• Genetic engineering and heterologous expression of the disorazol biosynthetic gene cluster via Red/ET recombineering.

      Tu, Qiang; Herrmann, Jennifer; Hu, Shengbiao; Raju, Ritesh; Bian, Xiaoying; Zhang, Youming; Müller, Rolf; Helmholtz-Institute for Pharmaceutical Research Saarland (HIPS),Saarland 9 University, 66123 Saarbrücken, Germany. (2016)
      Disorazol, a macrocyclic polykitide produced by the myxobacterium Sorangium cellulosum So ce12 and it is reported to have potential cytotoxic activity towards several cancer cell lines, including multi-drug resistant cells. The disorazol biosynthetic gene cluster (dis) from Sorangium cellulosum (So ce12) was identified by transposon mutagenesis and cloned in a bacterial artificial chromosome (BAC) library. The 58-kb dis core gene cluster was reconstituted from BACs via Red/ET recombineering and expressed in Myxococcus xanthus DK1622. For the first time ever, a myxobacterial trans-AT polyketide synthase has been expressed heterologously in this study. Expression in M. xanthus allowed us to optimize the yield of several biosynthetic products using promoter engineering. The insertion of an artificial synthetic promoter upstream of the disD gene encoding a discrete acyl transferase (AT), together with an oxidoreductase (Or), resulted in 7-fold increase in disorazol production. The successful reconstitution and expression of the genetic sequences encoding for these promising cytotoxic compounds will allow combinatorial biosynthesis to generate novel disorazol derivatives for further bioactivity evaluation.
    • Genome Analysis of the Fruiting Body-Forming Myxobacterium Chondromyces crocatus Reveals High Potential for Natural Product Biosynthesis.

      Zaburannyi, Nestor; Bunk, Boyke; Maier, Josef; Overmann, Jörg; Müller, Rolf; Helmholtz-Institute for Pharmaceutical Research Saarland (HIPS), Saarland University, Campus C2.3, D-66123 Saarbrücken, Germany. (2016)
      Here, we report the complete genome sequence of the type strain of the myxobacterial genus Chondromyces, Chondromyces crocatus Cm c5. It presents one of the largest prokaryotic genomes featuring a single circular chromosome and no plasmids. Analysis revealed an enlarged set of tRNA genes, along with reduced pressure on preferred codon usage compared to that of other bacterial genomes. The large coding capacity and the plethora of encoded secondary metabolite biosynthetic gene clusters are in line with the capability of Cm c5 to produce an arsenal of antibacterial, antifungal, and cytotoxic compounds. Known pathways of the ajudazol, chondramide, chondrochloren, crocacin, crocapeptin, and thuggacin compound families are complemented by many more natural compound biosynthetic gene clusters in the chromosome. Whole-genome comparison of the fruiting-body-forming type strain (Cm c5, DSM 14714) to an accustomed laboratory strain which has lost this ability (nonfruiting phenotype, Cm c5 fr-) revealed genetic changes in three loci. In addition to the low synteny found with the closest sequenced representative of the same family, Sorangium cellulosum, extensive genetic information duplication and broad application of eukaryotic-type signal transduction systems are hallmarks of this 11.3-Mbp prokaryotic genome.
    • The glucocorticoid-induced leucine zipper mediates statin-induced muscle damage.

      Hoppstädter, Jessica; Valbuena Perez, Jenny Vanessa; Linnenberger, Rebecca; Dahlem, Charlotte; Legroux, Thierry M; Hecksteden, Anne; Tse, William K F; Flamini, Sara; Andreas, Anastasia; Herrmann, Jennifer; et al. (Wiley, 2020-02-06)
      Statins, the most prescribed class of drugs for the treatment of hypercholesterolemia, can cause muscle-related adverse effects. It has been shown that the glucocorticoid-induced leucine zipper (GILZ) plays a key role in the anti-myogenic action of dexamethasone. In the present study, we aimed to evaluate the role of GILZ in statin-induced myopathy. Statins induced GILZ expression in C2C12 cells, primary murine myoblasts/myotubes, primary human myoblasts, and in vivo in zebrafish embryos and human quadriceps femoris muscle. Gilz induction was mediated by FOXO3 activation and binding to the Gilz promoter, and could be reversed by the addition of geranylgeranyl, but not farnesyl, pyrophosphate. Atorvastatin decreased Akt phosphorylation and increased cleaved caspase-3 levels in myoblasts. This effect was reversed in myoblasts from GILZ knockout mice. Similarly, myofibers isolated from knockout animals were more resistant toward statin-induced cell death than their wild-type counterparts. Statins also impaired myoblast differentiation, and this effect was accompanied by GILZ induction. The in vivo relevance of our findings was supported by the observation that gilz overexpression in zebrafish embryos led to impaired embryonic muscle development. Taken together, our data point toward GILZ as an essential mediator of the molecular mechanisms leading to statin-induced muscle damage.
    • Growth Medium-Dependent Glycine Incorporation into the Peptidoglycan of Caulobacter crescentus.

