• Bacterial type III polyketide synthases: phylogenetic analysis and potential for the production of novel secondary metabolites by heterologous expression in pseudomonads.

      Gross, Frank; Luniak, Nora; Perlova, Olena; Gaitatzis, Nikolaos; Jenke-Kodama, Holger; Gerth, Klaus; Gottschalk, Daniela; Dittmann, Elke; Müller, Rolf (2006-03-01)
      Type III polyketide synthases (PKS) were regarded as typical for plant secondary metabolism before they were found in microorganisms recently. Due to microbial genome sequencing efforts, more and more type III PKS are found, most of which of unknown function. In this manuscript, we report a comprehensive analysis of the phylogeny of bacterial type III PKS and report the expression of a type III PKS from the myxobacterium Sorangium cellulosum in pseudomonads. There is no precedent of a secondary metabolite that might be biosynthetically correlated to a type III PKS from any myxobacterium. Additionally, an inactivation mutant of the S. cellulosum gene shows no physiological difference compared to the wild-type strain which is why these type III PKS are assumed to be "silent" under the laboratory conditions administered. One type III PKS (SoceCHS1) was expressed in different Pseudomonas sp. after the heterologous expression in Escherichia coli failed. Cultures of recombinant Pseudomonas sp. harbouring SoceCHS1 turned red upon incubation and the diffusible pigment formed was identified as 2,5,7-trihydroxy-1,4-naphthoquinone, the autooxidation product of 1,3,6,8-tetrahydroxynaphthalene. The successful heterologous production of a secondary metabolite using a gene not expressed under administered laboratory conditions provides evidence for the usefulness of our approach to activate such secondary metabolite genes for the production of novel metabolites.
    • Bioactive Compounds Produced by Hypoxylon fragiforme against Staphylococcus aureus Biofilms.

      Yuyama, Kamila Tomoko; Chepkirui, Clara; Wendt, Lucile; Fortkamp, Diana; Stadler, Marc; Abraham, Wolf-Rainer; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-12-12)
      Treating infections organized in biofilms is a challenge due to the resistance of the pathogens against antibiotics and host immune cells. Many fungi grow in a wet environment, favorable for the growth of bacterial biofilms, and we speculated that fungi possess some strategies to control these bacterial biofilms. A fungus identified as Hypoxylon fragiforme, was collected in the Harz Mountains, Germany, and its mycelial culture was fermented in different culture media for 67 days to test its biological potential against bacterial biofilms. Sclerin, sclerin diacid and its 3-methyl monoester (methyl 1-(5-hydroxy-6-carboxylic-2,3,4-trimethylphenyl) propionate) are here described for the first time from this fungus. Sclerin and its diacid interfered with the biofilm formation of the pathogen Staphylococcus aureus, inhibiting 86% and 80% of the biofilm at 256 μg mL-1, respectively, but not killing the bacterium. Interestingly, the monomethylester of sclerin diacid was inactive. Although these compounds did not possess any activity against a pre-formed biofilm, they prevented its formation at subtoxic concentrations. Furthermore, sclerin and its diacid displayed a high specificity against Staphylococcus aureus, indicating a good strategy against pathogenic biofilms when combined with antibiotics.
    • Biofilm Inhibitory Abscisic Acid Derivatives from the Plant-Associated Dothideomycete Fungus, sp.

