexes afin de surveiller la modification de l’environnement

The intracellular proteome of the gut bacterium Bacteroides thetaiotaomicron is widely unaffected by a switch from glucose to sucrose as main carbohydrate source

Bacteroides thetaiotaomicron is a gram negative bacterium within the human gut microbiome that metabolizes a wide range of dietary and mucosal polysaccharides. Here, we analyze the proteome response of B. thetaiotaomicron cultivated on two different carbon sources, glucose and sucrose. Two quantitative LC-MS based proteomics approaches, encompassing label free quantification and isobaric labeling by tandem mass tags were applied. The results obtained by both workflows were compared with respect to the number of identified and quantified proteins, peptides supporting identification and quantification, sequence coverage, and reproducibility. A total of 1719 and 1696 proteins, respectively, were quantified, covering 35 % of the predicted B. thetaiotaomicron proteome. The data show that B. thetaiotaomicron widely maintains its intracellular proteome upon change of the carbohydrates and that major changes are observed solely in the machinery necessary to make use of the carbon sources provided. With respect to the central role of carbohydrates on gut health these data contribute to the understanding of how different carbohydrates contribute to shape bacterial community in the gut microbiome. All proteomics raw data have been uploaded to the ProteomeXchange Consortium via the PRIDE partner repository with the dataset identifier PXD033704

An Incidence of Multi-Year Sediment Storage on Channel Snowpack in the Canadian High Arctic

During June 2005, we identified the presence of sediment buried within multi-year channel snowpack of a small river located near Cape Bounty, Melville Island, Nunavut (74°55' N, 109°35' W). Photographic evidence indicates that the sediment was deposited during the 2003 season by the initial meltwater flowing on the snowpack, which was dammed by snow upstream of a channel constriction. The resulting pond covered a minimum area of 180 m2 and contained an estimated minimum 27 Mg of sediment. Suspended sediment measurements during the 2003 season indicate that deposition on the snowpack at this location represented 49%–65% of the sediment transport prior to the ponding and emplacement of the sediment on the snow, and approximately 20% of the measured sediment flux for the entire season. Multi-year snow accumulations immediately downstream exhibited similar sediment deposition on snow, but no evidence of multi-year sediment storage was present. By contrast, a similar stream in an adjacent watershed channelized rapidly, with minimal sediment deposition on the snow, and delivered a large pulse of sediment to the downstream lake. These results provide quantitative evidence for the magnitude of sediment storage on snowpack and point to the unique role that snow plays in the fluvial geomorphology of High Arctic watersheds.En juin 2005, nous avons dénoté la présence de sédiment enterré dans une plaque de neige datant de plusieurs années d’une petite rivière située près de cap Bounty, sur l’île Melville, au Nunavut (74°55' N, 109°35' O). D’après des preuves photographiques, le sédiment a été déposé pendant la saison 2003 par l’eau de fusion initiale s’écoulant sur la plaque de neige, qui avait été endiguée par la neige en amont d’un canal confiné. L’étang qui en a découlé recouvrait une aire minimale de 180 m2 et contenait, selon les estimations, au moins 27 Mg de sédiment. Les mesures de sédiment en suspension pendant la saison 2003 indiquent que ce dépôt sur la plaque de neige à cet endroit représentait entre 49 % et 65 % du transport de sédiment avant l’accumulation d’eau et l’emplacement de sédiment sur la neige, et environ 20 % du flux de sédiment mesuré pour toute la saison. Les accumulations de neige de plusieurs années immédiatement en aval comptaient des dépôts de sédiment semblables sur la neige, quoi qu’aucun emmagasinage de sédiment sur plusieurs années n’était présent. Par contraste, un cours d’eau similaire d’un bassin hydrographique adjacent s’est canalisé rapidement, avec peu de dépôts de sédiment sur la neige, puis a laissé une grande quantité de sédiment au lac en aval. Ces résultats fournissent des preuves quantitatives quant à l’ampleur de l’emmagasinage de sédiment sur la plaque de neige et laissent envisager le rôle unique que joue la neige sur la géomorphologie fluviale des bassins hydrographiques de l’Extrême-Arctique