      Takacs, Constantin N; Hocking, Jason; Cabeen, Matthew T; Bui, Nhat Khai; Poggio, Sebastian; Vollmer, Waldemar; Jacobs-Wagner, Christine; Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut, United States of America. (2013)
      The peptidoglycan (PG) is a macromolecular component of the bacterial cell wall that maintains the shape and integrity of the cell. The PG of , unlike that of many other Gram-negative bacteria, has repeatedly been shown to contain significant amounts of glycine. This compositional peculiarity has been deemed an intrinsic characteristic of this species. By performing a comprehensive qualitative and quantitative analysis of the PG by high-performance liquid chromatography (HPLC) and mass spectrometry (MS), we show here that glycine incorporation into the PG depends on the presence of exogenous glycine in the growth medium. High levels of glycine were detected at the fifth position of the peptide side chains of PG isolated from cells grown in the complex laboratory medium PYE or in defined medium (M2G) supplemented with casamino acids or glycine alone. In contrast, glycine incorporation was undetectable when cells were grown in M2G medium lacking glycine. Remarkably, glycine incorporation into peptidoglycan occurred even in the presence of low millimolar to sub-millimolar concentrations of free glycine. High glycine content in the PG had no obvious effects on growth rates, mode of PG incorporation or cell morphology. Hence, the PG is able to retain its physiological functions in cell growth and morphogenesis despite significant alterations in its composition, in what we deem to be unprecedented plasticity.
    • Heterologous expression of the atypical tetracycline chelocardin reveals the full set of genes required for its biosynthesis.

      Lukežič, Tadeja; Pikl, Špela; Zaburannyi, Nestor; Remškar, Maja; Petković, Hrvoje; Müller, Rolf; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (BMC (part of Springer), 2020-12-19)
      Background: Chelocardin (CHD) exhibits a broad-spectrum antibiotic activity and showed promising results in a small phase II clinical study conducted on patients with urinary tract infections. Importantly, CHD was shown to be active also against tetracycline-resistant Gram-negative pathogens, which is gaining even more importance in today’s antibiotic crisis. We have demonstrated that modifications of CHD through genetic engineering of its producer, the actinomycete Amycolatopsis sulphurea, are not only possible but yielded even more potent antibiotics than CHD itself, like 2-carboxamido-2-deacetyl-chelocardin (CD-CHD), which is currently in preclinical evaluation. A. sulphurea is difficult to genetically manipulate and therefore manipulation of the chd biosynthetic gene cluster in a genetically amenable heterologous host would be of high importance for further drug-discovery efforts. Results: We report heterologous expression of the CHD biosynthetic gene cluster in the model organism Streptomyces albus del14 strain. Unexpectedly, we found that the originally defined CHD gene cluster fails to provide all genes required for CHD formation, including an additional cyclase and two regulatory genes. Overexpression of the putative pathway-specific streptomyces antibiotic regulatory protein chdB in A. sulphurea resulted in an increase of both, CHD and CD-CHD production. Applying a metabolic-engineering approach, it was also possible to generate the potent CHD analogue, CD-CHD in S. albus. Finally, an additional yield increase was achieved in S. albus del14 by in-trans overexpression of the chdR exporter gene, which provides resistance to CHD and CDCHD. Conclusions: We identified previously unknown genes in the CHD cluster, which were shown to be essential for chelocardin biosynthesis by expression of the full biosynthetic gene cluster in S. albus as heterologous host. When comparing to oxytetracycline biosynthesis, we observed that the CHD gene cluster contains additional enzymes not found in gene clusters encoding the biosynthesis of typical tetracyclines (such as oxytetracycline). This finding probably explains the different chemistries and modes of action, which make CHD/CD-CHD valuable lead structures for clinical candidates. Even though the CHD genes are derived from a rare actinomycete A. sulphurea, the yield of CHD in the heterologous host was very good. The corrected nucleotide sequence of the CHD gene cluster now contains allgene products required for the production of CHD in a genetically amenable heterologous host, thus opening new possibilities towards production of novel and potent tetracycline analogues with a new mode of action.
    • A high-affinity fluorescence probe for copper(II) ions and its application in fluorescence lifetime correlation spectroscopy.

