Now showing items 1-20 of 3481

    • Buchwald-Hartwig versus Microwave-Assisted Amination of Chloroquinolines: En Route to the Pyoverdin Chromophore

      Seubert, Philipp; Freund, Marcel; Rudolf, Richard; Lin, Yulin; Altevogt, Luca; Bilitewski, Ursula; Baro, Angelika; Laschat, Sabine; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Thieme Verlag, 2020-07-22)
      The reaction of 2-chloro-3-nitroquinoline and a series of amines and aminoalkanoates under basic microwave-mediated conditions and Buchwald-Hartwig amination conditions is reported. The microwave irradiation favored the reaction with amines, resulting in yields up to 80%, while amino acid functionalization gave yields comparable to those of BuchwaldHartwig amination. (2R)-4-[(6,7-dimethoxy-3-nitroquinolinyl)amino]-2-hydroxybutanoate could be successfully cyclized to the pyoverdin chromophore, a subunit of siderophores.
    • Unsaturated Fatty Acids Control Biofilm Formation of and Other Gram-Positive Bacteria.

      Yuyama, Kamila Tomoko; Rohde, Manfred; Molinari, Gabriella; Stadler, Marc; Abraham, Wolf-Rainer; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-11-08)
      Infections involving biofilms are difficult to treat due to increased resistances against antibiotics and the immune system. Hence, there is an urgent demand for novel drugs against biofilm infections. During our search for novel biofilm inhibitors from fungi, we isolated linoleic acid from the ascomycete Hypoxylon fragiforme which showed biofilm inhibition of several bacteria at sub-MIC concentrations. Many fatty acids possess antimicrobial activities, but their minimum inhibitory concentrations (MIC) are high and reports on biofilm interferences are scarce. We demonstrated that not only linoleic acid but several unsaturated long-chain fatty acids inhibited biofilms at sub-MIC concentrations. The antibiofilm activity exerted by long-chain fatty acids was mainly against Gram-positive bacteria, especially against Staphylococcus aureus. Micrographs of treated S. aureus biofilms revealed a reduction in the extracellular polymeric substances, pointing to a possible mode of action of fatty acids on S. aureus biofilms. The fatty acids had a strong species specificity. Poly-unsaturated fatty acids had higher activities than saturated ones, but no obvious rule could be found for the optimal length and desaturation for maximal activity. As free fatty acids are non-toxic and ubiquitous in food, they may offer a novel tool, especially in combination with antibiotics, for the control of biofilm infections.
    • Synthetic rewiring and boosting type I interferon responses for visualization and counteracting viral infections.

      Gödecke, Natascha; Riedel, Jan; Herrmann, Sabrina; Behme, Sara; Rand, Ulfert; Kubsch, Tobias; Cicin-Sain, Luka; Hauser, Hansjörg; Köster, Mario; Wirth, Dagmar; et al. (Oxford Academic, 2020-11-18)
      Mammalian first line of defense against viruses is accomplished by the interferon (IFN) system. Viruses have evolved numerous mechanisms to reduce the IFN action allowing them to invade the host and/or to establish latency. We generated an IFN responsive intracellular hub by integrating the synthetic transactivator tTA into the chromosomal Mx2 locus for IFN-based activation of tTA dependent expression modules. The additional implementation of a synthetic amplifier module with positive feedback even allowed for monitoring and reacting to infections of viruses that can antagonize the IFN system. Low and transient IFN amounts are sufficient to trigger these amplifier cells. This gives rise to higher and sustained-but optionally de-activatable-expression even when the initial stimulus has faded out. Amplification of the IFN response induced by IFN suppressing viruses is sufficient to protect cells from infection. Together, this interfaced sensor/actuator system provides a toolbox for robust sensing and counteracting viral infections.
    • Expression, purification and crystal structure determination of a ferredoxin reductase from the actinobacterium Thermobifida fusca.

