| 1. |
- von Beek, Christopher, et al.
(författare)
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A two-step activation mechanism enables mast cells to differentiate their response between extracellular and invasive enterobacterial infection
- 2024
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Mast cells localize to mucosal tissues and contribute to innate immune defense against infection. How mast cells sense, differentiate between, and respond to bacterial pathogens remains a topic of ongoing debate. Using the prototype enteropathogen Salmonella Typhimurium (S.Tm) and other related enterobacteria, here we show that mast cells can regulate their cytokine secretion response to distinguish between extracellular and invasive bacterial infection. Tissue-invasive S.Tm and mast cells colocalize in the mouse gut during acute Salmonella infection. Toll-like Receptor 4 (TLR4) sensing of extracellular S.Tm, or pure lipopolysaccharide, causes a modest induction of cytokine transcripts and proteins, including IL-6, IL-13, and TNF. By contrast, type-III-secretion-system-1 (TTSS-1)-dependent S.Tm invasion of both mouse and human mast cells triggers rapid and potent inflammatory gene expression and >100-fold elevated cytokine secretion. The S.Tm TTSS-1 effectors SopB, SopE, and SopE2 here elicit a second activation signal, including Akt phosphorylation downstream of effector translocation, which combines with TLR activation to drive the full-blown mast cell response. Supernatants from S.Tm-infected mast cells boost macrophage survival and maturation from bone-marrow progenitors. Taken together, this study shows that mast cells can differentiate between extracellular and host-cell invasive enterobacteria via a two-step activation mechanism and tune their inflammatory output accordingly.
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| 2. |
- von Beek, Christopher, et al.
(författare)
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A two-step activation mechanism enables mast cells to differentiate their response between extracellular and invasive enterobacterial infection
- 2024
-
Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 15:1
-
Tidskriftsartikel (refereegranskat)abstract
- Mast cells localize to mucosal tissues and contribute to innate immune defense against infection. How mast cells sense, differentiate between, and respond to bacterial pathogens remains a topic of ongoing debate. Using the prototype enteropathogen Salmonella Typhimurium (S.Tm) and other related enterobacteria, here we show that mast cells can regulate their cytokine secretion response to distinguish between extracellular and invasive bacterial infection. Tissue-invasive S.Tm and mast cells colocalize in the mouse gut during acute Salmonella infection. Toll-like Receptor 4 (TLR4) sensing of extracellular S.Tm, or pure lipopolysaccharide, causes a modest induction of cytokine transcripts and proteins, including IL-6, IL-13, and TNF. By contrast, type-III-secretion-system-1 (TTSS-1)-dependent S.Tm invasion of both mouse and human mast cells triggers rapid and potent inflammatory gene expression and >100-fold elevated cytokine secretion. The S.Tm TTSS-1 effectors SopB, SopE, and SopE2 here elicit a second activation signal, including Akt phosphorylation downstream of effector translocation, which combines with TLR activation to drive the full-blown mast cell response. Supernatants from S.Tm-infected mast cells boost macrophage survival and maturation from bone-marrow progenitors. Taken together, this study shows that mast cells can differentiate between extracellular and host-cell invasive enterobacteria via a two-step activation mechanism and tune their inflammatory output accordingly.
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| 3. |
- Andersson, Kerstin, et al.
(författare)
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Yersinia pseudotuberculosis-induced calcium signaling in neutrophils is blocked by the virulence effector YopH
- 1999
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Ingår i: Infection and Immunity. - 0019-9567 .- 1098-5522. ; 67:5, s. 2567-2574
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Tidskriftsartikel (refereegranskat)abstract
- Pathogenic species of the genus Yersinia evade the bactericidal functions of phagocytes. This evasion is mediated through their virulence effectors, Yops, which act within target cells. In this study we investigated the effect of Yersinia pseudotuberculosis on Ca 2+ signaling in polymorphonuclear neutrophils. The intracellular free calcium concentration in single adherent human neutrophils was monitored during bacterial infection and, in parallel, the encounter between the bacteria and cells was observed. When a plasmid-cured strain was used for infection, adherence of a single bacterium to the cellular surface induced a β 1 integrin-dependent transient increase in the intracellular concentration of free calcium. This was, however, not seen with Yop-expressing wild-type bacteria, which adhered to the cell surface without generating any Ca 2+ signal. Importantly, the overall Ca 2+ homeostasis was not affected by the wild-type strain; the Ca 2+ signal mediated by the G-protein-coupled formyl-methionyl-leucyl- phenylalanine receptor was still functioning. Hence, the blocking effect was restricted to certain receptors and their signaling pathways. The use of different Yop mutant strains revealed that the protein tyrosine phosphatase YopH was responsible for the inhibition. This virulence determinant has previously been implicated in very rapid Yersinia-mediated effects on target cells as the key effector in the blockage of phagocytic uptake. The present finding, that Y. pseudotuberculosis, via YopH, specifically inhibits a self- induced immediate-early Ca 2+ signal in neutrophils, offers more-detailed information concerning the effectiveness of this virulence effector and implies an effect on Ca 2+-dependent, downstream signals.
