| 1. |
- Sandh, Gustaf, 1980-
(författare)
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Towards an understanding of diazocyte development and diazotrophy in the marine cyanobacterium Trichodesmium
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Trichodesmium is a filamentous cyanobacterium of great ecological significance as it contributes significantly to primary production in oceans through an efficient nitrogen fixation strategy, including a unique cell type, the diazocyte. The aim of this thesis was to generate a deeper understanding of the structural and molecular background related to the development of diazocytes and the maintenance of diazotrophy in Trichodesmium erythraeum IMS101. Data obtained demonstrated a diurnal separation of basic physiological processes, with nitrogen fixation and photosynthesis confined to the light and cell division and diazocyte development to the dark period. Diazocyte development was preceded by cell division and expression of the main regulator of heterocyst differentiation, hetR. In non-diazotrophic cultures, subject to nitrogen depletion, a developmental program was initiated in a subset of cells that differentiated into mature nitrogenase containing diazocytes, while addition of combined nitrogen abolished development. A nitrogen depletion signal initially enhanced transcription of the global nitrogen regulator ntcA and was followed by elevated expression of coxBII (respiration) and glnA (primary ammonia assimilation) and pronounced sub-cellular rearrangements. Comparative proteomic analysis further revealed a clear shift in the cellular metabolism depending on the nitrogen regime, with 94 proteins being differentially expressed in diazotrophic (with diazocytes) as opposed to in non-diazotrophic cultures. Proteins up-shifted in diazotrophic cultures were related to supporting the nitrogenase enzyme with reducing equivalents and a lower oxygen tension. In addition, two highly divergent flavodoxins were identified with different expression patterns in response to combined nitrogen additions and the data discourage the use of flavodoxins as indicators of iron stress in Trichodesmium populations.
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| 2. |
- Arvidsson, Susann
(författare)
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Health promoting factors in people with chronic musculoskeletal pain or with rheumatic diseases: a descriptive and interventional study
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aim: The overall aim of this thesis with a salutogenic approach was to describe health promoting factors in people with chronic musculoskeletal pain and in people with rheumatic diseases, and to evaluate the effects of an intervention study with a self-care promoting PBL-program for people with rheumatic diseases having chronic musculoskeletal pain, sleep disturbances and/or fatigue. Methods: This thesis is comprised of four samples: a randomly selected sample from a Swedish general population (study I) and three different samples containing people with rheumatic diseases registered at a hospital for rheumatic diseases in the southwest of Sweden (studies II, III and IV). Study I had a longitudinal cohort design with an eight-year follow-up in a general population. There were 1109 participants without chronic pain and 700 participants with chronic musculoskeletal pain. Study II had a longitudinal cohort design with participants with rheumatic diseases (n=185) 12 months after rehabilitation at a hospital for rheumatic diseases. Study III had a descriptive qualitative design with a phenomenological approach based on a reflective life-world perspective. Twelve participants were interviewed about their experiences about health-promoting self-care. Study IV had a randomised controlled design with post-test six months after the one-year self-care promoting problem-based learning (PBL) program for people with rheumatic diseases. The participants were randomly assigned to the experimental group, 54 participants, or to the control group, 148 participants. Data in studies I, II and IV were analysed with statistics. In study III a Husserlian phenomenological approach based on a reflective life-world perspective was used in the data collection and analysis. Results: Study I: Although participants without chronic musculoskeletal pain reported better health-related quality of life (HRQL) than participants with chronic musculoskeletal pain, similar health factors were found to promote a better HRQL in the eight-year follow-up. The most important factors were feeling rested after sleep and having good sleep structure. Study II: The most important factors promoting better outcome in HRQL 12 months after rehabilitation in participants with rheumatic diseases were having a strong sense of coherence (SOC), feeling rested after sleep, having work capacity, and having good sleep structure. Study III: The meaning of health-promoting self-care as experienced by people with rheumatic diseases was that self-care takes place against a background of continual hope and belief to be able to influence health in positive ways. Self-care was a way of life and implied being ready to understand and respond to signals from the body. Three interrelated constituents elucidated the experiences: dialogue, power struggle and choice. Study IV: At the six month follow-up the participants in the experimental group had stronger empowerment after participation in the self-care promoting PBL-program compared with the control group which only got standard care for people with rheumatic diseases. There were no differences in HRQL, self-care ability, SOC, pain, quality of sleep or fatigue between the experimental group and the control group. The participants in the experimental group also stated that they had implemented lifestyle changes which they had not done without the PBL-program. Conclusion: The results of this thesis provide a valuable and useful insight in health promoting factors in people with chronic musculoskeletal pain and in people with rheumatic diseases, but also in that people with rheumatic diseases have benefit from taking part in patient education with a self-care promoting PBL-program. These results contribute to evidence supporting the introduction of a more salutogenic approach in rheumatology care and research.
