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Während der hemdsärmelige Reporter lediglich für den Tag schreibt, schafft der Literat Texte für die Ewigkeit. Mit diesem über Jahrhunderte tradierten Klischee brechen zwei Autoren ganz bewusst, die in beiden Bereichen erfolgreich sind: Joseph Roth und Tom Wolfe - in Personalunion Journalisten wie Literaten - hinterfragen den Wertungsunterschied, der gemeinhin zwischen den Bereichen gemacht wird. Fanny Opitz zeichnet die diskursiven Umfelder nach, in denen die Debatte um die Leistung von Journalismus und Literatur breit geführt wurde: im Deutschland der 1920er Jahre im Kontext der gesamtkulturellen Strömung der Neuen Sachlichkeit und im US-amerikanischen New Journalism der 1960er und 1970er Jahre.
Giuseppe Prezzolini
(2019)
Der Journalist Giuseppe Prezzolini (1882–1982) gehört zu den prägenden italienischen Intellektuellen des 20. Jahrhunderts. Die von ihm begründete Kulturzeitschrift »La Voce« bot einflussreichen Stimmen der Zeit eine Bühne, darunter Giovanni Gentile, Benedetto Croce oder Benito Mussolini. Durch seine publizistische Arbeit avancierte er zu einem festen intellektuellen Bezugspunkt konservativer Kreise Italiens. Seine Forderungen u. a. nach einer Neugründung des italienischen Konservatismus abseits neofaschistischer Ideen begründeten seinen umstrittenen Ruf als Antikonformist.
Übergänge im Bildungssystem sind zentrale Stationen für die Generierung von sozialer Ungleichheit. Während die Bildungswege und die Bedeutung der sozialen Ungleichheit für den Schulbereich umfangreich untersucht wurden, liegen kaum Studien zu den nachschulischen Bildungsverläufen von Hochschulzugangsberechtigten und dem Einfluss der sozialen Herkunft bis zur Aufnahme einer Promotion vor. Daher ist es das Ziel der vorliegenden Arbeit, die Gestaltung nachschulischer Bildungsverläufe zu untersuchen sowie die Bedeutung der sozialen Herkunft vom Abitur bis zur Promotionsaufnahme zu analysieren. Den beiden Forschungsfragen wurde in vier Teilstudien nachgegangen. In Teilstudie 1 wurde die Relevanz von Merkmalen des Bildungsverlaufes für die Promotionsaufnahme untersucht. Der Schwerpunkt der drei folgenden Teilstudien lag auf der Bedeutung der sozialen Herkunft bei Aufnahme einer Promotion beziehungsweise der sozialen Ungleichheit in den relevanten Selektionsstufen des nachschulischen Bildungsverlaufs bis zur Promotionsaufnahme. In Teilstudie 2 wurden diesbezüglich soziale Herkunftseffekte bei der für eine Promotionsaufnahme bedeutsamen Wahl der Hochschulform untersucht, in Teilstudie 3 die Mechanismen hinter sozialen Herkunftseffekten bei Promotionsaufnahme analysiert und in Teilstudie 4 wurde soziale Ungleichheit bei Studienaufnahme und Promotionsaufnahme vergleichend betrachtet. Als Datengrundlage wurde die Längsschnittstudie BIJU (Bildungsverläufe und psychosoziale Entwicklung im Jugend- und jungen Erwachsenenalter) herangezogen. Die Befunde der Dissertation verweisen auf die Relevanz sozialer Ungleichheiten vom Eintritt in die Hochschule bis zum Übergang in die Promotion. Auch wenn ein abnehmender Herkunftseffekt vom Übertritt ins Studium zum Übertritt in die Promotion vorliegt, sind soziale Herkunftseffekte bei dem späten Bildungsübergang noch sichtbar. Zudem zeigt sich die Bedeutung von Pfadabhängigkeiten in Bildungsverläufen sowie von Leistungsunterschieden für eine Promotionsaufnahme.
Determining the relationship between genotype and phenotype is the key to understand the plasticity and robustness of phenotypes in nature. While the directly observable plant phenotypes (e.g. agronomic, yield and stress resistance traits) have been well-investigated, there is still a lack in our knowledge about the genetic basis of intermediate phenotypes, such as metabolic phenotypes. Dissecting the links between genotype and phenotype depends on suitable statistical models. The state-of-the-art models are developed for directly observable phenotypes, regardless the characteristics of intermediate phenotypes. This thesis aims to fill the gaps in understanding genetic architecture of intermediate phenotypes, and how they tie to composite traits, namely plant growth. The metabolite levels and reaction fluxes, as two aspects of metabolic phenotypes, are shaped by the interrelated chemical reactions formed in genome-scale metabolic network. Here, I attempt to answer the question: Can the knowledge of underlying genome-scale metabolic network improve the model performance for prediction of metabolic phenotypes and associated plant growth? To this end, two projects are investigated in this thesis. Firstly, we propose an approach that couples genomic selection with genome-scale metabolic network and metabolic profiles in Arabidopsis thaliana to predict growth. This project is the first integration of genomic data with fluxes predicted based on constraint-based modeling framework and data on biomass composition. We demonstrate that our approach leads to a considerable increase of prediction accuracy in comparison to the state-of-the-art methods in both within and across environment predictions. Therefore, our work paves the way for combining knowledge on metabolic mechanisms in the statistical approach underlying genomic selection to increase the efficiency of future plant breeding approaches. Secondly, we investigate how reliable is genomic selection for metabolite levels, and which single nucleotide polymorphisms (SNPs), obtained from different neighborhoods of a given metabolic network, contribute most to the accuracy of prediction. The results show that the local structure of first and second neighborhoods are not sufficient for predicting the genetic basis of metabolite levels in Zea mays. Furthermore, we find that the enzymatic SNPs can capture most the genetic variance and the contribution of non-enzymatic SNPs is in fact small. To comprehensively understand the genetic architecture of metabolic phenotypes, I extend my study to a local Arabidopsis thaliana population and their hybrids. We analyze the genetic architecture in primary and secondary metabolism as well as in growth. In comparison to primary metabolites, compounds from secondary metabolism were more variable and show more non-additive inheritance patterns which could be attributed to epistasis. Therefore, our study demonstrates that heterozygosity in local Arabidopsis thaliana population generates metabolic variation and may impact several tasks directly linked to metabolism. The studies in this thesis improve the knowledge of genetic architecture of metabolic phenotypes in both inbreed and hybrid population. The approaches I proposed to integrate genome-scale metabolic network with genomic data provide the opportunity to obtain mechanistic insights about the determinants of agronomically important polygenic traits.