      Rodriguez Buitrago, Jhon Alexander; Klünemann, Thomas; Blankenfeldt, Wulf; Schallmey, Anett; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Wiley & Sons, 2020-07-28)
      he ferredoxin reductase FdR9 from Thermobifida fusca, a member of the oxygenase-coupled NADH-dependent ferredoxin reductase (FNR) family, catalyses electron transfer from NADH to its physiological electron acceptor ferredoxin. It forms part of a putative three-component cytochrome P450 monooxygenase system in T. fusca comprising CYP222A1 and the [3Fe-4S]-cluster ferredoxin Fdx8 as well as FdR9. Here, FdR9 was overexpressed and purified and its crystal structure was determined at 1.9 Å resolution. The overall structure of FdR9 is similar to those of other members of the FNR family and is composed of an FAD-binding domain, an NAD-binding domain and a C-terminal domain. Activity measurements with FdR9 confirmed a strong preference for NADH as the cofactor. Comparison of the FAD- and NAD-binding domains of FdR9 with those of other ferredoxin reductases revealed the presence of conserved sequence motifs in the FAD-binding domain as well as several highly conserved residues involved in FAD and NAD cofactor binding. Moreover, the NAD-binding site of FdR9 contains a modified Rossmann-fold motif, GxSxxS, instead of the classical GxGxxG motif.
    • Patient satisfaction & use of health care: a cross-sectional study of asylum seekers in the Freiburg initial reception centre.

      Bockey, Annabelle J; Janda, Aleš; Braun, Cornelia; Müller, Anne-Maria; Stete, Katarina; Kern, Winfried V; Rieg, Siegbert R; Lange, Berit; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (BMC, 2020-08-03)
      Background: In response to a high number of incoming asylum seekers and refugees (AS&R) in Germany, initial reception centres were established to provide immediate shelter, food and health support. This study evaluates the satisfaction with and use of the health care available at the Freiburg initial reception centre (FIRC) where an integrated health care facility (ICF) was set up in 2015. Methods: We assessed use and satisfaction with health services available to resident AS&R within and outside the FIRC in a cross-sectional design. Data were collected in 2017 using a questionnaire with both open and closed ended items. Results: The majority of 102 included participants were young (mean age 24.2; 95%CI 22.9-25.5, range 18-43) males (93%), from Sub-Saharan Africa (92%). High use frequencies were reported from returning patients of the ICF; with 56% fortnightly use and 19% daily use reported. The summary of satisfaction scores indicated that 84% (CI95 76-89%) of respondents were satisfied with the ICF. Multivariate analysis showed female gender and non-English speaking as risk factors for low satisfaction. Outside the FIRC, the satisfaction scores indicated that 60% of participants (95%CI 50-69%) were satisfied with the health care received. Conclusion: Our study shows that AS&R residing in the FIRC are generally satisfied with the services at the ICF, though strategies to enhance care for females and non-English speakers should be implemented. Satisfaction with health care outside of the FIRC was not as high, indicating the need to improve quality of care and linkage to regular health care services.
    • B Cell Speed and B-FDC Contacts in Germinal Centers Determine Plasma Cell Output via Swiprosin-1/EFhd2.

      Reimer, Dorothea; Meyer-Hermann, Michael; Rakhymzhan, Asylkhan; Steinmetz, Tobit; Tripal, Philipp; Thomas, Jana; Boettcher, Martin; Mougiakakos, Dimitrios; Schulz, Sebastian R; Urbanczyk, Sophia; et al. (Elsevier (CellPress), 2020-08-11)
      Plasma cells secreting affinity-matured antibodies develop in germinal centers (GCs), where B cells migrate persistently and directionally over defined periods of time. How modes of GC B cell migration influence plasma cell development remained unclear. Through genetic deletion of the F-actin bundling protein Swiprosin-1/EF-hand domain family member 2 (EFhd2) and by two-photon microscopy, we show that EFhd2 restrains B cell speed in GCs and hapten-specific plasma cell output. Modeling the GC reaction reveals that increasing GC B cell speed promotes plasma cell generation. Lack of EFhd2 also reduces contacts of GC B cells with follicular dendritic cells in vivo. Computational modeling uncovers that both GC output and antibody affinity depend quantitatively on contacts of GC B cells with follicular dendritic cells when B cells migrate more persistently. Collectively, our data explain how GC B cells integrate speed and persistence of cell migration with B cell receptor affinity.
    • Mathematical Model Shows How Sleep May Affect Amyloid-β Fibrillization.

