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| 2. |
- Broman, T, et al.
(författare)
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Molecular Detection of Persistent Francisella tularensis Subspecies holarctica in Natural Waters
- 2011
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Ingår i: International Journal of Microbiology. - : Hindawi Publishing Corporation. - 1687-918X .- 1687-9198. ; 2011, s. Article ID 851946-
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Tidskriftsartikel (refereegranskat)abstract
- Tularemia, caused by the bacterium Francisella tularensis, where F. tularensis subspecies holarctica has long been the cause of endemic disease in parts of northern Sweden. Despite this, our understanding of the natural life-cycle of the organism is still limited. During three years, we collected surface water samples (n = 341) and sediment samples (n = 245) in two areas in Sweden with endemic tularemia. Real-time PCR screening demonstrated the presence of F. tularenis lpnA sequences in 108 (32%) and 48 (20%) of the samples, respectively. The 16S rRNA sequences from those samples all grouped to the species F. tularensis. Analysis of the FtM19InDel region of lpnA-positive samples from selected sampling points confirmed the presence of F. tularensis subspecies holarctica-specific sequences. These sequences were detected in water sampled during both outbreak and nonoutbreak years. Our results indicate that diverse F. tularensis-like organisms, including F. tularensis subsp. holarctica, persist in natural waters and sediments in the investigated areas with endemic tularemia.
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| 4. |
- Lampe, E. O., et al.
(författare)
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A study of virulence factors in the fish pathogen F. noatunensis ssp noatunensis
- 2013
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Ingår i: Fish and Shellfish Immunology. - : Elsevier. - 1050-4648 .- 1095-9947. ; 34:6, s. 1716-1716
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Tidskriftsartikel (refereegranskat)abstract
- The bacterium Francisella noatunensis ssp. noatunensis (in text: F. noatunensis) is the ethiological agent of the disease francisellosis in Atlantic cod. Francisellosis has been one of the major limiting factors in the development of Norwegian aquaculture industry based on Atlantic cod. Lacking an effective treatment or vaccine there is urgent need for studies related to the pathogenesis of the disease.The closely related human pathogen F. tularensis is more extensively studied and due to relatively high sequence similarity with F. noatunensis, indirect evidence on important virulence factors can be obtained by reverse genetics. The Francisella Pathogenicity Island (FPI) has been identified in all sequenced genomes of Francisella sp. and contains genes associated with the ability of the bacterium to survive and replicate within macrophages.To elucidate the pathogenesis of F. noatunensis, infection assays have been performed on primary cells extracted from the head kidney of Atlantic cod. Disruptive mutations of the potential virulence factors IglC, IglD (important for intracellular growth in F. tularensis subsp.) and ClpB (a heat shock protein identified in F. tularensis), have been constructed in F. noatunensis and the infection pattern is in the process of characterization. Model systems that are utilized in the characterization are the amoebae and professional phagocyte Dictyostelium discoideum, zebrafish and macrophages extracted from head kidney of Atlantic cod.
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| 5. |
- Sjöstedt, E, et al.
(författare)
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The first nurse-patient encounter in a psychiatric setting : discovering a moral commitment in nursing.
- 2001
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Ingår i: Nursing Ethics. - : SAGE Publications. - 0969-7330 .- 1477-0989. ; 8:4, s. 313-27
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to deepen nurses' understanding of the importance of carefully managing the first nurse-patient encounter in a psychiatric setting according to each patient's suffering and future hopes. The study was carried out using an action research approach. The action planned was the implementation of a conceptual model reflecting Eriksson's caring theory. Data were collected by interviews with nurses and observational notes kept in a research diary. The data analysis followed the procedure of qualitative content analysis. A generalization of the entire learning process shows the first nurse-patient encounter to be a moral commitment in nursing. A theoretical framework of nursing assessment conveying knowledge about the patient as unique and being a whole person can support the nurse in encouraging the patient to enter into a relationship. This insight stimulated the nurses in this study to reflect on the moral responsibility of continuing the relationship and initiating an ongoing nursing process. Awareness of this responsibility made them reflect more on the possibility of nurses taking autonomous actions in order not to abandon the patient and to avoid feeling guilty.
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| 6. |
- Alam, Athar, et al.
(författare)
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The Role of ClpB in Bacterial Stress Responses and Virulence
- 2021
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Ingår i: Frontiers in Molecular Biosciences. - : Frontiers Media S.A.. - 2296-889X. ; 8
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Forskningsöversikt (refereegranskat)abstract
- Bacterial survival within a mammalian host is contingent upon sensing environmental perturbations and initiating an appropriate counter-response. To achieve this, sophisticated molecular machineries are used, where bacterial chaperone systems play key roles. The chaperones are a prerequisite for bacterial survival during normal physiological conditions as well as under stressful situations, e.g., infection or inflammation. Specific stress factors include, but are not limited to, high temperature, osmolarity, pH, reactive oxidative species, or bactericidal molecules. ClpB, a member of class 1 AAA+ proteins, is a key chaperone that via its disaggregase activity plays a crucial role for bacterial survival under various forms of stress, in particular heat shock. Recently, it has been reported that ClpB also regulates secretion of bacterial effector molecules related to type VI secretion systems. In this review, the roles of ClpB in stress responses and the mechanisms by which it promotes survival of pathogenic bacteria are discussed.