Autour de 1990 en France et de 2005 en Allemagne, deux nouvelles catégories sont introduites dans le champ de la statistique de la population. Toutes deux, « immigré » et « Person mit Migrationshintergrund », font appel au registre de la migration pour qualifier un groupe de population. Notre analyse montre que ces deux événements sont révélateurs d’un changement de signification des catégorisations statistiques de la migration dans les deux pays, de la description de la mobilité vers l’observation de l’altérité de la population, changement lié au contexte de la politique publique dite d’« intégration » qui se développe en France et en Allemagne dans les années 1990-2000. La thèse interroge ainsi la manière dont la statistique rend la migration socialement pertinente pour construire l’altérité. Pour pouvoir comprendre le virage entrepris dans les nomenclatures statistiques et le resituer dans une perspective de longue durée, nous avons postulé qu’il fallait aller chercher dans l’histoire de la statistique ce qui avait tenu lieu de classification principale de la population, en lieu et place des nouvelles catégories inventées au tournant des XXe et XXIe siècles. Nous nous sommes donc interrogée sur la genèse et l’institutionnalisation des catégories de l’altérité et de la mobilité dans la période 1880-1914, alors que la France et l’Allemagne, à l’époque le Deutsches Kaiserreich, se constituent en États-nations et en empires coloniaux. Pour observer ces processus empiriquement, nous avons choisi de comparer les pratiques de catégorisation de l’altérité et la mobilité (1) en France et en Allemagne, (2) à deux périodes différentes, 1880-1914 et 1990-2010, et (3) dans le contexte métropolitain et colonial. L’analyse socio-historique comparée d’après la méthodologie de la comparaison en contexte a reposé sur une asymétrie assumée entre les deux périodes étudiées : tandis qu’il s’agissait de reconstruire la genèse des catégories « immigré » et « Person mit Migrationshintergrund » à deux moments distincts temporellement en France et en Allemagne, l’analyse de la période 1880-1914 a consisté à mettre au jour ruptures et continuités historiques des principes de classification sur l’ensemble de la période dans une perspective croisée. La démarche n’est ni chronologique ni rétrospective : elle contraste deux configurations historiques pour tenter d’identifier des ressemblances et des différences. Nos résultats montrent qu’entre 1880 et 1914, la catégorie de migration est majoritairement associée à un phénomène de mobilité dans les discours politiques et statistiques. À cette époque, la focale se porte sur l’émigration, redéfinie comme un déplacement géographique en dehors des frontières de la nation et de l’Empire. Le transport des « émigrants », catégorie de population qui nourrit le débat et les tableaux statistiques, fait l’objet des problématisations politiques. Les statistiques relatives à l’émigration comme mobilité étaient alors séparées de l’observation de la composition de la population, à travers le critère de la nationalité dans le contexte métropolitain et des schémas « raciaux » dans le contexte colonial. En 1990 en France et 2005 en Allemagne, le registre de la migration est mobilisé cette fois pour observer statistiquement la composition de la population. Nos résultats ont permis de mettre au jour trois principes de construction de l’altérité dans les deux pays et dans les deux périodes étudiées : un principe national, un principe colonial et un principe migratoire. La thèse développe ainsi une approche renouvelée des interactions entre observation statistique et politique publique, en testant empiriquement sur le terrain des statistiques relatives à la migration l’hypothèse de la « circularité du savoir et de l’action » mise au point par Alain Desrosières
En se penchant sur les réécritures de l'histoire pour le citoyen dans l’espace germanique et la France des Lumières et de la Révolution, ce livre apporte un regard nouveau et distancié sur les usages publics de l’histoire aujourd'hui, en France en particulier où le débat autour du roman national reste vif. La première partie de l’ouvrage, consacrée à l’exemplarité d’une histoire illustrée de gravures qui ont durablement marqué les représentations du passé, revisite la question des grands hommes, reproduit, traduit et analyse la circulation d’exemples édifiants entre les deux espaces.
La deuxième partie traite d’un mode de représentation pédagogique de l’histoire qui suscitait, et suscite toujours, la fascination tout en posant un défi de méthode: l’usage pédagogique d’un tableau permettant de saisir d’un seul coup d’oeil toute l’histoire d’un peuple voire de l’humanité tout entière, et d’en tirer des leçons politiques. L’idée, encore structurante aujourd’hui, d’un modèle politique ou pédagogique allemand ou français d’une écriture de l’histoire couplée, ou non, à la géographie est examinée ici au prisme des contextes précis où elle a été pensée.
This study assesses and explains international bureaucracies’ performance and role as policy advisors and as expert authorities from the perspective of domestic stakeholders. International bureaucracies are the secretariats of international organizations that carry out their work including generating knowledge, providing policy advice and implementing policy programs and projects. Scholars increasingly regard them as governance actors that are able to influence global and domestic policy making. In order to explain this influence, research has mainly focused on international bureaucracies’ formal features and/or staff characteristics. The way in which they are actually perceived by their domestic stakeholders, in particular by national bureaucrats, has not been systematically studied. Yet, this is equally important, given that they represent international bureaucracies’ addressees and are actors that (potentially) make use of international bureaucracies’ policy advice, which can be seen as an indicator for international bureaucracies’ influence. Accordingly, I argue that domestic stakeholders’ assessments can likewise contribute to explaining international bureaucracies’ influence.
The overarching research questions the study addresses are what are national stakeholders’ perspectives on international bureaucracies and under which conditions do they consider international bureaucracies’ policy advice? In answering these questions, I focus on three specific organizational features that the literature has considered important for international bureaucracies’ independent influence, namely international bureaucracies’ performance and their role as policy advisors and as expert authorities. These three features are studied separately in three independent articles, which are presented in Part II of this article-based dissertation.
To answer the research questions, I draw on novel data from a global survey among ministry officials of 121 countries. The survey captures ministry officials’ assessments of international bureaucracies’ features and their behavior with respect to international bureaucracies’ policy advice. The overall sample comprises the bureaucracies of nine global and nine regional international organizations in eight thematic areas in the policy fields of agriculture and finance.
The overall finding of this study is that international bureaucracies’ performance and their role as policy advisors and expert authorities as perceived by ministry officials are highly context-specific and relational. These features vary not only across international bureaucracies but much more intra-organizationally across the different thematic areas that an international bureaucracy addresses, i.e. across different thematic contexts. As far as to the relational nature of international bureaucracies’ features, the study generally finds strong variation across the assessments by ministry officials from different countries and across thematic areas. Hence, the findings highlight that it is likewise important to study international bureaucracies via the perspective of their stakeholders and to take account of the different thematic areas and contexts in which international bureaucracies operate.
The study contributes to current research on international bureaucracies in various ways. First, it directly surveys one important type of domestic stakeholders, namely national ministry officials, as to how they evaluate certain aspects of international bureaucracies instead of deriving them from their structural features, policy documents or assessments by their staff. Furthermore, the study empirically tests a range of theoretical hypotheses derived from the literature on international bureaucracies’ influence, as well as related literature. Second, the study advances methods of assessing international bureaucracies through a large-N, cross-national expert survey among ministry officials. A survey of this type of stakeholder and of this scope is – to my knowledge – unprecedented. Yet, as argued above, their perspectives are equally important for assessing and explaining international bureaucracies’ influence. Third, the study adapts common theories of international bureaucracies’ policy influence and expert authority to the assessments by ministry officials. In so doing, it tests hypotheses that are rooted in both rationalist and constructivist accounts and combines perspectives on international bureaucracies from both International Relations and Public Administration. Empirically supporting and challenging these hypotheses further complements the theoretical understanding of the determinants of international bureaucracies’ influence among national bureaucracies from both rationalist and constructivist perspectives.
Overall, this study advances our understanding of international bureaucracies by systematically taking into account ministry officials’ perspectives in order to determine under which conditions international bureaucracies are perceived to perform well and are able to have an effect as policy advisors and expert authorities among national bureaucracies. Thereby, the study helps to specify to what extent international bureaucracies – as global governance actors – are able to permeate domestic governance via ministry officials and, thus, contribute to the question of why some international bureaucracies play a greater role and are ultimately able to have more influence than others.
Was bleibt?
(2019)
In der jüdischen Familie im 19. Jahrhundert hatte das Testament primär die Funktion eines Rechtsakts. Mittels der Theorie der Gabe des französischen Anthropologen Marcel Mauss untersucht Doreen Kobelt in diesem Band, wie das Testament auch als eine Art Spiegel innerfamiliärer Veränderungen gelesen werden kann. Zentrale Bedeutung kommt dabei der Mitgift der Frau zu. Diese war im 19. Jahrhundert in der Mehrheitsgesellschaft wie auch in der innerjüdischen Debatte zunehmend umstritten.
Für die vorliegende Studie wurden 656 Testamente aus Hamburg und Altona mithilfe quantitativer und qualitativer Methoden analysiert. Neben vielen bisher unbekannten Testierenden werden auch die Familien Heine und Warburg betrachtet.