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| 3. |
- Bauer, Karolina, 1975-
(författare)
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Diazotrophy and diversity of benthic cyanobacteria in tropical coastal zones
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Discoveries in recent years have disclosed the importance of marine cyano-bacteria in the context of primary production and global nitrogen cycling. It is hypothesized here that microbial mats in tropical coastal habitats harbour a rich diversity of previously uncharacterized cyanobacteria and that benthic marine nitrogen fixation in coastal zones is substantial.A polyphasic approach was used to investigate cyanobacterial diversity in three tropical benthic marine habitats of different characters; an intertidal sand flat and a mangrove forest floor in the Indian Ocean, and a beach rock in the Pacific Ocean. In addition, nitrogenase activity was measured over diel cycles at all sites. The results revealed high cyanobacterial diversity, both morphologically and genetically. Substantial nitrogenase activity was observed, with highest rates at daytime where heterocystous species were present. However, the three habitats were dominated by non-heterocystous and unicellular genera such as Microcoleus, Lyngbya, Cyanothece and a large group of thin filamentous species, identified as members of the Pseudanabaenaceae family. In these consortia nocturnal nitrogenase activities were highest and nifH sequencing also revealed presence of non-cyanobacterial potential diazotrophs. A conclusive phylogenetic analysis of partial nifH sequences from the three sites and sequences from geographi-cally distant microbial mats revealed new clusters of benthic potentially ni-trogen-fixing cyanobacteria. Further, the non-heterocystous cyanobacterium Lyngbya majuscula was subjected to a physiological characterization to gain insights into regulatory aspects of its nitrogen fixation. The data demon-strated that nitrogenase activity is restricted to darkness, which called upon a re-evaluation of its diazotrophic behaviour.
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| 4. |
- Berntzon, Lotta, 1978-
(författare)
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Detection, transfer and role of an environmentally spread neurotoxin (BMAA) with focus on cyanobacteria and the Baltic Sea region
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- β-N-methylamino-L-alanine (BMAA) is one of the more recently discovered bioactive compounds produced by cyanobacteria. BMAA is a non-protein amino acid reported present in human brain tissues of patients deceased from a neurodegenerative disease, such as Alzheimer´s disease or amyotrophic lateral sclerosis (ALS). This observation in combination with its neurotoxic effects in eukaryotes (in vivo and in vitro) and its potential to incorporate into (human) proteins, causing protein aggregation, suggests BMAA as a possible causative environmental agent for neurodegenerative diseases. Due to the ubiquitous nature of cyanobacteria with a wide occurrence in both aquatic and terrestrial environments, BMAA could be globally spread. Hence, investigations of a possible coupling between BMAA and neurodegeneration are urgently needed as well as to identify sources of BMAA in Nature.The aim of this thesis was to examine the potential occurrence of BMAA in bloom forming cyanobacteria of the Baltic Sea and its possible transfer to other organisms of this ecosystem. Of importance was also to reveal any likely routes for human BMAA exposure in the Baltic Sea region and to further investigate BMAA as a triggering agent for neurodegenerative diseases. Acknowledged difficulties of analysing BMAA in biological samples also inferred method development as part of the experimental studies. Investigating the role of BMAA in its producers was another purpose of the thesis, which may be crucial for future management of BMAA-producing cyanobacteria.By screening natural populations of the major filamentous