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  • Online Resource  (12)
  • American Society for Microbiology  (12)
  • 1
    Online Resource
    Online Resource
    Roles of PilC and PilE Proteins in Pilus-Mediated Adherence of Neisseria gonorrhoeae and Neisseria meningitidis to Human Erythrocytes and Endothelial and Epithelial Cells
    American Society for Microbiology ; 1999
    In:  Infection and Immunity Vol. 67, No. 2 ( 1999-02), p. 834-843
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 67, No. 2 ( 1999-02), p. 834-843
    Abstract: Unlike other type 4 pili, the neisserial pili consist of at least two distinct proteins, the highly variable major subunit PilE forming the pilus fiber and the tip-associated adhesin PilC. PilC protein purified either from gonococci or from Escherichia coli interacted with different human epithelial cell lines, primary epithelial and endothelial cells. The binding of PilC protein efficiently prevented the attachment of piliated Neisseria gonorrhoeae and Neisseria meningitidis to these cell types. Fluorescent beads coated with pili prepared from piliated wild-type N. gonorrhoeae also adhered to these cells, in contrast to beads coated with pili prepared from a piliated PilC-deficient mutant. In the latter case, the binding of fluorescent beads was restored after pretreatment of the pilus-loaded beads with purified PilC. Piliated wild-type N. gonorrhoeae , the piliated PilC-deficient mutant, and N. gonorrhoeae pili assembled in Pseudomonas aeruginosa agglutinated human erythrocytes, while nonpiliated gonococci did not. Consistently, purified PilC did not agglutinate or bind to human erythrocytes, suggesting that N. gonorrhoeae PilE is responsible for pilus-mediated hemagglutination.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.67.2.834-843.1999
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 1999
    detail.hit.zdb_id: 1483247-1
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  • 2
    Online Resource
    Online Resource
    Low-Phosphate-Dependent Invasion Resembles a General Way for Neisseria gonorrhoeae To Enter Host Cells
    American Society for Microbiology ; 2006
    In:  Infection and Immunity Vol. 74, No. 7 ( 2006-07), p. 4266-4273
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 74, No. 7 ( 2006-07), p. 4266-4273
    Abstract: Obligate human-pathogenic Neisseria gonorrhoeae expresses numerous variant surface proteins mediating adherence to and invasion of target cells. The invariant major outer membrane porin PorB of serotype A (P.IA) gonococci triggers invasion into Chang cells only if the medium is devoid of phosphate. Since gonococci expressing PorB IA are frequently isolated from patients with severe disseminating infections, the interaction initiated by the porin may be of major relevance for the development of this serious disease. Here, we investigated the low-phosphate-dependent invasion and compared it to the well-known pathways of entry initiated by Opa proteins. P.IA-triggered invasion requires clathrin-coated pit formation and the action of actin and Rho GTPases. However, in contrast to Opa-initiated invasion via heparan sulfate proteoglycans, microtubules, acidic sphingomyelinase, phosphatidylinositol 3-kinase, and myosin light chain kinase are not involved in this entry pathway. Nor are Src kinases required, as they are in invasion, e.g., via the CEACAM3 receptor. Invasion by PorB IA occurs in a wide spectrum of cell types, such as primary human epithelial and endothelial cells and in cancer cells of human and animal origin. Low-phosphate-dependent invasion is thus a pathway of gonococcal entry distinct from Opa-mediated invasion.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.00215-06
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2006
    detail.hit.zdb_id: 1483247-1
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  • 3
    Online Resource
    Online Resource
    Neisseria gonorrhoeae Porin Modifies the Oxidative Burst of Human Professional Phagocytes
    American Society for Microbiology ; 2000
    In:  Infection and Immunity Vol. 68, No. 11 ( 2000), p. 6215-6222
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 68, No. 11 ( 2000), p. 6215-6222
    Type of Medium: Online Resource
    ISSN: 1098-5522 , 0019-9567
    URL: Article
    DOI: 10.1128/.68.11.6215-6222.2000
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2000
    detail.hit.zdb_id: 1483247-1
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  • 4
    Online Resource
    Online Resource
    Intracellular Staphylococcus aureus Perturbs the Host Cell Ca 2+ Homeostasis To Promote Cell Death
    American Society for Microbiology ; 2020
    In:  mBio Vol. 11, No. 6 ( 2020-12-22)
    Details
    In: mBio, American Society for Microbiology, Vol. 11, No. 6 ( 2020-12-22)