      Grüter, Andreas; Hoffmann, Michael; Müller, Rolf; Wohland, Thorsten; Jung, Gregor; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (Springer, 2019-04-26)
      Copper is one of the most important transition metals in many organisms where it catalyzes a manifold of different processes. As a result of copper's redox activity, organisms have to avoid unbound ions, and a dysfunctional copper homeostasis may lead to multifarious pathological processes in cells with very severe ramifications for the affected organisms. In many neurodegenerative diseases, however, the exact role of copper ions is still not completely clarified. In this work, a high-affinity and highly selective copper probe molecule, based on the naturally occurring tetrapeptide DAHK is synthesized. The sensor (log KD = - 12.8 ± 0.1) is tagged with a fluorescent BODIPY dye whose fluorescence lifetime distinctly decreases from 5.8 ns ± 0.2 ns to 0.4 ns ± 0.1 ns on binding to copper(II) cations. It is shown by using fluorescence lifetime correlation spectroscopy that the concentration of both probe and probe-copper complex can be simultaneously measured even at nanomolar concentration levels. This work presents a possible starting point for a new type of probe and method for future in vivo studies to further reveal the exact role of copper ions in organisms. Graphical abstract.
    • Homologous bd oxidases share the same architecture but differ in mechanism.

      Theßeling, Alexander; Rasmussen, Tim; Burschel, Sabrina; Wohlwend, Daniel; Kägi, Jan; Müller, Rolf; Böttcher, Bettina; Friedrich, Thorsten; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (Nature Publication group, 2019-11-13)
      Cytochrome bd oxidases are terminal reductases of bacterial and archaeal respiratory chains. The enzyme couples the oxidation of ubiquinol or menaquinol with the reduction of dioxygen to water, thus contributing to the generation of the protonmotive force. Here, we determine the structure of the Escherichia coli bd oxidase treated with the specific inhibitor aurachin by cryo-electron microscopy (cryo-EM). The major subunits CydA and CydB are related by a pseudo two fold symmetry. The heme b and d cofactors are found in CydA, while ubiquinone-8 is bound at the homologous positions in CydB to stabilize its structure. The architecture of the E. coli enzyme is highly similar to that of Geobacillus thermodenitrificans, however, the positions of heme b595 and d are interchanged, and a common oxygen channel is blocked by a fourth subunit and substituted by a more narrow, alternative channel. Thus, with the same overall fold, the homologous enzymes exhibit a different mechanism.
    • How to Study the Metabolism of New Psychoactive Substances for the Purpose of Toxicological Screenings-A Follow-Up Study Comparing Pooled Human Liver S9, HepaRG Cells, and Zebrafish Larvae.