Berlin, Leipziger Straße 3-4
(2019)
In der Leipziger Straße 3–4 in Berlin, in der seit Herbst 2000 der Deutsche Bundesrat residiert, waren seit jeher bedeutende Institutionen angesiedelt.
1904 errichtet für das Preußische Herrenhaus, wurde das Gebäude nach dem Ersten Weltkrieg von den Arbeiter- und Soldatenräten genutzt. In der Weimarer Republik teilten sich der Preußische Staatsrat und das Preußische Wohlfahrtsministerium das Haus. Im Nationalsozialismus arbeiteten hier u. a. das Reichskirchenministerium und die Reichsstelle für Raumordnung.
Bartek Wardecki bietet eine vollständige Darstellung der Geschichte dieser berühmten Adresse sowie eine Übersicht über annähernd 1000 Veranstaltungen, die hier ausgerichtet wurden.
Zwei grundlegende Herausforderungen der sozialen Inklusionsforschung werden im vorliegenden Beitrag erläutert: Die Operationalisierung sozialer Inklusion sowie sonderpädagogischer Förderbedarfe. Anhand der dargelegten Forschung wird untersucht, ob die beiden methodischen Aspekte zu fehlerhaften Schlüssen und widersprüchlichen Forschungsergebnissen über die soziale Inklusion von Kindern mit sonderpädagogischem Förderbedarf führen. Dementsprechend wird die Vermeidung fehlerhafter Schlüsse und widersprüchlicher Forschungsergebnisse mittels einer Optimierung der Operationalisierung sozialer Inklusion sowie sonderpädagogischer Förderbedarfe thematisiert. Die vorliegende Forschung fokussiert sich hierbei vorrangig auf die soziometrischen Methoden zur Erfassung sozialer Inklusion sowie auf schulisches Problemverhalten im Sinne des Förderbedarfs emotional-soziale Entwicklung (insbesondere internalisierende aber auch externalisierende Verhaltensprobleme).
The business model has emerged as a construct to understand how firms drive innovation through emerging technologies. It is defined as the ‘architecture of the firm’s value creation, delivery and appropriation mechanisms’ (Foss & Saebi, 2018, p. 5). The architecture is characterized by complex functional interrelations between activities that are conducted by various actors, some within and some outside of the firm. In other words, a firm’s value architecture is embedded within a wider system of actors that all contribute to the output of the value architecture.
The question of what drives innovation within this system and how the firm can shape and navigate this innovation is an essential question within innova- tion management research. This dissertation is a compendium of four individual research articles that examine how the design of a firm’s value architecture can fa- cilitate system-wide innovation in the context of Artificial Intelligence and Block- chain Technology. The first article studies how firms use Blockchain Technology to design a governance infrastructure that enables innovation within a platform ecosystem. The findings propose a framework for blockchain-enabled platform ecosystems that address the essential problem of opening the platform to allow for innovation while also ensuring that all actors get to capture their share of the value. The second article analyzes how German Artificial Intelligence startups design their business models. It identifies three distinct types of startup with dif- ferent underlying business models. The third article aims to understand the role of a firm’s value architecture during the socio-technical transition process of Arti- ficial Intelligence. It identifies three distinct ways in which Artificial Intelligence startups create a shared understanding of the technology. The last article exam- ines how corporate venture capital units configure value-adding services for their venture portfolios. It derives a taxonomy of different corporate venture capital types, driven by different strategic motivations.
Ultimately, this dissertation provides novel empirical insights into how a firm’s value architecture determines it’s role within a wider system of actors and how that role enables the firm to facilitate innovation. In that way, it contributes to both business model and innovation management literature.
Sprachliche Kompetenzen spielen für den Bildungserfolg von Schülerinnen und Schülern eine grundlegende Rolle. Die besonderen sprachlichen Anforderungen der Bildungsinstitutionen stellen einige Kinder und Jugendliche vor Herausforderungen, die ihnen eine erfolgreiche Bildungslaufbahn erschweren. Um allen Lernenden den Zugang zu Bildung zu gewähren, sollten sprachliche Kompetenzen im Rahmen des schulischen Alltags und insbesondere des Fachunterrichts gefördert werden. Um Lehrerinnen und Lehrer für diese Aufgabe zu qualifizieren, sind wirksame Fortbildungen essenziell. Fortbildungen sind allerdings nicht per se wirksam. Vielmehr wird ihre Wirksamkeit von einer Vielzahl von Faktoren bedingt und sie variiert je nach Bereich. Inwieweit Merkmale und Bedingungen wirksamer Fortbildungen sowie Gesamteffekte, die bereichsübergreifend und für einige spezifische Bereiche bekannt sind, auch für Lehrkräftefortbildungen zur fachintegrierten Sprachförderung gelten, ist bisher ungeklärt. Im deutschen Raum fehlt es an Evaluationsstudien, die die Wirksamkeit solcher Fortbildungen und ihre Gelingensbedingungen untersuchen. Im internationalen Raum sind solche Studien zwar vorhanden, in ihrer Gesamtheit jedoch schwer zu überblicken, sodass sich bislang keine umfassenden Aussagen über den Erfolg dieser Fortbildungen treffen lassen. Vor diesem Hintergrund beschäftigt sich die vorliegende Dissertation anhand von drei Teilstudien mit der Wirksamkeit von Fortbildungen, die Lehrkräfte dafür qualifizieren sollen, eine in die Fächer und Lernbereiche der Schule integrierte Sprachförderung umzusetzen.
In einem systematischen Review (Studie 1) wurden die vorhandenen englischsprachigen Studien, in denen solche Fortbildungsmaßnahmen evaluiert wurden, systematisch ausgewertet. Insgesamt wurden 38 Studien einbezogen. Anhand dieser wurde qualitativ-inhaltsanalytisch untersucht, ob Merkmale wirksamer Lehrkräftefortbildung, die aus der fächerübergreifenden Forschung bekannt sind, für das spezifische Feld der Sprachförderung im Fachunterricht ebenfalls von Bedeutung sind oder ob dort andere Merkmale eine Rolle spielen. Die Studien deuten darauf hin, dass alle evaluierten Fortbildungen zumindest in gewissem Maß wirksam waren. Im Ergebnis zeigte sich, dass die Maßnahmen viele Eigenschaften teilen, die für eine erfolgreiche Lehrkräftefortbildung über verschiedene Fächer hinweg wichtig sind. Sie enthalten darüber hinaus einige Merkmale, die spezifisch für Fortbildung zur fachintegrierten Sprachförderung zu sein scheinen. Das Review stützt die Annahme, dass Fortbildungen die Kognitionen und die Unterrichtspraxis von Lehrkräften verändern und den Schülerinnen und Schülern zugutekommen kann, wenn bestimmte Merkmale bei der Gestaltung und Umsetzung berücksichtigt werden.
Aufbauend auf das Review wurden mit einer Meta-Analyse (Studie 2) die Effekte aus denjenigen zehn Studien aggregiert, die sich auf quantitative Weise analysieren ließen. Es wurde der Gesamteffekt der Fortbildungen sowohl auf die Kognitionen (z. B. Überzeugungen) der Lehrkräfte als auch auf das unterrichtspraktische Handeln (z. B. Verwendung sprachförderlicher Strategien) der Lehrkräfte ermittelt. Außerdem wurde untersucht, welche Rolle Merkmale der einbezogenen Studien sowie der Fortbildungen für die Ausprägung der Effekte spielen. Die Analysen ergaben einen kleinen Fortbildungseffekt auf die Kognitionen und einen mittleren bis großen Effekt auf das unterrichtspraktische Handeln der Lehrkräfte. Studienmerkmale, die die methodische Qualität der Studien betrafen, moderierten die Effekte. Dennoch deuten die Ergebnisse darauf hin, dass Fortbildung zur fachintegrierten Sprachförderung sich günstig auf die Kognitionen und Handlungen von Lehrkräften auswirkt.
