| 1. |
- Delgado, Camila, et al.
(författare)
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Pseudomonas aeruginosa Regulated Intramembrane Proteolysis : Protease MucP Can Overcome Mutations in the AlgO Periplasmic Protease To Restore Alginate Production in Nonmucoid Revertants
- 2018
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Ingår i: Journal of Bacteriology. - : American Society for Microbiology. - 0021-9193 .- 1098-5530. ; 200:16
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Tidskriftsartikel (refereegranskat)abstract
- The progression of cystic fibrosis (CF) from an acute to a chronic disease is often associated with the conversion of the opportunistic pathogen Pseudomonas aeruginosa from a nonmucoid form to a mucoid form in the lung. This conversion involves the constitutive synthesis of the exopolysaccharide alginate, whose production is under the control of the AlgT/U sigma factor. This factor is regulated posttranslationally by an extremely unstable process and has been commonly attributed to mutations in the algT (algU) gene. By exploiting this unstable phenotype, we isolated 34 spontaneous nonmucoid variants arising from the mucoid strain PDO300, a PAO1 derivative containing the mucA22 allele commonly found in mucoid CF isolates. Complementation analysis using a minimal tiling path cosmid library revealed that most of these mutants mapped to two protease-encoding genes, algO, also known as prc or PA3257, and mucP. Interestingly, our algO mutations were complemented by both mucP and algO, leading us to delete, clone, and overexpress mucP, algO, mucE, and mucD in both wild-type PAO1 and PDO300 backgrounds to better understand the regulation of this complex regulatory mechanism. Our findings suggest that the regulatory proteases follow two pathways for regulated intramembrane proteolysis (RIP), where both the AlgO/MucP pathway and MucE/AlgW pathway are required in the wild-type strain but where the AlgO/MucP pathway can bypass the MucE/AlgW pathway in mucoid strains with membrane-associated forms of MucA with shortened C termini, such as the MucA22 variant. This work gives us a better understanding of how alginate production is regulated in the clinically important mucoid variants of Pseudomonas aeruginosa. IMPORTANCE Infection by the opportunistic pathogen Pseudomonas aeruginosa is the leading cause of morbidity and mortality seen in CF patients. Poor patient prognosis correlates with the genotypic and phenotypic change of the bacteria from a typical nonmucoid to a mucoid form in the CF lung, characterized by the overproduction of alginate. The expression of this exopolysaccharide is under the control an alternate sigma factor, AlgT/U, that is regulated posttranslationally by a series of proteases. A better understanding of this regulatory phenomenon will help in the development of therapies targeting alginate production, ultimately leading to an increase in the length and quality of life for those suffering from CF.
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| 2. |
- Ericson Jogsten, Ingrid, 1980-, et al.
(författare)
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Microbial binding of perfluoroalkyl substances (PFASs)
- 2018
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Ingår i: INEF 2018. ; , s. 33-34
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Per- and polyfluorinated alkyl substances (PFASs) are environmental pollutants of global concern due to their persistence and widespread occurrence in humans, wildlife and the environment. These compounds have been extensively used in various commercial and industrial applications since the mid-1900. In 2009, perfluorooctane sulfonic acid (PFOS) was added to the Stockholm convention to protect humans and wildlife from harmful effects. In Sweden, severe PFAS contamination in drinking water has resulted in elevated blood PFAS concentrations in residents living in contaminated areas.The present study evaluated microbial binding of PFASs was tested. The binding capacity was assessed in both live and dead Escherichia coli for various PFOS concentrations. The binding capacity of dead cells was higher (286-3324 μg/g of bacterial pellet) compared to live E. coli cells, showing a 5 – 7 fold lower binding capacity (38-675 μg/g of bacterial pellet). For PFOS, the affinity of branched isomers was similar to that of linear compounds. . Furthermore, other species of bacteria were tested for binding capacity of various mixtures of PFASs from both technical products and contaminated environmental waters, including Pseudomonas nitroreducens and Acidovorax delafieldii. After treatment, bacteria pellets were extracted and analyzed using liquid chromatography tandem mass spectrometry (LC-MS/MS). Preliminary results indicate preferential binding for PFOS, the contaminant present in the highest concentration in both contaminated environmental water and spiked water of the sum of eleven PFASs recommended for analysis by the Swedish Food agency.This study gives increased knowledge of microbial binding of perfluoroalkyl substances giving insight on PFAS transport in the environment and at different trophic levels. The phenomenon of microbial binding of PFASs could also be used to establish a more cost effective remediation of PFAS contaminated waters. Further, it could lead to increased understanding of toxicological effects of PFASs related to the gut microbiota.