      Wagmann, Lea; Frankenfeld, Fabian; Park, Yu Mi; Herrmann, Jennifer; Fischmann, Svenja; Westphal, Folker; Müller, Rolf; Flockerzi, Veit; Meyer, Markus R; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (Frontiers, 2020-07-17)
      The new psychoactive substances (NPS) market continues to be very dynamic. A large number of compounds belonging to diverse chemical groups continue to emerge. This makes their detection in biological samples challenging for clinical and forensic toxicologists. Knowledge of the metabolic fate of NPS is crucial for developing comprehensive screening procedures. As human studies are not feasible due to ethical concerns, the current study aimed to compare the NPS' metabolic pattern in incubations with pooled human liver S9 fraction (pHLS9), human liver HepaRG cells, and zebrafish larvae. The latter model was recently shown to be a promising preclinical surrogate for human hepatic metabolism of a synthetic cannabinoid. However, studies concerning other NPS classes are still missing and therefore an amphetamine-based N-methoxybenzyl (NBOMe) compound, a synthetic cathinone, a pyrrolidinophenone analog, a lysergamide, as well as another synthetic cannabinoid were included in the current study. Liquid chromatography coupled to Orbitrap-based high-resolution tandem mass spectrometry was used to analyze metabolic data. Zebrafish larvae were found to produce the highest number of phase I but also phase II metabolites (79 metabolites in total), followed by HepaRG cells (66 metabolites). Incubations with pHLS9 produced the least metabolites (57 metabolites). Furthermore, the involvement of monooxygenases and esterases in the metabolic phase I transformations of 4F-MDMB-BINACA was elucidated using single-enzyme incubations. Several cytochrome P450 (CYP) isozymes were shown to contribute, and CYP3A5 was involved in all CYP-catalyzed reactions, while amide and ester hydrolysis were catalyzed by the human carboxylesterase (hCES) isoforms hCES1b and/or hCES1c. Finally, metabolites were compared to those present in human biosamples if data were available. Overall, the metabolic patterns in HepaRG cells provided the worst overlap with that in human biosamples. Zebrafish larvae experiments agreed best with data found in human plasma and urine analysis. The current study underlines the potential of zebrafish larvae as a tool for elucidating the toxicokinetics of NPS in the future.
    • Human microbial metabolite mimicry as a strategy to expand the chemical space of potential drugs.

      Li, Hao; Ranhotra, Harmit S; Mani, Sridhar; Dvořák, Zdeněk; Sokol, Harry; Müller, Rolf; HIRI, Helmholtz-Institut für RNA-basierte Infektionsforschung, Josef-Shneider Strasse 2, 97080 Würzburg, Germany. (Elsevier, 2020-06-17)
      he concept of small-molecule mimicry even of weak microbial metabolites present in rodents and humans, as a means to expand drug repertoires, is new. Hitherto, there are few proof-of-concept papers demonstrating utility of this concept. More recently, papers demonstrating mimicry of intestinal microbial metabolites could expand the drug repertoire for diseases such as inflammatory bowel disease (IBD). We opine that, as more functional metabolite-receptor pairings are discovered, small-molecule metabolite mimicry could be a significant effort in drug discovery.
    • Inactivation of SACE_3446, a TetR family transcriptional regulator, stimulates erythromycin production in Saccharopolyspora erythraea.

      Wu, Hang; Wang, Yansheng; Yuan, Li; Mao, Yongrong; Wang, Weiwei; Zhu, Lin; Wu, Panpan; Fu, Chengzhang; Müller, Rolf; Weaver, David T; et al. (2016-03)
      Erythromycin A is a widely used antibiotic produced by Saccharopolyspora erythraea; however, its biosynthetic cluster lacks a regulatory gene, limiting the yield enhancement via regulation engineering of S. erythraea. Herein, six TetR family transcriptional regulators (TFRs) belonging to three genomic context types were individually inactivated in S. erythraea A226, and one of them, SACE_3446, was proved to play a negative role in regulating erythromycin biosynthesis. EMSA and qRT-PCR analysis revealed that SACE_3446 covering intact N-terminal DNA binding domain specifically bound to the promoter regions of erythromycin biosynthetic gene eryAI, the resistant gene ermE and the adjacent gene SACE_3447 (encoding a long-chain fatty-acid CoA ligase), and repressed their transcription. Furthermore, we explored the interaction relationships of SACE_3446 and previously identified TFRs (SACE_3986 and SACE_7301) associated with erythromycin production. Given demonstrated relatively independent regulation mode of SACE_3446 and SACE_3986 in erythromycin biosynthesis, we individually and concomitantly inactivated them in an industrial S. erythraea WB. Compared with WB, the WBΔ3446 and WBΔ3446Δ3986 mutants respectively displayed 36% and 65% yield enhancement of erythromycin A, following significantly elevated transcription of eryAI and ermE. When cultured in a 5 L fermentor, erythromycin A of WBΔ3446 and WBΔ3446Δ3986 successively reached 4095 mg/L and 4670 mg/L with 23% and 41% production improvement relative to WB. The strategy reported here will be useful to improve antibiotics production in other industrial actinomycete.
    • Insights into the complex biosynthesis of the leupyrrins in Sorangium cellulosum So ce690.