bloom forming cyanobacteria of the Baltic Sea, we discovered the presence of BMAA throughout the entire summer season of two consecutive years, using a highly specific analytical method (liquid chromatography-tandem mass spectrometry; LC-MS/MS). BMAA was found to bioaccumulate in zooplankton and fish, as well as in mussels and oysters from the Swedish west coast. To improve the understanding of BMAA analyses in natural samples, the formation of carbamate adducts in the presence of bicarbonate was examined. Using two derivatization techniques in combination with LC-MS/MS, we could show that BMAA detection was not hindered by carbamate formation. Exogenously added BMAA inhibited nitrogen fixation in the model cyanobacterium Nostoc sp. PCC 7120, which was also hampered in growth and displayed signs of nitrogen starvation. Finally, BMAA was detected in cerebrospinal fluid in three of 25 Swedish test individuals, and represents the first confirmation of BMAA in the human central nervous system using LC-MS/MS as the primary analytical method. However, the association of BMAA to neurodegenerative diseases could not be verified as BMAA was present in both control individuals (two) and in one ALS-patient. Nevertheless, the finding of a known neurotoxic compound in the human central nervous system is alarming and potential consequences should be investigated.The discovery of the neurotoxic compound BMAA in Baltic Sea organisms, and in the central nervous system of humans potentially consuming fish from this ecosystem is concerning and warrants continued investigations of BMAA occurrence and human exposure. Further knowledge on the function and regulation of BMAA may help in developing strategies aiming to minimise human exposure.
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| 5. |
- Hamisi, Mariam, 1976-
(författare)
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Genetic variability and nitrogenase activity of cyanobacterial communities associated with tropical seagrass meadows (western Indian Ocean)
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tropical seagrass ecosystems are highly productive and important for sustaining marine life and associated coastal societies. In this study, the diversity and role of nitrogen-fixing cyanobacteria associated with five common seagrass genera in coastal regions of the western Indian Ocean (WIO; Tanzania) were examined, as well as the impact of anthropogenic activities. Cyanobacteria were characterized morphologically and genetically (16S rRNA and nifH gene phylogeny), as were diel variations in nifH gene expression, NifH protein levels and nitrogenase activity. The results revealed that WIO seagrass beds supported rich cyanobacterial diversity and that these represented approx. 83% of total clones obtained (DNA and RNA nifH clone libraries). Non-heterocystous genera, such as Oscillatoria, Lyngbya, Leptolyngbya, Phormidium and Microcoleus dominated, while heterocystous morphotypes such as Calothrix were less frequent and unicellular morphotypes (e.g. Gloeocapsa, Chroococcus and Chroococcidiopsis) were few. Additionally, the phylogenetic analysis revealed several novel uncharacterized cyanobacterial clades. Cyanobacterial composition and nitrogenase activity varied over seasons and between the seagrass species. Day time nitrogenase activity originated primarily from heterocystous phylotypes, while non-heterocystous filamentous phylotypes fixed nitrogen at night. The highest activity in the diel cycle was 358 ± 232 nmol C2H4 g-1 h-1at 09.00 associated with epiphytes of the seagrass Cymodocea. Nitrogenase activity was consistently lower in anthropogenically disturbed (eutrophication) seagrass sites. Such data suggest that diazotrophic cyanobacteria may be a significant source of ‘new’ nitrogen in the often oligotrophic coastal regions of tropical oceans. It is also proposed that the rapid shifts in the cyanobacterial population and function found may also be used as early disturbance indicator in coastal management practices.
