Stochastic modelling of bacterial dynamics : adhesion & range expansion

Bacteria, as one of the three domains in the tree of life, play an important role in many phenomena such as biocorrosion, pipe clogging and infections. Since treatment with antibiotics or mechanical removal can be difficult, it is paramount to understand the initial attachment to a substrate and the subsequent colony growth. To this end, this thesis investigates first the adhesion process of Staphylococcus aureus by Monte Carlo simulations and helps to reveal that the bacterium uses different binding mechanisms on hydrophobic and hydrophilic substrates. On hydrophobic substrates, the bacterium's macromolecules bind freely. Subsequently, the bacteria show large cell-to-cell variation in adhesion forces but only small variations by repetitions with the same cell. On hydrophilic substrates, the macromolecules need to overcome a potential barrier. This leads to a comparable variability between repetitions with the same cell and the cell-to-cell variance. As a second model system, I investigated the competitive range expansion of microbial colonies with heterogeneous mechanical interactions by stochastic simulations. This is, for instance, realised by a network of piliated bacteria such as Neisseria gonorrhoeae. The simulations reveal that a heterogeneous susceptibility to division generated pushing significantly affects the competition dynamics of growing bacteria. Furthermore, homogeneous pushing leads to a small but standing variation of a disadvantaged subpopulation inside the expanding colony.Bakterien spielen in vielen Lebensbereichen wie beispielsweise Biokorrosion, Verstopfung von Rohren oder Infektionen eine zentrale Rolle. Da sich ihre Entfernung mittels Antibiotika oder mechanischer Methoden als schwierig erweisen kann, ist es wichtig die initiale Adhäsion und das nachfolgende Wachstum grundlegend zu verstehen. Zuerst wurde das Adhäsionsverhalten von Staphylococcus aureus auf hydrophilen und hydrophoben Oberflächen mittels Monte Carlo Simulationen untersucht. Es zeigt sich, dass die Adhäsion durch Makromoleküle der Zellwand vermittelt wird, von denen viele auf hydrophoben Oberflächen binden können. Dies resultiert in einer hohen Variabilität der Adhäsionskräfte innerhalb der Population, während Wiederholungen mit derselben Zelle ähnlich verlaufen. Auf hydrophilen Oberflächen selektiert jedoch eine Potentialbarriere stochastisch die bindenden Makromoleküle. Dies führt zu einer vergleichbaren Variabilität der Adhäsionskräfte zwischen Wiederholungen mit derselben Zelle und der Gesamtpopulation. Als zweites Modellsystem betrachtete ich das kompetitivem Koloniewachstum von pilierten Neisseria gonorrhoeae Bakterien. Zur Beschreibung dieser entwickelte ich ein minimales stochastisches Model von kompetitivem Koloniewachstum mit heterogenen mechanischen Wechselwirkungen. Die Simulationen zeigen, dass eine heterogene Suszeptibilität der Bakterien gegenüber Kräften, welche durch Zellteilung generiert werden, das kompetitive Wachstum maßgeblich beeinflussen

Theoretical modelling of competitive microbial range expansion with heterogeneous mechanical interactions

Microbial range expansion experiments provide insight into the complex link between dynamic structure, pattern formation and evolutionary dynamics of growing populations. In this work, we develop a theoretical model in order to investigate the interplay of growth statistics and mechanical interactions which are implemented as division driven pushing and swapping of cells. For the case of the competitive growth of a strongly and a weakly interacting strain we investigate the influence of different mean division times, as well as different mechanical interactions on the development of the colony. Our results show that the susceptibility to cell division induced pushing has a much stronger influence on the structure of the colony than cell sorting towards the colony’s perimeter. Motivated by microbial range expansion experiments of Neisseria gonorrhoeae bacteria, we also consider the influence of mutating cells on the structure of the colony. We show that the outgrowth of the three different strains is strongly influenced by the relative strengths of their mechanical interaction. The experimentally observed patterns are reproduced for mechanical interactions of the mutants, which range between those of the strongly and weakly interacting strain

Traffic crime and its prevention

Obvious from the headline, the theme of this theses is traffic crime and its prevention. Although traffic crime is by society quite overlooked kind of criminality, it is more probable that any person will become one of the traffic criminals or a victim of someone elses' criminal behaviour within traffic, rather than he or she will find him or herself being a victim or a perpetrator of a crime from another crime field. Losses of lives, health or property losses which are unfortunately huge part of it are also not insignificant. Being aware of the fact that the most severe consequences of traffic crime happen at the time of transport accidents, considerable part of the thesis is dedicated to the problematics of such accidents. Although traffic crime is not unusual within various kinds of transport it is much less frequent than in the case of road transport which is the kind of transport the theses talks about. The aim of this work is to highlight not only the meaning of transport crime and accidents connected to it but also the possibilities of its prevention. The theses consists of the introduction, four chapters and the conclusion. The first chapter provides an insight into the traffic crime in general, its peculiarities and crimes which can be committed in connection with transport. The second...Tématem této diplomové práce je dopravní kriminalita a její prevence. Dopravní kriminalita je společností přehlíženým druhem kriminality. Přitom pravděpodobnost, že se jedinec stane pachatelem trestné činnosti v dopravě anebo obětí této trestné činnosti je mnohem vyšší, než je tomu u jiných druhů kriminality. Zanedbatelné nejsou ani ztráty na životech, zdraví a majetku, které s sebou přináší. Vzhledem ke skutečnosti, že k nejzávažnějším následkům dopravní kriminality dochází při dopravních nehodách, je v této práci kladen značný důraz na problematiku dopravních nehod. Pozornost je věnována pouze dopravě silniční. Byť se dopravní kriminalita vyskytuje i u jiných druhů dopravy, tak je její četnost ve srovnání s dopravní kriminalitou v dopravě silniční v podstatě zanedbatelná. Cílem mé práce je upozornit nejen na význam dopravní kriminality a dopravních nehod, ale také na možné způsoby jejich prevence. Diplomová práce se skládá z úvodu, čtyř kapitol a závěru. První kapitola je věnována dopravní kriminalitě obecně, jejím zvláštnostem a trestným činům, jichž je možno se dopustit v souvislosti s dopravou. Ve druhé kapitole podrobně rozebírám dopravní nehody, jejich jednotlivé příčiny, četnost a vývoj v čase. Ve třetí kapitole se zabývám alkoholem a jinými omamnými a psychotropními látkami v dopravě,...Katedra trestního právaDepartment of Criminal LawFaculty of LawPrávnická fakult