      Phukhamsakda, Chayanard; Macabeo, Allan Patrick G; Yuyama, Kamila Tomoko; Hyde, Kevin David; Stadler, Marc; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (2018-08-30)
      Roussoella species are well recorded from both monocotyledons and dicotyledons. As part of a research program to discover biologically active compounds from plant-associated Dothideomycetes in Thailand, the strain Roussoella sp. (MFLUCC 17-2059), which represents an undescribed species, was isolated from Clematis subumbellata Kurz, fermented in yeast-malt medium and explored for its secondary metabolite production. Bioassay-guided fractionation of the crude extract yielded the new abscisic acid derivative, roussoellenic acid (1), along with pestabacillin B (2), a related congener, and the cyclodipeptide, cyclo(S-Pro-S-Ile) (3). The structure of 1 was determined by 2D NMR spectroscopy and HR-ESIMS data analysis. Compounds 1 and 2 showed inhibitory activity on biofilm formation by Staphylococcus aureus. The biofilm formation of S. aureus was reduced to 34% at 16 µg/mL by roussoellenic acid (1), while pestabacillin B (2) only showed 36% inhibition at 256 µg/mL. In addition, compound 1 also had weak cytotoxic effects on L929 murine fibroblasts and human KB3-1 cancer cells.
    • 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.
    • The Biomolecular Spectrum Drives Microbial Biology and Functions in Agri-Food-Environments.

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

      Kuhnert, Eric; Surup, Frank; Wiebach, Vincent; Bernecker, Steffen; Stadler, Marc; Helmholtz Centre for infection research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. (2015-09)
      In the course of our screening for new bioactive natural products, a culture of Hypoxylon rickii, a xylariaceous ascomycete collected from the Caribbean island Martinique, was identified as extraordinary prolific producer of secondary metabolites. Ten metabolites of terpenoid origin were isolated from submerged cultures of this species by preparative HPLC. Their structures were elucidated using spectral techniques including 2D NMR and HRESIMS. Three of the compounds were elucidated as new botryanes (1-3) along with three known ones, i.e. (3aS)-3a,5,5,8-tetramethyl-3,3a,4,5-tetrahydro-1H-cyclopenta[de]isochromen-1-one (4), (3aS,8R)-3a,5,5,8-tetramethyl-3,3a,4,5,7,8-hexahydro-1H-cyclopenta[de]isochromen-1-one (5) and botryenanol (6). Further three new sesquiterpenoids featured a 14-noreudesmane-type skeleton and were named hypoxylan A-C (7-9); the diterpenoid rickitin A (10) contains an abietane-type backbone. Compounds 1, 2, 3, 7, and 10 showed cytotoxic effects against murine cells.
    • Carolacton - A macrolide ketocarbonic acid that reduces biofilm formation by the caries- and endocarditis-associated bacterium Streptococcus mutans

      Jansen, Rolf; Microbial Drugs, Helmholtz Centre for Infection Research, Inhoffenstr. 7, 38124 Braunschweig (Germany) (Wiley Interscience, 2010-03)
    • Characterizing the Epothilone Binding Site on β-Tubulin by Photoaffinity Labeling: Identification of β-Tubulin Peptides TARGSQQY and TSRGSQQY as Targets of an Epothilone Photoprobe for Polymerized Tubulin.

      Ranade, Adwait R; Higgins, LeeAnn; Markowski, Todd W; Glaser, Nicole; Kashin, Dmitry; Bai, Ruoli; Hong, Kwon Ho; Hamel, Ernest; Höfle, Gerhard; Georg, Gunda I; et al. (2016-04-14)
      Photoaffinity labeling with an epothilone A photoprobe led to the identification of the β-tubulin peptides TARGSQQY and TSRGSQQY as targets of the photoprobe for polymerized tubulin. These peptides represent residues 274-281 in different β-tubulin isotypes. Placing the carbene producing 21-diazo/triazolo moiety of the photoprobe in the vicinity of the TARGSQQY peptide in a homology model of TBB3 predicted a binding pose and conformation of the photoprobe that are very similar to the ones reported for 1) the high resolution cocrystal structure of epothilone A with an α,β-tubulin complex and for 2) a saturation transfer difference NMR and transferred NOESY NMR study of dimeric and polymerized tubulin. Our findings thus provide additional support for these models as physiologically the most relevant among several modes of binding that have been proposed for epothilone A in the taxane pocket of β-tubulin.
    • Chlorotonil A, a macrolide with a unique gem-dichloro-1,3-dione functionality from Sorangium cellulosum, So ce1525.

