| 1. |
- Engman, Jakob, et al.
(författare)
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Neisseria meningitidis Polynucleotide Phosphorylase Affects Aggregation, Adhesion, and Virulence
- 2016
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Ingår i: Infection and Immunity. - 0019-9567 .- 1098-5522. ; 84:5, s. 1501-1513
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Tidskriftsartikel (refereegranskat)abstract
- Neisseria meningitidis autoaggregation is an important step during attachment to human cells. Aggregation is mediated by type IV pili and can be modulated by accessory pilus proteins, such as PilX, and posttranslational modifications of the major pilus subunit PilE. The mechanisms underlying the regulation of aggregation remain poorly characterized. Polynucleotide phosphorylase ( PNPase) is a 3'-5' exonuclease that is involved in RNA turnover and the regulation of small RNAs. In this study, we biochemically confirm that NMC0710 is the N. meningitidis PNPase, and we characterize its role in N. meningitidis pathogenesis. We show that deletion of the gene encoding PNPase leads to hyperaggregation and increased adhesion to epithelial cells. The aggregation induced was found to be dependent on pili and to be mediated by excessive pilus bundling. PNPase expression was induced following bacterial attachment to human cells. Deletion of PNPase led to global transcriptional changes and the differential regulation of 469 genes. We also demonstrate that PNPase is required for full virulence in an in vivo model of N. meningitidis infection. The present study shows that PNPase negatively affects aggregation, adhesion, and virulence in N. meningitidis.
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| 2. |
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| 3. |
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| 4. |
- Sigurlásdóttir, Sara, et al.
(författare)
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Host cell-derived lactate functions as an effector molecule in Neisseria meningitidis microcolony dispersal
- 2017
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Ingår i: PLoS Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- The development of meningococcal disease, caused by the human pathogen Neisseria meningitidis, is preceded by the colonization of the epithelial layer in the nasopharynx. After initial adhesion to host cells meningococci form aggregates, through pilus-pilus interactions, termed microcolonies from which the bacteria later detach. Dispersal from microcolonies enables access to new colonization sites and facilitates the crossing of the cell barrier; however, this process is poorly understood. In this study, we used live-cell imaging to investigate the process of N. meningitidis microcolony dispersal. We show that direct contact with host cells is not required for microcolony dispersal, instead accumulation of a host-derived effector molecule induces microcolony dispersal. By using a host-cell free approach, we demonstrated that lactate, secreted from host cells, initiate rapid dispersal of microcolonies. Interestingly, metabolic utilization of lactate by the bacteria was not required for induction of dispersal, suggesting that lactate plays a role as a signaling molecule. Furthermore, Neisseria gonorrhoeae microcolony dispersal could also be induced by lactate. These findings reveal a role of host-secreted lactate in microcolony dispersal and virulence of pathogenic Neisseria.
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| 5. |
- Sigurlásdóttir, Sara, et al.
(författare)
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Deletion of D-Lactate Dehydrogenase A in Neisseria meningitidis Promotes Biofilm Formation Through Increased Autolysis and Extracellular DNA Release
- 2019
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Neisseria meningitidis is a Gram-negative bacterium that asymptomatically colonizes the human nasopharyngeal mucosa. Pilus-mediated initial adherence of N. meningitidis to the epithelial mucosa is followed by the formation of three-dimensional aggregates, called microcolonies. Dispersal from microcolonies contributes to the transmission of N. meningitidis across the epithelial mucosa. We have recently discovered that environmental concentrations of host cell-derived lactate influences N. meningitidis microcolony dispersal. Here, we examined the ability of N. meningitidis mutants deficient in lactate metabolism to form biofilms. A lactate dehydrogenease A (idhA) mutant had an increased level of biofilm formation. Deletion of IdhA increased the N. meningitidis cell surface hydrophobicity and aggregation. In this study, we used FAM20, which belongs to clonal complex ST-11 that forms biofilms independently of extracellular DNA (eDNA). However, treatment with DNase I abolished the increased biofilm formation and aggregation of the ldhA-delicient mutant, suggesting a critical role for eDNA. Compared to wild-type, the IdhA-deficient mutant exhibited an increased autolytic rate, with significant increases in the eDNA concentrations in the culture supernatants and in biofilms. Within the IdhA mutant biofilm, the transcription levels of the capsule, pilus, and bacterial lysis genes were downregulated, while norB, which is associated with anaerobic respiration, was upregulated. These findings suggest that the absence of IdhA in N. meningitidis promotes biofilm formation and aggregation through autolysis-mediated DNA release.