Gestational hypercalciuria causes pathological urine calcium oxalate supersaturations

Gestational hypercalciuria causes pathological urine calcium oxalate supersaturations. Although normal pregnant women are more hypercal-ciuric than women with calcium oxalate nephrolithiasis (243 ± 23 mg/day vs. 194 ± 5 mg/day), pregnancy is not an established stone-forming state and pregnant women do not exhibit pathological crystalluria. One hypothesis to explain their lack of overt stone formation and pathological crystalluria is that pregnancy does not raise urine supersaturation with respect to stone forming salts such as calcium oxalate or calcium monohydrogen phosphate (brushite) to levels as high as in stone forming women. To test this hypothesis, we studied eleven normal women during each trimester of pregnancy, and between six and eight weeks post-partum. During pregnancy, hypercalciuria occurs with unchanged urine volume, citrate and magnesium excretions do not increase proportionally with calcium excretion, and urine pH increases. Supersaturations with respect to calcium oxalate (CaOx) and brushite (Br) are as high as those of women with calcium nephrolithiasis. The lack of pathological crystalluria and stones during pregnancy is not due to a failure of supersaturations to increase; urinary potential for crystallization is as high as in patients with established stone disease

Different binding mechanisms of Staphylococcus aureus to hydrophobic and hydrophilic surfaces

Bacterial adhesion to surfaces is a crucial step in initial biofilm formation. In a combined experimental and computational approach, we studied the adhesion of the pathogenic bacterium Staphylococcus aureus to hydrophilic and hydrophobic surfaces. We used atomic force microscopy-based single-cell force spectroscopy and Monte Carlo simulations to investigate the similarities and differences of adhesion to hydrophilic and hydrophobic surfaces. Our results reveal that binding to both types of surfaces is mediated by thermally fluctuating cell wall macromolecules that behave differently on each type of substrate: on hydrophobic surfaces, many macromolecules are involved in adhesion, yet only weakly tethered, leading to high variance between individual bacteria, but low variance between repetitions with the same bacterium. On hydrophilic surfaces, however, only few macromolecules tether strongly to the surface. Since during every repetition with the same bacterium different macromolecules bind, we observe a comparable variance between repetitions and different bacteria. We expect these findings to be of importance for the understanding of the adhesion behaviour of many bacterial species as well as other microorganisms and even nanoparticles with soft, macromolecular coatings, used e.g. for biological diagnostics

Traffic crime and its prevention

Obvious from the headline, the theme of this theses is traffic crime and its prevention. Although traffic crime is by society quite overlooked kind of criminality, it is more probable that any person will become one of the traffic criminals or a victim of someone elses' criminal behaviour within traffic, rather than he or she will find him or herself being a victim or a perpetrator of a crime from another crime field. Losses of lives, health or property losses which are unfortunately huge part of it are also not insignificant. Being aware of the fact that the most severe consequences of traffic crime happen at the time of transport accidents, considerable part of the thesis is dedicated to the problematics of such accidents. Although traffic crime is not unusual within various kinds of transport it is much less frequent than in the case of road transport which is the kind of transport the theses talks about. The aim of this work is to highlight not only the meaning of transport crime and accidents connected to it but also the possibilities of its prevention. The theses consists of the introduction, four chapters and the conclusion. The first chapter provides an insight into the traffic crime in general, its peculiarities and crimes which can be committed in connection with transport. The second..

Wirtschaftsethik: Grundzüge, Vereinbarkeit, Gegensätze - Eine Einführung in die Gedankenwelt der Ethik

Ethik und Wirtschaft werden sehr oft als gegensätzlich und unvereinbar beschrieben. Viele Systemtheoretiker erklären eine Wirtschaftsethik als undenkbar. Niklas Luhmann z. B. sagt: "Es gibt Wirtschaft, es gibt Ethik - aber es gibt keine Wirtschaftsethik" Dieses Werk ist als vorlesungsbegleitendes Skript entstanden und entwickelte sich im Laufe der Zeit zu einer Sammlung von Erklärungsversuchen zu den verschiedenen ethischen Denkrichtungen. Es wird der Weg von den „Alten Denkern“ bis hin zu den Begründern der modernen und sehr fortschrittlichen Wirtschaftsethik aufgezeigt und eine logische Brücke von der Antike bis hinein in die Zukunft gebaut. In sehr verständlicher Art und Weise wird dem Leser die logische Weiterentwicklung des ethischen Begriffes erklärt und ihm im Anhang mit sehr praktischen und anschaulichen Beispielen näher gebracht

How an unsuccessful metropolitan magazine can make a successful re-entry into the marketplace : the revitalization of "Evansville close up"

There is no abstract available for this creative project.Department of Journalism"Evansville close-up" July-August, 1981 (52 p.) inserted.Thesis (M.A.