This is the institutional Repository of the Helmholtz Centre for Infection Research in Braunschweig/Germany (HZI), the Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Saarbrücken/Germany, the TWINCORE Zentrum für Exprerimentelle und Klinische Infektionsforschung, Hannover/Germany,Helmholtz-Institut für RNA-basierte Infektionsforschung (HIRI), Braunschweig Integrated Centre for Systems biology (BRICS), Centre for Structural Systems Biology (CSSB) the Study Centre Hannover, Hannover/Germany and the Centre for Individualised Infection Medicine (CiiM).

 

  • Capsule and fimbriae modulate the invasion of Haemophilus influenzae in a human blood-cerebrospinal fluid barrier model.

    Häuser, Svenja; Wegele, Christian; Stump-Guthier, Carolin; Borkowski, Julia; Weiss, Christel; Rohde, Manfred; Ishikawa, Hiroshi; Schroten, Horst; Schwerk, Christian; Adam, Rüdiger; et al. (Elsevier, 2018-07-17)
    The Gram-negative bacterium Haemophilus influenzae (H. influenzae) can commensally colonize the upper respiratory tract, but also cause life threatening disease including epiglottitis, sepsis and meningitis. The H. influenzae capsule protects the bacteria against both phagocytosis and opsonization. Encapsulated H. influenzae strains are classified into serotypes ranging from a to f dependent on their distinct polysaccharide capsule. Due to the implementation of vaccination the incidence of invasive H. influenzae type b (Hib) infections has strongly decreased and infections with other capsulated types, including H. influenzae type f (Hif), are emerging. The pathogenesis of H. influenzae meningitis is not clarified. To enter the central nervous system (CNS) the bacteria generally have to cross either the blood-brain barrier (BBB) or the blood-cerebrospinal fluid barrier (BSCFB). Using a cell culture model of the BCSFB based on human choroid plexus papilloma (HIBCPP) cells and different H. influenzae strains we investigated whether Hib and Hif invade the cells, and if invasion differs between encapsulated vs. capsular-deficient and fimbriated vs. non-fimbriated variants. We find that Hib can adhere to and invade into HIBCPP cells. Invasion occurs in a strongly polar fashion, since the bacteria enter the cells preferentially from the basolateral "blood "side. Fimbriae and capsule attenuate invasion into choroid plexus (CP) epithelial cells, and capsulation can influence the bacterial distribution pattern. Finally, analysis of clinical Hib and Hif isolates confirms the detected invasive properties of H. influenzae. Our data point to roles of capsule and fimbriae during invasion of CP epithelial cells.
  • The guide sRNA sequence determines the activity level of box C/D RNPs.

    Graziadei, Andrea; Gabel, Frank; Kirkpatrick, John; Carlomagno, Teresa; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstraße 7, 38124 Braunschweig, Germany. (eLife Sciences Publications, 2020-03-23)
    2'-O-rRNA methylation, which is essential in eukaryotes and archaea, is catalysed by the Box C/D RNP complex in an RNA-guided manner. Despite the conservation of the methylation sites, the abundance of site-specific modifications shows variability across species and tissues, suggesting that rRNA methylation may provide a means of controlling gene expression. As all Box C/D RNPs are thought to adopt a similar structure, it remains unclear how the methylation efficiency is regulated. Here, we provide the first structural evidence that, in the context of the Box C/D RNP, the affinity of the catalytic module fibrillarin for the substrate-guide helix is dependent on the RNA sequence outside the methylation site, thus providing a mechanism by which both the substrate and guide RNA sequences determine the degree of methylation. To reach this result, we develop an iterative structure-calculation protocol that exploits the power of integrative structural biology to characterize conformational ensembles.
  • Variations in microbiota composition of laboratory mice influence Citrobacter rodentium infection via variable short-chain fatty acid production.