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| 4. |
- Avican, Kemal, et al.
(författare)
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RNA atlas of human bacterial pathogens uncovers stress dynamics linked to infection
- 2021
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial processes necessary for adaption to stressful host environments are potential targets for new antimicrobials. Here, we report large-scale transcriptomic analyses of 32 human bacterial pathogens grown under 11 stress conditions mimicking human host environments. The potential relevance of the in vitro stress conditions and responses is supported by comparisons with available in vivo transcriptomes of clinically important pathogens. Calculation of a probability score enables comparative cross-microbial analyses of the stress responses, revealing common and unique regulatory responses to different stresses, as well as overlapping processes participating in different stress responses. We identify conserved and species-specific ‘universal stress responders’, that is, genes showing altered expression in multiple stress conditions. Non-coding RNAs are involved in a substantial proportion of the responses. The data are collected in a freely available, interactive online resource (PATHOgenex).
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| 5. |
- Bergonzini, Anna, 1990-
(författare)
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Effects of bacterial genotoxins on immune modulation, chronic inflammation and cancer development
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The intestinal microbiome of Inflammatory Bowel Disease and colorectal cancer patients is enriched in genotoxin-producing bacteria, which cause DNA damage in the host cells.Genotoxins have recently been identified as a novel family of effectors produced by pathogenic and commensal bacteria. At present, only three types of bacterial genotoxins have been identified: colibactin, produced by some Escherichia coli strains; cytolethal distending toxins, produced by several Gram-negative pathogens; and the typhoid toxin, produced by Salmonella enterica serovar Typhi.Exposure to high toxin doses activates the classical DNA damage response, which consequently blocks proliferation and eventually induces death in mammalian cells. However, exposure to low toxin doses has shown to promote classical signs of carcinogenesis in vitro, such as cell survival and acquisition of genomic instability. Despite an extensive characterization of their mode of action in vitro, we have a poor understanding of genotoxins´ role in chronic infection and, considering the genotoxic potential, of their carcinogenic capacity. To investigate further the role played by the genotoxins, we focused specifically on Salmonella Typhi, since it is the only genotoxin-producing bacterium that induces a chronic infection associated with increased risk of tumor development in humans. The results presented in this thesis show that these unusual bacterial effectors are not classical toxins, but rather act as immunomodulators, highlighting a complex and tissue-specific crosstalk between two highly conserved stress responses: the immune response and the DNA damage response. Our data indicate that the impact of genotoxin-producing bacteria on the modulation of the host mucosal response is still poorly characterized and suggest that the host-microbe interaction and the tissue microenvironment are the key players in determining the outcome of the infection and the toxin carcinogenic potential.
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| 6. |
- Fernández, Leyden, et al.
(författare)
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Co-PATHOgenex web application for assessing complex stress responses in pathogenic bacteria
- 2024
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Ingår i: Microbiology Spectrum. - : American Society for Microbiology. - 2165-0497. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Pathogenic bacteria encounter various stressors while residing in the host. They respond through intricate mechanisms of gene expression regulation, ensuring their survival and adaptation. Understanding how bacteria adapt to different stress conditions through regulatory processes of specific genes requires exploring complex transcriptional responses using gene co-expression networks. We employed a large transcriptome data set comprising 32 diverse human bacterial pathogens exposed to the same 11 host-mimicking stress conditions. Using the weighted gene co-expression network analysis algorithm, we generated bacterial gene co-expression networks. By associating modular eigengene expression with specific stress conditions, we identified gene co-expression modules and stress-specific stimulons, including genes with unique expression patterns under specific stress conditions. Suggesting a new potential role of the frm operon in responding to bile stress in enteropathogenic bacteria demonstrates the effectiveness of our approach. We also revealed the regulation of streptolysin S genes, involved in the production, processing, and export of streptolysin S, a toxin responsible for the beta-hemolytic phenotype of group A Streptococcus. In a comparative analysis of stress responses in three Escherichia coli strains from the core transcriptome, we revealed shared and unique expression patterns across the strains, offering insights into convergent and divergent stress responses. To help researchers perform similar analyses, we created the user-friendly web application Co-PATHOgenex. This tool aids in deepening our understanding of bacterial adaptation to stress conditions and in deciphering complex transcriptional responses of bacterial pathogens.IMPORTANCEUnveiling gene co-expression networks in bacterial pathogens has the potential for gaining insights into their adaptive strategies within the host environment. Here, we developed Co-PATHOgenex, an interactive and user-friendly web application that enables users to construct networks from gene co-expressions using custom-defined thresholds (https://avicanlab.shinyapps.io/copathogenex/). The incorporated search functions and visualizations within the tool simplify the usage and facilitate the interpretation of the analysis output. Co-PATHOgenex also includes stress stimulons for various bacterial species, which can help identify gene products not previously associated with a particular stress condition. Unveiling gene co-expression networks in bacterial pathogens has the potential for gaining insights into their adaptive strategies within the host environment. Here, we developed Co-PATHOgenex, an interactive and user-friendly web application that enables users to construct networks from gene co-expressions using custom-defined thresholds (https://avicanlab.shinyapps.io/copathogenex/). The incorporated search functions and visualizations within the tool simplify the usage and facilitate the interpretation of the analysis output. Co-PATHOgenex also includes stress stimulons for various bacterial species, which can help identify gene products not previously associated with a particular stress condition.