      Hoore, Masoud; Khailaie, Sahamoddin; Montaseri, Ghazal; Mitra, Tanmay; Meyer-Hermann, Michael; BRICS, Braunschweiger Zentrum für Systembiologie, Rebenring 56,38106 Braunschweig, Germany; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Elsevier (CellPress), 2020-07-22)
      Deposition of amyloid-β (Aβ) fibers in the extracellular matrix of the brain is a ubiquitous feature associated with several neurodegenerative disorders, especially Alzheimer's disease (AD). Although many of the biological aspects that contribute to the formation of Aβ plaques are well addressed at the intra- and intercellular levels in short timescales, an understanding of how Aβ fibrillization usually starts to dominate at a longer timescale despite the presence of mechanisms dedicated to Aβ clearance is still lacking. Furthermore, no existing mathematical model integrates the impact of diurnal neural activity as emanated from circadian regulation to predict disease progression due to a disruption in the sleep-wake cycle. In this study, we develop a minimal model of Aβ fibrillization to investigate the onset of AD over a long timescale. Our results suggest that the diseased state is a manifestation of a phase change of the system from soluble Aβ (sAβ) to fibrillar Aβ (fAβ) domination upon surpassing a threshold in the production rate of sAβ. By incorporating the circadian rhythm into our model, we reveal that fAβ accumulation is crucially dependent on the regulation of the sleep-wake cycle, thereby indicating the importance of good sleep hygiene in averting AD onset. We also discuss potential intervention schemes to reduce fAβ accumulation in the brain by modification of the critical sAβ production rate.
    • Stieleriacines, N-Acyl Dehydrotyrosines From the Marine Planctomycete Stieleria neptunia sp. nov.

      Sandargo, Birthe; Jeske, Olga; Boedeker, Christian; Wiegand, Sandra; Wennrich, Jan-Peer; Kallscheuer, Nicolai; Jogler, Mareike; Rohde, Manfred; Jogler, Christian; Surup, Frank; et al. (Frontiers, 2020-07-16)
      Bacteria of the phylum Planctomycetes occur ubiquitously in marine environments and play important roles in the marine nitrogen- and carbon cycle, for example as scavengers after phototrophic blooms. Here, we describe the isolation and characterization of the planctomycetal strain Enr13T isolated from a Posidonia sp. biofilm obtained from seawater sediment close to Panarea Island, Italy. Phylogenetic tree reconstruction based on 16S rRNA gene sequences and multi-locus sequence analysis supports the delineation of strain Enr13T from characterized species part of the phylum of Planctomycetes. HPLC-MS analysis of culture broth obtained from strain Enr13T revealed the presence of lipophilic metabolites, of which the major compound was isolated by preparative reversed-phase HPLC. The structure of this compound, named stieleriacine D (1), was elucidated utilizing HRESIMS, 1D- and 2D-NMR data as a new N-acylated dehydrotyrosine derivative. Its biosynthesis was proposed based on an in silico gene cluster analysis. Through analysis of the MS/MS spectrum of 1 and its minor derivative, stieleriacine E (2), it was possible to assign the structure of 2 without isolation. 1 showed antibacterial activity, however, the wide distribution of structurally related compounds indicates a potential role as a signaling molecule.
    • MicroRNA-221: A Fine Tuner and Potential Biomarker of Chronic Liver Injury.

      Markovic, Jovana; Sharma, Amar Deep; Balakrishnan, Asha; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-07-23)
      The last decade has witnessed significant advancements in our understanding of how small noncoding RNAs, such as microRNAs (miRNAs), regulate disease progression. One such miRNA, miR-221, has been shown to play a key role in the progression of liver fibrosis, a common feature of most liver diseases. Many reports have demonstrated the upregulation of miR-221 in liver fibrosis caused by multiple etiologies such as viral infections and nonalcoholic steatohepatitis. Inhibition of miR-221 via different strategies has shown promising results in terms of the suppression of fibrogenic gene signatures in vitro, as well as in vivo, in independent mouse models of liver fibrosis. In addition, miR-221 has also been suggested as a noninvasive serum biomarker for liver fibrosis and cirrhosis. In this review, we discuss the biology of miR-221, its significance and use as a biomarker during progression of liver fibrosis, and finally, potential and robust approaches that can be utilized to suppress liver fibrosis via inhibition of miR-221.
    • Multisystem combined uranium resistance mechanisms and bioremediation potential of Stenotrophomonas bentonitica BII-R7: Transcriptomics and microscopic study

