Modellierung und Simulation von bakterieller Adhäsion und intrazellulärem Transport in realer Geometrie

In dieser Arbeit wurden zwei Themenkomplexe behandelt, die Entwicklung eines Modells für intrazellulären Transport in realer Geometrie und die Adhäsion von Staphylococcus aureus auf abiotischen Oberflächen. Beide Vorgänge sind von hoher Bedeutung im medizinischen Bereich. Für das Transportmodell wurde aus Mikroskopieaufnahmen einer Zelle die Form der Zellmembran rekonstruiert und die erhaltene Oberfläche trianguliert. Kombiniert mit einem Modell des Zytoskeletts und einem Modell für molekulare Motoren liefert dieses System ein einfaches Modell einer Zelle mit dem fundamentale Prozesse wie Transportvorgänge oder die Bildung von Membranröhren untersucht werden können. Dieses System liefert damit einen Beitrag auf dem Weg zur Entwicklung eines vollständigen Zellmodells. Die Adhäsion von Staphylococcus aureus wurde mittels eines kombinierten Ansatzes aus Experiment und Simulationen untersucht. Die Experimente bestanden aus AFM Kraftspektroskopie einzelner Bakterienproben. Basierend auf den Experimenten wurde ein vereinfachtes Modell der Adhäsion entwickelt und mit Hilfe von Monte Carlo Simulationen untersucht. Dieser Ansatz ermöglichte ein tieferes Verständnis des Adhäsionsprozesses. Die Anhaftung funktioniert über Proteine in der Membran des Bakteriums. Diese Proteine binden in großer Zahl an der Oberfläche, die Stärke und Reichweite der Bindung ist dabei von Parametern wie der Zahl der bindenden Proteine, der Tiefe und Reichweite des Oberflächenpotentials oder der Länge der Proteine abhängig.In this thesis, two subjects are treated, the development of a model for intracellular transport in a real geometry and the adhesion of Staphylococcus aureus on abiotic surfaces. Both processes are of high importance in the medical area. The transport model is based on the reconstruction of the membran of a real cell using microscopy images. The received shape was triangulated und combined with a model of the cytoskeleton and a model for molecular motors. This gives a simplified model of a cell which can be used to analyze fundamental processes like transport or the formation of membran tubes. Thus, this system gives a contribution on the way to develop a full cell model. The adhesion of Staphylococcus aureus was studied using a combined approach of experiments and simulations. The experiments consist of AFM force spectroscopy of single bacteria cells. Based on these experiments a simplified adhesion model was developed and analyzed using Monte Carlo simulations. This approach gave a deeper understanding of the adhesion process. The adhesion works via proteins anchored in the bacterial membrane. A large number of these proteins bind to the surface, the strenght and range of this binding depends on parameters such as the number of binding proteins, the depth and range of the surface binding potential and the size of the proteins

Stochastic binding of Staphylococcus aureus to hydrophobic surfaces

The adhesion of pathogenic bacteria to surfaces is of immense importance for health care applications. Via a combined experimental and computational approach, we studied the initiation of contact in the adhesion process of the pathogenic bacterium Staphylococcus aureus. AFM force spectroscopy with single cell bacterial probes paired with Monte Carlo simulations enabled an unprecedented molecular investigation of the contact formation. Our results reveal that bacteria attach to a surface over distances far beyond the range of classical surface forces via stochastic binding of thermally fluctuating cell wall proteins. Thereby, the bacteria are pulled into close contact with the surface as consecutive proteins of different stiffnesses attach. This mechanism greatly enhances the attachment capability of S. aureus. It, however, can be manipulated by enzymatically/chemically modifying the cell wall proteins to block their consecutive binding. Our study furthermore reveals that fluctuations in protein density and structure are much more relevant than the exact form of the binding potential

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

Dietary modification for women after breast cancer treatment: a narrative review

Diet is thought to account for about 25% of cancers in developed countries. It is well documented that the risks associated with both the breast cancer itself and its treatments are important for women previously treated for breast cancer. Women are at risk of recurrence of the primary disease and prone to develop treatment-induced co-morbidities, some of which are thought to be modified by diet. With a view to making dietary recommendations for the breast cancer patients we encounter in our clinical nursing research, we mined the literature to scope the most current robust evidence concerning the role of the diet in protecting women against the recurrence of breast cancer and its potential to ameliorate some of the longer-term morbidities associated with the disease. We found that the evidence about the role of the diet in breast cancer recurrence is largely inconclusive. However, drawing on international guidelines enabled us to make three definitive recommendations. Women at risk of breast cancer recurrence, or who experience co-morbidities as a result of treatment, should limit their exposure to alcohol, moderate their nutritional intake so it does not contribute to postmenopausal weight gain, and should adhere to a balanced diet. Nursing education planned for breast cancer patients about dietary issues should ideally be individually tailored, based on a good understanding of the international recommendations and the evidence underpinning the

Tailoring communication in consultations with women from high risk breast cancer families

