• Biosynthesis of oxygenated brasilane terpene glycosides involves a promiscuous N-acetylglucosamine transferase.

      Feng, Jin; Surup, Frank; Hauser, Maurice; Miller, Anna; Wennrich, Jan-Peer; Stadler, Marc; Cox, Russell J; Kuhnert, Eric; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Royal Sciety of Chemistry, 2020-09-16)
      Investigation of the metabolome of the ascomycete Annulohypoxylon truncatum led to the identification of novel oxygenated brasilane glycosides and the revision of the stereochemistry of the brasilane A octahydro-1H-indene core scaffold to trans. The bra biosynthetic gene cluster containing five genes (braA-braE) was identified and verified by heterologous expression experiments in Aspergillus oryzae demonstrating that BraC is a multifunctional P450 monooxygenase. In vitro studies of BraB revealed it to be a very rare fungal UDP-GlcNAc dependent N-acetylglucosamine transferase. UDP-glucose is also accepted as a donor, and a broad acceptor substrate tolerance for various primary and secondary alcohols was observed.
    • Diversely Functionalised Cytochalasins through Mutasynthesis and Semi-Synthesis.

      Wang, Chongqing; Lambert, Christopher; Hauser, Maurice; Deuschmann, Adrian; Zeilinger, Carsten; Rottner, Klemens; Stradal, Theresia E B; Stadler, Marc; Skellam, Elizabeth J; Cox, Russell J; et al. (Wiley-VCH, 2020-06-02)
      Mutasynthesis of pyrichalasin H from Magnaporthe grisea NI980 yielded a series of unprecedented 4'-substituted cytochalasin analogues in titres as high as the wild-type system (≈60 mg L-1 ). Halogenated, O-alkyl, O-allyl and O-propargyl examples were formed, as well as a 4'-azido analogue. 4'-O-Propargyl and 4'-azido analogues reacted smoothly in Huisgen cycloaddition reactions, whereas p-Br and p-I compounds reacted in Pd-catalysed cross-coupling reactions. A series of examples of biotin-linked, dye-linked and dimeric cytochalasins was rapidly created. In vitro and in vivo bioassays of these compounds showed that the 4'-halogenated and azido derivatives retained their cytotoxicity and antifungal activities; but a unique 4'-amino analogue was inactive. Attachment of larger substituents attenuated the bioactivities. In vivo actin-binding studies with adherent mammalian cells showed that actin remains the likely intracellular target. Dye-linked compounds revealed visualisation of intracellular actin structures even in the absence of phalloidin, thus constituting a potential new class of actin-visualisation tools with filament-barbed end-binding specificity.
    • Microfungi associated with Clematis (Ranunculaceae) with an integrated approach to delimiting species boundaries