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| 6. |
- Koch, Andrea
(författare)
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Clinical Aspects of Inflammation in Non-small Cell Lung Cancer
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lung cancer is the most common cause of cancer death worldwide, with about 1.2 million deaths every year. In Sweden, about 3500 new cases are diagnosed every year. The majority of patients presents with advanced non-small cell lung cancer (NSCLC) and is treated with palliative intent. Standard treatment in these patients in performance status 0-2 is combination chemotherapy. Radiotherapy may be added for palliative purposes. Median survival time with such treatment is 6-10 months. New treatment strategies are urgently needed. There is growing evidence for a link between cancer and inflammation and consequently, inflammation may be a possible target for the treatment of lung cancer.The aim of this thesis was to study clinical aspects of inflammation in non-small cell lung cancer. A central issue was to adapt the projects as close to clinical routine as possible.In a retrospective study of 289 patients (paper I), we investigated the prognostic value of Creactive protein (CRP), a nonspecific marker of systemic inflammation, and smoking in patients with advanced NSCLC treated with palliative first-line chemotherapy. We found that patients with elevated CRP values (≥10 mg/ml) and current smokers at onset of treatment had inferior survival compared to patients with normal CRP values and patients who were not smoking. CRP and smoking status were independent prognostic factors and provided additional information to established prognostic factors such as stage of disease and performance status.The expression of COX-2, an important enzyme involved in inflammation, was prospectively analysed in 53 patients with cytologically diagnosed lung cancer (paper II). The study showed that the analysis of COX-2 expression in cytological material is technically easy to perform with routine diagnostic methods and results in good quality slides. There was great variation in the proportion of COX-2 positive cells between the patients as well as in the intensity of staining between individual cells in many single cases.The major project (paper III) of this thesis was the CYCLUS study, an academic, randomised, double-blind, phase III trial. The scientific question was if addition of the COX-2 inhibitor celecoxib to first-line palliative chemotherapy would prolong survival in patients with advanced NSCLC. 316 patients were included at 13 centres in Sweden. There was no survival difference between the treatment arms. Celecoxib appeared to have more favourable effect on survival in women than in men, but the differences were not significant. Small but not statistically significant differences in global quality of life and pain were seen favouring the celecoxib group. No increased incidence of cardiovascular events was observed in the celecoxib group.
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| 7. |
- Larsson, John, 1981-
(författare)
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Cyanobacterial genome evolution subsequent to domestication by a plant (Azolla)
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cyanobacteria are an ancient and globally distributed group of photosynthetic prokaryotes including species capable of fixing atmospheric dinitrogen (N2) into biologically available ammonia via the enzyme complex nitrogenase. The ability to form symbiotic interactions with eukaryotic hosts is a notable feature of cyanobacteria and one which, via an ancient endosymbiotic event, led to the evolution of chloroplasts and eventually to the plant dominated biosphere of the globe. Some cyanobacteria are still symbiotically competent and form symbiotic associations with eukaryotes ranging from unicellular organisms to complex plants. Among contemporary plant-cyanobacteria associations, the symbiosis formed between the small fast-growing aquatic fern Azolla and its cyanobacterial symbiont (cyanobiont), harboured in specialized cavities in each Azolla leaf, is the only one which is perpetual and in which the cyanobiont has lost its free-living capacity, suggesting a long-lasting co-evolution between the two partners. In this study, the genome of the cyanobiont in Azolla filiculoides was sequenced to completion and analysed. The results revealed that the genome is in an eroding state, evidenced by a high proportion of pseudogenes and transposable elements. Loss of function was most predominant in genetic categories related to uptake and metabolism of nutrients, response to environmental stimuli and in the DNA maintenance machinery. Conversely, function was retained in key symbiotic processes such as nitrogen-fixation and cell differentiation. A comparative analysis shows that the size of the cyanobiont genome has remained relatively stable, and that few genes have been completely eliminated, since the symbiotic establishment. Indications of genes acquired via horizontal gene transfer were discovered in thec yanobiont genome, some of which may have originated from the bacterial community in the Azolla leaf-cavities. It is concluded that the perpetual nature of the Azolla symbiosis has resulted in pronounced ongoing streamlining of the cyanobiont genome around core symbiotic functions, a process not described previously for complex cyanobacteria or for any bacterial plant symbiont. Further, the status of the genome indicates that the cyanobiont is at an early stage of adapting to its host-restricted environment and continued co-evolution with the plant may result in additional genome reductions. However, although a vertical transmission process is already established, the unusual extracellular location of the cyanobiont and the intricate nature of the symbiosis, may still impose restrictions on such a reductive process.