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| 7. |
- Gurung, Jyoti Mohan, 1984-
(författare)
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Coordinating type III secretion system biogenesis in Yersinia pseudotuberculosis
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Various Gram-negative bacteria utilize type III secretion system (T3SS) to deliver effectors into eukaryotic host cells and establish mutualistic or pathogenic interactions. An example is the Ysc-Yop T3SS of pathogenic Yersinia species. The T3SS resembles a molecular syringe with a wide cylindrical membrane-spanning basal body that scaffolds a hollow extracellular needle with a pore-forming translocon complex crowned at the needle tip. Together they form a continuous conduit between bacteria and host cells that allow delivery of effector proteins. Dedicated actions of cytoplasmic chaperones, regulators and components of the cytoplasmic complex orchestrates hierarchical assembly of T3SS. On the basis of secretion hierarchy, proteins can be categorized as ‘early’ needle complex proteins, ‘middle’ translocators and ‘late’ Yop effectors. However, how the system recognizes, prepares and mediates temporal delivery of T3S substrates is not fully understood. Herein, we have investigated the roles of YscX and YscY (present specifically in the Ysc family of T3SS), as well as YopN-TyeA (broadly distributed among T3SS families) to provide a better understanding of some of the molecular mechanisms governing spatiotemporal control of T3SS assembly.Despite reciprocal YscX-YscY binary and YscX-YscY-SctV ternary interactions between the member proteins, functional interchangeability in Yersinia was not successful. This revealed YscX and YscY must perform functions unique to Yersinia T3SS. Defined domain swapping and site-directed mutagenesis identified two highly conserved cysteine residues important for YscX function. Moreover, the N-terminal region of YscX harboured an independent T3S signal. Manipulating the YscX N-terminus by exchanging it with equivalent secretion signals from different T3S substrates abrogated T3S activity. This was explained by the need for the YscX N-terminus to correctly localize and/or assemble the ‘early’ SctI inner adapter and SctF needle protein. Therefore, N-terminal YscX performs dual functions; one as a secretion signal and the other as a structural signal to control early stage assembly of T3SS.In Ysc-Yop T3SS, YopN-TyeA complex is involved in the later stage of T3SS assembly, inhibiting Yops secretion until host cell contact is achieved. Analysis of the YopN C-terminus identified a specific domain stretching 279-287 critical for regulating Ysc-Yop T3SS activity. The regulation was mediated by specific hydrophobic contacts between W279 of YopN and F8 of TyeA.In conclusion, this work has provided novel molecular mechanisms regarding the spatiotemporal assembly of T3SS. While the N-terminal region of YscX contributes to the early stage of T3SS assembly, the C-terminal region of YopN is critical for regulating Ysc-Yop activity at a later stage of T3SS assembly.
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| 8. |
- Lindell, Kristoffer, 1979-, et al.