Mit einer quasi-experimentellen Tagebuchstudie (Studie 3) wurde eine in Deutschland umgesetzte Fortbildung zur integrierten Sprachförderung formativ evaluiert. Die zentrale Frage war, inwiefern die fortgebildeten Grundschullehrkräfte in der Maßnahme vermittelte Sprachförderstrategien nach eigenen Angaben häufiger anwenden als ihre Kolleginnen und Kollegen, die nicht an der Fortbildung teilgenommen hatten. Untersucht wurde außerdem, inwiefern Faktoren wie die berichtete Kooperation im Kollegium mit der berichteten Häufigkeit der Strategieanwendung zusammenhängen. Mit einem standardisierten Tagebuch wurden 59 Grundschullehrkräfte befragt. Die mehrebenenanalytische Auswertung der Daten ergab keine signifikanten Unterschiede in der angegebenen Häufigkeit der Strategieanwendung zwischen den beiden Gruppen. Allerdings wurde die Nutzung einiger Strategien häufiger berichtet, wenn die Kooperation im Kollegium höher eingeschätzt wurde. Zudem fühlten sich die fortgebildeten Lehrkräfte im Vergleich zu den nicht fortgebildeten in der Anwendung der Strategien sicherer.
Die zentralen Ergebnisse dieser Dissertation werden abschließend zusammengefasst und diskutiert. Implikationen für zukünftige Forschung, Fortbildungspraxis und Bildungspolitik werden formuliert.
The African weakly electric fish genus Campylomormyrus is a well-investigated fish group of the species-rich family Mormyridae. They are able to generate species-specific electric organ discharges (EODs) which vary in their waveform characteristics including polarity, phase umber and duration. In mormyrid species EODs are used for communication, species discrimination and mate recognition, and it is thought hat they serve as pre-zygotic isolation mechanism driving sympatric speciation by promoting assortative mating. The EOD diversification, its volutionary effects and the link to species divergence have been examined histologically, behaviorally, and genetically. Molecular analyses are a major tool to identify species and their phenotypic traits by studying the underlying genes. The genetic variability between species further provides information from which evolutionary processes, such as speciation, can be deduced. Hence, the ultimate aim of this study is the investigation of genetic variability within the African weakly electric fish genus Campylomormyrus to better understand their sympatric speciation and comprehend their evolutionary drivers. In order to extend the current knowledge and gain more insights into its species history, karyological and genomic approaches are being pursued considering species differences. Previous studies have shown that species with different EOD duration have specific gene expression patterns and single nucleotide polymorphisms (SNPs). As EODs play a crucial role during the evolution of Campylomormyrus species, the identification of its underlying genes may suggest how the EOD diversity evolved and whether this trait is based on a complex network of genetic processes or is regulated by only a few genes. The results obtained in this study suggest that genes with non-synonymous SNPs, which are exclusive to C. tshokwe with an elongated EOD, have frequent functions ssociated with tissue morphogenesis and transcriptional regulation. Therefore, it is proposed that these processes likely co-determine EOD characteristics of Campylomormyrus species. Furthermore, genome-wide analyses confirm the genetic difference among most Campylomormyrus species. In contrast, the same analyses reveal genetic similarity among individuals of the alces-complex showing different EOD waveforms. It is therefore hypothesized that the low genetic variability and high EOD diversity represents incipient sympatric speciation. The karyological description of a Campylomormyrus species provides crucial information about chromosome number and shapes. Its diploid chromosome number of 2n=48 supports the conservation of this trait within Mormyridae. Differences have been detected in the number of bi-armed chromosomes which is unusually high compared to other mormyrid species. This high amount can be due to chromosome rearrangements which could cause genetic incompatibility and reproductive isolation. Hence an alternative hypothesis regarding processes which cause sympatric speciation is that chromosome differences are involved in the speciation process of Campylomormyrus by acting as postzygotic isolation mechanism. In summary, the karyological and genomic investigations conducted in this study contributed to the increase of knowledge about Campylomormyrus species, to the solution of some existing ambiguities like phylogenetic relationships and to the raising of new hypothesis explaining the sympatric speciation of those African weakly electric fish. This study provides a basis for future genomic research to obtain a complete picture for causes and results of evolutionary processes in Campylomormyrus.
This thesis puts the citizen-state interaction at its center. Building on a comprehensive model incorporating various perspectives on this interaction, I derive selected research gaps. The three articles, comprising this thesis, tackle these gaps. A focal role plays the citizens’ administrative literacy, the relevant competences and knowledge necessary to successfully interact with public organizations. The first article elaborates on the different dimensions of administrative literacy and develops a survey instrument to assess these. The second study shows that public employees change their behavior according to the competences that citizens display during public encounters. They treat citizens preferentially that are well prepared and able to persuade them of their application’s potential. Thereby, they signal a higher success potential for bureaucratic success criteria which leads to the employees’ cream-skimming behavior. The third article examines the dynamics of employees’ communication strategies when recovering from a service failure. The study finds that different explanation strategies yield different effects on the client’s frustration. While accepting the responsibility and explaining the reasons for a failure alleviates the frustration and anger, refusing the responsibility leads to no or even reinforcing effects on the client’s frustration. The results emphasize the different dynamics that characterize the nature of citizen-state interactions and how they establish their short- and long-term outcomes.
Selenite pseudomorphs
(2019)
STERILE APETALA (SAP) is known to be an essential regulator of flower development for over 20 years. Loss of SAP function in the model plant Arabidopsis thaliana is associated with a reduction of floral organ number, size and fertility. In accordance with the function of SAP during early flower development, its spatial expression in flowers is confined to meristematic stages and to developing ovules. However, to date, despite extensive research, the molecular function of SAP and the regulation of its spatio-temporal expression still remain elusive.
In this work, amino acid sequence analysis and homology modeling revealed that SAP belongs to the rare class of plant F-box proteins with C-terminal WD40 repeats. In opisthokonts, this type of F-box proteins constitutes the substrate binding subunit of SCF complexes, which catalyze the ubiquitination of proteins to initiate their proteasomal degradation. With LC-MS/MS-based protein complex isolation, the interaction of SAP with major SCF complex subunits was confirmed. Additionally, candidate substrate proteins, such as the growth repressor PEAPOD 1 and 2 (PPD1/2), could be revealed during early stages of flower development. Also INDOLE-3-BUTYRIC ACID RESPONSE 5 (IBR5) was identified among putative interactors. Genetic analyses indicated that, different from substrate proteins, IBR5 is required for SAP function. Protein complex isolation together with transcriptome profiling emphasized that the SCFSAP complex integrates multiple biological processes, such as proliferative growth, vascular development, hormonal signaling and reproduction. Phenotypic analysis of sap mutant and SAP overexpressing plants positively correlated SAP function with plant growth during reproductive and vegetative development.
Furthermore, to elaborate on the transcriptional regulation of SAP, publicly available ChIP-seq data of key floral homeotic proteins were reanalyzed. Here, it was shown that the MADS-domain transcription factors APETALA 1 (AP1), APETALA 3 (AP3), PISTILLATA (PI), AGAMOUS (AG) and SEPALLATA 3 (SEP3) bind to the SAP locus, which indicates that SAP is expressed in a floral organ-specific manner. Reporter gene analyses in combination with CRISPR/Cas9-mediated deletion of putative regulatory regions further demonstrated that the intron contains major regulatory elements of SAP in Arabidopsis thaliana.
In conclusion, these data indicate that SAP is a pleiotropic developmental regulator that acts through tissue-specific destabilization of proteins. The presumed transcriptional regulation of SAP by the floral MADS-domain transcription factors could provide a missing link between the specification of floral organ identity and floral organ growth pathways.