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| 7. |
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| 8. |
- Bruhn, Anders Dalhoff, et al.
(författare)
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Terrestrial Dissolved Organic Matter Mobilized From Eroding Permafrost Controls Microbial Community Composition and Growth in Arctic Coastal Zones
- 2021
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Ingår i: Frontiers in Earth Science. - : Frontiers Media SA. - 2296-6463. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Climate warming is accelerating erosion along permafrost-dominated Arctic coasts. This results in the additional supply of organic matter (OM) and nutrients into the coastal zone. In this study we investigate the impact of coastal erosion on the marine microbial community composition and growth rates in the coastal Beaufort Sea. Dissolved organic matter (DOM) derived from three representative glacial deposit types (fluvial, lacustrine, and moraine) along the Yukon coastal plain, Canada, were used as substrate to cultivate marine bacteria using a chemostat setup. Our results show that DOM composition (inferred from UV-Visible spectroscopy) and biodegradability (inferred from DOC concentration, bacterial production and respiration) significantly differ between the three glacial deposit types. DOM derived from fluvial and moraine types show clear terrestrial characteristics with low aromaticity (Sr: 0.63 ± 0.02 and SUVA254: 1.65 ± 0.06 L mg C−1 m−1 & Sr: 0.68 ± 0.01 and SUVA254: 1.17 ± 0.06 L mg C−1 m−1, respectively) compared to the lacustrine soil type (Sr: 0.71 ± 0.02 and SUVA254: 2.15 ± 0.05 L mg C−1 m−1). The difference in composition of DOM leads to the development of three different microbial communities. Whereas Alphaproteobacteria dominate in fluvial and lacustrine deposit types (67 and 87% relative abundance, respectively), Gammaproteobacteria is the most abundant class for moraine deposit type (88% relative abundance). Bacterial growth efficiency (BGE) is 66% for DOM from moraine deposit type, while 13 and 28% for DOM from fluvial and lacustrine deposit types, respectively. The three microbial communities therefore differ strongly in their net effect on DOM utilization depending on the eroded landscape type. The high BGE value for moraine-derived DOM is probably caused by a larger proportion of labile colorless DOM. These results indicate that the substrate controls marine microbial community composition and activities in coastal waters. This suggests that biogeochemical changes in the Arctic coastal zone will depend on the DOM character of adjacent deposit types, which determine the speed and extent of DOM mineralization and thereby carbon channeling into the microbial food web. We conclude that marine microbes strongly respond to the input of terrestrial DOM released by coastal erosion and that the landscape type differently influence marine microbes.
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| 9. |
- Bröms, Jeanette E, 1974-, et al.
(författare)
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A conserved α-helix essential for a type VI secretion-like system of Francisella tularensis
- 2009
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Ingår i: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 191:8, s. 2431-2446
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Tidskriftsartikel (refereegranskat)abstract
- Francisella tularensis harbors genes with similarity to genes encoding components of a type VI secretion system (T6SS) recently identified in several gram-negative bacteria. These include iglA and iglB, the homologues of which are conserved in most T6SSs. We used a yeast two-hybrid system to study the interaction of the Igl proteins of F. tularensis LVS. We identified a region of IglA, encompassing residues 33-132, necessary for efficient binding to IglB as well as for IglAB protein stability and intra-macrophage growth. In particular, residues 103-122, overlapping with a highly conserved alpha-helix, played an absolutely essential role. Point mutations within this domain caused modest defects in IglA-IglB binding in yeast, but markedly impaired intra-macrophage replication and phagosomal escape, resulting in severe attenuation of LVS in mice. Thus, IglA-IglB complex formation is clearly crucial for Francisella pathogenicity. This interaction may be universal to T6S, since IglAB homologues of Yersinia pseudotuberculosis, Pseudomonas aeruginosa, Vibrio cholerae, Salmonella typhimurium and Escherichia coli were also shown to interact in yeast and the interaction was dependent on the preservation of the same alpha-helix. Heterologous interactions formed between non-native IglAB proteins further supported the notion of a conserved binding site. Thus, IglA-IglB complex formation is clearly crucial for Francisella pathogenicity and the same interaction is conserved in other human pathogens.
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| 10. |
- Bröms, Jeanette E., et al.
(författare)
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A functional VipA-VipB interaction is required for the type VI secretion system activity of Vibrio cholerae O1 strain A1552
- 2013
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Ingår i: BMC Microbiology. - London, England : BioMed Central. - 1471-2180. ; 13, s. 96-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Many Gram-negative bacteria rely on a type VI secretion system (T6SS) to infect eukaryotic cells or to compete against other microbes. Common to these systems is the presence of two conserved proteins, in Vibrio cholerae denoted VipA and VipB, which have been shown to interact in many clinically relevant pathogens. In this study, mutagenesis of a defined region within the VipA protein was used to identify residues important for VipB binding in V. cholerae O1 strain A1552. Results: A dramatically diminished interaction was shown to correlate with a decrease in VipB stability and a loss of hemolysin co-regulated protein (Hcp) secretion and rendered the bacterium unable to compete with Escherichia coli in a competition assay. Conclusions: This confirms the biological relevance of the VipA-VipB interaction, which is essential for the T6SS activity of many important human pathogens.
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