(författare)
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Lipopolysaccharide O-Antigen Prevents Phagocytosis of Vibrio anguillarum by Rainbow Trout (Oncorhynchus mykiss) Skin Epithelial Cells
- 2012
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Ingår i: PLOS ONE. - San Francisco : Public Library of Science. - 1932-6203. ; 7:5, s. e37678-
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Tidskriftsartikel (refereegranskat)abstract
- Colonization of host tissues is a first step taken by many pathogens during the initial stages of infection. Despite the impact of bacterial disease on wild and farmed fish, only a few direct studies have characterized bacterial factors required for colonization of fish tissues. In this study, using live-cell and confocal microscopy, rainbow trout skin epithelial cells, the main structural component of the skin epidermis, were demonstrated to phagocytize bacteria. Mutant analyses showed that the fish pathogen Vibrio anguillarum required the lipopolysaccharide O-antigen to evade phagocytosis and that O-antigen transport required the putative wzm-wzt-wbhA operon, which encodes two ABC polysaccharide transporter proteins and a methyltransferase. Pretreatment of the epithelial cells with mannose prevented phagocytosis of V. anguillarum suggesting that a mannose receptor is involved in the uptake process. In addition, the O-antigen transport mutants could not colonize the skin but they did colonize the intestines of rainbow trout. The O-antigen polysaccharides were also shown to aid resistance to the antimicrobial factors, lysozyme and polymyxin B. In summary, rainbow trout skin epithelial cells play a role in the fish innate immunity by clearing bacteria from the skin epidermis. In defense, V. anguillarum utilizes O-antigen polysaccharides to evade phagocytosis by the epithelial cells allowing it to colonize rapidly fish skin tissues.
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| 9. |
- Mahmud, A. K. M. Firoj, et al.
(författare)
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A core transcriptional response for biofilm formation by Y. pseudotuberculosis
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Previous transcriptional profiling of the enteropathogen Yersinia pseudotuberculosis during persistent stages of colonisation of mouse cecal lymphoid follicles indicated the possible involvement of biofilm in infection maintenance. Not much is known about the mechanisms responsible for biofilm formation by this pathogen, and most current knowledge is based on results of experiments conducted using the related Y. pestis pathogen that forms biofilm in the flea gut. In this study, we performed transcriptional profiling of Y. pseudotuberculosis in biofilms from different biofilm-inducing conditions, bile exposure, amino acid deprivation and in vivo mimicking conditions with and without oxygen. The comparison of differential expression of genes in biofilm versus planktonic bacteria showed a set of 54 core genes that were similarly regulated, independent of inducing condition. This set included many genes that were previously shown to be associated with biofilms, such as hutG, hsmF, hmsT and cpxP that were upregulated and other genes such as hmsP and rfaH that were downregulated. There were also novel biofilm-associated genes, including genes encoding hypothetical proteins. To identify the genes involved in inducing biofilm formation, the gene expression of bacteria during an early initial phase when biofilm starts to form after induction by bile or amino acid depletion was determined. Comparisons of the resulting gene expression profiles with the profiles of non-induced bacteria incubated for the same period of time showed a set of core genes associated with early biofilm formation. This set included genes involved in quorum sensing, pili biogenesis and genes indicative of a potential metabolic shift involving nitrogen utilisation. Genes encoding components of sugar phosphotransferase systems were also upregulated during biofilm induction. Assays of biofilm formation by bacteria deleted of some of these core genes showed that strains lacking hpr and luxS, which are known to be important for functional sugar phosphotransferase systems and quorum sensing, as well as glnL encoding a sensory histidine kinase were most negatively affected. Most of the deletion mutant strains tested were affected, but the effect was less severe, suggesting high levels of redundancy in the pathways involved in biofilm formation by this pathogen.
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| 10. |
- Mahmud, A. K. M. Firoj, et al.
(författare)
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Genome-Scale Mapping Reveals Complex Regulatory Activities of RpoN in Yersinia pseudotuberculosis
- 2020
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Ingår i: mSystem. - 2379-5077. ; 5:6
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Tidskriftsartikel (refereegranskat)abstract
- RpoN, an alternative sigma factor commonly known as σ54, is implicated in persistent stages of Yersinia pseudotuberculosis infections in which genes associated with this regulator are upregulated. We here combined phenotypic and genomic assays to provide insight into its role and function in this pathogen. RpoN was found essential for Y. pseudotuberculosis virulence in mice, and in vitro functional assays showed that it controls biofilm formation and motility. Mapping genome-wide associations of Y. pseudotuberculosis RpoN using chromatin immunoprecipitation coupled with next-generation sequencing identified an RpoN binding motif located at 103 inter- and intragenic sites on both sense and antisense strands. Deletion of rpoN had a large impact on gene expression, including downregulation of genes encoding proteins involved in flagellar assembly, chemotaxis, and quorum sensing. There were also clear indications of cross talk with other sigma factors, together with indirect effects due to altered expression of other regulators. Matching differential gene expression with locations of the binding sites implicated around 130 genes or operons potentially activated or repressed by RpoN. Mutagenesis of selected intergenic binding sites confirmed both positive and negative regulatory effects of RpoN binding. Corresponding mutations of intragenic sense sites had less impact on associated gene expression. Surprisingly, mutating intragenic sites on the antisense strand commonly reduced expression of genes carried by the corresponding sense strand.
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