      Phukhamsakda, Chayanard; McKenzie, Eric H. C.; Phillips, Alan J. L.; Gareth Jones, E. B.; Jayarama Bhat, D.; Stadler, Marc; Bhunjun, Chitrabhanu S.; Wanasinghe, Dhanushka N.; Thongbai, Benjarong; Camporesi, Erio; et al. (Springer Science and Business Media LLC, 2020-07-07)
      The cosmopolitan plant genus Clematis contains many climbing species that can be found worldwide. The genus occurs in the wild and is grown commercially for horticulture. Microfungi on Clematis were collected from Belgium, China, Italy, Thailand and the UK. They are characterized by morphology and analyses of gene sequence data using an integrated species concept to validate identifications. The study revealed two new families, 12 new genera, 50 new species, 26 new host records with one dimorphic character report, and ten species are transferred to other genera. The new families revealed by multigene phylogeny are Longiostiolaceae and Pseudomassarinaceae in Pleosporales (Dothideomycetes). New genera are Anthodidymella (Didymellaceae), Anthosulcatispora and Parasulcatispora (Sulcatisporaceae), Fusiformispora (Amniculicolaceae), Longispora (Phaeosphaeriaceae), Neobyssosphaeria (Melanommataceae), Neoleptosporella (Chaetosphaeriales, genera incertae sedis), Neostictis (Stictidaceae), Pseudohelminthosporium (Neomassarinaceae), Pseudomassarina (Pseudomassarinaceae), Sclerenchymomyces (Leptosphaeriaceae) and Xenoplectosphaerella (Plectosphaerellaceae). The newly described species are Alloleptosphaeria clematidis, Anthodidymella ranunculacearum, Anthosulcatispora subglobosa, Aquadictyospora clematidis, Brunneofusispora clematidis, Chaetosphaeronema clematidicola, C. clematidis, Chromolaenicola clematidis, Diaporthe clematidina, Dictyocheirospora clematidis, Distoseptispora clematidis, Floricola clematidis, Fusiformispora clematidis, Hermatomyces clematidis, Leptospora clematidis, Longispora clematidis, Massariosphaeria clematidis, Melomastia clematidis, M. fulvicomae, Neobyssosphaeria clematidis, Neoleptosporella clematidis, Neoroussoella clematidis, N. fulvicomae, Neostictis nigricans, Neovaginatispora clematidis, Parasulcatispora clematidis, Parathyridaria clematidis, P. serratifoliae, P. virginianae, Periconia verrucose, Phomatospora uniseriata, Pleopunctum clematidis, Pseudocapulatispora clematidis, Pseudocoleophoma clematidis, Pseudohelminthosporium clematidis, Pseudolophiostoma chiangraiense, P. clematidis, Pseudomassarina clematidis, Ramusculicola clematidis, Sarocladium clematidis, Sclerenchymomyces clematidis, Sigarispora clematidicola, S. clematidis, S. montanae, Sordaria clematidis, Stemphylium clematidis, Wojnowiciella clematidis, Xenodidymella clematidis, Xenomassariosphaeria clematidis and Xenoplectosphaerella clematidis. The following fungi are recorded on Clematis species for the first time: Angustimassarina rosarum, Dendryphion europaeum, Dermatiopleospora mariae, Diaporthe ravennica, D. rudis, Dichotomopilus ramosissimum, Dictyocheirospora xishuangbannaensis, Didymosphaeria rubi-ulmifolii, Fitzroyomyces cyperacearum, Fusarium celtidicola, Leptospora thailandica, Memnoniella oblongispora, Neodidymelliopsis longicolla, Neoeutypella baoshanensis, Neoroussoella heveae, Nigrograna chromolaenae, N. obliqua, Pestalotiopsis verruculosa, Pseudoberkleasmium chiangmaiense, Pseudoophiobolus rosae, Pseudoroussoella chromolaenae, P. elaeicola, Ramusculicola thailandica, Stemphylium vesicarium and Torula chromolaenae. The new combinations are Anthodidymella clematidis (≡ Didymella clematidis), A. vitalbina (≡ Didymella vitalbina), Anthosulcatispora brunnea (≡ Neobambusicola brunnea), Fuscohypha kunmingensis (≡ Plectosphaerella kunmingensis), Magnibotryascoma rubriostiolata (≡ Teichospora rubriostiolata), Pararoussoella mangrovei (≡ Roussoella mangrovei), Pseudoneoconiothyrium euonymi (≡ Roussoella euonymi), Sclerenchymomyces jonesii (≡ Neoleptosphaeria jonesii), Stemphylium rosae (≡ Pleospora rosae), and S. rosae-caninae (≡ Pleospora rosae-caninae). The microfungi on Clematis is distributed in several classes of Ascomycota. The analyses are based on morphological examination of specimens, coupled with phylogenetic sequence data. To the best of our knowledge, the consolidated species concept approach is recommended in validating species.
    • Molecular Phylogeny and Morphology of (=Lepteutypa ) (Amphisphaeriaceae).