    Osbelt, Lisa; Thiemann, Sophie; Smit, Nathiana; Lesker, Till Robin; Schröter, Madita; Gálvez, Eric J C; Schmidt-Hohagen, Kerstin; Pils, Marina C; Mühlen, Sabrina; Dersch, Petra; et al. (PLOS, 2020-03-24)
    The composition of the intestinal microbiota influences the outcome of enteric infections in human and mice. However, the role of specific members and their metabolites contributing to disease severity is largely unknown. Using isogenic mouse lines harboring distinct microbiota communities, we observed highly variable disease kinetics of enteric Citrobacter rodentium colonization after infection. Transfer of communities from susceptible and resistant mice into germ-free mice verified that the varying susceptibilities are determined by microbiota composition. The strongest differences in colonization were observed in the cecum and could be maintained in vitro by coculturing cecal bacteria with C. rodentium. Cohousing of animals as well as the transfer of cultivable bacteria from resistant to susceptible mice led to variable outcomes in the recipient mice. Microbiome analysis revealed that a higher abundance of butyrate-producing bacteria was associated with the resistant phenotype. Quantification of short-chain fatty acid (SCFA) levels before and after infection revealed increased concentrations of acetate, butyrate and propionate in mice with delayed colonization. Addition of physiological concentrations of butyrate, but not of acetate and/or propionate strongly impaired growth of C. rodentium in vitro. In vivo supplementation of susceptible, antibiotic-treated and germ-free mice with butyrate led to the same level of protection, notably only when cecal butyrate concentration reached a concentration higher than 50 nmol/mg indicating a critical threshold for protection. In the recent years, commensal-derived primary and secondary bacterial metabolites emerged as potent modulators of hosts susceptibility to infection. Our results provide evidence that variations in SCFA production in mice fed fibre-rich chow-based diets modulate susceptibility to colonization with Enterobacteriaceae not only in antibiotic-disturbed ecosystems but even in undisturbed microbial communities. These findings emphasise the need for microbiota normalization across laboratory mouse lines for infection experiments with the model-pathogen C. rodentium independent of investigations of diet and antibiotic usage.
  • Microbiota Alters Urinary Bladder Weight and Gene Expression.

    Roje, Blanka; Elek, Anamaria; Palada, Vinko; Bom, Joana; Iljazović, Aida; Šimić, Ana; Sušak, Lana; Vilović, Katarina; Strowig, Till; Vlahoviček, Kristian; et al. (MDPI, 2020-03-17)
    We studied the effect of microbiota on the transcriptome and weight of the urinary bladder by comparing germ-free (GF) and specific pathogen-free (SPF) housed mice. In total, 97 genes were differently expressed (fold change > ±2; false discovery rate (FDR) p-value < 0.01) between the groups, including genes regulating circadian rhythm (Per1, Per2 and Per3), extracellular matrix (Spo1, Spon2), and neuromuscular synaptic transmission (Slc18a3, Slc5a7, Chrnb4, Chrna3, Snap25). The highest increase in expression was observed for immunoglobulin genes (Igkv1-122, Igkv4-68) of unknown function, but surprisingly the absence of microbiota did not change the expression of the genes responsible for recognizing microbes and their products. We found that urinary bladder weight was approximately 25% lighter in GF mice (p = 0.09 for males, p = 0.005 for females) and in mice treated with broad spectrum of antibiotics (p = 0.0002). In conclusion, our data indicate that microbiota is an important determinant of urinary bladder physiology controlling its gene expression and size.
  • The Biomolecular Spectrum Drives Microbial Biology and Functions in Agri-Food-Environments.

    Sharma, Minaxi; Singh, Dhananjaya Pratap; Rangappa, Kanchugarakoppal S; Stadler, Marc; Mishra, Pradeep Kumar; Silva, Roberto Nascimento; Prasad, Ram; Gupta, Vijai Kumar; HZI, Helmholtz Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (MDPI, 2020-03-04)
    Microbial biomolecules have huge commercial and industrial potential. In nature, biological interactions are mostly associated with biochemical and biological diversity, especially with the discovery of associated biomolecules from microbes. Within cellular or subcellular systems, biomolecules signify the actual statuses of the microorganisms. Understanding the biological prospecting of the diverse microbial community and their complexities and communications with the environment forms a vital basis for active, innovative biotechnological breakthroughs. Biochemical diversity rather than the specific chemicals that has the utmost biological importance. The identification and quantification of the comprehensive biochemical diversity of the microbial molecules, which generally consequences in a diversity of biological functions, has significant biotechnological potential. Beneficial microbes and their biomolecules of interest can assist as potential constituents for the wide-range of natural product-based preparations and formulations currently being developed on an industrial scale. The understanding of the production methods and functions of these biomolecules will contribute to valorisation of agriculture, food bioprocessing and biopharma, and prevent human diseases related to the environment.

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