Efficiency of the flagellar propulsion of Escherichia coli in confined microfluidic geometries

Bacterial movement in confined spaces is routinely encountered either in a natural environment or in artificial structures. Consequently, the ability to understand and predict the behavior of motile bacterial cells in confined geometries is essential to many applications, spanning from the more classical, such as the management complex microbial networks involved in diseases, biomanufacturing, mining, and environment, to the more recent, such as single cell DNA sequencing and computation with biological agents. Fortunately, the development of this understanding can be helped by the decades-long advances in semiconductor microfabrication, which allow the design and the construction of complex confining structures used as test beds for the study of bacterial motility. To this end, here we use microfabricated channels with varying sizes to study the interaction of Escherichia coli with solid confining spaces. It is shown that an optimal channel size exists for which the hydrostatic potential allows the most efficient movement of the cells. The improved understanding of how bacteria move will result in the ability to design better microfluidic structures based on their interaction with bacterial movement

Hair Cortisol in Twins : Heritability and Genetic Overlap with Psychological Variables and Stress-System Genes

A. Palotie on työryhmän jäsen.Hair cortisol concentration (HCC) is a promising measure of long-term hypothalamus-pituitary-adrenal (HPA) axis activity. Previous research has suggested an association between HCC and psychological variables, and initial studies of inter-individual variance in HCC have implicated genetic factors. However, whether HCC and psychological variables share genetic risk factors remains unclear. The aims of the present twin study were to: (i) assess the heritability of HCC; (ii) estimate the phenotypic and genetic correlation between HPA axis activity and the psychological variables perceived stress, depressive symptoms, and neuroticism; using formal genetic twin models and molecular genetic methods, i.e. polygenic risk scores (PRS). HCC was measured in 671 adolescents and young adults. These included 115 monozygotic and 183 dizygotic twin-pairs. For 432 subjects PRS scores for plasma cortisol, major depression, and neuroticism were calculated using data from large genome wide association studies. The twin model revealed a heritability for HCC of 72%. No significant phenotypic or genetic correlation was found between HCC and the three psychological variables of interest. PRS did not explain variance in HCC. The present data suggest that HCC is highly heritable. However, the data do not support a strong biological link between HCC and any of the investigated psychological variables.Peer reviewe

The behaviour of microorganisms in microfluidic networks

This thesis focuses on the characterisation of microorganisms and their responses to poly( dimethylsiloxane) (PDMS) based three-dimensional microfluidic structures. Experiments based on observations of the responses of individual cells to their environment have the potential to make enormous contributions to cell biology and biomedicine. Chapter 1 presents the thesis aims. In chapter 2, an overview of bacteria and filamentous fungi including their physiology and motility mechanisms are presented. The applications of lithography techniques including soft-lithography for studying cells and microorganisms behaviour over flat and profiled surfaces as well as within microfluidic devices are also reviewed. Chapter 3 described the methodology for the fabrication and-manipulation of the PDMS-based networks "",,, employed for experimentation and for data analysis. Chapter 4 investigates the mechanisms that allow fungi to partition the space and negotiate micro-confined networks. Armillaria mellea has been introduced in networks of various shapes. A. mellea was able to grow through every network exhibiting similar geometry-induced mechanisms. The species growth behaviour was mainly influenced by the geometry of the networks which changed the tip extension velocity and the branching angles. The-results obtained suggest that thigmotropism in which hyphal growth occurs is an important parameter in fungal growth dynamics. The hyphae could also find their way toward a network without any wall contact. This suggests that sensing mechanisms does not rely exclusively on thigmotropism but also on the integration of the extra-cellular environment. In chapter 5 the swimming behaviour of Serratia marcescens and Pseudomonas stutzeri in different networks were compared to their behaviour in non-confined environment. Large channels of 100 urn in width had no effect on the bacterial species as the bacteria swam randomly over the surface with gradual changes in their swimming direction and were seen to trace out circular trajectories. Channels of less than 10 urn in width could control bacterial movements in one direction and close to the boundaries. Complex networks of different shape not only revealed similar behaviour for both species but also showed the ability of bacteria to turn corner, to perform 360 0 turn and to follow very intricate paths. The complexity of the network through which the bacteria swam as well as the channels size were identified as the dominating factors in predicting their motility. In chapter 6 the behaviour of S. marcescens swarming phenotype was investigated after modifying the extra-cellular environment of the networks. Changes in the viscosity of the solution to 3.7 cP for channels that are 15 urn in width showed elongated swarming cells of a size reaching 8 urn to 10 urn in length. 10 urn wide channels were used to observe the swimming-swarming behaviour of S. marcescens within a wide range of concentration of Ficoll 400 and caused a decrease in cell velocity in comparison to that measured in LB broth only. The maximum cells size observed was 5.3 urn. Chapter 7 summarises the thesis main findings and the contributions in the field. Future work is also described.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The behaviour of microorganisms in microfluidic networks