      Samarakoon, Milan C; Maharachchikumbura, Sajeewa S N; Liu, Jian-Kui Jack; Hyde, Kevin D; Promputtha, Itthayakorn; Stadler, Marc; HZI, Helmholtz Zentrum für Infektionsforschung, GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (MDPI, 2020-09-17)
      Amphisphaeriaceous taxa (fungi) are saprobes on decaying wood in terrestrial, mangrove, and freshwater habitats. The generic boundaries of the family have traditionally been based on morphology, and the delimitation of genera has always been challenging. Amphisphaeria species have clypeate ascomata and 1-septate ascospores and a coelomycetous asexual morph. Lepteutypa is different from Amphisphaeria in having eutypoid stromata and more than 1-septate ascospores. These main characters have been used for segregation of Lepteutypa from Amphisphaeria for a long time. However, the above characters are overlapping among Amphisphaeria and Lepteutypa species. Therefore, here we synonymized Lepteutypa under Amphisphaeria based on holomorphic morphology and multigene phylogeny. Further, our cluster analysis reveals the relationship between seven morphological traits among Amphisphaeria/Lepteutypa species and suggests those morphologies are not specific to either genus. Three new species (i.e., Amphisphaeria camelliae, A. curvaticonidia, and A. micheliae) are introduced based on morphology and LSU-ITS-RPB2-TUB2 phylogenies. Furthermore, the monotypic genus Trochilispora, which had been accepted in Amphisphaeriaceae, is revisited and synonymized under Hymenopleella and placed in Sporocadaceae.
    • Re-Evaluation of the Order Sordariales: Delimitation of Lasiosphaeriaceae s. str., and Introduction of the New Families Diplogelasinosporaceae, Naviculisporaceae, and Schizotheciaceae.

      Marin-Felix, Yasmina; Miller, Andrew N; Cano-Lira, José F; Guarro, Josep; García, D; Stadler, Marc; Huhndorf, Sabine M; Stchigel, Alberto M; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-09-17)
      The order Sordariales includes the polyphyletic family Lasiosphaeriaceae, which comprises approximately 30 genera characterized by its paraphysate ascomata, asci with apical apparati, and mostly two-celled ascospores, which have a dark apical cell and a hyaline lower cell, frequently ornamented with mucilaginous appendages[...].
    • Amidochelocardin Overcomes Resistance Mechanisms Exerted on Tetracyclines and Natural Chelocardin.

      Hennessen, Fabienne; Miethke, Marcus; Zaburannyi, Nestor; Loose, Maria; Lukežič, Tadeja; Bernecker, Steffen; Hüttel, Stephan; Jansen, Rolf; Schmiedel, Judith; Fritzenwanker, Moritz; et al. (MDPI, 2020-09-18)
      The reassessment of known but neglected natural compounds is a vital strategy for providing novel lead structures urgently needed to overcome antimicrobial resistance. Scaffolds with resistance-breaking properties represent the most promising candidates for a successful translation into future therapeutics. Our study focuses on chelocardin, a member of the atypical tetracyclines, and its bioengineered derivative amidochelocardin, both showing broad-spectrum antibacterial activity within the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) panel. Further lead development of chelocardins requires extensive biological and chemical profiling to achieve favorable pharmaceutical properties and efficacy. This study shows that both molecules possess resistance-breaking properties enabling the escape from most common tetracycline resistance mechanisms. Further, we show that these compounds are potent candidates for treatment of urinary tract infections due to their in vitro activity against a large panel of multidrug-resistant uropathogenic clinical isolates. In addition, the mechanism of resistance to natural chelocardin was identified as relying on efflux processes, both in the chelocardin producer Amycolatopsis sulphurea and in the pathogen Klebsiella pneumoniae. Resistance development in Klebsiella led primarily to mutations in ramR, causing increased expression of the acrAB-tolC efflux pump. Most importantly, amidochelocardin overcomes this resistance mechanism, revealing not only the improved activity profile but also superior resistance-breaking properties of this novel antibacterial compound.
    • Phylogenetic Assignment of the Fungicolous (Ascomycota, Xylariales) and Investigation of its Secondary Metabolites.

