Refine
Has Fulltext
- yes (149) (remove)
Is part of the Bibliography
- yes (149)
Year of publication
Document Type
- Journal article (128)
- Doctoral Thesis (20)
- Other (1)
Language
- English (149) (remove)
Keywords
- Neisseria meningitidis (21)
- Echinococcus (10)
- Fuchsbandwurm (6)
- Tanzania (6)
- meningococcal disease (6)
- Aspergillus (4)
- Germany (4)
- antimicrobial resistance (4)
- infection (4)
- inflammation (4)
- neisseria meningitidis (4)
- stem cells (4)
- COVID-19 (3)
- Insulin (3)
- MLST (3)
- MRSA (3)
- Meningitis (3)
- Neisseria gonorrhoeae (3)
- SARS-CoV-2 (3)
- Serotonin (3)
- meningitis (3)
- multilocularis (3)
- ARONJ (2)
- Apoptosis (2)
- Aspergillus fumigatus (2)
- BDG (2)
- Brain endothelial cells (2)
- C5aR1 (2)
- Candida auris (2)
- Echinococcosis (2)
- Fusarium (2)
- Genregulation (2)
- Group B Streptococcus (2)
- HBMEC (2)
- Haemophilus influenzae (2)
- Helicobacter pylori (2)
- Komplement <Immunologie> (2)
- MITE (2)
- Meningococci (2)
- Rhizopus (2)
- Sphingolipide (2)
- Stem cell (2)
- Tapeworm (2)
- Ureaplasma parvum (2)
- Ureaplasma urealyticum (2)
- alveolar echinococcosis (2)
- antigen (2)
- antigen testing (2)
- antimicrobial stewardship (2)
- bacteria (2)
- bacterial meningitis (2)
- bacterial pathogens (2)
- benzimidazole (2)
- beta-D-glucan (2)
- blood–brain barrier (2)
- brain endothelial cells (2)
- candidemia (2)
- chemotherapy (2)
- children (2)
- colonization (2)
- comparative genomics (2)
- dendritic cells (2)
- diagnosis (2)
- echinococcus multilocularis (2)
- epidemiology (2)
- flatworm (2)
- galactomannan (2)
- gene conversion (2)
- gene expression (2)
- genome sequencing (2)
- granulocytes (2)
- haemophilus influenzae (2)
- homologous recombination (2)
- host-pathogen interaction (2)
- immunology (2)
- infection control (2)
- innate immunity (2)
- men who have sex with men (2)
- microbiology (2)
- neuroinflammation (2)
- neutrophils (2)
- osteonecrosis of the jaw (2)
- osteoradionecrosis (2)
- outer membrane protein (2)
- pathogens (2)
- platyhelminthes (2)
- sepsis (2)
- serology (2)
- sphingolipids (2)
- surgical site infection (2)
- tapeworm (2)
- transcriptome (2)
- 5-methyl cytosine (1)
- Abl (1)
- Acetylated tubulin (1)
- Acinetobacter baumannii (1)
- Adhäsine (1)
- Alkaline phosphatase (1)
- Alternaria (1)
- Anaphylatoxine (1)
- Anaphylatoxinrezeptoren (1)
- Argonaute (1)
- Ascaris lumbricoides (1)
- AurisID (1)
- B neisseria meningitidis (1)
- BacT/ALERT (1)
- Bacterial meningitis (1)
- Bakterielle Hirnhautentzündung (1)
- Bakterielle Infektion (1)
- Bakterien (1)
- Bandwürmer (1)
- Basigin (1)
- Benzimidazolderivate (1)
- Benzimidazoles (1)
- Biohazard (1)
- Blut-Hirn-Schranke (1)
- Blut-Liquor-Schranke (1)
- Brugia Malayi (1)
- C-reactive protein (1)
- C3a (1)
- C3aR (1)
- C5a (1)
- C5aR2 (1)
- CCL3 (1)
- CCL4 (1)
- CCL5 (1)
- CD147 (1)
- COVID-19 testing (1)
- COVID‐19 (1)
- CPG binding domain (1)
- Calibration (1)
- Cancer treatment (1)
- Candida albicans (1)
- Candida lusitaniae (1)
- Caspase (1)
- Ceramide (1)
- Cestoda (1)
- Cestoda Taeniidae (1)
- Cestode (1)
- Chagas disease (1)
- Chemotherapie (1)
- Chemotherapy (1)
- Circinella (1)
- Clinical prediction rule (1)
- Colombia (1)
- Colonization (1)
- Community-acquired methicillin-resistant Staphylococcus aureus (1)
- Cyclo-AMP (1)
- DNA methylation (1)
- DNA recombination (1)
- Dendritic cell (1)
- Dendritische Zelle (1)
- Densovirus (1)
- Disaster response (1)
- Doxycycline (1)
- Doxyzyklin (1)
- EGFR (1)
- ESBL (1)
- ESKAPE (1)
- ET-15 clone (1)
- Echinokokkus (1)
- Efflux transport (1)
- Eingeweidewürmer (1)
- Elderly (1)
- EmERK (1)
- Emergence (1)
- Endosymbiont (1)
- Enterobacteriaceae (1)
- Entwicklung (1)
- Epidermal growth factor receptor (1)
- Epigenetic (1)
- Escherichia coli K1 (1)
- Escherichia coli infections (1)
- Europe (1)
- Expansion microscopy (1)
- False positive reactions (1)
- FarR (1)
- Filariose (1)
- FinO family (1)
- Fks1 (1)
- Flagellin (1)
- Flagelline (1)
- Fox tapeworm (1)
- FoxQ2 (1)
- Fungiplex Candida Auris (1)
- GM (1)
- Genanalyse (1)
- Gene silencing (1)
- Genexpression (1)
- Genom-Vergleich (1)
- Geriatric care (1)
- Geriatrics (1)
- Germinative cell (1)
- Glutathione (1)
- Golgi (1)
- HFQ (1)
- HIV (1)
- Heilmittel (1)
- Helicobacter (1)
- Helminth (1)
- Helminths (1)
- Hfq (1)
- High throughput screening (1)
- Hirnendothelzellen (1)
- Hospital emergency plan (1)
- Host-parasite interaction (1)
- Host-pathogen interactions (1)
- I-lactate (1)
- IA (1)
- ICM (1)
- IDSA (1)
- IMD (1)
- IctP (1)
- Imatinib (1)
- Immunmodulation (1)
- Immunomodulation (1)
- In-vitro-Kultur (1)
- Inducible Clindamycin Resistance (1)
- Induzierte pluripotente Stammzelle (1)
- Infection control (1)
- Infektion (1)
- Inhibitor (1)
- Innate immunity (1)
- Jurkat cells (1)
- Kinase inhibitor (1)
- Komplement C3a (1)
- Komplement C5a (1)
- Konfokale Mikroskopie (1)
- LTR retrotransposons (1)
- Larvae (1)
- Leptomeningeal cells (1)
- Leptomeningealzellen (1)
- Lichtheimia (1)