      Pinel-Cabello, M.; Jroundi, F.; López-Fernández, M.; Geffers, R.; Jarek, M.; Jauregui, R.; Link, A.; Vílchez-Vargas, R.; Merroun, M. L.; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Elsevier, 2021-02-05)
      The potential use of microorganisms in the bioremediation of U pollution has been extensively described. However, a lack of knowledge on molecular resistance mechanisms has become a challenge for the use of these technologies. We reported on the transcriptomic and microscopic response of Stenotrophomonas bentonitica BII-R7 exposed to 100 and 250 μM of U. Results showed that exposure to 100 μM displayed up-regulation of 185 and 148 genes during the lag and exponential phases, respectively, whereas 143 and 194 were down-regulated, out of 3786 genes (>1.5-fold change). Exposure to 250 μM of U showed up-regulation of 68 genes and down-regulation of 290 during the lag phase. Genes involved in cell wall and membrane protein synthesis, efflux systems and phosphatases were up-regulated under all conditions tested. Microscopic observations evidenced the formation of U-phosphate minerals at membrane and extracellular levels. Thus, a biphasic process is likely to occur: the increased cell wall would promote the biosorption of U to the cell surface and its precipitation as U-phosphate minerals enhanced by phosphatases. Transport systems would prevent U accumulation in the cytoplasm. These findings contribute to an understanding of how microbes cope with U toxicity, thus allowing for the development of efficient bioremediation strategies.
    • Combined high-throughput library screening and next generation RNA sequencing uncover microRNAs controlling human cardiac fibroblast biology

      Schimmel, Katharina; Stojanović, Stevan D.; Huang, Cheng Kai; Jung, Mira; Meyer, Martin H.; Xiao, Ke; Grote-Levi, Lea; Bär, Christian; Pfanne, Angelika; Mitzka, Saskia; et al. (Elsevier, 2021-01-01)
      Background: Myocardial fibrosis is a hallmark of the failing heart, contributing to the most common causes of deaths worldwide. Several microRNAs (miRNAs, miRs) controlling cardiac fibrosis were identified in recent years; however, a more global approach to identify miRNAs involved in fibrosis is missing. Methods and results: Functional miRNA mimic library screens were applied in human cardiac fibroblasts (HCFs) to identify annotated miRNAs inducing proliferation. In parallel, miRNA deep sequencing was performed after subjecting HCFs to proliferating and resting stimuli, additionally enabling discovery of novel miRNAs. In-depth in vitro analysis confirmed the pro-fibrotic nature of selected, highly conserved miRNAs miR-20a-5p and miR-132-3p. To determine downstream cellular pathways and their role in the fibrotic response, targets of the annotated miRNA candidates were modulated by synthetic siRNA. We here provide evidence that repression of autophagy and detoxification of reactive oxygen species by miR-20a-5p and miR-132-3p explain some of their pro-fibrotic nature on a mechanistic level. Conclusion: We here identified both miR-20a-5p and miR-132-3p as crucial regulators of fibrotic pathways in an in vitro model of human cardiac fibroblast biology.
    • The impact of the digital revolution 
on human brain and behavior: where 
do we stand?

      Korte, Martin; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany.
      This overview will outline the current results of neuroscience research on the possible effects of digital media use on the human brain, cognition, and behavior. This is of importance due to the significant amount of time that individuals spend using digital media. Despite several positive aspects of digital media, which include the capability to effortlessly communicate with peers, even over a long distance, and their being used as training tools for students and the elderly, detrimental effects on our brains and minds have also been suggested. Neurological consequences have been observed related to internet/gaming addiction, language development, and processing of emotional signals. However, given that much of the neuroscientific research conducted up to now relies solely on self-reported parameters to assess social media usage, it is argued that neuroscientists need to include datasets with higher precision in terms of what is done on screens, for how long, and at what age.
    • Flotillin-mediated membrane fluidity controls peptidoglycan synthesis and MreB movement.