      Becker, Kevin; Lambert, Christopher; Wieschhaus, Jörg; Stadler, Marc; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-09-11)
      The ascomycete Hypoxylon invadens was described in 2014 as a fungicolous species growing on a member of its own genus, H.fragiforme, which is considered a rare lifestyle in the Hypoxylaceae. This renders H.invadens an interesting target in our efforts to find new bioactive secondary metabolites from members of the Xylariales. So far, only volatile organic compounds have been reported from H.invadens, but no investigation of non-volatile compounds had been conducted. Furthermore, a phylogenetic assignment following recent trends in fungal taxonomy via a multiple sequence alignment seemed practical. A culture of H.invadens was thus subjected to submerged cultivation to investigate the produced secondary metabolites, followed by isolation via preparative chromatography and subsequent structure elucidation by means of nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HR-MS). This approach led to the identification of the known flaviolin (1) and 3,3-biflaviolin (2) as the main components, which had never been reported from the order Xylariales before. Assessment of their antimicrobial and cytotoxic effects via a panel of commonly used microorganisms and cell lines in our laboratory did not yield any effects of relevance. Concurrently, genomic DNA from the fungus was used to construct a multigene phylogeny using ribosomal sequence information from the internal transcribed spacer region (ITS), the 28S large subunit of ribosomal DNA (LSU), and proteinogenic nucleotide sequences from the second largest subunit of the DNA-directed RNA polymerase II (RPB2) and β-tubulin (TUB2) genes. A placement in a newly formed clade with H.trugodes was strongly supported in a maximum-likelihood (ML) phylogeny using sequences derived from well characterized strains, but the exact position of said clade remains unclear. Both, the chemical and the phylogenetic results suggest further inquiries into the lifestyle of this unique fungus to get a better understanding of both, its ecological role and function of its produced secondary metabolites hitherto unique to the Xylariales.
    • Biological and chemical diversity go hand in hand: Basidiomycota as source of new pharmaceuticals and agrochemicals.

      Sandargo, Birthe; Chepkirui, Clara; Cheng, Tian; Chaverra-Muñoz, Lillibeth; Thongbai, Benjarong; Stadler, Marc; Hüttel, Stephan; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Elsevier, 2019-02-07)
      The Basidiomycota constitutes the second largest higher taxonomic group of the Fungi after the Ascomycota and comprises over 30.000 species. Mycelial cultures of Basidiomycota have already been studied since the 1950s for production of antibiotics and other beneficial secondary metabolites. Despite the fact that unique and selective compounds like pleuromutilin were obtained early on, it took several decades more until they were subjected to a systematic screening for antimicrobial and anticancer activities. These efforts led to the discovery of the strobilurins and several hundreds of further compounds that mainly constitute terpenoids. In parallel the traditional medicinal mushrooms of Asia were also studied intensively for metabolite production, aimed at finding new therapeutic agents for treatment of various diseases including metabolic disorders and the central nervous system. While the evaluation of this organism group has in general been more tedious as compared to the Ascomycota, the chances to discover new metabolites and to develop them further to candidates for drugs, agrochemicals and other products for the Life Science industry have substantially increased over the past decade. This is owing to the revolutionary developments in -OMICS techniques, bioinformatics, analytical chemistry and biotechnological process technology, which are steadily being developed further. On the other hand, the new developments in polythetic fungal taxonomy now also allow a more concise selection of previously untapped organisms. The current review is dedicated to summarize the state of the art and to give an outlook to further developments.
    • Investigating the Function of Cryptic Cytochalasan Cytochrome P450 Monooxygenases Using Combinatorial Biosynthesis.