- Listeria monocytogenes (1)
- MAP kinase (1)
- MAP-Kinase (1)
- MRONJ (1)
- MSIS (1)
- Mass critical care (1)
- Medicine (1)
- Medizin (1)
- Meningitis cerebrospinalis epidemica (1)
- Meningitis, Meningococcal (1)
- Meningococcal infection (1)
- Meningococcal polysaccharide caccine (1)
- Meningococcal serogroup C (1)
- Meningokokken (1)
- Mesocestoides corti (1)
- Mesocestoides vogae (1)
- Metacestode (1)
- Methicillin resistant Staphylococcus aureus (1)
- Methicillin-resistant Staphylococcus aureus (1)
- Methicillin-resistant staphylococcus aureus (1)
- Mikrobiologie (1)
- Mobile genetic element (1)
- Mucin (1)
- Mucor (1)
- Mucorales (1)
- Multiplex PCR (1)
- Mwanza (1)
- Mycobacterium marinum (1)
- N-oleoyl serinol (1)
- NAS (1)
- NK-DC cross-talk (1)
- NadA (1)
- Nanos (1)
- Nasal Carriage (1)
- Neisseria (1)
- Neisseria meningitdis (1)
- Neisseria meningitis (1)
- Neoblast (1)
- Nervous system (1)
- Neuroinfectiology (1)
- Neuroinflammation (1)
- Neuropeptide (1)
- Non-coding RNA (1)
- Nursing homes (1)
- ONJ (1)
- Onchozerkose (1)
- One Health (1)
- P-glycoprotein (1)
- P-gp (1)
- P. aeruginosa (1)
- PMNs (1)
- Parvovirus (1)
- Pathogenität (1)
- Pathogens (1)
- Pentastomiasis (1)
- Pneumococci (1)
- Predictive value of tests (1)
- Prevalence (1)
- ProQ (1)
- Proliferation (1)
- Protoscolex (1)
- Purpureocillium (1)
- RNA (1)
- RNA chaperone Hfq (1)
- RNA sequencing (1)
- Receptor kinase (1)
- Regulatorischer T-Lymphozyt (1)
- Regulatory T-cell (1)
- RelA (1)
- Rhizomucor (1)
- S. aureus (1)
- S1P (1)
- S1PR (1)
- SARS‐CoV‐2 (1)
- SFRP (1)
- ST 772 (1)
- ST1797 (1)
- ST88 (1)
- Scedosporium (1)
- Schistosoma mansoni (1)
- Sequence motif analysis (1)
- Serum (1)
- Serumresistenz (1)
- Sierra Nevada (1)
- Signaltransduktion (1)
- Six3/6 Wnt (1)
- Skin (1)
- Small non-messenger RNS (1)
- Sphingosine 1-phosphate (1)
- Sphingosine 1-phosphate receptor (1)
- Sphingosinkinase (1)
- Stammzelle (1)
- Staphylococcus aureus (1)
- Stem cells (1)
- Streptococcus agalactiae (1)
- Streptococcus pneumoniae (1)
- Streptococcus pyogenes (1)
- Streptococcus suis (1)
- Stringent response (1)
- Stringente Antwort (1)
- Stringente Kontrolle (1)
- Supercoiling (1)
- Surgery (1)
- T Cells (1)
- T cells (1)
- TGF-BETA (1)
- TLR5 (1)
- TNF-alpha (1)
- Talaromyces (1)
- Telomerase (1)
- Thioredoxin (1)
- Toll like Rezeptor 4 (1)
- Toll like receptor 4 (1)
- Transkription <Genetik> (1)
- Transkriptionsregulation (1)
- Transkriptomanalyse (1)
- Transposon (1)
- Tropheryma whipplei (1)
- Tuberculosis (1)
- Typisierung (1)
- Ureaplasma (1)
- Ureaplasma species (1)
- Vaccination (1)
- Valentine Leukocidin Genes (1)
- Vesicles (1)
- Virulenzfaktor (1)
- WBC (1)
- Whipple's disease (1)
- Wolbachia (1)
- Würmer (1)
- Xenopus oocytes (1)
- Zelldifferenzierung (1)
- Zellzyklus (1)
- Zink (1)
- Zinkmangel (1)
- acute watery diarrhea (1)
- admission screening (1)
- agar (1)
- agar diffusion test (1)
- alloSCT patients (1)
- alternative pig farming (1)
- alveoar echinococcosis (1)
- ampicillin (1)
- anaphylatoxin receptors (1)
- anaphylatoxins (1)
- angeborene Immunität (1)
- anidulafungin (1)
- antero-posterior axis (1)
- antibiotic bone concentration (1)
- antibiotic prescription behavior (1)
- antibiotic use (1)
- antibodies (1)
- anticoagulants (1)
- antifungal susceptibility (1)
- antifungals (1)
- antigen-B (1)
- antigens (1)
- antimicrobial (1)
- antimicrobial responses (1)
- antimicrobial susceptibility (1)
- antimicrobials (1)
- antiresorptive drug-related osteonecrosis of the jaw (1)
- anxiety (1)
- assay (1)
- attitude of health personnel (1)
- atypical chemokine receptor 3 (1)
- aureus infections (1)
- autochthonous infection (1)
- azole resistance (1)
- bactericidal activity (1)
- beta-lactam (1)
- beta-tubulin (1)
- beta‐d‐glucan (1)
- biological techniques (1)
- biomarker (1)
- biosynthesis (1)
- blood (1)
- blood fluke (1)
- blood stream infections (1)
- blood-brain barrier (1)
- blood-cerebrospinal fluid barrier (1)
- bloodstream infection (1)
- brain barrier (1)
- brain endothelial cell (1)
- breakthrough (1)
- bronchoalveolar lavage fluid (1)
- cAMP (1)
- campylobacteriosis (1)
- cardiovascular MRI (1)
- caspase-3 (1)
- caspofungin (1)
- cattle (1)
- cell staining (1)
- cell wall (1)
- cells (1)
- central-nervous-system (1)
- cephalosporin-resistant gram-negative bacteria (1)
- ceramide (1)
- ceramide analogs (1)
- cestodes (1)
- chaperone (1)
- chemical properties (1)
- chorioamnionitis (1)
- choroid-plexus (1)
- circulating (1)
- coagulase-negative staphylococci (1)
- commercial kits (1)
- community settings (1)
- complement system (1)
- complex (1)
- computational biology and bioinformatics (1)
- computational models (1)
- cord blood (1)
- corticosteroids (1)
- cryptic (1)
- cutibacteria (1)
- cytokines (1)
- dRNA-seq (1)
- depression (1)
- detection limits (1)
- development (1)
- differential age distribution (1)
- digital phenotyping (1)
- disease-associated (1)
- dual function (1)
- echinocandin (1)
- echinocandins (1)