    Abstract: The opportunistic human pathogen Staphylococcus aureus causes serious infectious diseases that range from superficial skin and soft tissue infections to necrotizing pneumonia and sepsis. While classically regarded as an extracellular pathogen, S. aureus is able to invade and survive within human cells. Host cell exit is associated with cell death, tissue destruction, and the spread of infection. The exact molecular mechanism employed by S. aureus to escape the host cell is still unclear. In this study, we performed a genome-wide small hairpin RNA (shRNA) screen and identified the calcium signaling pathway as being involved in intracellular infection. S. aureus induced a massive cytosolic Ca 2+ increase in epithelial host cells after invasion and intracellular replication of the pathogen. This was paralleled by a decrease in endoplasmic reticulum Ca 2+ concentration. Additionally, calcium ions from the extracellular space contributed to the cytosolic Ca 2+ increase. As a consequence, we observed that the cytoplasmic Ca 2+ rise led to an increase in mitochondrial Ca 2+ concentration, the activation of calpains and caspases, and eventually to cell lysis of S. aureus -infected cells. Our study therefore suggests that intracellular S. aureus disturbs the host cell Ca 2+ homeostasis and induces cytoplasmic Ca 2+ overload, which results in both apoptotic and necrotic cell death in parallel or succession. IMPORTANCE Despite being regarded as an extracellular bacterium, the pathogen Staphylococcus aureus can invade and survive within human cells. The intracellular niche is considered a hideout from the host immune system and antibiotic treatment and allows bacterial proliferation. Subsequently, the intracellular bacterium induces host cell death, which may facilitate the spread of infection and tissue destruction. So far, host cell factors exploited by intracellular S. aureus to promote cell death are only poorly characterized. We performed a genome-wide screen and found the calcium signaling pathway to play a role in S. aureus invasion and cytotoxicity. The intracellular bacterium induces a cytoplasmic and mitochondrial Ca 2+ overload, which results in host cell death. Thus, this study first showed how an intracellular bacterium perturbs the host cell Ca 2+ homeostasis.
    Type of Medium: Online Resource
    ISSN: 2161-2129 , 2150-7511
    URL: Article
    DOI: 10.1128/mBio.02250-20
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2020
    detail.hit.zdb_id: 2557172-2
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  • 5
    Online Resource
    Online Resource
    Central Role of Sibling Small RNAs NgncR_162 and NgncR_163 in Main Metabolic Pathways of Neisseria gonorrhoeae
    American Society for Microbiology ; 2023
    In:  mBio Vol. 14, No. 1 ( 2023-02-28)
    Details
    In: mBio, American Society for Microbiology, Vol. 14, No. 1 ( 2023-02-28)
    Abstract: Small bacterial regulatory RNAs (sRNAs) have been implicated in the regulation of numerous metabolic pathways. In most of these studies, sRNA-dependent regulation of mRNAs or proteins of enzymes in metabolic pathways has been predicted to affect the metabolism of these bacteria. However, only in a very few cases has the role in metabolism been demonstrated. Here, we performed a combined transcriptome and metabolome analysis to define the regulon of the sibling sRNAs NgncR_162 and NgncR_163 (NgncR_162/163) and their impact on the metabolism of Neisseria gonorrhoeae . These sRNAs have been reported to control genes of the citric acid and methylcitric acid cycles by posttranscriptional negative regulation. By transcriptome analysis, we now expand the NgncR_162/163 regulon by several new members and provide evidence that the sibling sRNAs act as both negative and positive regulators of target gene expression. Newly identified NgncR_162/163 targets are mostly involved in transport processes, especially in the uptake of glycine, phenylalanine, and branched-chain amino acids. NgncR_162/163 also play key roles in the control of serine-glycine metabolism and, hence, probably affect biosyntheses of nucleotides, vitamins, and other amino acids via the supply of one-carbon (C 1 ) units. Indeed, these roles were confirmed by metabolomics and metabolic flux analysis, which revealed a bipartite metabolic network with glucose degradation for the supply of anabolic pathways and the usage of amino acids via the citric acid cycle for energy metabolism. Thus, by combined deep RNA sequencing (RNA-seq) and metabolomics, we significantly extended the regulon of NgncR_162/163 and demonstrated the role of NgncR_162/163 in the regulation of central metabolic pathways of the gonococcus. IMPORTANCE Neisseria gonorrhoeae is a major human pathogen which infects more than 100 million people every year. An alarming development is the emergence of gonococcal strains that are resistant against virtually all antibiotics used for their treatment. Despite the medical importance and the vanishing treatment options of gonococcal infections, the bacterial metabolism and its regulation have been only weakly defined until today. Using RNA-seq, metabolomics, and 13 C-guided metabolic flux analysis, we here investigated the gonococcal metabolism and its regulation by the previously studied sibling sRNAs NgncR_162/163. The results demonstrate the regulation of transport processes and metabolic pathways involved in the biosynthesis of nucleotides, vitamins, and amino acids by NgncR_162/163. In particular, the combination of transcriptome and metabolic flux analyses provides a heretofore unreached depth of understanding the core metabolic pathways and their regulation by the neisserial sibling sRNAs. This integrative approach may therefore also be suitable for the functional analysis of a growing number of other bacterial metabolic sRNA regulators.