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| 3. |
- Lopes, Jose Pedro, 1986-, et al.
(författare)
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Evasion of Immune Surveillance in Low Oxygen Environments Enhances Candida albicans Virulence
- 2018
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Ingår i: mBio. - : American Society for Microbiology. - 2161-2129 .- 2150-7511. ; 9:6
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Tidskriftsartikel (refereegranskat)abstract
- Microbial colonizers of humans have evolved to adapt to environmental cues and to sense nutrient availability. Oxygen is a constantly changing environmental parameter in different host tissues and in different types of infection. We describe how Candida albicans, an opportunistic fungal pathogen, can modulate the host response under hypoxia and anoxia. We found that high infiltration of polymorphonuclear leukocytes (PMNs) to the site of infection contributes to a low oxygen milieu in a murine subdermal abscess. A persistent hypoxic environment did not affect viability or metabolism of PMNs. Under oxygen deprivation, however, infection with C. albicans disturbed specific PMN responses. PMNs were not able to efficiently phagocytose, produce ROS, or release extracellular DNA traps. Failure to launch an adequate response was caused by C. albicans cell wall masking of β-glucan upon exposure to low oxygen levels which hindered PAMP sensing by Dectin-1 on the surfaces of PMNs. This in turn contributed to immune evasion and enhanced fungal survival. The cell wall masking effect is prolonged by the accumulation of lactate produced by PMNs under low oxygen conditions. Finally, adaptation to oxygen deprivation increased virulence of C. albicans which we demonstrated using a Caenorhabditis elegans infection model.IMPORTANCESuccessful human colonizers have evolved mechanisms to bypass immune surveillance. Infiltration of PMNs to the site of infection led to the generation of a low oxygen niche. Exposure to low oxygen levels induced fungal cell wall masking, which in turn hindered pathogen sensing and antifungal responses by PMNs. The cell wall masking effect was prolonged by increasing lactate amounts produced by neutrophil metabolism under oxygen deprivation. In an invertebrate infection model, C. albicans was able to kill infected C. elegans nematodes within 2 days under low oxygen conditions, whereas the majority of uninfected controls and infected worms under normoxic conditions survived. These results suggest that C. albicans benefited from low oxygen niches to increase virulence. The interplay of C. albicans with innate immune cells under these conditions contributed to the overall outcome of infection. Adaption to low oxygen levels was in addition beneficial for C. albicans by reducing susceptibility to selected antifungal drugs. Hence, immunomodulation of host cells under low oxygen conditions could provide a valuable approach to improve current antifungal therapies.
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| 4. |
- Thunström Salzer, Anna, et al.
(författare)
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Assessment of Neutrophil Chemotaxis Upon G-CSF Treatment of Healthy Stem Cell Donors and in Allogeneic Transplant Recipients
- 2018
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Ingår i: Frontiers in Immunology. - : Frontiers Media S.A.. - 1664-3224. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Neutrophils are crucial for the human innate immunity and constitute the majority of leukocytes in circulation. Thus, blood neutrophil counts serve as a measure for the immune system's functionality. Hematological patients often have low neutrophil counts due to disease or chemotherapy. To increase neutrophil counts and thereby preventing infections in high-risk patients, recombinant G-CSF is widely used as adjunct therapy to stimulate the maturation of neutrophils. In addition, G-CSF is utilized to recruit stem cells (SCs) into the peripheral blood of SC donors. Still, the actual functionality of neutrophils resulting from G-CSF treatment remains insufficiently understood. We tested the ex vivo functionality of neutrophils isolated from blood of G-CSF-treated healthy SC donors. We quantified chemotaxis, oxidative burst, and phagocytosis before and after treatment and detected significantly reduced chemotactic activity upon G-CSF treatment. Similarly, in vitro treatment of previously untreated neutrophils with G-CSF led to reduced chemotactic activity. In addition, we revealed that this effect persists in the allogeneic SC recipients up to 4 weeks after neutrophil engraftment. Our data indicates that neutrophil quantity, as a sole measure of immunocompetence in high-risk patients should be considered cautiously as neutrophil functionality might be affected by the primary treatment.
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