This thesis focuses on the characterisation of microorganisms and their responses to poly( dimethylsiloxane) (PDMS) based three-dimensional microfluidic structures. Experiments based on observations of the responses of individual cells to their environment have the potential to make enormous contributions to cell biology and biomedicine. Chapter 1 presents the thesis aims. In chapter 2, an overview of bacteria and filamentous fungi including their physiology and motility mechanisms are presented. The applications of lithography techniques including soft-lithography for studying cells and microorganisms behaviour over flat and profiled surfaces as well as within microfluidic devices are also reviewed. Chapter 3 described the methodology for the fabrication and-manipulation of the PDMS-based networks "",,, employed for experimentation and for data analysis. Chapter 4 investigates the mechanisms that allow fungi to partition the space and negotiate micro-confined networks. Armillaria mellea has been introduced in networks of various shapes. A. mellea was able to grow through every network exhibiting similar geometry-induced mechanisms. The species growth behaviour was mainly influenced by the geometry of the networks which changed the tip extension velocity and the branching angles. The-results obtained suggest that thigmotropism in which hyphal growth occurs is an important parameter in fungal growth dynamics. The hyphae could also find their way toward a network without any wall contact. This suggests that sensing mechanisms does not rely exclusively on thigmotropism but also on the integration of the extra-cellular environment. In chapter 5 the swimming behaviour of Serratia marcescens and Pseudomonas stutzeri in different networks were compared to their behaviour in non-confined environment. Large channels of 100 urn in width had no effect on the bacterial species as the bacteria swam randomly over the surface with gradual changes in their swimming direction and were seen to trace out circular trajectories. Channels of less than 10 urn in width could control bacterial movements in one direction and close to the boundaries. Complex networks of different shape not only revealed similar behaviour for both species but also showed the ability of bacteria to turn corner, to perform 360 0 turn and to follow very intricate paths. The complexity of the network through which the bacteria swam as well as the channels size were identified as the dominating factors in predicting their motility. In chapter 6 the behaviour of S. marcescens swarming phenotype was investigated after modifying the extra-cellular environment of the networks. Changes in the viscosity of the solution to 3.7 cP for channels that are 15 urn in width showed elongated swarming cells of a size reaching 8 urn to 10 urn in length. 10 urn wide channels were used to observe the swimming-swarming behaviour of S. marcescens within a wide range of concentration of Ficoll 400 and caused a decrease in cell velocity in comparison to that measured in LB broth only. The maximum cells size observed was 5.3 urn. Chapter 7 summarises the thesis main findings and the contributions in the field. Future work is also described.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Åldersanpassat informationsmaterial för små barn i en cytostatikabehandling. : Hur ser det ut och hur kan det användas?

Barncancer drabbar 300 barn i Sverige varje år. Bland dessa barn är många väldigt små och har inte på samma självklara sätt som äldre barn och ungdomar lika lätt att ta till sig information om sin sjukdom eller om sin behandling. Detta arbete behandlar utformandet av en pekbok för barn mellan 0-3 år med fokus på förberedande information inför cytostatikabehandling (cellgiftsbehandling). Pekboken har tagits fram i samarbete med Barncancerfonden och Lunds Universitetssjukhus där både observationer av barn under behandling samt utprovning av pekboksmaterialet har gjorts. Arbetet belyser barns kognitiva utveckling, det tidiga mötet med barnlitteratur och beskriver de kommunikativa ställningstaganden som har tagits i utformandet av boken.Childhood cancer affects 300 children in Sweden annually. Among those, many children are very young and don’t have the ability to easily assimilate information about their decease or their treatment. This thesis treats the creation of a picture book for children with cancer, focussing on preparatory information before a chemotherapy treatment. The picture book has been created in co-operation with the Swedish Childhood Cancer Foundation and The University Hospital of Lund where both observation and evaluation have been performed. The thesis illustrates children’s cognitive development, the early meeting with children’s literature and describes the communicational considerations made in the creation of the book

Åldersanpassat informationsmaterial för små barn i en cytostatikabehandling. : Hur ser det ut och hur kan det användas?

Barncancer drabbar 300 barn i Sverige varje år. Bland dessa barn är många väldigt små och har inte på samma självklara sätt som äldre barn och ungdomar lika lätt att ta till sig information om sin sjukdom eller om sin behandling. Detta arbete behandlar utformandet av en pekbok för barn mellan 0-3 år med fokus på förberedande information inför cytostatikabehandling (cellgiftsbehandling). Pekboken har tagits fram i samarbete med Barncancerfonden och Lunds Universitetssjukhus där både observationer av barn under behandling samt utprovning av pekboksmaterialet har gjorts. Arbetet belyser barns kognitiva utveckling, det tidiga mötet med barnlitteratur och beskriver de kommunikativa ställningstaganden som har tagits i utformandet av boken.Childhood cancer affects 300 children in Sweden annually. Among those, many children are very young and don’t have the ability to easily assimilate information about their decease or their treatment. This thesis treats the creation of a picture book for children with cancer, focussing on preparatory information before a chemotherapy treatment. The picture book has been created in co-operation with the Swedish Childhood Cancer Foundation and The University Hospital of Lund where both observation and evaluation have been performed. The thesis illustrates children’s cognitive development, the early meeting with children’s literature and describes the communicational considerations made in the creation of the book