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| 6. |
- Sigurlásdóttir, Sara, 1985-
(författare)
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Influence of host and bacterial factors during Neisseria meningitidis colonization
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The human-restricted pathogen Neisseria meningitidis is a major cause of bacterial meningitis and sepsis worldwide. Colonization of the mucosal layer in the upper respiratory tract is essential to establish an asymptomatic carrier state and invasive disease. N. meningitidis encounters diverse environmental challenges during colonization and has evolved multiple strategies and virulence factors to survive and adapt within the host.Upon initial adhesion to the host epithelial cells, N. meningitidis forms pilus-mediated aggregates called microcolonies, which are characterized by interbacterial and host-cell interactions. Microcolonies promote long-term asymptomatic colonization within the host. However, the dispersal of single bacteria from microcolonies can help N. meningitidis to develop close contact with host cells and facilitate the invasion of mucosal surfaces or transmission to a new host.This thesis focuses on understanding how the interplay between the host, environment, and virulence factors influences N. meningitidis colonization. Paper I shows that the host-derived metabolite lactate induces rapid dispersal of N. meningitidis microcolonies. Further molecular characterization in Paper II revealed that lactate-induced dispersal is mediated by pilus retraction, occurs in a density-dependent manner, and is responsive to temperature. Paper III shows that the deletion of D-lactate dehydrogenase LdhA in N. meningitidis promotes aggregation and biofilm formation through an increase in the autolysis-mediated release of extracellular DNA. Finally, Paper IV examines the role of polynucleotide phosphorylase (PNPase) in the virulence of N. meningitidis. The deletion of PNPase resulted in a pilus-dependent increase in the aggregation and adhesion to epithelial cells. A PNPase mutant was growth deficient and highly attenuated in an in vivo mouse model. Transcriptional analysis revealed that PNPase plays a role as a major regulator in N. meningitidis.
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| 8. |
- Sigurlásdóttir, Sara, et al.
(författare)
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Lactate-Induced Dispersal of Neisseria meningitidis Microcolonies Is Mediated by Changes in Cell Density and Pilus Retraction and Is Influenced by Temperature Change
- 2021
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Ingår i: Infection and Immunity. - 0019-9567 .- 1098-5522. ; 89:10
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Tidskriftsartikel (refereegranskat)abstract
- Neisseria meningitidis is the etiologic agent of meningococcal meningitis and sepsis. Initial colonization of meningococci in the upper respiratory tract epithelium is crucial for disease development. The colonization occurs in several steps and expression of type IV pili (Tfp) is essential for both attachment and microcolony formation of encapsulated bacteria. Previously, we have shown that host-derived lactate induces synchronized dispersal of meningococcal microcolonies. In this study, we demonstrated that lactate-induced dispersal is dependent on bacterial concentration but not on the quorum-sensing system autoinducer-2 or the two-component systems NarP/NarQ, PilR/PilS, NtrY/NtrX, and MisR/MisS. Further, there were no changes in expression of genes related to assembly, elongation, retraction, and modification of Tfp throughout the time course of lactate induction. By using pilT and pptB mutants, however, we found that lactate-induced dispersal was dependent on PilT retraction but not on phosphoglycerol modification of Tfp even though the PptB activity was important for preventing reaggregation postdispersal. Furthermore, protein synthesis was required for lactate-induced dispersal. Finally, we found that at a lower temperature, lactate-induced dispersal was delayed and unsynchronized, and bacteria reformed microcolonies. We conclude that lactate-induced microcolony dispersal is dependent on bacterial concentration, PilT-dependent Tfp retraction, and protein synthesis and is influenced by environmental temperature.
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| 9. |
- Wassing, Gabriela M., et al.
(författare)
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DNA Blocks the Lethal Effect of Human Beta-Defensin 2 Against Neisseria meningitidis
- 2021
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Neisseria meningitidis is a gram-negative bacterium that often asymptomatically colonizes the human nasopharyngeal tract. These bacteria cross the epithelial barrier can cause life-threatening sepsis and/or meningitis. Antimicrobial peptides are one of the first lines of defense against invading bacterial pathogens. Human beta-defensin 2 (hBD2) is an antimicrobial peptide with broad antibacterial activity, although its mechanism of action is poorly understood. Here, we investigated the effect of hBD2 on N. meningitidis. We showed that hBD2 binds to and kills actively growing meningococcal cells. The lethal effect was evident after 2 h incubation with the peptide, which suggests a slow killing mechanism. Further, the membrane integrity was not changed during hBD2 treatment. Incubation with lethal doses of hBD2 decreased the presence of diplococci; the number and size of bacterial microcolonies/aggregates remained constant, indicating that planktonic bacteria may be more susceptible to the peptide. Meningococcal DNA bound hBD2 in mobility shift assays and inhibited the lethal effect of hBD2 in a dose-dependent manner both in suspension and biofilms, supporting the interaction between hBD2 and DNA. Taken together, the ability of meningococcal DNA to bind hBD2 opens the possibility that extracellular DNA due to bacterial lysis may be a means of N. meningitidis to evade immune defenses.
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