- echinococcosis (1)
- ecological momentary assessment (1)
- ecology (1)
- efflux pumps (1)
- elucidation (1)
- endophthalmitis (1)
- endothelial cells (1)
- epgenetics (1)
- epidermal growth factor (1)
- epithelial cells (1)
- excretory-secretory (1)
- expert recommendation (1)
- extracellular (1)
- eye infection (1)
- factor H (1)
- feasibility study (1)
- field gel-electrophoreresis (1)
- flagella (1)
- flow cytometry (1)
- fluorescence microscopy (1)
- foxtapeworm (1)
- fungal antigens (1)
- fungal infection (1)
- fungal molecular diagnostics (1)
- fungi (1)
- fungicidal activity (1)
- galectin-2 (1)
- gangliosides and lipid rafts (1)
- gen (1)
- gene (1)
- general practice (1)
- general practitioner (1)
- generalized anxiety disorder (1)
- genetic loci (1)
- genetic variation (1)
- genetics (1)
- genome (1)
- genome comparison (1)
- genomic databases (1)
- genomic libraries (1)
- genomics (1)
- germinative cell (1)
- germinative cells (1)
- global regulators (1)
- globale Regulatoren (1)
- glucan synthase (1)
- glutamate dehydrogenase (1)
- glutathione (1)
- granulosus (1)
- group-B (1)
- heart (1)
- helminth (1)
- helminths (1)
- hematopoietic stem cell transplantation (1)
- hemihepatectomy (1)
- hospital-acquired methicillin-resistant Staphylococcus aureus (1)
- host defense (1)
- host response (1)
- host-pathogen interactions (1)
- host–pathogen interaction (1)
- human behaviour (1)
- human brain microvascular endothelial cells (1)
- hydatid disease (1)
- hydrogels (1)
- hyphae (1)
- identification (1)
- image processing (1)
- imaging (1)
- immune evasion (1)
- immune impairment (1)
- immune response (1)
- immunogenetics (1)
- immunomodulation (1)
- immunoprecipitation (1)
- immunotherapy (1)
- in vitro (1)
- in vivo (1)
- indigenous (1)
- induced pluripotent stem cells (1)
- infection prevention (1)
- infectious diseases management (1)
- innate immune evasions (1)
- innate immune response (1)
- insulin (1)
- interstage aspiration (1)
- intervention strategies (1)
- intravenous ceftriaxone (1)
- intravitreal vancomycin and amikacin (1)
- invasive aspergillosis (1)
- invasive disease (1)
- invasive fungal infection (1)
- invasive meningococcal disease (1)
- invasive meningococcal diseases (1)
- invasive pulmonary aspergillosis (1)
- jaw bone (1)
- joint aspiration (1)
- joint infection (1)
- keratitis (1)
- killing (1)
- kinase (1)
- knowledge (1)
- laboratory techniques and procedures (1)
- large animal models (1)
- larvae (1)
- leptomeningeal cells (1)
- leucocyte count (1)
- liver (1)
- liver resection (1)
- livestock-associated staphylococci (1)
- long noncoding RNA (1)
- longitudinal studies (1)
- mammalian genomics (1)
- mannan (1)
- marker (1)
- matrix metallopeptidase-1 (1)
- maximum liklihood (1)
- mebendazole (1)
- meningeal blood-csf barrier (1)
- meningococcal lineages (1)
- meningococcal polysaccharides (1)
- meningococci (1)
- meningococcus (1)
- metabolism (1)
- metacestode vesicles (1)
- metamorphosis (1)
- methyltransferase homolog (1)
- micafungin (1)
- mice (1)
- microRNA (1)
- microbial surface component recognising adhesive matrix molecules (1)
- microbiological culture (1)
- microbiology techniques (1)
- microscopy (1)
- microvascular endothelial cells (1)
- microvascular endothelial-cells (1)
- mitochondria (1)
- mitochondrial dynamics (1)
- mitochondrial morphology (1)
- mobile crowdsensing (1)
- mobile health (1)
- molecular characterization (1)
- molecular epidemiology (1)
- monoclonal antibody (1)
- monocytes (1)
- mouse model (1)
- mouse models (1)
- multifaceted approaches (1)
- multiple myeloma (1)
- mycobacterial infection (1)
- mycophenolic acid (1)
- myocyte (1)
- natamycin (1)
- natural killer cell (1)
- natural killer cells (1)
- natural transformation (1)
- neglected diseases (1)
- neglected groups (1)
- nematodes (1)
- neoblast (1)
- neonatal morbidity (1)
- niche adaptation (1)
- nitrite respiration (1)
- nitrites (1)
- non-aureus staphylococci (1)
- nonautonomous (1)
- nosocomial transmission (1)
- nuclear magnetic resonance (1)
- ocular infection (1)
- one-health approach (1)
- oral cefpodoxime (1)
- oral doxycycline (1)
- oral microbiome (1)
- organic farming (1)
- organoid (1)
- outpatient (1)
- oxidative stress (1)
- panton-valentine leukocidin (1)
- paradoxical effect (1)
- paradoxical growth (1)
- parapneumonic pleural effusion (1)
- parasite biology (1)
- parasitic diseases (1)
- pathometabolism (1)
- pediatric (1)
- pediatrician (1)
- periprosthetic joint infection (1)
- phase variation (1)
- phylotypic (1)
- pig (1)
- pig farming methods (1)
- piperacillin (1)
- piperacillin/tazobactam (1)
- planarian (1)
- pleural empyema (1)
- pleural fluid (1)
- plexus epithelial-cells (1)
- pluripotency (1)
- polymorphonuclear neutrophils (1)
- population biology (1)
- population genetics (1)
- post-operative antibiotic treatment (1)
- primary care (1)
- primary cells (1)
- probe-based real-time PCR (1)
- protein kinases (1)
- proteins (1)