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| 8. |
- Ran, Liang, 1974-
(författare)
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Proteomic profiles and gene expressions in the symbiotically competent cyanobacterium Nostoc sp. PCC 73102
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nostoc PCC 73102 is an evolutionary important cyanobacterium with multiple phenotypic traits and symbiotic capacities. Based on two-dimensional gel electrophoresis (2-DE) and MALDI-TOF mass spectrometry, a proteomic approach was developed in order to obtain protein profiles of this symbiotically competent cyanobacterium during three trophic types/life stages: free-living photo-autotrophic and diazotrophic growth conditions, dark heterotrophic conditions and hormogonium formation. The proteomic data obtained revealed a total of 82 proteins that could be organized into 12 functional categories. The majority of proteins identified were involved in carbon, nitrogen and energy metabolism. The analysis also indicates that a thioredoxin-dependent redox regulation is vital under photo-autotrophic and diazotrophic growth conditions. The differentiation of vegetative filaments into hormogonia led to distinct morphological as well as drastic changes in C and N metabolism, with levels of Rubisco large subunit and glutamine synthetase clearly down-regulated, while glycogen synthesis (C storage) was enhanced, a metabolic specialisation maintained in symbiosis. RT-PCR and quantitative real-time PCR showed that gene transcription related to surface structures and hormogonium function was affected early during the developmental process: genes encoding proteins involved in motility (pil genes) and gas vesicle formation (gvp genes) were up-regulated, but also genes encoding proteins involved in DNA replication (dnaA) and cell division (ftsZ, ftsA and ftn2) and proteolysis (hetR). Dark heterotrophy, mimicking symbiosis, led to a repression of CO2 fixation, while sugar uptake, the glycolysis pathway and N2-fixation were stimulated. In addition, three proteins involved in light adaptation processes were upregulated. Collectively, these data contribute to our understanding and the definition of ‘symbiotic competence’ and suggest that the cyanobacterium behaves like a cyanobiont even before getting into physical contact with host plants if subject to the appropriate signals.
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| 9. |
- Vigil Stenman, Carl Theoden, 1972-
(författare)
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Effects and Dynamics of Insertion Sequences in the Evolution of Cyanobacteria
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cyanobacteria are globally widespread and ecologically highly significant photoautotrophic microorganisms, with diverse geno- and phenotypic characters unprecedented among prokaryotes. This phylum embraces representatives with an exclusive adaptability in highly specialized environments, from oligotrophic ocean waters to the interior of cells in symbiotic plants, the most extreme being the chloroplasts. Insertion sequences (ISs) are short (~1000 bp) mobile genetic elements prevalent in microbial genomes, potentially representing potent adaptive forces.In this thesis, hypotheses tested that ISs play significant roles in both reductive and adaptive evolution in physiologically versatile cyanobacteria, using two model systems. First, the genome of an obligate plant (Azolla) symbiont, the cyanobacterium ‘Nostoc azollae 0708’, was sequenced, which led to the discovery of a highly ‘eroding’ genome (5,48 Mbp), loaded with ISs covering 14% of the genome, a situation likely caused by the relaxed selection pressure within the plant. The ISs were located in close proximity to the extremely numerous pseudogenes identified, although genes with key functions in a symbiotic context escaped IS mediated erosion (e.g. nitrogen fixation and differentiation genes). Some ISs were shown to have transposed short distances within the genome (‘local hoping’), and to be likely causative agents in pseudogene formation, and thus pivotal actors in the reductive evolution discovered.To widen the scope of ISs further, additionally 66 phylogenetically diverse microorganisms with a variety of life styles (free-living, symbionts, pathogens) were examined in regards to ISs influence. The data verified their over-all importance in shaping microbial genomes.Finally, natural