      Gerth, Klaus; Steinmetz, Heinrich; Höfle, Gerhard; Jansen, Rolf; Helmholtz-Zentrum für Infektionsforschung, Inhoffenstrasse 7, 38124 Braunschweig, Germany. (2008)
    • Comparative analyses of the Hymenoscyphus fraxineus and Hymenoscyphus albidus genomes reveals potentially adaptive differences in secondary metabolite and transposable element repertoires.

      Elfstrand, Malin; Chen, Jun; Cleary, Michelle; Halecker, Sandra; Ihrmark, Katarina; Karlsson, Magnus; Davydenko, Kateryna; Stenlid, Jan; Stadler, Marc; Durling, Mikael Brandström; et al. (BMC, 2021-07-04)
      Background: The dieback epidemic decimating common ash (Fraxinus excelsior) in Europe is caused by the invasive fungus Hymenoscyphus fraxineus. In this study we analyzed the genomes of H. fraxineus and H. albidus, its native but, now essentially displaced, non-pathogenic sister species, and compared them with several other members of Helotiales. The focus of the analyses was to identify signals in the genome that may explain the rapid establishment of H. fraxineus and displacement of H. albidus. Results: The genomes of H. fraxineus and H. albidus showed a high level of synteny and identity. The assembly of H. fraxineus is 13 Mb longer than that of H. albidus', most of this difference can be attributed to higher dispersed repeat content (i.e. transposable elements [TEs]) in H. fraxineus. In general, TE families in H. fraxineus showed more signals of repeat-induced point mutations (RIP) than in H. albidus, especially in Long-terminal repeat (LTR)/Copia and LTR/Gypsy elements. Comparing gene family expansions and 1:1 orthologs, relatively few genes show signs of positive selection between species. However, several of those did appeared to be associated with secondary metabolite genes families, including gene families containing two of the genes in the H. fraxineus-specific, hymenosetin biosynthetic gene cluster (BGC). Conclusion: The genomes of H. fraxineus and H. albidus show a high degree of synteny, and are rich in both TEs and BGCs, but the genomic signatures also indicated that H. albidus may be less well equipped to adapt and maintain its ecological niche in a rapidly changing environment.
    • Considerations and consequences of allowing DNA sequence data as types of fungal taxa.

      Zamora, Juan Carlos; Svensson, Måns; Kirschner, Roland; Olariaga, Ibai; Ryman, Svengunnar; Parra, Luis Alberto; Geml, József; Rosling, Anna; Adamčík, Slavomír; Ahti, Teuvo; et al. (2018-06-01)
      Nomenclatural type definitions are one of the most important concepts in biological nomenclature. Being physical objects that can be re-studied by other researchers, types permanently link taxonomy (an artificial agreement to classify biological diversity) with nomenclature (an artificial agreement to name biological diversity). Two proposals to amend the International Code of Nomenclature for algae, fungi, and plants (ICN), allowing DNA sequences alone (of any region and extent) to serve as types of taxon names for voucherless fungi (mainly putative taxa from environmental DNA sequences), have been submitted to be voted on at the 11th International Mycological Congress (Puerto Rico, July 2018). We consider various genetic processes affecting the distribution of alleles among taxa and find that alleles may not consistently and uniquely represent the species within which they are contained. Should the proposals be accepted, the meaning of nomenclatural types would change in a fundamental way from physical objects as sources of data to the data themselves. Such changes are conducive to irreproducible science, the potential typification on artefactual data, and massive creation of names with low information content, ultimately causing nomenclatural instability and unnecessary work for future researchers that would stall future explorations of fungal diversity. We conclude that the acceptance of DNA sequences alone as types of names of taxa, under the terms used in the current proposals, is unnecessary and would not solve the problem of naming putative taxa known only from DNA sequences in a scientifically defensible way. As an alternative, we highlight the use of formulas for naming putative taxa (candidate taxa) that do not require any modification of the ICN.
    • Corallopyronin A for short-course anti-wolbachial, macrofilaricidal treatment of filarial infections.