      Wang, Chongqing; Becker, Kevin; Pfütze, Sebastian; Kuhnert, Eric; Stadler, Marc; Cox, Russell J; Skellam, Elizabeth; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (ACS, 2019-10-23)
      Tailoring enzymes in cytochalasan biosynthesis are relatively promiscuous. Exploiting this property, we deduced the function of four cryptic cytochrome P450 monooxygenases via heterologous expression of six cytochrome P450-encoding genes, originating from Hypoxylon fragiforme and Pyricularia oryzae, in pyrichalasin H ΔP450 strains. Three cryptic cytochrome P450 enzymes (HffD, HffG, and CYP1) restored pyrichalasin H production in mutant strains, while CYP3 catalyzed a site-selective epoxidation leading to the isolation of three novel cytochalasans.
    • Seven New Cytotoxic and Antimicrobial Xanthoquinodins from Jugulospora vestita.

      Shao, Lulu; Marin-Felix, Yasmina; Surup, Frank; Stchigel, Alberto M; Stadler, Marc; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-09-25)
      During the course of a screening for novel biologically active secondary metabolites produced by the Sordariomycetes (Ascomycota, Fungi), the ex-type strain of Jugulospora vestita was found to produce seven novel xanthone-anthraquinone heterodimers, xanthoquinodin A11 (1) and xanthoquinodins B10-15 (2-7), together with the already known compound xanthoquinodin B4 (8). The structures of the xanthoquinodins were determined by analysis of the nuclear magnetic resonance (NMR) spectroscopic and mass spectrometric data. Moreover, the absolute configurations of these metabolites were established by analysis of the 1H-1H coupling constants, nuclear Overhauser effect spectroscopy (NOESY) correlations, and Electronic Circular Dichroism (ECD) spectroscopic data. Antifungal and antibacterial activities as well as cytotoxicity of all compounds were tested. Xanthoquinodin B11 showed fungicidal activities against Mucor hiemalis [minimum inhibitory concentration (MIC) 2.1 µg/mL], Rhodotorula glutinis (MIC 2.1 µg/mL), and Pichia anomala (MIC 8.3 µg/mL). All the compounds 1-8 displayed anti-Gram-positive bacteria activity (MIC 0.2-8.3 µg/mL). In addition, all these eight compounds showed cytotoxicity against KB 3.1, L929, A549, SK-OV-3, PC-3, A431, and MCF-7 mammalian cell lines. The six novel compounds (1-3, 5-7), together with xanthoquinodin B4, were also found in the screening of other strains belonging to Jugulospora rotula, revealing the potential chemotaxonomic significance of the compound class for the genus.
    • Phylogenetic and chemotaxonomic studies confirm the affinities of Stromatoneurospora phoenix to the Coprophilous xylariaceae

      Becker, Kevin; Wongkanoun, Sarunyou; Wessel, Anna Charleen; Bills, Gerald F.; Stadler, Marc; Luangsa-ard, J. Jennifer; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-09-01)
      The genus Stromatoneurospora was erected in 1973 by Jong and Davis to accommodate the pyrophilic pyrenomycete Sphaeria phoenix and has traditionally been placed in the family Xylariaceae based on morphological features. However, no living culture of this genus has so far been available in the public domain. Molecular data were restricted to an internal transcribed spacer (ITS) sequence that only confirmed the familial position, and was generated from a strain that is not deposited in a public culture collection. We have recently collected fresh material and were able to culture this fungus from Thailand. The secondary metabolites of this strains were analysed after fermentation in multiple media. The the prominent components of these fermentation were purified, using preparative chromatography. Aside from two new eremophilane sesquiterpenoids named phoenixilanes A-B (1-2), four other components that are known from species of the xylariaceous genera Xylaria and Poronia were identified by spectral methods (nuclear magnetic resonance spectroscopy and high resolution mass spectrometry). Notably, (-)-(R)-6-hydroxy-3-methyl-4-dihydroisocoumarin-5-carboxylic acid (6) has not been reported as a natural product before. Moreover, DNA sequences of Stromatoneurospora phoenix clustered with members of the genera Poronia and Podosordaria in a multi-locus molecular phylogeny. These results confirmed that the genus belongs to the same evolutionary lineage as the coprophilic Xylariaceae. The results also suggest that this lineage has evolved independently from the plant-inhabiting saprotrophs and endophytes that are closely related to the genus Xylaria. These findings are discussed in relation to some theories about the endophytic vs. the pyrophilic/coprophilic fungal life style.
    • Ten reasons why a sequence-based nomenclature is not useful for fungi anytime soon.