      Zielińska, Aleksandra; Savietto, Abigail; de Sousa Borges, Anabela; Martinez, Denis; Berbon, Melanie; Roelofsen, Joël R; Hartman, Alwin M; de Boer, Rinse; Van der Klei, Ida J; Hirsch, Anna Kh; et al. (eLife Sciences Publications, Ltd., 2020-07-14)
      Every living cell is enclosed by a flexible membrane made of molecules known as phospholipids, which protects the cell from harmful chemicals and other threats. In bacteria and some other organisms, a rigid structure known as the cell wall sits just outside of the membrane and determines the cell’s shape. There are several proteins in the membrane of bacteria that allow the cell to grow by assembling new pieces of the cell wall. To ensure these proteins expand the cell wall at the right locations, another protein known as MreB moves and organizes them to the appropriate place in the membrane and controls their activity. Previous studies have found that another class of proteins called flotillins are involved in arranging proteins and phospholipid molecules within membranes. Bacteria lacking these proteins do not grow properly and are unable to maintain their normal shape. However, the precise role of the flotillins remained unclear. Here, Zielińska, Savietto et al. used microscopy approaches to study flotillins in a bacterium known as Bacillus subtilis. The experiments found that, in the presence of flotillins, MreB moved around the membrane more quickly (suggesting it was more active) than when no flotillins were present. Similar results were observed when bacterial cells lacking flotillins were treated with a chemical that made membranes more ‘fluid’ – that is, made it easier for the molecules within the membrane to travel around. Further experiments found that flotillins allowed the phospholipid molecules within an artificial membrane to move around more freely, which increases the fluidity of the membrane. These findings suggest that flotillins make the membranes of bacterial cells more fluid to help cells expand their walls and perform several other processes. Understanding how bacteria control the components of their membranes will further our understanding of how many currently available antibiotics work and may potentially lead to the design of new antibiotics in the future.
    • Hybridorubrins A-D, novel azaphilone heterodimers from stromata of Hypoxylon fragiforme and insights into the biosynthetic machinery for azaphilone diversification.

      Becker, Kevin; Pfütze, Sebastian; Kuhnert, Eric; Cox, Russell; Stadler, Marc; Surup, Frank; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Wiley-VCH, 2020-08-04)
      The diversity of azaphilones in stromatal extracts of the fungus Hypoxylon fragiforme was investigated and linked to their biosynthetic machineries using bioinformatics. Nineteen azaphilone-type compounds were isolated and characterized by NMR spectroscopy and mass spectrometry, with their absolute stereoconfigurations assigned using Mosher ester analysis and ECD spectroscopy. Four unprecedented bisazaphilones, named hybridorubrins A-D ( 1 - 4 ), were elucidated, in addition to new fragirubrins F-G ( 5 - 6 ) and various known mitorubrin derivatives. Only the hybridorubrins, which are composed of mitorubrin and fragirubrin moieties, exhibited strong inhibition of Staphylococcus aureus biofilm formation. Analysis of the genome of H. fragiforme revealed the presence of two separate biosynthetic gene clusters (BGC) hfaza1 and hfaza2 responsible for azaphilone formation. While the hfaza1 BGC likely encodes the assembly of the backbone and addition of fatty acid moieties to yield the ( R )-configured series of fragirubrins, the hfaza2 BGC contains the necessary genes to synthesise the widely distributed ( S )-mitorubrins. This study is the first example of two distant cross-acting fungal BGC collaborating to produce two families of azaphilones and bisazaphilones derived thereof.
    • YB-1 Mediates TNF-Induced Pro-Survival Signaling by Regulating NF-κB Activation.