      Schiefer, Andrea; Hübner, Marc P; Krome, Anna; Lämmer, Christine; Ehrens, Alexandra; Aden, Tilman; Koschel, Marianne; Neufeld, Helene; Chaverra-Muñoz, Lillibeth; Jansen, Rolf; et al. (PLOS, 2020-12-07)
      Current efforts to eliminate the neglected tropical diseases onchocerciasis and lymphatic filariasis, caused by the filarial nematodes Onchocerca volvulus and Wuchereria bancrofti or Brugia spp., respectively, are hampered by lack of a short-course macrofilaricidal-adult-worm killing-treatment. Anti-wolbachial antibiotics, e.g. doxycycline, target the essential Wolbachia endosymbionts of filariae and are a safe prototype adult-worm-sterilizing and macrofilaricidal regimen, in contrast to standard treatments with ivermectin or diethylcarbamazine, which mainly target the microfilariae. However, treatment regimens of 4-5 weeks necessary for doxycycline and contraindications limit its use. Therefore, we tested the preclinical anti-Wolbachia drug candidate Corallopyronin A (CorA) for in vivo efficacy during initial and chronic filarial infections in the Litomosoides sigmodontis rodent model. CorA treatment for 14 days beginning immediately after infection cleared >90% of Wolbachia endosymbionts from filariae and prevented development into adult worms. CorA treatment of patently infected microfilaremic gerbils for 14 days with 30 mg/kg twice a day (BID) achieved a sustained reduction of >99% of Wolbachia endosymbionts from adult filariae and microfilariae, followed by complete inhibition of filarial embryogenesis resulting in clearance of microfilariae. Combined treatment of CorA and albendazole, a drug currently co-administered during mass drug administrations and previously shown to enhance efficacy of anti-Wolbachia drugs, achieved microfilarial clearance after 7 days of treatment at a lower BID dose of 10 mg/kg CorA, a Human Equivalent Dose of 1.4 mg/kg. Importantly, this combination led to a significant reduction in the adult worm burden, which has not yet been published with other anti-Wolbachia candidates tested in this model. In summary, CorA is a preclinical candidate for filariasis, which significantly reduces treatment times required to achieve sustained Wolbachia depletion, clearance of microfilariae, and inhibition of embryogenesis. In combination with albendazole, CorA is robustly macrofilaricidal after 7 days of treatment and fulfills the Target Product Profile for a macrofilaricidal drug.
    • Current insights into fungal species diversity and perspective on naming the environmental DNA sequences of fungi

      Wu, Bing; Hussain, Muzammil; Zhang, Weiwei; Stadler, Marc; Liu, Xingzhong; Xiang, Meichun; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Taylor&Francis, 2019-07-03)
      The global bio-diversity of fungi has been extensively investigated and their species number has been estimated. Notably, the development of molecular phylogeny has revealed an unexpected fungal diversity and utilisation of culture-independent approaches including high-throughput amplicon sequencing has dramatically increased number of fungal operational taxonomic units. A number of novel taxa including new divisions, classes, orders and new families have been established in last decade. Many cryptic species were identified by molecular phylogeny. Based on recently generated data from culture-dependent and -independent survey on same samples, the fungal species on the earth were estimated to be 12 (11.7–13.2) million compared to 2.2–3.8 million species recently estimated by a variety of the estimation techniques. Moreover, it has been speculated that the current use of high-throughput sequencing techniques would reveal an even higher diversity than our current estimation. Recently, the formal classification of environmental sequences and permission of DNA sequence data as fungal names’ type were proposed but strongly objected by the mycologist community. Surveys on fungi in unusual niches have indicated that many previously regarded “unculturable fungi” could be cultured on certain substrates under specific conditions. Moreover, the high-throughput amplicon sequencing, shotgun metagenomics and a single-cell genomics could be a powerful means to detect novel taxa. Here, we propose to separate the fungal types into physical type based on specimen, genome DNA (gDNA) type based on complete genome sequence of culturable and uncluturable fungal specimen and digital type based on environmental DNA sequence data. The physical and gDNA type should have priority, while the digital type can be temporal supplementary before the physical type and gDNA type being available. The fungal name based on the “digital type” could be assigned as the “clade” name + species name. The “clade” name could be the name of genus, family or order, etc. which the sequence of digital type affiliates to. Facilitating future cultivation efforts should be encouraged. Also, with the advancement in knowledge of fungi inhabiting various environments mostly because of rapid development of new detection technologies, more information should be expected for fungal diversity on our planet. © 2019, © 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
    • Cyclic depsipeptides, ichthyopeptins A and B, from Microcystis ichthyoblabe.