- proteomic analysis (1)
- public health (1)
- qPCR (1)
- quality of life (1)
- real-time PCR (1)
- recombinant proteins (1)
- regulation (1)
- regulator (1)
- regulatory T cells (1)
- relA (1)
- research infrastructure (1)
- resistance (1)
- retrotransposition (1)
- revision arthroplasty (1)
- schistoma mansoni (1)
- sensitivity (1)
- sensitivity and specificity (1)
- septic (1)
- sequence (1)
- sequence assembly tools (1)
- serogroup B (1)
- serogroup-Y (1)
- seroprevalence (1)
- serum (1)
- serum resistance (1)
- signaltransduction (1)
- single-molecule tracking (1)
- sirolimus (1)
- small RNA (1)
- small interfering RNAs (1)
- software (1)
- soluble factors (1)
- spa typing (1)
- sporidia (1)
- state-based model (1)
- stem cell transplantation (1)
- strain MC58 (1)
- strain specificity (1)
- stringent response (1)
- structural determination (1)
- super-resolution microscopy (1)
- surgical intra-abdominal infections (1)
- survey (1)
- systems biology (1)
- taxonomy (1)
- tazobactam (1)
- testing strategy (1)
- therapy (1)
- thermophile (1)
- throat (1)
- tight junctions (1)
- topic ofloxacin (1)
- transcription factors (1)
- transcriptional regulation (1)
- transcriptome data analysis (1)
- transcriptomics (1)
- translational research (1)
- transplantation (1)
- transposable elements (1)
- typing (1)
- ultrahigh-field MRI (1)
- under five children (1)
- upper extremity (1)
- utilization (1)
- vaccine development (1)
- vaccines (1)
- vesicles (1)
- viral load (1)
- virulence (1)
- virulenceregulatory evolution (1)
- vitrectomy (1)
- water microbiology (1)
- white blood cell count (1)
- whole blood ex vivo model (1)
- whole-blood infection assay (1)
- whole-blood model (1)
- zinc cluster transcription factor (1)
- zinc limitation (1)
- γ-glutamyl cycle (1)
Institute
- Institut für Hygiene und Mikrobiologie (149) (remove)
Sonstige beteiligte Institutionen
- Department of Hematology and Oncology, Sana Hospital Hof, Hof, Germany (1)
- Department of Laboratory Medicine and Medicine Huddinge, Karolinska Institutet and University Hospital, Stockholm, Sweden (1)
- Department of Medicine A, University Hospital of Münster, Münster, Germany (1)
- Instituto de Higiene, Universidad de la República, Montevideo, Uruguay (1)
- Instituto de Hygiene Montevideo, Uruguay (1)
- Krankenhaushygiene und Antimicrobial Stewardship (1)
- Krankenhaushygiene und Antimicrobial Stewardship (Universitätsklinikum) (1)
- Research Center for Infectious Diseases (ZINF), University of Würzburg, Würzburg, Germany (1)
EU-Project number / Contract (GA) number
- 2016 FGR 0053 (1)
- 278864 (1)
- 715466 (1)
- 847507 (1)
The role of DNA supercoiling in the coordinated regulation of gene expression in Helicobacter pylori
(2004)
Summary Mechanisms of global gene regulation in bacteria are not well characterized yet. Changes in global or local supercoiling of chromosomal DNA are thought to play a role in global gene silencing and gene activation. In Helicobacter pylori, a bacterium with few dedicated transcriptional regulators, the structure of some promoters indicates a dependency on DNA topology. For example, the promoter of the major flagellar subunit gene flaA (ó28-dependent) has a shorter spacing of 13 nucleotides (nt) in comparison to the consensus promoter (15 nt). Supercoiling changes might be a mechanism of gene-specific and global transcriptional regulation in this bacterium. The aim of this study was to elucidate, if changes in global supercoiling have an influence on global gene regulation in H. pylori, and on the temporal regulation of the flagellar biosynthesis pathway in this organism. In the present work, global DNA supercoiling in H. pylori was visualized for the first time, by determining the supercoiling state of plasmids under different growth conditions. Using this method, we showed that cellular supercoiling was clearly growth phase-dependent in H. pylori. Coinciding with increased supercoiling during the growth phases, transcription of the flaA gene was increased, while the transcription of a second ó28-dependent gene with regular promoter spacing (HP0472) was reduced, supporting the hypothesis that growth phase-dependency of promoters might be mediated by changes of DNA topology. Supercoiling in H. pylori could be influenced in a reproducible fashion by inhibition of gyrase using novobiocin, which led to DNA relaxation and to a concomitant decrease of flaA transcript levels. Promoter spacer mutagenesis of the flaA promoter was performed. With flaA promoters of increased or reduced length, transcription of flaA was reduced, less susceptible to supercoiling changes, and, under specific conditions, inverted as compared to the wild type promoter. Transcriptional interdependence between the coupled topA-flaB genes and flaA was found by analysis of the flaA promoter mutants. Chromosomally linked gyrA-flgR, and topA-flaB genes were all dependent on supercoiling and coregulated with each other. Comprehensive transcript profiling (DNA microarrays) of