Browsing by Author "Becker, Anke"

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Open Access
Feature Pyramid Fusion for Detection and Segmentation of Morphologically Complex Eukaryotic Cells
Korfhage, Nikolaus; Ringshandl, Stephan; Becker, Anke; Schmeck, Bernd; Mühling, Markus; Freisleben, Bernd
Open Access
Lipid A in outer membrane vesicles shields bacteria from polymyxins
(Philipps-Universität Marburg, 2024-12-18) Burt, Marie; Angelidou, Georgia; Mais, Christopher Nils; Preußer, Christian; Glatter, Timo; Heimerl, Thomas; Groß, Rüdiger; Serrania, Javier; Boosarpu, Gowtham; Pogge von Strandmann, Elke; Müller, Janis A. (0000-0002-0347-416X); Bange, Gert; Becker, Anke; Lehmann, Mareike; Jonigk, Danny; Neubert, Lavinia; Freitag, Hinrich; Paczia, Nicole; Schmeck, Bernd; Jung, Anna Lena (0000-0002-7762-4597)
The continuous emergence of multidrug-resistant bacterial pathogens poses a major global healthcare challenge, with Klebsiella pneumoniae being a prominent threat. We conducted a comprehensive study on K. pneumoniae's antibiotic resistance mechanisms, focusing on outer membrane vesicles (OMVs) and polymyxin, a last-resort antibiotic. Our research demonstrates that OMVs protect bacteria from polymyxins. OMVs derived from Polymyxin B (PB)-stressed K. pneumoniae exhibited heightened protective efficacy due to increased vesiculation, compared to OMVs from unstressed Klebsiella. OMVs also shield bacteria from different bacterial families. This was validated ex vivo and in vivo using precision cut lung slices (PCLS) and Galleria mellonella. In all models, OMVs protected K. pneumoniae from PB and reduced the associated stress response on protein level. We observed significant changes in the lipid composition of OMVs upon PB treatment, affecting their binding capacity to PB. The altered binding capacity of single OMVs from PB stressed K. pneumoniae could be linked to a reduction in the lipid A amount of their released vesicles. Although the amount of lipid A per vesicle is reduced, the overall increase in the number of vesicles results in an increased protection because the sum of lipid A and therefore PB binding sites have increased. This unravels the mechanism of the altered PB protective efficacy of OMVs from PB stressed K. pneumoniae compared to control OMVs. The lipid A-dependent protective effect against PB was confirmed in vitro using artificial vesicles. Moreover, artificial vesicles successfully protected Klebsiella from PB ex vivo and in vivo. The findings indicate that OMVs act as protective shields for bacteria by binding to polymyxins, effectively serving as decoys and preventing antibiotic interaction with the cell surface. Our findings provide valuable insights into the mechanisms underlying antibiotic cross-protection and offer potential avenues for the development of novel therapeutic interventions to address the escalating threat of multidrug-resistant bacterial infections.
Open Access
Screening for eukaryotic motifs in Legionella pneumophila reveals Smh1 as bacterial deacetylase of host histones
(Philipps-Universität Marburg, 2023-10-04) Herbel, Stefanie M.; Moyon, Lambert; Christ, Marvin; Elsayed, Eslam M.; Caffrey, Brian E.; Malmsheimer, Silke; Grin, Iwan; Hoffmann, Kerstin; Surmann, Kristin; Blankenburg, Sascha; Jung, Anna Lena; Herkt, Christina E.; Borsò, Marco; Bozdag, Beyza; Imhof, Axel; Becker, Anke; Wagner, Samuel; Bange, Gert; Völker, Uwe; Bertrams, Wilhelm; Marsico, Annalisa; Schmeck, Bernd (0000-0002-2767-3606)
Legionella pneumophila (L.p.) is a bacterial pathogen which is a common causative agent of pneumonia. In humans, it infects alveolar macrophages and transfers hundreds of virulence factors that interfere with cellular signalling pathways and the transcriptomic landscape to sustain its own replication. By this interaction, it has acquired eukaryote-like protein motifs by gene transfer events that partake in the pathogenicity of Legionella. In a computational screening approach for eukaryotic motifs in the transcriptome of Legionella, we identified the L.p. strain Corby protein ABQ55614 as putative histone-deacetylase and named it “suppressing modifier of histones 1” (Smh1). During infection, Smh1 is translocated from the Legionella vacuole into the host cytosol. When expressed in human macrophage THP-1 cells, Smh1 was localized predomi-nantly in the nucleus, leading to broad histone H3 and H4 deacetylation, blunted expression of a large number of genes (e.g. IL-1β and IL-8), and fostered intracellular bacterial replication. L.p. with a Smh1 knockdown grew normally in media but showed a slight growth defect inside the host cell. Furthermore, Smh1 showed a very potent histone deacetylation activity in vitro, e.g. at H3K14, that could be inhibited by targeted mutation of the putative catalytic center inferred by analogy with eukaryotic HDAC8, and with the deacetylase inhibitor trichostatin A. In summary, Smh1 displays functional homology with class I/II type HDACs. We identified Smh1 as a new Legionella virulence factor with a eukaryote-like histone-deacetylase activity that moderates host gene expression and might pave the way for further histone modifications. Legionella pneumophila (L.p.) is a prominent bacterial pathogen, which is a common causative agent of pneumonia. In order to survive inside the host cell, the human macrophage, it profoundly interacts with host cell processes to advance its own replication. In this study, we identify a bacterial factor, Smh1, with yet unknown function as a host histone deacetylase. The activity of this factor in the host cell leads to attenuated gene expression and increased intracellular bacterial replication.