Infection on the move
(2019)
Movement plays a major role in shaping population densities and contact rates among individuals, two factors that are particularly relevant for disease outbreaks. Although any differences in movement behaviour due to individual characteristics of the host and heterogeneity in landscape structure are likely to have considerable consequences for disease dynamics, these mechanisms are neglected in most epidemiological studies. Therefore, developing a general understanding how the interaction of movement behaviour and spatial heterogeneity shapes host densities, contact rates and ultimately pathogen spread is a key question in ecological and epidemiological research.
In my thesis, I address this gap using both theoretical and empirical modelling approaches. In the theoretical part of my thesis, I investigated bottom-up effects of individual movement behaviour and landscape structure on host density, contact rates, and ultimately disease dynamics. I extended an established agent-based model that simulates ecological and epidemiological key processes to incorporate explicit movement of host individuals and landscape complexity. Neutral landscape models are a powerful basis for spatially-explicit modelling studies to imitate the complex characteristics of natural landscapes. In chapter 2, the first study of my thesis, I introduce two complementary R packages, NLMR and landscapetools, that I have co-developed to simplify the workflow of simulation and customization of such landscapes. To demonstrate the use of the packages I present a case study using the spatially explicit eco-epidemiological model and show that landscape complexity per se increases the probability of disease persistence. By using simple rules to simulate explicit host movement, I highlight in chapter 3 how disease dynamics are affected by population-level properties emerging from different movement rules leading to differences in the realized movement distance, spatiotemporal host density, and heterogeneity in transmission rates. As a consequence, mechanistic movement decisions based on the underlying landscape or conspecific competition led to considerably higher probabilities than phenomenological random walk approaches due directed movement leading to spatiotemporal differences in host densities. The results of these two chapters highlight the need to explicitly consider spatial heterogeneity and host movement behaviour when theoretical approaches are used to assess control measures to prevent outbreaks or eradicate diseases.
In the empirical part of my thesis (chapter 4), I focus on the spatiotemporal dynamics of Classical Swine Fever in a wild boar population by analysing epidemiological data that was collected during an outbreak in Northern Germany persisting for eight years. I show that infection risk exhibits different seasonal patterns on the individual and the regional level. These patterns on the one hand show a higher infection risk in autumn and winter that may arise due to onset of mating behaviour and hunting intensity, which result in increased movement ranges. On the other hand, the increased infection risk of piglets, especially during the birth season, indicates the importance of new susceptible host individuals for local pathogen spread. The findings of this chapter underline the importance of different spatial and temporal scales to understand different components of pathogen spread that can have important implications for disease management.
Taken together, the complementary use of theoretical and empirical modelling in my thesis highlights that our inferences about disease dynamics depend heavily on the spatial and temporal resolution used and how the inclusion of explicit mechanisms underlying hosts movement are modelled. My findings are an important step towards the incorporation of spatial heterogeneity and a mechanism-based perspective in eco-epidemiological approaches. This will ultimately lead to an enhanced understanding of the feedbacks of contact rates on pathogen spread and disease persistence that are of paramount importance to improve predictive models at the interface of ecology and epidemiology.
Background and objectives: Drop jumps (DJs) are well-established exercise drills during plyometric training. Several sports are performed under unstable surface conditions (e.g., soccer, beach volleyball, gymnastics). To closely mimic sport-specific demands, plyometric training includes DJs on both stable and unstable surfaces. According to the mechanical properties of the unstable surface (e.g., thickness, stiffness), altered temporal, mechanical, and physiological demands have been reported from previous cross-sectional studies compared with stable conditions. However, given that the human body simultaneously interacts with various factors (e.g., drop height, footwear, gender) during DJs on unstable surfaces, the investigation of isolated effects of unstable surface conditions might not be sufficient for designing an effective and safe DJ stimulus. Instead, the combined investigation of different factors and their interaction with surface instability have to be taken into consideration. Therefore, the present doctoral thesis seeks to complement our knowledge by examining the main and interaction effects of surface instability, drop height, footwear, and gender on DJ performance, knee joint kinematics, and neuromuscular activation.
Methods: Healthy male and female physically active sports science students aged 19-26 years participated in the cross-sectional studies. Jump performance, sagittal and frontal plane knee joint kinematics, and leg muscle activity were measured during DJs on stable (i.e., firm force plate) and (highly) unstable surfaces (i.e., one or two AIREX® balance pads) from different drop heights (i.e., 20 cm, 40 cm, 60 cm) or under multiple footwear conditions (i.e., barefoot, minimal shoes, cushioned shoes).
Results: Findings revealed that surface instability caused a DJ performance decline, reduced sagittal plane knee joint kinematics, and lower leg muscle activity during DJs. Sagittal plane knee joint kinematics as well as leg muscle activity decreased even more with increasing surface instability (i.e., two vs. one AIREX® balance pads). Higher (60 cm) compared to lower drop heights (≤ 40 cm) resulted in a DJ performance decline. In addition, increased sagittal plane knee joint kinematics as well as higher shank muscle activity were found during DJs from higher (60 cm) compared to lower drop heights (≤ 40 cm). Footwear properties almost exclusively affected frontal plane knee joint kinematics, indicating larger maximum knee valgus angles when performing DJs barefoot compared to shod. Between the different shoe properties (i.e., minimal vs. cushioned shoes), no significant differences during DJs were found at all. Only a few significant surface-drop height as well as surface-footwear interactions were found during DJs. They mainly indicated that drop height- and footwear-related effects are more pronounced during DJs on unstable compared to stable surfaces. In this regard, the maximum knee valgus angle was significantly greater when performing DJs from high drop heights (60 cm), but only on highly unstable surface. Further, braking and push-off times were significantly longer when performing DJs barefoot compared to shod, but only on unstable surface. Finally, analyses indicated no significant interactions with the gender factor.
Conclusions: The findings of the present cumulative thesis indicate that stable rather than unstable surfaces as well as moderate (≤ 40 cm) rather than high (60 cm) drop heights provide sufficient stimuli to perform DJs. Furthermore, findings suggest that DJs on highly unstable surfaces (i.e., two AIREX® balance pads) from high drop heights (60 cm) as well as barefoot compared to shod seem to increase maximal knee valgus angle/stress by providing a more harmful DJ stimulus. Neuromuscular activation strategies appear to be modified by surface instability and drop height. However, leg muscle activity is only marginally effected by footwear and by the interactions of various external factors i.e., surface instability, drop height, footwear). Finally, gender did not significantly modulate the main or interaction effects of the observed external factors during DJs.
Although the search for promising business models (BMs) is crucial for every profit-oriented venture, searching for those challenges in particular entrepreneurs. Limited resources, missing expertise and absolute uncertainty call entrepreneurs to strongly rely on their cognition in searching for a promising BM. However, as prior studies have examined cognitive search activities in isolation and neglected cognitive differences, explanations of how cognitive factors affect the BM process and outcomes are thus far insufficient.
Addressing the overall question of how BMs emerge, the dissertation contributes to the cognitive perspective in entrepreneurship and BM research. Building on the dual-process theory from cognitive psychology, the micro-foundations of managerial decision-making and insights from framing literature, this dissertation explicitly investigates the impacts of different cognitive dispositions, search activities and visual framing effects. The core assumption is that cognitive dispositions and entrepreneurs’ searches for information determine their BM decision-making. Furthermore, BM visualisations have become popular instruments with which to explain and manage today’s complex business interactions. As they abstract from reality, they can also unfold impacts on the cognitive processes.
This dissertation offers new explanations to these aspects and consists of three studies and one reflective article. The first study explores the impacts of differences in search activities and cognitive dispositions in a qualitative study with 70 entrepreneurship students. The second qualitative study explores the cognitive impacts of 103 BM visualisations. Third, a quantitative PLS-SEM experiment with 197 entrepreneurs illuminates the link between BM visualisations and cognition. The reflective article expresses the results’ meaning for the teaching of BMs.