      Kopp, Maren; Irschik, Herbert; Gemperlein, Katja; Buntin, Kathrin; Meiser, Peter; Weissman, Kira J; Bode, Helge B; Müller, Rolf; Helmholtz Institute for Pharmaceutical Research, Helmholtz Center for Infection Research and Department of Pharmaceutical Biotechnology, Saarland University, PO Box 151150, 66041 Saarbrücken, Germany. (2011-05)
      The anti-fungal leupyrrins are secondary metabolites produced by several strains of the myxobacterium Sorangium cellulosum. These intriguing compounds incorporate an atypically substituted γ-butyrolactone ring, as well as pyrrole and oxazolinone functionalities, which are located within an unusual asymmetrical macrodiolide. Previous feeding studies revealed that this novel structure arises from the homologation of four distinct structural units, nonribosomally-derived peptide, polyketide, isoprenoid and a dicarboxylic acid, coupled with modification of the various building blocks. Here we have attempted to reconcile the biosynthetic pathway proposed on the basis of the feeding studies with the underlying enzymatic machinery in the S. cellulosum strain So ce690. Gene products can be assigned to many of the suggested steps, but inspection of the gene set provokes the reconsideration of several key transformations. We support our analysis by the reconstitution in vitro of the biosynthesis of the pyrrole carboxylic starter unit along with gene inactivation. In addition, this study reveals that a significant proportion of the genes for leupyrrin biosynthesis are located outside the core cluster, a 'split' organization which is increasingly characteristic of the myxobacteria. Finally, we report the generation of four novel deshydroxy leupyrrin analogues by genetic engineering of the pathway.
    • Integrating Culture-based Antibiotic Resistance Profiles with Whole-genome Sequencing Data for 11,087 Clinical Isolates.

      Galata, Valentina; Laczny, Cédric C; Backes, Christina; Hemmrich-Stanisak, Georg; Schmolke, Susanne; Franke, Andre; Meese, Eckart; Herrmann, Mathias; von Müller, Lutz; Plum, Achim; et al. (Elsevier, 2019-05-14)
      Emergingantibiotic resistanceis a major global health threat. The analysis of nucleic acidsequences linked to susceptibility phenotypes facilitates the study of genetic antibiotic resistancedeterminants to inform molecular diagnostics and drug development. We collected genetic data(11,087 newly-sequenced whole genomes) and culture-based resistance profiles (10,991 out of the11,087 isolates comprehensively tested against 22 antibiotics in total) of clinical isolates including18 main species spanning a time period of 30 years. Species and drug specific resistance patternswere observed including increased resistance rates forAcinetobacter baumanniito carbapenemsand forEscherichia colito fluoroquinolones. Species-levelpan-genomeswere constructed to reflectthe genetic repertoire of the respective species, including conserved essential genes and known resis-tance factors. Integrating phenotypes and genotypes through species-level pan-genomes allowed toinfer gene–drug resistance associations using statistical testing. The isolate collection and the analysis results have been integrated into GEAR-base, a resource available for academic research use free of charge athttps://gear-base.com
    • Interrogation of Streptomyces avermitilis for efficient production of avermectins

      Chen, Jinsong; Liu, Mei; Liu, Xueting; Miao, Jin; Fu, Chengzhang; Gao, Heyong; Müller, Rolf; Zhang, Qing; Zhang, Lixin; Helmholtz-Institute for Pharmaceutical Research Saarland (HIPS),Saarland Universitätscampus E8.1, 66123 Saarbrücken, Germany. (2016-03)
    • Investigation of cytochromes P450 in myxobacteria: excavation of cytochromes P450 from the genome of Sorangium cellulosum So ce56.