      Thines, Marco; Crous, Pedro W; Aime, M Catherine; Aoki, Takayuki; Cai, Lei; Hyde, Kevin D; Miller, Andrew N; Zhang, Ning; Stadler, Marc; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (BMC, 2018-05-28)
      The large number of species still to be discovered in fungi, together with an exponentially growing number of environmental sequences that cannot be linked to known taxa, has fuelled the idea that it might be necessary to formally name fungi on the basis of sequence data only. Here we object to this idea due to several shortcomings of the approach, ranging from concerns regarding reproducibility and the violation of general scientific principles to ethical issues. We come to the conclusion that sequence-based nomenclature is potentially harmful for mycology as a discipline. Additionally, a classification based on sequences as types is not within reach anytime soon, because there is a lack of consensus regarding common standards due to the fast pace at which sequencing technologies develop.
    • The planctomycete Stieleria maiorica Mal15 employs stieleriacines to alter the species composition in marine biofilms.

      Kallscheuer, Nicolai; Jeske, Olga; Sandargo, Birthe; Boedeker, Christian; Wiegand, Sandra; Bartling, Pascal; Jogler, Mareike; Rohde, Manfred; Petersen, Jörn; Medema, Marnix H; et al. (Nature publishing group(NPG), 2020-06-12)
      Bacterial strains of the phylum Planctomycetes occur ubiquitously, but are often found on surfaces of aquatic phototrophs, e.g. alga. Despite slower growth, planctomycetes are not outcompeted by faster-growing bacteria in biofilms on such surfaces; however, strategies allowing them to compensate for slower growth have not yet been investigated. Here, we identified stieleriacines, a class of N-acylated tyrosines produced by the novel planctomycete Stieleria maiorica Mal15T, and analysed their effects on growth of the producing strain and bacterial species likely co-occurring with strain Mal15T. Stieleriacines reduced the lag phase of Mal15T and either stimulated or inhibited biofilm formation of two bacterial competitors, indicating that Mal15T employs stieleriacines to specifically alter microbial biofilm composition. The genetic organisation of the putative stieleriacine biosynthetic cluster in strain Mal15T points towards a functional link of stieleriacine biosynthesis to exopolysaccharide-associated protein sorting and biofilm formation.
    • Discovery of a new species of the Hypoxylon rubiginosum complex from Iran and antagonistic activities of spp. against the Ash Dieback pathogen, Hymenoscyphus fraxineus,, in dual culture.

      Pourmoghaddam, Mohammad Javad; Lambert, Christopher; Surup, Frank; Khodaparast, Seyed Akbar; Krisai-Greilhuber, Irmgard; Voglmayr, Hermann; Stadler, Marc; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (PenSoft Publishers, 2020-04-24)
      During a survey of xylarialean fungi in Northern Iran, several specimens that showed affinities to the Hypoxylon rubiginosum complex were collected and cultured. A comparison of their morphological characters, combined with a chemotaxonomic study based on high performance liquid chromatography, coupled with diode array detection and mass spectrometry (HPLC-DAD/MS) and a multi-locus phylogeny based on ITS, LSU, rbp2 and tub2 DNA sequences, revealed a new species here described as Hypoxylon guilanense. In addition, Hypoxylon rubiginosumsensu stricto was also encountered. Concurrently, an endophytic isolate of the latter species showed strong antagonistic activities against the Ash Dieback pathogen, Hymenoscyphus fraxineus, in a dual culture assay in our laboratory. Therefore, we decided to test the new Iranian fungi for antagonistic activities against the pathogen, along with several cultures of other Hypoxylon species that are related to H. rubiginosum. Our results suggest that the antagonistic effects of Hypoxylon spp. against Hym. fraxineus are widespread and that they are due to the production of antifungal phomopsidin derivatives in the presence of the pathogen.
    • Polyketide-Derived Secondary Metabolites from a Dothideomycetes Fungus, . et . ., (Muyocopronales) with Antimicrobial and Cytotoxic Activities.