In sum, the studies have resulted in a new theory of stabilising factors explaining how cognitive dispositions, search activities and visual framing determine entrepreneurs’ decisions to imitate or deviate from existing BMs. It indicates that the decision depends on the context-dependent strategic orientation and cognitive disposition-dependent cognitive safety, that is the correspondence between characteristics of cognitive dispositions and search activities. Moreover, the studies identified five visual framing effects that are independent of cognitive dispositions and prior experiences. This provides fertile contributions to the literature on BM methods and how BM visualisations affect decisions. Most importantly, BM visualisations provide an emotionally stabilising function to rational entrepreneurs, a cognitively stabilising function to experiential participants and do not affect indifferent participants in general.
Deutschland und Frankreich benötigen stetige Metallimporte, um ihr Wirtschaftsmodell aufrechtzuerhalten. Internationale Kooperation ist unerlässlich, damit diese Importe zuverlässig und nachhaltig verlaufen. Doch welche Potenziale bieten sich in diesem Bereich, welche Grenzen sind dabei zu erkennen? Dieser Frage geht Yann Wernert durch einen Fallstudienvergleich mit prozessanalytischen Methoden und auf der theoretischen Grundlage des neoliberalen Institutionalismus nach. Er zeigt, dass beide Länder ihre Bemühungen als reaktive Mittelmächte gestalten. Sie wollen durch staatliche Rohstoffstrategien wirtschaftliche, strategische und Nachhaltigkeitsziele erreichen. Während die Analyse durchaus Kooperationspotenziale ausmacht, fallen diese je nach Ländergruppe und Politikbereich sehr unterschiedlich aus.
This thesis covers the synthesis of conjugates of 2-Deoxy-D-ribose-5-phosphate aldolase (DERA) with suitable polymers and the subsequent immobilization of these conjugates in thin films via two different approaches.
2-Deoxy-D-ribose-5-phosphate aldolase (DERA) is a biocatalyst that is capable of converting acetaldehyde and a second aldehyde as acceptor into enantiomerically pure mono- and diyhydroxyaldehydes, which are important structural motifs in a number of pharmaceutically active compounds. Conjugation and immobilization renders the enzyme applicable for utilization in a continuously run biocatalytic process which avoids the common problem of product inhibition. Within this thesis, conjugates of DERA and poly(N-isopropylacrylamide) (PNIPAm) for immobilization via a self-assembly approach were synthesized and isolated, as well as conjugates with poly(N,N-dimethylacrylamide) (PDMAA) for a simplified and scalable spray-coating approach. For the DERA/PNIPAm-conjugates different synthesis routes were tested, including grafting-from and grafting-to, both being common methods for the conjugation. Furthermore, both lysines and cysteines were addressed for the conjugation in order to find optimum conjugation conditions. It turned out that conjugation via lysine causes severe activity loss as one lysine plays a key role in the catalyzing mechanism. The conjugation via the cysteines by a grafting-to approach using pyridyl disulfide (PDS) end-group functionalized polymers led to high conjugation efficiencies in the presence of polymer solubilizing NaSCN. The resulting conjugates maintained enzymatic activity and also gained high acetaldehyde tolerance which is necessary for their use later on in an industrial relevant process after their immobilization.
The resulting DERA/PNIPAm conjugates exhibited enhanced interfacial activity at the air/water interface compared to the single components, which is an important pre-requisite for the immobilization via the self-assembly approach. Conjugates with longer polymer chains formed homogeneous films on silicon wafers and glass slides while the ones with short chains could only form isolated aggregates. On top of that, long chain conjugates showed better activity maintenance upon the immobilization.
The crosslinking of conjugates, as well as their fixation on the support materials, are important for the mechanical stability of the films obtained from the self-assembly process. Therefore, in a second step, we introduced the UV-crosslinkable monomer DMMIBA to the PNIPAm polymers to be used for conjugation. The introduction of DMMIBA reduced the lower critical solution temperature (LCST) of the polymer and thus the water solubility at ambient conditions, resulting in lower conjugation efficiencies and in turn slightly poorer acetaldehyde tolerance of the resulting conjugates. Unlike the DERA/PNIPAm, the conjugates from the copolymer P(NIPAM-co-DMMIBA) formed continuous, homogenous films only after the crosslinking step via UV-treatment. For a firm binding of the crosslinked films, a functionalization protocol for the model support material cyclic olefin copolymer (COC) and the final target support, PAN based membranes, was developed that introduces analogue UV-reactive groups to the support surface. The conjugates immobilized on the modified COC films maintained enzymatic activity and showed good mechanical stability after several cycles of activity assessment. Conjugates with longer polymer chains, however, showed a higher degree of crosslinking after the UV-treatment leading to a pronounced loss of activity. A porous PAN membrane onto which the conjugates were immobilized as well, was finally transferred to a dead end filtration membrane module to catalyze the aldol reaction of the industrially relevant mixture of acetaldehyde and hexanal in a continuous mode. Mono aldol product was detectable, but yields were comparably low and the operational stability needs to be further improved
Another approach towards immobilization of DERA conjugates that was followed, was to generate the conjugates in situ by simply mixing enzyme and polymer and spray coat the mixture onto the membrane support. Compared to the previous approach, the focus was more put on simplicity and a possible scalability of the immobilization. Conjugates were thus only generated in-situ and not further isolated and characterized. For the conjugation, PDMAA equipped with N-2-thiolactone acrylamide (TlaAm) side chains was used, an amine-reactive comonomer that can react with the lysine residues of DERA, as well as with amino groups introduced to a desired support surface. Furthermore disulfide formation after hydrolysis of the Tla groups causes a crosslinking effect. The synthesized copolymer poly(N,N-Dimethylacrylamide-co-N-2-thiolactone acrylamide) (P(DMAA-co-TlaAm)) thus serves a multiple purpose including protein binding, crosslinking and binding to support materials. The mixture of DERA and polymer could be immobilized on the PAN support by spray-coating under partial maintenance of enzymatic activity. To improve the acetaldehyde tolerance, the polymer in used was further equipped with cysteine reactive PDS end-groups that had been used for the conjugation as described in the first part of the thesis. The generated conjugates indeed showed good acetaldehyde tolerance and were thus used to be coated onto PAN membrane supports. Post treatment with a basic aqueous solution of H2O2 was supposed to further crosslink the spray-coated film hydrolysis and oxidation of the thiolactone groups. However, a washing off of the material was observed. Optimization is thus still necessary.
During lower sea levels in glacial periods, deep permafrost formed on large continental shelf areas of the Arctic Ocean. Subsequent sea level rise and coastal erosion created subsea permafrost, which generally degrades after inundation under the influence of a complex suite of marine, near-shore processes. Global warming is especially pronounced in the Arctic, and will increase the transition to and the degradation of subsea permafrost, with implications for atmospheric climate forcing, offshore infrastructure, and aquatic ecosystems.
This thesis combines new geophysical, borehole observational and modelling approaches to enhance our understanding of subsea permafrost dynamics. Three specific areas for advancement were identified: (I) sparsity of observational data, (II) lacking implementation of salt infiltration mechanisms in models, and (III) poor understanding of the regional differences in key driving parameters. This study tested the combination of spectral ratios of the ambient vibration seismic wavefield, together with estimated shear wave velocity from seismic interferometry analysis, for estimating the thickness of the unfrozen sediment overlying the ice-bonded permafrost offshore. Mesoscale numerical calculations (10^1 to 10^2 m, thousands of years) were employed to develop and solve the coupled heat diffusion and salt transport equations including phase change effects. Model soil parameters were constrained by borehole data, and the impact of a variety of influences during the transgression was tested in modelling studies. In addition, two inversion schemes (particle swarm optimization and a least-square method) were used to reconstruct temperature histories for the past 200-300 years in the Laptev Sea region in Siberia from two permafrost borehole temperature records. These data were evaluated against larger scale reconstructions from the region.