      Khatri, Yogan; Hannemann, Frank; Perlova, Olena; Müller, Rolf; Bernhardt, Rita (2011-06-06)
      The exploitation of cytochromes P450 for novel biotechnological application and for the investigation of their physiological function is of great scientific interest in this post genomic era, where an extraordinary biodiversity of P450 genes has been derived from all forms of life. The study of P450s in the myxobacterium Sorangium cellulosum strain So ce56, the producer of novel secondary metabolites of pharmaceutical interest is the research topic, in which we were engaged since the beginning of its genome sequencing project. We herein disclosed the cytochrome P450 complements (CYPomes) of spore-forming myxobacterial species, Stigmatella aurantiaca DW4/3-1, Haliangium ochraceum DSM 14365 and Myxococcus xanthus DK1622, and their potential pharmaceutical significance has been discussed.
    • Investigations to the Antibacterial Mechanism of Action of Kendomycin.

      A Elnakady, Yasser; Chatterjee, Indranil; Bischoff, Markus; Rohde, Manfred; Josten, Michaele; Sahl, Hans-Georg; Herrmann, Mathias; Müller, Rolf; Helmholtz Institute for Pharmaceutical Research Saarland, Helmholtz Centre for Infection Research and Department of Pharmaceutical Biotechnology, Saarland University, Saarbrücken, Germany. (2016)
      The emergence of bacteria that are resistant to many currently used drugs emphasizes the need to discover and develop new antibiotics that are effective against such multi-resistant strains. Kendomycin is a novel polyketide that has a unique quinone methide ansa structure and various biological properties. This compound exhibits strong antibacterial activity against Gram-negative and Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Despite the promise of kendomycinin in several therapeutic areas, its mode of action has yet to be identified.
    • Leben und Überleben im Boden

      Volz, Carsten; Krug, Daniel; Müller, Rolf; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (Wiley-VCH, 2020-12-07)
      Myxobacteria - survivalists in soil. Myxobacteria like Myxococccus xanthus are soil-living microorganisms featuring a complex lifestyle, including movement by coordinated swarming on surfaces, predatory feeding on other microorganisms, and the formation of multicellular fruiting bodies when unfavorable environmental conditions are encountered. Bioinformatic analysis of the large myxobacterial genomes has enabled fascinating insights into the molecular basis for the biosynthesis of complex secondary metabolite structures by myxobacteria, and has set the stage for the discovery of novel natural products. Moreover, well-characterized myxobacteria like M. xanthus increasingly play a role as “biochemical factories” for the biotechnological production of bioactive molecules using synthetic biology approaches
    • Linoleic and palmitoleic acid block streptokinase-mediated plasminogen activation and reduce severity of invasive group A streptococcal infection

      Rox, Katharina; Jansen, Rolf; Loof, Torsten G.; Gillen, Christine M.; Bernecker, Steffen; Walker, Mark J.; Chhatwal, Gursharan Singh; Müller, Rolf; Helmholtz-Institut für pharmazeutische Forschung Saarland,Universitätscampus E8.1, 66123 Saarbrücken, Germany. (2017-09-18)
      In contrast to mild infections of Group A Streptococcus (GAS) invasive infections of GAS still pose a serious health hazard: GAS disseminates from sterile sites into the blood stream or deep tissues and causes sepsis or necrotizing fasciitis. In this case antibiotics do not provide an effective cure as the bacteria are capable to hide from them very quickly. Therefore, new remedies are urgently needed. Starting from a myxobacterial natural products screening campaign, we identified two fatty acids isolated from myxobacteria, linoleic and palmitoleic acid, specifically blocking streptokinase-mediated activation of plasminogen and thereby preventing streptococci from hijacking the host’s plasminogen/plasmin system. This activity is not inherited by other fatty acids such as oleic acid and is not attributable to the killing of streptococci. Moreover, both fatty acids are superior in their inhibitory properties compared to two clinically used drugs (tranexamic or ε-amino caproic acid) as they show 500–1000 fold lower IC50 values. Using a humanized plasminogen mouse model mimicking the clinical situation of a local GAS infection that becomes systemic, we demonstrate that these fatty acids ameliorate invasive GAS infection significantly. Consequently, linoleic and palmitoleic acid are possible new options to combat GAS invasive diseases.
    • Mast cells as protectors of health.