      Shah, Aneri; Plaza-Sirvent, Carlos; Weinert, Sönke; Buchbinder, Jörn H; Lavrik, Inna N; Mertens, Peter R; Schmitz, Ingo; Lindquist, Jonathan A; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-08-05)
      Cell fate decisions regulating survival and death are essential for maintaining tissue homeostasis; dysregulation thereof can lead to tumor development. In some cases, survival and death are triggered by the same receptor, e.g., tumor necrosis factor (TNF)-receptor 1 (TNFR1). We identified a prominent role for the cold shock Y-box binding protein-1 (YB-1) in the TNF-induced activation and nuclear translocation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65. In the absence of YB-1, the expression of TNF receptor-associated factor 2 (TRAF2), a central component of the TNF receptor signaling complex required for NF-κB activation, is significantly reduced. Therefore, we hypothesized that the loss of YB-1 results in a destabilization of TRAF2. Consistent with this hypothesis, we observed that YB-1-deficient cells were more prone to TNF-induced apoptotic cell death. We observed enhanced effector caspase-3 activation and could successfully rescue the cells using the pan-caspase inhibitor zVAD-fmk, but not necrostatin-1. Taken together, our results indicate that YB-1 plays a central role in promoting cell survival through NF-κB activation and identifies a novel mechanism by which enhanced YB-1 expression may contribute to tumor development.
    • Controlling Supramolecular Structures of Drugs by Light.

      Wiest, Johannes; Kehrein, Josef; Saedtler, Marco; Schilling, Klaus; Cataldi, Eleonora; Sotriffer, Christoph A; Holzgrabe, Ulrike; Rasmussen, Tim; Böttcher, Bettina; Cronin-Golomb, Mark; et al. (American Chemical Society (ACS), 2020-10-29)
      Controlling physicochemical properties of light-unresponsive drugs, by light, prima facie, a paradox approach. We expanded light control by ion pairing light-unresponsive salicylate or ibuprofen to photoswitchable azobenzene counterions, thereby reversibly controlling supramolecular structures, hence the drugs' physicochemical and kinetic properties. The resulting ion pairs photoliquefied into room-temperature ionic liquids under ultraviolet light. Aqueous solutions showed trans-cis-dependent supramolecular structures under a light with wormlike aggregates decomposing into small micelles and vice versa. Light control allowed for permeation through membranes of cis-ibuprofen ion pairs within 12 h in contrast to the trans ion pairs requiring 72 h. In conclusion, azobenzene ion-pairing expands light control of physicochemical and kinetic properties to otherwise light-unresponsive drugs.
    • Evaluation of Bacterial RNA Polymerase Inhibitors in a -Based Wound Infection Model in SKH1 Mice.

      Haupenthal, Jörg; Kautz, Yannik; Elgaher, Walid A M; Pätzold, Linda; Röhrig, Teresa; Laschke, Matthias W; Tschernig, Thomas; Hirsch, Anna K H; Molodtsov, Vadim; Murakami, Katsuhiko S; et al. (American Chemical Society (ACS), 2020-09-21)
      Chronic wounds infected with pathogens such as Staphylococcus aureus represent a worldwide health concern, especially in patients with a compromised immune system. As antimicrobial resistance has become an immense global problem, novel antibiotics are urgently needed. One strategy to overcome this threatening situation is the search for drugs targeting novel binding sites on essential and validated enzymes such as the bacterial RNA polymerase (RNAP). In this work, we describe the establishment of an in vivo wound infection model based on the pathogen S. aureus and hairless Crl:SKH1-Hrhr (SKH1) mice. The model proved to be a valuable preclinical tool to study selected RNAP inhibitors after topical application. While rifampicin showed a reduction in the loss of body weight induced by the bacteria, an acceleration of wound healing kinetics, and a reduced number of colony forming units in the wound, the ureidothiophene-2-carboxylic acid 1 was inactive under in vivo conditions, probably due to strong plasma protein binding. The cocrystal structure of compound 1 with RNAP, that we hereby also present, will be of great value for applying appropriate structural modifications to further optimize the compound, especially in terms of plasma protein binding.
    • Mining zebrafish microbiota reveals key community-level resistance against fish pathogen infection.