      Mapook, Ausana; Macabeo, Allan Patrick G; Thongbai, Benjarong; Hyde, Kevin D; Stadler, Marc; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-04-08)
      Pseudopalawania siamensisgen. et sp. nov., from northern Thailand, is introduced based on multi-gene analyses and morphological comparison. An isolate was fermented in yeast malt culture broth and explored for its secondary metabolite production. Chromatographic purification of the crude ethyl acetate (broth) extract yielded four tetrahydroxanthones comprised of a new heterodimeric bistetrahydroxanthone, pseudopalawanone (1), two known dimeric derivatives, 4,4'-secalonic acid D (2) and penicillixanthone A (3), the corresponding monomeric tetrahydroxanthone paecilin B (4), and the known benzophenone, cephalanone F (5). Compounds 1-3 showed potent inhibitory activity against Gram-positive bacteria. Compounds 2 and 3 were inhibitory against Bacillus subtilis with minimum inhibitory concentrations (MIC) of 1.0 and 4.2 μg/mL, respectively. Only compound 2 showed activity against Mycobacterium smegmatis. In addition, the dimeric compounds 1-3 also showed moderate cytotoxic effects on HeLa and mouse fibroblast cell lines, which makes them less attractive as candidates for development of selectively acting antibiotics.
    • New Peptaibiotics and a Cyclodepsipeptide from : Isolation, Identification, Cytotoxic and Nematicidal Activities.

      Moussa, Ashaimaa Y; Lambert, Christopher; Stradal, Theresia E B; Ashrafi, Samad; Maier, Wolfgang; Stadler, Marc; Helaly, Soleiman E; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-03-22)
      Fungal associations with nematodes have attracted scientific attention because of the need to develop new biocontrol agents. In this context, Ijuhya vitellina, an antagonistic fungus previously isolated from the plant parasitic cyst nematode Heterodera filipjevi, was selected to carry out an in-depth metabolomic study for its active metabolites. Herein, three new nonapeptide peptaibols with leucinostatin based sequences were isolated and identified by 1, 2D NMR, and HR-ESI-MS-MS. The absolute configuration was assigned based on Marfay's analysis and Mosher ester formation. The new leucinostatins manifested moderate nematicidal effect against the plant pathogenic nematode Pratylenchus penetrans with LD90 values ranging from 5 to 7 µg/mL. Furthermore, a cyclodepsipeptide, named arthrichitin D, with five amino acid residues attached to a 3-hydroxy-2,4-dimethylhexadeca-4,6-dienoic fatty acid chain was discovered and showed weak nematicidal effect against Caenorhabditis elegans. Chaetoglobosin B and its 19-O-acetyl derivative were also obtained as minor metabolites, and the activity of chaetoglobosin B on the actin cytoskeleton of mammalian cells was assessed.
    • Viridistratins A-C, Antimicrobial and Cytotoxic Benzo[]fluoranthenes from Stromata of (Hypoxylaceae, Ascomycota).

      Becker, Kevin; Wessel, Anna-Charleen; Luangsa-Ard, J Jennifer; Stadler, Marc; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-05-23)
      During the course of our search for novel biologically active metabolites from tropical fungi, we are using chemotaxonomic and taxonomic methodology for the preselection of interesting materials. Recently, three previously undescribed benzo[j]fluoranthenes (1-3) together with the known derivatives truncatones A and C (4, 5) were isolated from the stromata of the recently described species Annulohypoxylon viridistratum collected in Thailand. Their chemical structures were elucidated by means of spectral methods, including nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HR-MS). The new compounds, for which we propose the trivial names viridistratins A-C, exhibited weak-to-moderate antimicrobial and cytotoxic activities in cell-based assays.
    • Diversity of Myxobacteria-We Only See the Tip of the Iceberg.