    Type of Medium: Online Resource
    ISSN: 2150-7511
    URL: Article
    DOI: 10.1128/mbio.03093-22
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2023
    detail.hit.zdb_id: 2557172-2
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  • 6
    Online Resource
    Online Resource
    Neisseria gonorrhoeae Porin Modifies the Oxidative Burst of Human Professional Phagocytes
    American Society for Microbiology ; 2000
    In:  Infection and Immunity Vol. 68, No. 11 ( 2000-11), p. 6215-6222
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 68, No. 11 ( 2000-11), p. 6215-6222
    Abstract: A hallmark of infection with the gram-negative bacterium Neisseria gonorrhoeae is the local infiltration and subsequent activation of polymorphonuclear neutrophils. Several gonococcal outer membrane proteins are involved in the interaction with and the activation of these phagocytes, including gonococcal porin, the most abundant protein in the outer membrane. Previous work suggests that this porin plays a role in various cellular processes, including inhibiting neutrophils activation and phagosome maturation in professional phagocytes. Here we investigated the ability of porin to modify the oxidative metabolism of human peripheral blood neutrophils and monocytes in response to particulate stimuli (including live gonococci) and soluble agents. The activation of the oxidative metabolism was determined by chemiluminescence amplified with either luminol or lucigenin. We found that treatment of the phagocytes with porin inhibits the release of reactive oxygen species measured as luminol-enhanced chemiluminescence in response to zymosan, latex particles, and gonococci. The engulfment of these particles was not, however, affected by porin treatment. Similar effects of porin on the chemiluminescence response were observed in cytochalasin B-treated neutrophils exposed to the soluble chemotactic peptide N -formylmethionyl-leucyl-phenylalanine. This indicates that porin selectively inhibits granule fusion with those cellular membranes that are in direct contact with porin, namely, the phagosomal and plasma membranes. This porin-induced downregulation of oxidative metabolism may be a potent mechanism by which gonococci modulate oxygen-dependent reactions by activated phagocytes at inflammation sites.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.68.11.6215-6222.2000
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2000
    detail.hit.zdb_id: 1483247-1
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  • 7
    Online Resource
    Online Resource
    Epithelial Cells Infected with Chlamydophila pneumoniae ( Chlamydia pneumoniae ) Are Resistant to Apoptosis
    American Society for Microbiology ; 2001
    In:  Infection and Immunity Vol. 69, No. 12 ( 2001-12), p. 7880-7888
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 69, No. 12 ( 2001-12), p. 7880-7888
    Abstract: The obligate intracellular pathogen Chlamydophila pneumoniae ( Chlamydia pneumoniae ) initiates infections in humans via the mucosal epithelia of the respiratory tract. Here, we report that epithelial cells infected with C. pneumoniae are resistant to apoptosis induced by treatment with drugs or by death receptor ligation. The induction of protection from apoptosis depended on the infection conditions since only cells containing large inclusions were protected. The underlying mechanism of infection-induced apoptosis resistance probably involves mitochondria, the major integrators of apoptotic signaling. In the infected cells, mitochondria did not respond to apoptotic stimuli by the release of apoptogenic factors required for the activation of caspases. Consequently, active caspase-3 was absent in infected cells. Our data suggest a direct modulation of apoptotic pathways in epithelial cells by C. pneumoniae .
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.69.12.7880-7888.2001
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2001
    detail.hit.zdb_id: 1483247-1
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  • 8
    Online Resource
    Online Resource
    Modulation of Host Cell Metabolism by Chlamydia trachomatis
    American Society for Microbiology ; 2019
    In:  Microbiology Spectrum Vol. 7, No. 3 ( 2019-05-31)
    Details
    In: Microbiology Spectrum, American Society for Microbiology, Vol. 7, No. 3 ( 2019-05-31)
    Abstract: Propagation of the intracellular bacterial pathogen Chlamydia trachomatis is strictly bound to its host cells. The bacterium has evolved by minimizing its genome size at the cost of being completely dependent on its host. Many of the vital nutrients are synthesized only by the host, and this has complex implications. Recent advances in loss-of-function analyses and the metabolomics of human infected versus noninfected cells have provided comprehensive insight into the molecular changes that host cells undergo during the stage of infection. Strikingly, infected cells acquire a stage of high metabolic activity, featuring distinct aspects of the Warburg effect, a condition originally assigned to cancer cells. This condition is characterized by aerobic glycolysis and an accumulation of certain metabolites, altogether promoting the synthesis of crucial cellular building blocks, such as nucleotides required for DNA and RNA synthesis. The altered metabolic program enables tumor cells to rapidly proliferate as well as C. trachomatis -infected cells to feed their occupants and still survive. This program is largely orchestrated by a central control board, the tumor suppressor protein p53. Its downregulation in C. trachomatis -infected cells or mutation in cancer cells not only alters the metabolic state of cells but also conveys the prevention of programmed cell death involving mitochondrial pathways. While this points toward common features in the metabolic reprogramming of infected and rapidly proliferating cells, it also forwards novel treatment options against chronic intracellular infections involving well-characterized host cell targets and established drugs.