wildtype H. pylori with and without novobiocin treatment identified a number of genes (10% of total genes), including flagellin, virulence and housekeeping genes, which were strongly dependent on and appeared to be synchronized by supercoiling changes (transcriptional up- or downregulation). These findings indicate a tightly coupled temporal regulation of flagellar biogenesis and metabolism in H. pylori, dependent on global supercoiling. A specific group of genes was also regulated in H. pylori by overexpression of Topoisomerase I, as detected by genome-wide analysis (DNA microarray). The DNA-bending protein HU is thought to be responsible for influencing the negative supercoiling of DNA, through its ability to wrap DNA. HU is encoded by the hup single gene in H. pylori, and constitutively expressed during the whole growth curve. An H. pylori hup mutant was constructed. H. pylori cells lacking HU protein were viable, but exhibited a severe growth defect. Our data indicate that the lack of HU dramatically changes global DNA supercoiling, indicating an important function of HU in chromosome structuring in H. pylori. Transcriptome analyses were performed and demonstrated that a total of 66 genes were differentially transcribed upon hup deletion, which include virulence genes and many other cell functions. The data indicate that HU might act as further important global regulator in H. pylori. Increased gene expression of heat shock proteins and a decreased transcription of the urease gene cluster may indicate a co-ordinated response of H. pylori to changes of environmental conditions in its specific ecological niche, mediated by HU. After the whole genomic sequences of H. pylori strains 26695 and J99 were published, two ORFs (HP0116 and HP0440) were presumptively annotated as topoisomerase I orthologs. HP0116 is the functional H. pylori topoisomerase I (TopA). HP0440 (topA2) was found in only few (5 of 43) strains. Western blot analysis indicated that TopA2 is antigenically different from TopA. TopA2 is transcribed in H. pylori, but the protein must be functionally different from TopA, since it is lacking one functionally essential zinc finger motif, and was not able to functionally complement a TopA-deficient E. coli. Like topA, topA2 was also transcribed in a growth phase-dependent manner. We did not find a function of TopA2 in DNA structuring or topology, but, in the present study, we were able for the first time to establish a unique function for TopA2 in global gene regulation, by comprehensive transcriptome analysis (DNA microarray). Transcriptome analysis showed that a total of 46 genes were differentially regulated upon topA2 deletion, which included flagellar genes and urease genes. These results suggest that TopA2 might act as a novel important regulator of both flagellar biosynthesis and urease in H. pylori.
In the present thesis, two projects on the use of microarray technology for molecular epidemiology of Neisseria meningitidis have been followed. The first one evaluated microarrays based on polymorphism-directed oligonucleotide design for typing of N. meningitidis adopting the multilocus sequence typing (MLST) concept. The number of oligonucleotides needed to cover all known polymorphisms was much lower compared to the number needed if a tiling strategy would have been chosen. Initial experiments using oligonucleotides 28-32 nucleotides in length, revealed that the applied hybridisation protocols were highly specific. However, despite of several optimisation steps, the rate of misidentification of oligonucleotides remained >1.8% in consecutive validation experiments using arrays representing the genetic diversity at three MLST loci. This finding led to the assumption that the high density of polymorphic sites and extensive GC-content variations at N. meningitidis MLST loci hindered the successful implementation of MLST microarrays based on polymorphism-directed oligonucleotide design. In the 1980s, the ET-15 clone emerged within the ST-11 complex of N. meningitidis. This new clone was associated with severe meningococcal disease and outbreaks world-wide. Therefore, the goal of the second project was to identify genetic differences between ET-15 strains and other ST-11 strains using whole genome microarray technology. Three genes encoding hypothetical proteins were identified to be present in all ET-15 strains but absent in other ST-11 strains. This finding together with unpublished observation from our group suggested that several genome alterations occurred before the clonal expansion of the ET-15 clone started. The role that these three genes play in the pathogenicity of the ET-15 clone is unclear. The genome comparisons revealed furthermore that studies of the ET-15 clone displayed approximately two-fold less gene content variation than ST-11 strains not belonging to the ET-15 clone. This finding is in accordance with the recent emergence and clonal expansion of the ET-15 variant.