      Mohr, Kathrin I; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2018-08-11)
      The discovery of new antibiotics is mandatory with regard to the increasing number of resistant pathogens. One approach is the search for new antibiotic producers in nature. Among actinomycetes, Bacillus species, and fungi, myxobacteria have been a rich source for bioactive secondary metabolites for decades. To date, about 600 substances could be described, many of them with antibacterial, antifungal, or cytostatic activity. But, recent cultivation-independent studies on marine, terrestrial, or uncommon habitats unequivocally demonstrate that the number of uncultured myxobacteria is much higher than would be expected from the number of cultivated strains. Although several highly promising myxobacterial taxa have been identified recently, this so-called Great Plate Count Anomaly must be overcome to get broader access to new secondary metabolite producers. In the last years it turned out that especially new species, genera, and families of myxobacteria are promising sources for new bioactive metabolites. Therefore, the cultivation of the hitherto uncultivable ones is our biggest challenge.
    • Labyrinthopeptins as virolytic inhibitors of respiratory syncytial virus cell entry.

      Blockus, Sebastian; Sake, Svenja M; Wetzke, Martin; Grethe, Christina; Graalmann, Theresa; Pils, Marina; Le Goffic, Ronan; Galloux, Marie; Prochnow, Hans; Rox, Katharina; et al. (Elsevier, 2020-03-18)
      Acute lower respiratory tract infections (ALRI) caused by respiratory syncytial virus (RSV) are associated with a severe disease burden among infants and elderly patients. Treatment options are limited. While numerous drug candidates with different viral targets are under development, the utility of RSV entry inhibitors is challenged by a low resistance barrier and by single mutations causing cross-resistance against a wide spectrum of fusion inhibitor chemotypes. We developed a cell-based screening assay for discovery of compounds inhibiting infection with primary RSV isolates. Using this system, we identified labyrinthopeptin A1 and A2 (Laby A1/A2), lantibiotics isolated from Actinomadura namibiensis, as effective RSV cell entry inhibitors with IC50s of 0.39 μM and 4.97 μM, respectively, and with favourable therapeutic index (>200 and > 20, respectively). Both molecules were active against multiple RSV strains including primary isolates and their antiviral activity against RSV was confirmed in primary human airway cells ex vivo and a murine model in vivo. Laby A1/A2 were antiviral in prophylactic and therapeutic treatment regimens and displayed synergistic activity when applied in combination with each other. Mechanistic studies showed that Laby A1/A2 exert virolytic activity likely by binding to phosphatidylethanolamine moieties within the viral membrane and by disrupting virus particle membrane integrity. Probably due to its specific mode of action, Laby A1/A2 antiviral activity was not affected by common resistance mutations to known RSV entry inhibitors. Taken together, Laby A1/A2 represent promising candidates for development as RSV inhibitors. Moreover, the cell-based screening system with primary RSV isolates described here should be useful to identify further antiviral agents.
    • Nonocarbolines A-E, -Carboline Antibiotics Produced by the Rare Actinobacterium sp. from Indonesia.

      Primahana, Gian; Risdian, Chandra; Mozef, Tjandrawati; Sudarman, Enge; Köck, Matthias; Wink, Joachim; Stadler, Marc; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MDPI, 2020-03-17)
      During the course of our ongoing screening for novel biologically active secondary metabolites, the rare Actinobacterium, Nonomuraea sp. 1808210CR was found to produce five unprecedented β-carboline derivatives, nonocarbolines A-E (1-5). Their structures were elucidated from high-resolution mass spectrometry, 1D and 2D nuclear magnetic resonance spectroscopy, and the absolute configuration of 4 was determined by using the modified Mosher method. Nonocarboline B (2) displayed moderate antifungal activity against Mucor hiemalis, while nonocarboline D (4) exhibited significant cytotoxic activity against the human lung carcinoma cell line A-549 with the IC50 value of 1.7 µM.