    Type of Medium: Online Resource
    ISSN: 2165-0497
    URL: Article
    DOI: 10.1128/microbiolspec.BAI-0012-2019
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2019
    detail.hit.zdb_id: 2807133-5
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  • 9
    Online Resource
    Online Resource
    Long Noncoding RNA SSR42 Controls Staphylococcus aureus Alpha-Toxin Transcription in Response to Environmental Stimuli
    American Society for Microbiology ; 2018
    In:  Journal of Bacteriology Vol. 200, No. 22 ( 2018-11-15)
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 200, No. 22 ( 2018-11-15)
    Abstract: Staphylococcus aureus is a human pathogen causing a variety of diseases by versatile expression of a large set of virulence factors that most prominently features the cytotoxic and hemolytic pore-forming alpha-toxin. Expression of alpha-toxin is regulated by an intricate network of transcription factors. These include two-component systems sensing quorum and environmental signals as well as regulators reacting to the nutritional status of the pathogen. We previously identified the repressor of surface proteins (Rsp) as a virulence regulator. Acute cytotoxicity and hemolysis are strongly decreased in rsp mutants, which are characterized by decreased transcription of toxin genes as well as loss of transcription of a 1,232-nucleotide (nt)-long noncoding RNA (ncRNA), SSR42. Here, we show that SSR42 is the effector of Rsp in transcription regulation of the alpha-toxin gene, hla . SSR42 transcription is enhanced after exposure of S. aureus to subinhibitory concentrations of oxacillin which thus leads to an SSR42-dependent increase in hemolysis. Aside from Rsp, SSR42 transcription is under the control of additional global regulators, such as CodY, AgrA, CcpE, and σ B , but is positioned upstream of the two-component system SaeRS in the regulatory cascade leading to alpha-toxin production. Thus, alpha-toxin expression depends on two long ncRNAs, SSR42 and RNAIII, which control production of the cytolytic toxin on the transcriptional and translational levels, respectively, with SSR42 as an important regulator of SaeRS-dependent S. aureus toxin production in response to environmental and metabolic signals. IMPORTANCE Staphylococcus aureus is a major cause of life-threatening infections. The bacterium expresses alpha-toxin, a hemolysin and cytotoxin responsible for many of the pathologies of S. aureus . Alpha-toxin production is enhanced by subinhibitory concentrations of antibiotics. Here, we show that this process is dependent on the long noncoding RNA, SSR42. Further, SSR42 itself is regulated by several global regulators, thereby integrating environmental and nutritional signals that modulate hemolysis of the pathogen.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/JB.00252-18
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2018
    detail.hit.zdb_id: 1481988-0
    SSG: 12
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  • 10
    Online Resource
    Online Resource
    Septins Arrange F-Actin-Containing Fibers on the Chlamydia trachomatis Inclusion and Are Required for Normal Release of the Inclusion by Extrusion
    American Society for Microbiology ; 2014
    In:  mBio Vol. 5, No. 5 ( 2014-10-31)
    Details
    In: mBio, American Society for Microbiology, Vol. 5, No. 5 ( 2014-10-31)
    Abstract: Chlamydia trachomatis is a frequent bacterial pathogen throughout the world, causing mostly eye and genital infections. C. trachomatis can develop only inside host cells; it multiplies inside a membranous vacuole in the cytosol, termed an inclusion. The inclusion is covered by cytoskeletal “coats” or “cages,” whose organization and function are poorly understood. We here report that a relatively little-characterized group of proteins, septins, is required to organize actin fibers on the inclusion and probably through actin the release of the inclusion. Septins are a group of GTP-binding proteins that can organize into heteromeric complexes and then into large filaments. Septins have previously been found to be involved in the interaction of the cell with bacteria in the cytosol. Our observation that they also organize a reaction to bacteria living in vacuoles suggests that they have a function in the recognition of foreign compartments by a parasitized human cell.
    Type of Medium: Online Resource
    ISSN: 2161-2129 , 2150-7511
    URL: Article
    DOI: 10.1128/mBio.01802-14
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2014
    detail.hit.zdb_id: 2557172-2
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