Helicobacter pylori (H. pylori) is a gram-negative, microaerophilic, spiral-shaped bacterium. It resides in the gastric mucous layer and epithelial lining of the stomach, often clustering at the junction of epithelial cells. H. pylori colonization usually occurs during childhood, and, when left untreated, generally persists for the host’s lifetime. Persistent H. pylori infection can cause chronic superficial gastritis and gastric duodenal ulcers, which is possibly linked to the development of gastric carcinoma and primary gastric lymphoma, especially of the mucosa-associated lymphoid tissue (MALT) type. It was recently defined as a class 1 carcinogen. The gastric inflammatory response to H. pylori infection is characterized by infiltration of the mucosa by neutrophils, T and B cells, plasma cells and macrophages. This reaction is initially induced by H. pylori attachment, followed by cytokine release by gastric epithelial cells. Epidemiological studies revealed that more than 50% of adults are infected with H. pylori all over the world. However, interestingly, only a subset of individuals develops serious H. pylori-related disease, while most infected individuals show no clinical symptoms. Gastric epithelial cells, like intestinal epithelial cells, express a subset of Toll-like receptors (TLRs) and similar pattern recognition receptors, which are important for the activation of the innate immune system. Bacterial components such as lipopeptides, peptidoglycan, LPS, flagellin, and CpG DNA are the ligands of TLRs. Thus, TLRs in gastric epithelial cells might be able to contribute to innate immune responses to H. pylori infection. However, there is scant knowledge about the mechanisms of innate immune response to acute and chronic H. pylori infection. This study is focused on host cell interaction with H. pylori flagellins, which are major components of the flagellar apparatus, and innate immune responses against them. The flagellins, which are essential for bacterial motility, are important for H. pylori to survive in the stomach mucus during the whole infectious cycle. Flagellins are known to act as the main determinant of many mucosal pathogenic bacteria that mediates proinflammatory signaling, including transcriptional factor NF-B activation via TLR5. In the first part of the study, we investigated the effects of H. pylori flagellins on TLR5 expression, NF-B activation and IL-8 production in various human intestinal and gastric epithelial cell lines by using Western blotting, semi-quantitative RT-PCR and ELISA. IL-8 is a potent neutrophil-activating chemokine expressed by gastric epithelial cells. When we stimulated the cells with the native form of or E. coli-expressed recombinant H. pylori flagellins, FlaA and FlaB, IL-8 was not induced in any case, while S. typhimurium flagellin (FliC) induced it significantly. H. pylori was able to modulate TLR5 protein expression and NF-B activation in epithelial cells regardless of the presence of flagellins. Having established the finding that H. pylori flagellins have unusually low immune-stimulatory properties, we further investigated to find out possible reasons why H. pylori flagellins are distinct from other flagellins of pathogenic bacteria in terms of immune-stimulatory activity. From amino acid sequence comparisons, we found that some regions in the terminal D0D1 protein domains of H. pylori flagellins are different from flagellins of other pathogenic bacteria. D0D1 is the domain which is known to interact with TLR5 in Salmonella FliC. To examine whether the differences endow H. pylori flagellins with low immune-stimulatory properties, we created several mutated H. pylori flagellins (FlaA and FlaB) by site-directed mutagenesis that contain one to four epitopes of Salmonella flagellin D0D1 domain amino acid sequences. The mutant flagellins expressed both in H. pylori and E. coli were used to determine their influence on TLR5-signaling mediators and cytokines, such as MAPkinases, (ERK, p38), NF-B, IL-8, and MIP-3. Salmonella FliC expressed in E. coli induced activation of p38, IB and NF-B leading to IL-8 and MIP-3 production in gastric epithelial cells. However, none of the H. pylori flagellin mutants activated MAP kinases or induced those cytokines. In a co-immunoprecipitation assay none of the recombinant wild type or mutated H. pylori flagellins showed any direct physical interaction with TLR5, while Salmonella FliC significantly co-precipitated with TLR5. Interestingly, we found H. pylori flagellins bind to the surface of gastric epithelial cells like FliC, although they do not bind to or stimulate TLR5. Based on the physical interaction of H. pylori flagellins and FliC with human gastric epithelial cells, we further analyzed transcriptional regulation by H. pylori flagellin in these host cells using microarray analysis. The result showed that H. pylori flagellins modulate host cell gene expression, and many of the identified regulation events overlap with the genes regulated by FliC. These findings imply that H. pylori flagellins do play a role in gene regulation of host cells probably through still unknown factors or receptors, although they do not trigger TLR5-related signaling pathways. The results of our study suggest that, in addition to the low immune-stimulatory activity of H. pylori LPS, the evolutionary reduction in stimulating activity of H. pylori flagellins on the local innate immune responses in the stomach in vivo might be a further strategy of this chronic mucosal pathogen to evade and minimize deleterious host responses, thereby promoting life-long persistence in the host, and possibly contributing to cancerogenesis.
The insulin receptor ortholog EmIR of the fox-tapeworm Echinococcus multilocularis displays significant structural homology to the human insulin receptor (HIR) and has been suggested to be involved in insulin sensing mechanisms of the parasite’s metacestode larval stage. In the present work, the effects of host insulin on Echinococcus metacestode vesicles and the proposed interaction between EmIR and mammalian insulin have been studied using biochemical and cell-biological approaches. Human insulin, exogenously added to in vitro cultivated parasite larvae, (i) significantly stimulated parasite survival and growth, (ii) induced DNA de novo synthesis in Echinococcus, (iii) affected overall protein phosphorylation in the parasite, and (iv) specifically induced the phosphorylation of the parasite’s Erk-like MAP kinase orthologue EmMPK1. These results clearly indicated that Echinococcus metacestode vesicles are able to sense exogenous host insulin which induces a mitogenic response. To investigate whether EmIR mediates these effects, anti-EmIR antibodies were produced and utilized in biochemical assays and immunohistochemical analyses. EmIR was shown to be expressed in the germinal layer of the parasite both on the surface of glycogen storing cells and undifferentiated germinal cells. Upon addition of exogenous insulin to metacestode vesicles, the phosphorylation of EmIR was significantly induced, an effect which was suppressed in the presence of specific inhibitors of insulin receptor-like tyrosine kinases. Furthermore, upon expression of EmIR/HIR receptor chimera containing the extracellular ligand binding domain of EmIR in HEK 293 cells, a specific autophosphorylation of the chimera could be induced through the addition of exogenous insulin. These results indicated the capability of EmIR to sense and to transmit host insulin signals to the Echinococcus signaling machinery. The importance of insulin signaling mechanisms for parasite survival and growth were underscored by in vitro cultivation experiments in which the addition of an inhibitor of insulin receptor tyrosine kinases led to vesicle degradation and death. Based on the above outlined molecular data on the interaction between EmIR and mammalian insulin, the parasite’s insulin receptor orthologue most probably mediates the insulin effects on parasite growth and is, therefore, a potential candidate factor for host-parasite communication via evolutionary conserved pathways. In a final set of experiments, signaling mechanisms that act downstream of EmIR have been analyzed. These studies revealed significant differences between insulin signaling in Echinococcus and the related cestode parasite Taenia solium. These differences could be associated with differences in the organo-tropism of both species.