This multicentre study examined the influence of patient demographic, disease status and psychological variables on clinical geneticists/genetic counsellors (consultants) behaviours in initial consultations with women from high-risk breast cancer families. One hundred and fifty-eight women completed a pre-clinic self-report questionnaire. The consultations were audiotaped, transcribed verbatim and coded. Consultants did not vary their behaviour according to women's expectations. However, significantly more aspects of genetic testing were discussed with women who were affected with breast cancer (P<0.001), screening and management with unaffected women (P=0.01) and breast cancer prevention with younger women (P=0.01). Prophylactic mastectomy was discussed more frequently with women with medical and allied health training (P=0.02), and prophylactic oophorectomy with women affected with breast cancer (P=0.03), those in non-professional occupations (P=0.04) and with a family history of breast and ovarian cancer (P<0.001). Consultants used significantly more behaviours to facilitate understanding with women who were in non-professional occupations (P=0.04); facilitated active patient involvement more with women affected with breast cancer (P<0.001) and used more supportive and counselling behaviours with affected women (P=0.02). This study showed that patient demographics were more likely to predict consultants' communication behaviours than the woman's psychological status. Methods to facilitate assessment of psychological morbidity are needed to allow more tailored communication

Adenylyl Cyclase Plays a Regulatory Role in Development, Stress Resistance and Secondary Metabolism in Fusarium fujikuroi

The ascomycete fungus Fusarium fujikuroi (Gibberella fujikuroi MP-C) produces secondary metabolites of biotechnological interest, such as gibberellins, bikaverin, and carotenoids. Production of these metabolites is regulated by nitrogen availability and, in a specific manner, by other environmental signals, such as light in the case of the carotenoid pathway. A complex regulatory network controlling these processes is recently emerging from the alterations of metabolite production found through the mutation of different regulatory genes. Here we show the effect of the targeted mutation of the acyA gene of F. fujikuroi, coding for adenylyl cyclase. Mutants lacking the catalytic domain of the AcyA protein showed different phenotypic alterations, including reduced growth, enhanced production of unidentified red pigments, reduced production of gibberellins and partially derepressed carotenoid biosynthesis in the dark. The phenotype differs in some aspects from that of similar mutants of the close relatives F. proliferatum and F. verticillioides: contrary to what was observed in these species, ΔacyA mutants of F. fujikuroi showed enhanced sensitivity to oxidative stress (H2O2), but no change in heavy metal resistance or in the ability to colonize tomato tissue, indicating a high versatility in the regulatory roles played by cAMP in this fungal group

Ferroptosis in health and disease.

Ferroptosis is a pervasive non-apoptotic form of cell death highly relevant in various degenerative diseases and malignancies. The hallmark of ferroptosis is uncontrolled and overwhelming peroxidation of polyunsaturated fatty acids contained in membrane phospholipids, which eventually leads to rupture of the plasma membrane. Ferroptosis is unique in that it is essentially a spontaneous, uncatalyzed chemical process based on perturbed iron and redox homeostasis contributing to the cell death process, but that it is nonetheless modulated by many metabolic nodes that impinge on the cells susceptibility to ferroptosis. Among the various nodes affecting ferroptosis sensitivity, several have emerged as promising candidates for pharmacological intervention, rendering ferroptosis-related proteins attractive targets for the treatment of numerous currently incurable diseases. Herein, the current members of a Germany-wide research consortium focusing on ferroptosis research, as well as key external experts in ferroptosis who have made seminal contributions to this rapidly growing and exciting field of research, have gathered to provide a comprehensive, state-of-the-art review on ferroptosis. Specific topics include: basic mechanisms, in vivo relevance, specialized methodologies, chemical and pharmacological tools, and the potential contribution of ferroptosis to disease etiopathology and progression. We hope that this article will not only provide established scientists and newcomers to the field with an overview of the multiple facets of ferroptosis, but also encourage additional efforts to characterize further molecular pathways modulating ferroptosis, with the ultimate goal to develop novel pharmacotherapies to tackle the various diseases associated with - or caused by - ferroptosis

Non-resonant electromagnetic energy harvester for car-key applications

This paper presents a novel non-resonant electromagnetic energy harvester for application in a remote car-key, to extend the lifetime of the battery or even to realize a fully energy autonomous, maintenance-free car-key product. Characteristic for a car-key are low frequency and large amplitude motions during normal daily operation. The basic idea of this non-resonant generator is to use a round flat permanent magnet moving freely in a round flat cavity, which is packaged on both sides by printed circuit boards embedded with multi-layer copper coils. The primary goal of this structure is to easily integrate the energy harvester with the existing electrical circuit module into available commercial car-key designs. The whole size of the energy harvester is comparable to a CR2032 coin battery. To find out the best power-efficient and optimal design, several magnets with different dimensions and magnetizations, and various layouts of copper coils were analysed and built up for prototype testing. Experimental results show that with an axially magnetized NdFeB magnet and copper coils of design variant B a maximum open circuit voltage of 1.1V can be observed