      Dudeck, Anne; Köberle, Martin; Goldmann, Oliver; Meyer, Nicole; Dudeck, Jan; Lemmens, Stefanie; Rohde, M; Roldán, Nestor González; Dietze-Schwonberg, Kirsten; Orinska, Zane; et al. (Elsevier, 2018-11-20)
      Mast cells (MC), well known for their effector functions in Th2 skewed allergic and also autoimmune inflammation, become increasingly acknowledged for their role in protection of health. It is now clear that they are also key modulators of immune responses at interface organs like skin or gut. MC can prime tissues for adequate inflammatory responses and cooperate with dendritic cells in T cell activation. They also regulate harmful immune responses in trauma and help to successfully orchestrate pregnancy. This review focusses on the beneficial effects of mast cells on tissue homeostasis and elimination of toxins or venoms. MC can enhance pathogen clearance in many bacterial, viral, and parasite infections, e.g. by TLR2 triggered degranulation, secretion of antimicrobial cathelicidins, recruiting neutrophils or by providing extracellular DNA traps. The role of MC in tumors is more ambiguous, however, encouraging new findings show they can change the tumor microenvironment towards anti-tumor immunity when adequately triggered. Uterine tissue remodeling by α-chymase (MCP-5) is crucial for successful embryo implantation. MCP-4 and the tryptase MCP-6 emerge to be protective in CNS trauma by reducing inflammatory damage and excessive scar formation, thereby protecting axon growth. Last but not least, we see proteases like carboxypeptidase A released by FcεRI activated MC detoxify an increasing number of venoms and endogenous toxins. A better understanding of the plasticity of MC will help to improve these advantageous effects, and hint on ways to cut down detrimental MC actions.
    • Metabolic and Biosynthetic Diversity in Marine Myxobacteria.

      Gemperlein, Katja; Zaburannyi, Nestor; Garcia, Ronald; La Clair, James J; Müller, Rolf; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (2018-09-05)
      Prior to 2005, the vast majority of characterized myxobacteria were obtained from terrestrial habitats. Since then, several species of halotolerant and even obligate marine myxobacteria have been described. Chemical analyses of extracts from these organisms have confirmed their ability to produce secondary metabolites with unique chemical scaffolds. Indeed, new genera of marine-derived myxobacteria, particularly Enhygromyxa, have been shown to produce novel chemical scaffolds that differ from those observed in soil myxobacteria. Further studies have shown that marine sponges and terrestrial myxobacteria are capable of producing similar or even identical secondary metabolites, suggesting that myxobacterial symbionts may have been the true producers. Recent in silico analysis of the genome sequences available from six marine myxobacteria disclosed a remarkably versatile biosynthetic potential. With access to ever-advancing tools for small molecule and genetic evaluation, these studies suggest a bright future for expeditions into this yet untapped resource for secondary metabolites
    • Metabolic Profiling to Determine Bactericidal or Bacteriostatic Effects of New Natural Products using Isothermal Microcalorimetry.

      Cirnski, Katarina; Coetzee, Janetta; Herrmann, Jennifer; Müller, Rolf; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (MyJove Corporation, 2020-10-29)
      Due to the global threat of rising antimicrobial resistance, novel antibiotics are urgently needed. We investigate natural products from Myxobacteria as an innovative source of such new compounds. One bottleneck in the process is typically the elucidation of their mode-of-action. We recently established isothermal microcalorimetry as part of a routine profiling pipeline. This technology allows for investigating the effect of antibiotic exposure on the total bacterial metabolic response, including processes that are decoupled from biomass formation. Importantly, bacteriostatic and bactericidal effects are easily distinguishable without any user intervention during the measurements. However, isothermal microcalorimetry is a rather new approach and applying this method to different bacterial species usually requires pre-evaluation of suitable measurement conditions. There are some reference thermograms available of certain bacteria, greatly facilitating interpretation of results. As the pool of reference data is steadily growing, we expect the methodology to have increasing impact in the future and expect it to allow for in-depth fingerprint analyses enabling the differentiation of antibiotic classes.