Introduction: This study investigates the role of Wolbachia bacteria in the pathogenesis of O. volvulus keratitis in a mouse model. Wolbachia bacteria are essential symbionts of most filarial nematodes of importance for mankind. Methods: Using a mouse model for river blindness in which soluble extracts of filarial nematodes are injected in the corneal stroma, changes in stromal thickness and haze of the cornea are observed by in vivo confocal microscopy, followed by immunohistochemical staining for neutrophils and PECAM-1, as well as ELISA of corneal chemokines. Reactions to filarial extracts containing Wolbachia are compared to those without the endosymbiont. Results: The approach of characterizing Wolbachia’s role in river blindness in this study is threefold. Firstly, Wolbachia-depleted extracts from doxycycline treated onchocerciasis patients led to a diminished inflammatory response in corneas of C57BL/6 mice compared to untreated, i.e. Wolbachia containing antigen. The decreased cell recruitment observed with doxycycline treated extracts involved neutrophils, but not eosinophils. This finding demonstrated that the presence of Wolbachia increases neutrophil recruitment. Secondly, extracts from Wolbachia-containing B. malayi revealed markedly more pathology than endosymbiont-free A. viteae antigen. This again pointed at the role of Wolbachia in development of disease. Thirdly, Toll-like Receptor 4 (TLR4) dependence was shown to exist for the inflammatory response to Wolbachia harboring O. volvulus antigen by looking at the corneal pathology in TLR4-mutant C3H/HeJ mice, compared to the wild-type C3H/HeN strain. Investigating further Wolbachia mediated mechanisms of neutrophil recruitment to the cornea, this study also showed that expression of the adhesion molecule PECAM-1 in limbal vessels, as well as upregulation of the CXC chemokines KC and MIP-2 were dependent on the presence of functional TLR4 and Wolbachia respectively. Conclusions: This study indicates that the innate immune system and Wolbachia endobacteria play an important role in the inflammatory response associated with the pathogenesis of onchocerca keratitis, suggesting a complete alteration in our understanding of the immunopathology of filariasis.
Echinococcus multilocularis is the causative agent of alveolar echinococcosis (AE), a life-threatening disease with limited options of chemotherapeutic treatment. Anti-AE chemotherapy is currently based on a single class of drugs, the benzimidazoles. Although acting parasitocidic in vitro, benzimidazoles are merely parasitostatic during in vivo treatment of AE and cause severe site effects. In the case of operable lesions, the resection of parasite tissue needs to be supported by a prolonged chemotherapy. Thus, the current treatment options for AE are inadequate and require alternatives. In the present work, the flatworm signaling pathways were analyzed to establish potential targets for novel therapeutic approaches. I focused on factors that are involved in development and proliferation of E. multilocularis using molecular, biochemical and cell biological methods. Among the analysed factors were three MAP kinases of the parasite, EmMPK1, an Erk-1/2 orthologue, EmMPK2, a p38 orthologue and EmMPK3, an Erk7/8 orthologue. Further, I identified and characterized EmMKK2, a MEK1/2 orthologue of the parasite, which, together with the known kinases EmRaf and EmMPK1, forms an Erk1/2-like MAPK module. Moreover, I was able to demonstrate several influences of host growth factors such as EGF (epidermal growth factor) and insulin on worm signaling mechanisms and larval growth, including the phosphorylation of Elp, an ezrin-radixin-moesin like protein, EmMPK1, EmMPK3 and increased mitotic activity of Echinococcus cells. In addition, several substances were examined for their efficacy against the parasite including (i) general tyrosine kinase inhibitors (PP2, leflunamide), (ii) compounds designed to inhibit the activity of receptor tyrosine kinases, (iii) anti-neoplastic agents (miltefosine, perifosine), (iv) serine/threonine kinase inhibitors that have been designed to block the Erk1/2 MAPK cascade and (v) inhibitors of p38 MAPKs. In these studies, EmMPK2 proved to be a promising drug target for the following reasons. Amino acid sequence analysis disclosed several differences to human p38 MAPKs, which is likely to be the reason for the observed enhanced basal activity of recombinant EmMPK2 towards myelin basic protein in comparison to human recombinant p38 MAPK-α. In addition, the prominent auto-phosphorylation activity of the recombinant EmMPK2 protein together with the absence of an interaction with the Echinococcus MKKs suggest a different mechanism of regulation compared to the human enzyme. EmMPK2 activity could be effectively inhibited in vitro and in cultivated metacestode vesicles by treatment with SB202190 and ML3403, two ATP-competitive pyridinyl imidazole inhibitors of p38 MAPKs, in a concentration-dependent manner. Moreover, both compounds, in particular ML3403, caused parasite vesicle inactivation at concentrations which did not affect cultured mammalian cells. Likewise, during the cultivation of Echinococcus primary cells, the presence of ML3403 prevented the generation of new vesicles. Targeting members of the EGF signaling pathway, particulary of the Erk1/2-like MAPK cascade, with Raf and MEK inhibitors prevented the phosphorylation of EmMPK1 in metacestodes cultivated in vitro. However, although parasite growth was prevented under these conditions, the structural integrity of the metacestode vesicles maintained during long-term cultivation in the presence of the MAPK cascade inhibitors. Similar results were obtained when studying the effects of other drugs mentioned above. Taken together, several targets could be identified that reacted with high sensitivity to the presence of inhibitory substances, but did not cause the parasite’s death with one exception, the pyridinyl imidazoles. Based on the presented data, I suggest pyridinyl imidazoles as a novel class of anti-Echinococcus drugs and imply EmMPK2 as survival signal mediating factor, the inhibition of which could be used for the treatment of AE.