It was found (I) that peaks in spectral ratios modelled for three-layer, one-dimensional systems corresponded with thaw depths. Around Muostakh Island in the central Laptev Sea seismic receivers were deployed on the seabed. Derived depths of the ice-bonded permafrost table were between 3.7-20.7 m ± 15 %, increasing with distance from the coast. (II) Temperatures modelled during the transition to subsea permafrost resembled isothermal conditions after about 2000 years of inundation at Cape Mamontov Klyk, consistent with observations from offshore boreholes. Stratigraphic scenarios showed that salt distribution and infiltration had a large impact on the ice saturation in the sediments. Three key factors were identified that, when changed, shifted the modelled permafrost thaw depth most strongly: bottom water temperatures, shoreline retreat rate and initial temperature before inundation. Salt transport based on diffusion and contribution from arbitrary density-driven mechanisms only accounted for about 50 % of observed thaw depths at offshore sites hundreds to thousands of years after inundation. This bias was found consistently at all three sites in the Laptev Sea region. (III) In the temperature reconstructions, distinct differences in the local temperature histories between the western Laptev Sea and the Lena Delta sites were recognized, such as a transition to warmer temperatures a century later in the western Laptev Sea as well as a peak in warming three decades later. The local permafrost surface temperature history at Sardakh Island in the Lena Delta was reminiscent of the circum-Arctic regional average trends. However, Mamontov Klyk in the western Laptev Sea was consistent to Arctic trends only in the most recent decade and was more similar to northern hemispheric mean trends. Both sites were consistent with a rapid synoptic recent warming.
In conclusion, the consistency between modelled response, expected permafrost distribution, and observational data suggests that the passive seismic method is promising for the determination of the thickness of unfrozen sediment on the continental Arctic shelf. The quantified gap between currently modelled and observed thaw depths means that the impact of degradation on climate forcing, ecosystems, and infrastructure is larger than current models predict. This discrepancy suggests the importance of further mechanisms of salt penetration and thaw that have not been considered – either pre-inundation or post-inundation, or both. In addition, any meaningful modelling of subsea permafrost would have to constrain the identified key factors and their regional differences well. The shallow permafrost boreholes provide missing well-resolved short-scale temperature information in the coastal permafrost tundra of the Arctic. As local differences from circum-Arctic reconstructions, such as later warming and higher warming magnitude, were shown to exist in this region, these results provide a basis for local surface temperature record parameterization of climate and, in particular, permafrost models. The results of this work bring us one step further to understanding the full picture of the transition from terrestrial to subsea permafrost.
Pillars of Salt
(2019)
Parlamentarier als Beruf
(2019)
Die politische Professionalisierung hat innerhalb der institutionellen Rahmenbedingungen zur Sozialfigur des Berufspolitikers geführt. Diese Entwicklung wird im theoretischen Teil der Arbeit hergeleitet und im empirischen Teil mit umfangreichen Daten belegt. Bemerkenswert ist, dass es dabei nicht zu erheblichen Veränderungen in den Rekrutierungsmustern und Karriereverläufen der Abgeordneten gekommen ist. Vielmehr erweisen sich die von Dietrich Herzog herausgearbeiteten Karrieretypen auch heute noch als gültig und mussten nur moderat angepasst werden. Es zeigt sich damit eine erstaunliche Kontinuität in der politischen Elitenbildung. Die in Deutschland sehr gefestigten institutionellen Rahmenbedingungen, die den Zugang und die Attraktivität politischer Karrieren determinieren, haben offensichtlich auch zu einer Stabilisierung der Karrieretypen geführt.
Im Mittelpunkt dieser Arbeit standen Analysen zur Charakterisierung der periplasmatischen Aldehyd Oxidoreduktase aus E. coli. Kinetische Untersuchungen mit Ferricyanid als Elektronenakzeptor unter anaeroben Bedingungen zeigten für dieses Enzym eine höhere Aktivität als unter aeroben Bedingungen. Die getroffene Hypothese, dass PaoABC fähig ist Elektronen an molekularen Sauerstoff weiter zu geben, konnte bestätigt werden. Für den Umsatz aromatischer Aldehyde mit molekularem Sauerstoff wurde ein Optimum von pH 6,0 ermittelt. Dies steht im Gegensatz zur Reaktion mit Ferricyanid, mit welchem ein pH-Optimum von 4,0 gezeigt wurde. Die Reaktion von PaoABC mit molekularem Sauerstoff generiert zwar Wasserstoffperoxid, die Produktion von Superoxid konnte dagegen nicht beobachtet werden. Dass aerobe Bedingungen einen Einfluss auf das Auslösen der Expression von PaoABC haben, wurde in dieser Arbeit ebenfalls ermittelt.
Im Zusammenhang mit der Produktion von ROS durch PaoABC wurde die Funktion eines kürzlich in Elektronentransfer-Distanz zum FAD identifizierten [4Fe4S]-Clusters untersucht. Ein Austausch der für die Bindung des Clusters zuständigen Cysteine führte zur Instabilität der Proteinvarianten, weswegen für diese keine weiteren Untersuchungen erfolgten. Daher wird zumindest ein struktur-stabilisierender Einfluss des [4Fe4S]-Clusters angenommen. Zur weiteren Untersuchung der Funktion dieses Clusters, wurde ein zwischen FAD und [4Fe4S]-Cluster lokalisiertes Arginin gegen ein Alanin ausgetauscht. Diese Proteinvariante zeigte eine reduzierte Geschwindigkeit der Reaktion gegenüber dem Wildtyp. Die Bildung von Superoxid konnte auch hier nicht beobachtet werden. Die Vermutung, dass dieser Cluster einen elektronen-sammelnden Mechanismus unterstützt, welcher die Radikalbildung verhindert, kann trotz allem nicht ausgeschlossen werden. Da im Umkreis des Arginins weitere geladene und aromatische Aminosäuren lokalisiert sind, können diese den notwendigen Elektronentransfer übernehmen.
Neben der Ermittlung eines physiologischen Elektronenakzeptors und dessen Einfluss auf die Expression von PaoABC zeigt diese Arbeit auch, dass die Chaperone PaoD und MocA während der Reifung des MCD-Kofaktor eine gemeinsame Bindung an PaoABC realisieren. Es konnte im aktiven Zentrum von PaoABC ein Arginin beschrieben werden, welches auf Grund der engen Nachbarschaft zum MCD-Kofaktor und zum Glutamat (PaoABC-EC692) am Prozess der Substratbindung beteiligt ist. Im Zusammenhang mit dem Austausch dieses Arginins gegen ein Histidin oder ein Lysin wurden die Enzymspezifität und der Einfluss physiologischer Bedingungen, wie pH und Ionenstärke, auf die Reaktion des Enzyms untersucht. Gegenüber dem Wildtyp zeigten die Varianten mit molekularem Sauerstoff eine geringere Affinität zum Substrat aber auch eine höhere Geschwindigkeit der Reaktion. Vor allem für die Histidin-Variante konnte im gesamten pH-Bereich ein instabiles Verhalten bestimmt werden. Der Grund dafür wurde durch das Lösen der Struktur der Histidin-Variante beschreiben. Durch den Austausch der Aminosäuren entfällt die stabilisierende Wirkung der delokalisierten Elektronen des Arginins und es kommt zu einer Konformationsänderung im aktiven Zentrum.
Neben der Reaktion von PaoABC mit einer Vielzahl aromatischer Aldehyde konnte auch der Umsatz von Salicylaldehyd zu Salicylsäure durch PaoABC in einer Farbreaktion bestimmt werden. Durch Ausschluss von molekularem Sauerstoff als terminaler Elektronenakzeptor, in einer enzym-gekoppelten Reaktion, erfolgte ein Elektronentransport auf Ferrocencarboxylsäure. Die Kombination aus beiden Methoden ermöglichte eine Verwendung von Ferrocen-Derivaten zur Generierung einer enzym-gekoppelten Reaktion mit PaoABC.