      Stressmann, Franziska A; Bernal-Bayard, Joaquín; Perez-Pascual, David; Audrain, Bianca; Rendueles, Olaya; Briolat, Valérie; Bruchmann, Sebastian; Volant, Stevenn; Ghozlane, Amine; Häussler, Susanne; et al. (Springer Nature, 2020-10-19)
      The long-known resistance to pathogens provided by host-associated microbiota fostered the notion that adding protective bacteria could prevent or attenuate infection. However, the identification of endogenous or exogenous bacteria conferring such protection is often hindered by the complexity of host microbial communities. Here, we used zebrafish and the fish pathogen Flavobacterium columnare as a model system to study the determinants of microbiota-associated colonization resistance. We compared infection susceptibility in germ-free, conventional and reconventionalized larvae and showed that a consortium of 10 culturable bacterial species are sufficient to protect zebrafish. Whereas survival to F. columnare infection does not rely on host innate immunity, we used antibiotic dysbiosis to alter zebrafish microbiota composition, leading to the identification of two different protection strategies. We first identified that the bacterium Chryseobacterium massiliae individually protects both larvae and adult zebrafish. We also showed that an assembly of 9 endogenous zebrafish species that do not otherwise protect individually confer a community-level resistance to infection. Our study therefore provides a rational approach to identify key endogenous protecting bacteria and promising candidates to engineer resilient microbial communities. It also shows how direct experimental analysis of colonization resistance in low-complexity in vivo models can reveal unsuspected ecological strategies at play in microbiota-based protection against pathogens.
    • Notch and TLR signaling coordinate monocyte cell fate and inflammation.

      Gamrekelashvili, Jaba; Kapanadze, Tamar; Sablotny, Stefan; Ratiu, Corina; Dastagir, Khaled; Lochner, Matthias; Karbach, Susanne; Wenzel, Philip; Sitnow, Andre; Fleig, Susanne; et al. (elife Sciences, 2020-07-29)
      Conventional Ly6Chi monocytes have developmental plasticity for a spectrum of differentiated phagocytes. Here we show, using conditional deletion strategies in a mouse model of Toll-like receptor (TLR) 7-induced inflammation, that the spectrum of developmental cell fates of Ly6Chi monocytes, and the resultant inflammation, is coordinately regulated by TLR and Notch signaling. Cell-intrinsic Notch2 and TLR7-Myd88 pathways independently and synergistically promote Ly6Clo patrolling monocyte development from Ly6Chi monocytes under inflammatory conditions, while impairment in either signaling axis impairs Ly6Clo monocyte development. At the same time, TLR7 stimulation in the absence of functional Notch2 signaling promotes resident tissue macrophage gene expression signatures in monocytes in the blood and ectopic differentiation of Ly6Chi monocytes into macrophages and dendritic cells, which infiltrate the spleen and major blood vessels and are accompanied by aberrant systemic inflammation. Thus, Notch2 is a master regulator of Ly6Chi monocyte cell fate and inflammation in response to TLR signaling.
    • Non-Heme Monooxygenase ThoJ Catalyzes Thioholgamide β-Hydroxylation.

      Sikandar, Asfandyar; Lopatniuk, Maria; Luzhetskyy, Andriy; Koehnke, Jesko; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (American Chemical Society (ACS), 2020-10-01)
      Thioviridamide-like compounds, including thioholgamides, are ribosomally synthesized and post-translationally modified peptide natural products with potent anticancer cell activity and an unprecedented structure. Very little is known about their biosynthesis, and we were intrigued by the β-hydroxy-N1, N3-dimethylhistidinium moiety found in these compounds. Here we report the construction of a heterologous host capable of producing thioholgamide with a 15-fold increased yield compared to the wild-type strain. A knockout of thoJ, encoding a predicted nonheme monooxygenase, shows that ThoJ is essential for thioholgamide β-hydroxylation. The crystal structure of ThoJ exhibits a typical mono/dioxygenase fold with conserved key active-site residues. Yet, ThoJ possesses a very large substrate binding pocket that appears suitable to receive a cyclic thioholgamide intermediate for hydroxylation. The improved production of the heterologous host will enable the dissection of the individual biosynthetic steps involved in biosynthesis of this exciting RiPP family.