Disruption of the blood-brain barrier (BBB) is a hallmark event in the pathophysiology of bacterial meningitis. Several inflammatory mediators, such as tumor necrosis factor alpha (TNF-a), nitric oxide and matrix metalloproteinases (MMPs), contribute to this disruption. Here we show that infection of human brain microvascular endothelial cells (HBMEC) with Neisseria meningitidis induced an increase of permeability at prolonged time of infection. This was paralleled by an increase in MMP-8 activity in supernatants collected from infected cells. A detailed analysis revealed that MMP-8 was involved in the proteolytic cleavage of the tight junction protein occludin, resulting in its disappearance from the cell periphery and cleavage to a lower-sized 50-kDa protein in infected HBMEC. Abrogation of MMP-8 activity by specific inhibitors as well as transfection with MMP-8 siRNA abolished production of the cleavage fragment and occludin remained attached to the cell periphery. In addition, MMP-8 affected cell adherence to the underlying matrix. A similar temporal relationship was observed for MMP activity and cell detachment. Injury of the HBMEC monolayer suggested the requirement of direct cell contact because no detachment was observed when bacteria were placed above a transwell membrane or when bacterial supernatant was directly added to cells. Inhibition of MMP-8 partially prevented detachment of infected HBMEC and restored BBB permeability. Together, we established that MMP-8 activity plays a crucial role in disassembly of cell junction components and cell adhesion during meningococcal infection.
Introduction: Chronic nonbacterial osteomyelitis (CNO) is an inflammatory disorder of unknown etiology. In children and adolescents CNO predominantly affects the metaphyses of the long bones, but lesions can occur at any site of the skeleton. Prospectively followed cohorts using a standardized protocol in diagnosis and treatment have rarely been reported. Methods: Thirty-seven children diagnosed with CNO were treated with naproxen continuously for the first 6 months. If assessment at that time revealed progressive disease or no further improvement, sulfasalazine and short-term corticosteroids were added. The aims of our short-term follow-up study were to describe treatment response in detail and to identify potential risk factors for an unfavorable outcome. Results: Naproxen treatment was highly effective in general, inducing a symptom-free status in 43% of our patients after 6 months. However, four nonsteroidal anti-inflammatory drug (NSAID) partial-responders were additionally treated with sulfasalazine and short-term corticosteroids. The total number of clinical detectable lesions was significantly reduced. Mean disease activity estimated by the patient/physician and the physical aspect of health-related quality of life including functional ability (global assessment/childhood health assessment questionnaire and childhood health assessment questionnaire) and pain improved significantly. Forty-one percent of our patients showed radiological relapses, but 67% of them were clinically silent. Conclusions: Most children show a favorable clinical course in the first year of anti-inflammatory treatment with NSAIDs. Relapses and new radiological lesions can occur at any time and at any site in the skeleton but may not be clinically symptomatic. Whole-body magnetic resonance imaging proved to be very sensitive for initial and follow-up diagnostics.
Neisseria meningitidis is a facultatively pathogenic human commensal and strictly adapted to its niche within the human host, the nasopharynx. Not much is known about the regulatory processes required for adaptation to this environment. Therefore the role of the transcriptional regulator NMB1843, one of the two predicted regulators of the MarR family in the meningococcal genome, was investigated. As this gene displayed a high sequence homology to FarR, the Fatty acid resistance Regulator in N. gonorrhoeae, we designated the meningococcal protein FarR (NmFarR). Homology modeling of this protein revealed a dimeric structure with the characteristic winged helix-turn-helix DNA binding motif of the MarR family. NmFarR is highly conserved among meningococcal strains and expression of farR during exponential growth is controlled post-transcriptionally, being highest in the late exponential phase. By means of electrophoretic mobility shift assays (EMSAs) the direct and specific binding of FarR to the farAB promoter region was shown, comparable to its homologue in gonococci. As FarR is involved in fatty acid resistance in N. gonorrhoeae, susceptibility assays with the medium chain lauric acid (C12:0), the long chain saturated palmitic acid (C16:0) and the long chain unsaturated linoleic acid (C18:2) were performed, testing a wide variety of strains of both species. In contrast to the unusually susceptible gonococci, a high intrinsic fatty acid resistance was detected in almost all meningococcal isolates. The molecular basis for this intrinsic resistance in N. meningitidis was elucidated, showing that both a functional FarAB efflux pump system as well as an intact lipopolysaccharide (LPS) are responsible for palmitic acid resistance. However, even despite circumvention of the intrinsic resistance, FarR could not be connected with fatty acid resistance in meningococci. Instead, FarR was shown to directly and specifically repress expression of the Neisseria adhesin A (nadA), a promising vaccine candidate absent in N. gonorrhoeae. Microarray analyses verified these results and disclosed no further similarly regulated genes, rendering the FarR regulon the smallest regulon in meningococci reported until now. The exact FarR binding site within the nadA promoter region was identified as a 16 bp palindromic repeat and its influence on nadA transcription was proved by reporter gene fusion assays. This repression was also shown to be relevant for infection as farR deficient mutant strains displayed an increased attachment to epithelial cells. Furthermore, farR transcription was attested to be repressed upon contact with active complement components within human serum. Concluding, it is shown that FarR adopted a role in meningococcal host niche adaptation, holding the balance between immune evasion by repressing the highly antigenic nadA and host cell attachment via this same adhesin.