Die Untersuchungen zu PaoABC zeigen, dass die Vielfalt der durch das Enzym katalysierten Rektionen weitere Möglichkeiten der enzymatischen Bestimmung biokatalytischer Prozesse bietet.
The importance of cryptic diversity in rotifers is well understood regarding its ecological consequences, but there remains an in depth comprehension of the underlying molecular mechanisms and forces driving speciation. Temperature has been found several times to affect species spatio-temporal distribution and organisms’ performance, but we lack information on the mechanisms that provide thermal tolerance to rotifers. High cryptic diversity was found recently in the freshwater rotifer “Brachionus calyciflorus”, showing that the complex comprises at least four species: B. calyciflorus sensu stricto (s.s.), B. fernandoi, B. dorcas, and B. elevatus. The temporal succession among species which have been observed in sympatry led to the idea that temperature might play a crucial role in species differentiation.
The central aim of this study was to unravel differences in thermal tolerance between species of the former B. calyciflorus species complex by comparing phenotypic and gene expression responses. More specifically, I used the critical maximum temperature as a proxy for inter-species differences in heat-tolerance; this was modeled as a bi-dimensional phenotypic trait taking into consideration the intention and the duration of heat stress. Significant differences on heat-tolerance between species were detected, with B. calyciflorus s.s. being able to tolerate higher temperatures than B. fernandoi.
Based on evidence of within species neutral genetic variation, I further examined adaptive genetic variability within two different mtDNA lineages of the heat tolerant B. calyciflorus s.s. to identify SNPs and genes under selection that might reflect their adaptive history. These analyses did not reveal adaptive genetic variation related to heat, however, they show putatively adaptive genetic variation which may reflect local adaptation. Functional enrichment of putatively positively selected genes revealed signals of adaptation in genes related to “lipid metabolism”, “xenobiotics biodegradation and metabolism” and “sensory system”, comprising candidate genes which can be utilized in studies on local adaptation. An absence of genetically-based differences in thermal adaptation between the two mtDNA lineages, together with our knowledge that B. calyciflorus s.s. can withstand a broad range of temperatures, led to the idea to further investigate shared transcriptomic responses to long-term exposure to high and low temperatures regimes. With this, I identified candidate genes that are involved in the response to temperature imposed stress. Lastly, I used comparative transcriptomics to examine responses to imposed heat-stress in heat-tolerant and heat-sensitive Brachionus species. I found considerably different patterns of gene expression in the two species. Most striking are patterns of expression regarding the heat shock proteins (hsps) between the two species. In the heat-tolerant, B. calyciflorus s.s., significant up-regulation of hsps at low temperatures was indicative of a stress response at the cooler end of the temperature regimes tested here. In contrast, in the heat-sensitive B. fernandoi, hsps generally exhibited up-regulation of these genes along with rising temperatures. Overall, identification of differences in expression of genes suggests suppression of protein biosynthesis to be a mechanism to increase thermal tolerance. Observed patterns in population growth are correlated with the hsp gene expression differences, indicating that this physiological stress response is indeed related to phenotypic life history performance.
Weakly electric mormyrid fish comprise about 200 species. 15 species of the genus Campylomormyrus have been described. These are very diverse concerning the trunk-like snout and the shape and duration of the electric organ discharge (EOD) and the anatomy of the electric organ. In this dissertation data on the reproduction in captivity of four species and on the ontogeny of the EOD and the EO of three species are presented.
Reproduction of the four species C. compressirostris, C. rhynchophorus, C. tshokwe and C. numenius: Cyclical reproduction was provoked by changing only water conductivity (C): decreasing C led to gonadal recrudescence, an increase induced gonad regression. Data on the reproduction and development of three species are presented (in C. numenius gonad development could only be achieved in males). Agonistic behavior in the C. tshokwe pair forced us to divide the breeding tank; therefore, only ovipositions occurred. However, injection of an artificial GnRH hormone allowed us to obtain ripe eggs and sperm and to perform successful artificial reproduction. All three species (C. compressirostris, C. rhynchophorus, C. tshokwe) are indeterminate fractional spawners. Spawnings/ovipositions occurred during the second half of the night; no parental care was observed; no special spawning substrates were necessary. C. compressirostris successfully spawned in breeding groups, C. rhynchophorus as pair. Spawning intervals ranged from 6 to 66 days in C. rhynchophorus, 10–75 days in C. tshokwe, and 18 days in C. compressirostris (calculated values). Fecundities (eggs per fractional spawning) ranged from 70 to 1570 eggs in C. rhynchophorus, 100–1192 in C. tshokwe, and 38–246 in C. compressirostris. All three species produce yolky, slightly sticky eggs. Egg diameter ranges from 2.3–3.0 mm. Hatching occurred on day 3, feeding started on day 11. Transition from larval to juvenile stage occurred at around 20 mm total length (TL). At this size C. rhynchophorus developed a higher body than the two other species and differences between the species in the melanin pigmentation of the unpaired fins occurred. Between 32 and 35 mm TL the upper and lower jaws developed.
C. compressirostris and C. tamandua are similar in morphology and both produce short EODs of ca. 150-200 μs duration. Both species reproduce easily in captivity. We tried to obtain natural hybrids in two breeding groups, 1) four males of C. compressirostris and three females of C. tamandua and 2) six females of C. compressirostris and four males of C. tamandua. In both combinations several times oviposition occurred, however, we never found fertilized eggs. In subsequent experiments, not described here, we obtained hybrids between these two species by means of artificial reproduction.
Ontogeny of the EOD and the EO: The Campylomormyrus species are very diverse both concerning the shape and the duration of their EODs. There are species with very short EODs, e.g. C. compressirostris duration, a species with an EOD length of about 4-8 ms duration (C. tshokwe) and species with very long EODs of about 25 ms duration (e.g. C. rhynchophorus). Due to the successful breeding of the three species in captivity, we were able to investigate in detail the ontogeny of the EOD. Larvae of the three species C. compressirostris, C. tshokwe and C. rhynchophorus first produce a biphasic larval EOD typical for these small larvae. The first activity of the adult electric organ in the caudal peduncle is a biphasic juvenile EOD. Juvenile C. compressirostris and C. tshokwe start out with a short biphasic EOD of about 160 – 200 μs duration at sizes between 25 mm (C. compressirostris) and 37 mm (C. tshokwe). Adult C. compressirostris show an EOD identical to that of the juvenile. In C. tshokwe, the juvenile EOD changes continuously during development both concerning duration, amplitude increase and shape. 18 cm long C. tshokwe still do not yet produce an EOD typical for the adult fish. Juveniles of C. rhynchophorus produce at 33 mm total length a juvenile biphasic EOD, however, of longer duration (about 640 μs) than the two species mentioned above. This juvenile EOD changes continuously both in form, amplitude increase and duration with growth until the adult EOD waveform appears at about 15 cm body length. In juveniles about seven cm long the triphasic feature of the EOD starts to develop due to the appearance of a second head positive phase. Specific EOD stages are produced in relation to size and not to age. Individual differences in the EOD both concerning shape and duration are very small. The basic anatomy of the electrocytes is very similar in all three species: the main stalk which receives the innervation, is located at the caudal face of the electrocyte. Membrane penetrations of the stalks do not occur. However, there are differences in the fine structure of the electrocytes in the three species. Papillae, proliferations of the membrane, which increase the surface area of the electrocyte and are thought to incrase the EOD-duration, are only found in C. tshokwe and C. rhynchophorus. In these two species in addition, holes develop in the electrocytes during ontogeny. This might also have an impact on EOD duration.