microbial populations in the Baltic Sea, a semi-enclosed geologically young (~10,000 years) brackish water body offering steep gradients in salinity and nutrient loads, were examined using metatranscriptomics and metagenomics. A large proportion of the metagenome was devoted to ISs and most importantly a large fraction of the metatranscriptome consisted of IS transcripts (~1%), which may be suggestive of a high IS activity. These phenomena were most apparent in cyanobacteria in central parts of the Baltic Sea. The presence of an especially rich abundance of ISs in brackish waters was further substantiated by their low frequency (< 0.1%) in microbes of marine waters. Hence, ISs may facilitate both adaptations (short term) and adaptive evolution (long term) in microbes entering brackish water, otherwise unable to cross the distinct limnic-to-marine salinity-divide. Together, the data reveal high genomic loads of ISs in cyanobacteria subject to highly demanding conditions and stress the importance of locally migrating ISs (and pseudogenization) as important facilitators in adaptation and evolution, being a more rapid process than hitherto expected. The findings strongly support current theories stating a crucial role of ISs in shaping microbial genomes to render fitness.
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| 10. |
- Larsson, Ingrid
(författare)
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Person-centred care in rheumatology nursing in patients undergoing biological therapy : An explorative and interventional study
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aim: The overall aim was to explore and evaluate rheumatology nursing from a person-centred care perspective in patients undergoing biological therapy.Methods: This thesis focuses on patients with chronic inflammatory arthritis (CIA) who were undergoing biological therapy at a rheumatology clinic in Sweden. Papers I and II had an explorative descriptive design with a phenomenographic approach. The 40 participants were interviewed about their dependence on or independence of a nurse for the administration of their infusions or injections. Paper III had a randomized controlled design involving 107 patients in the trial. The objective of the intervention was to replace every second monitoring visit at a rheumatologist-led clinic by a visit to a nurse-led rheumatology clinic, based on person-centred care. Paper IV had an explorative descriptive design with a qualitative content analysis approach. Interviews were conducted with 20 participants who attended the nurse-led rheumatology clinic.Findings: Dependence on a rheumatology nurse for administration of intravenous infusions was described as invigorating due to the regular contact with the nurse, which provided security and involvement (paper I). Independence of a nurse for subcutaneous injections was understood by the patients in different ways and was achieved by struggling to cope with injecting themselves, learning about and participating in drug treatment (paper II). Patients with stable CIA receiving biological therapy were monitored by a nurse-led rheumatology clinic without any difference in outcome when compared to monitoring carried out at a rheumatologist-led clinic, as measured by the Disease Activity Score 28. Replacing one of the two annual rheumatologist outpatient follow-up visits by a visit to a nurse-led clinic for the monitoring of biological therapy was found to be safe and effective (paper III). A nurse-led rheumatology clinic, based on person-centred care, added value to the follow-up care of patients with stable CIA undergoing biological therapy by providing a sense of security, familiarity and participation (paper IV).Conclusions: This thesis contributes a valuable insight into person-centred care as the core of rheumatology nursing in the area of biological therapy. The rheumatology nurse adds value to patient care when she/he gives patients an opportunity to talk about themselves as a person and allow their illness narrative to constitute a starting point for building collaboration, which encourages and empowers patients to be an active part in their biological therapy and become autonomous. A nurse who provides person-centred care and keeps the patients’ resources and needs in focus serves as an important guide during their healthcare journey.
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