USE OF GROWTH ANALYSIS TO EVALUATE GENETIC MECHANISMS AFFECTING ACHENE YIELD FORMATION OF SUNFLOWER

The main objective of this study was to investigate the process of dry matter accumulation (DMA) in achenes during the grain-filling period of fifty sunflower genotypes by using the functional method of growth analysis in a field trial at Bicsérd, Hungary. The Hunt-formula of lnY= P0 + P1*X + P2*X2 was fitted to data. Maximum yield (Ymax), the average of the absolute growth rate (AGRavg), maximum growth rate (AGRmax), date of the maximum growth rate (Xagrmax), and the average of the relative growth rate (RGRavg) were calculated from growth curves for hybrids and replications. Significant differences among hybrids and their interaction with sampling dates indicate hybrid differences in the intensity of DMA accumulation. The strongest correlation was observed between the parameters of Ymax and AGRmax

Spatial variability in carbon dioxide exchange processes within wet sedge meadows in the Canadian High Arctic

Wet sedge meadows are the most productive plant communities in the High Arctic. However, the controls on carbon dioxide (CO2) exchange processes within wet sedge communities – and the scale at which they operate – are poorly understood. Here, the factors controlling CO2 exchange of wet sedge meadows experiencing different moisture regimes are examined. Environmental data are used to create predictive models of CO2 exchange on multiple temporal scales. Automated chamber systems recorded CO2 fluxes at 30-minute intervals at wet sedge sites in the Canadian High Arctic from June to August in 2014 and 2015. Static chambers were also deployed over a larger spatial extent in 2014. Our results show that wet sedge communities were strong CO2 sinks during the growing season (−7.67 to −44.36 g C·m−2). CO2 exchange rates in wetter and drier areas within wet sedge meadows differed significantly (Wilcoxon, p<0.001), suggesting that soil moisture regimes within vegetation types influence net CO2 balance. Random Forest models explained a significant amount of the variability in CO2 flux rates over time (R2=0.46 to 0.90). The models showed that the drivers of CO2 exchange in these communities vary temporally. Variable moisture regimes indirectly influenced CO2 fluxes given that they exhibit different vegetation and temperature-response characteristics. We suggest that the response of a single vegetation type to environmental changes may vary depending on microenvironment variability within that community

Determining the terrain characteristics related to the surface expression of subsurface water pressurization in permafrost landscapes using susceptibility modelling

Abstract. Warming of the Arctic in recent years has led to changes in the active layer and uppermost permafrost. In particular, thick active layer formation results in more frequent thaw of the ice-rich transient layer. This addition of moisture, as well as infiltration from late season precipitation, results in high pore-water pressures (PWPs) at the base of the active layer and can potentially result in landscape degradation. To predict areas that have the potential for subsurface pressurization, we use susceptibility maps generated using a generalized additive model (GAM). As model response variables, we used active layer detachments (ALDs) and mud ejections (MEs), both formed by high PWP conditions at the Cape Bounty Arctic Watershed Observatory, Melville Island, Canada. As explanatory variables, we used the terrain characteristics elevation, slope, distance to water, topographic position index (TPI), potential incoming solar radiation (PISR), distance to water, normalized difference vegetation index (NDVI; ME model only), geology, and topographic wetness index (TWI). ALDs and MEs were accurately modelled in terms of susceptibility to disturbance across the study area. The susceptibility models demonstrate that ALDs are most probable on hill slopes with gradual to steep slopes and relatively low PISR, whereas MEs are associated with higher elevation areas, lower slope angles, and areas relatively far from water. Based on these results, this method identifies areas that may be sensitive to high PWPs and helps improve our understanding of geomorphic sensitivity to permafrost degradation.</jats:p