      Zainuddin, Elmi N; Mentel, Renate; Wray, Victor; Jansen, Rolf; Nimtz, Manfred; Lalk, Michael; Mundt, Sabine; Institute of Pharmacy, Friedrich-Ludwig-Jahnstrasse 17, Ernst-Moritz-Arndt University, D-17487 Greifswald, Germany. (2007-07)
      Bioassay-guided isolation of antiviral compounds from the cultured cyanobacterium Microcystis ichthyoblabe provided two novel cyclic depsipeptides, ichthyopeptins A (1) and B (2). Their structures were determined by 1D (1H and 13C) and 2D (COSY, TOCSY, ROESY, HMQC, and HMBC) NMR spectra, ESIMS-MS, and amino acid analysis. The fraction containing both cyclic depsipeptides exhibited antiviral activity against influenza A virus with an IC50 value of 12.5 microg/mL.
    • Cycloheximide-Producing Associated With and Fungus-Farming Ambrosia Beetles.

      Grubbs, Kirk J; Surup, Frank; Biedermann, Peter H W; McDonald, Bradon R; Klassen, Jonathan L; Carlson, Caitlin M; Clardy, Jon; Currie, Cameron R; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Frontiers, 2020-09-24)
      Symbiotic microbes help a myriad of insects acquire nutrients. Recent work suggests that insects also frequently associate with actinobacterial symbionts that produce molecules to help defend against parasites and predators. Here we explore a potential association between Actinobacteria and two species of fungus-farming ambrosia beetles, Xyleborinus saxesenii and Xyleborus affinis. We isolated and identified actinobacterial and fungal symbionts from laboratory reared nests, and characterized small molecules produced by the putative actinobacterial symbionts. One 16S rRNA phylotype of Streptomyces (XylebKG-1) was abundantly and consistently isolated from the galleries and adults of X. saxesenii and X. affinis nests. In addition to Raffaelea sulphurea, the symbiont that X. saxesenii cultivates, we also repeatedly isolated a strain of Nectria sp. that is an antagonist of this mutualism. Inhibition bioassays between Streptomyces griseus XylebKG-1 and the fungal symbionts from X. saxesenii revealed strong inhibitory activity of the actinobacterium toward the fungal antagonist Nectria sp. but not the fungal mutualist R. sulphurea. Bioassay guided HPLC fractionation of S. griseus XylebKG-1 culture extracts, followed by NMR and mass spectrometry, identified cycloheximide as the compound responsible for the observed growth inhibition. A biosynthetic gene cluster putatively encoding cycloheximide was also identified in S. griseus XylebKG-1. The consistent isolation of a single 16S phylotype of Streptomyces from two species of ambrosia beetles, and our finding that a representative isolate of this phylotype produces cycloheximide, which inhibits a parasite of the system but not the cultivated fungus, suggests that these actinobacteria may play defensive roles within these systems.
    • Cystobactamids 920-1 and 920-2: Assignment of the Constitution and Relative Configuration by Total Synthesis.

      Planke, Therese; Moreno, María; Hüttel, Stephan; Fohrer, Jörg; Gille, Franziska; Norris, Matthew D; Siebke, Maik; Wang, Liangliang; Müller, Rolf; Kirschning, Andreas; et al. (ACS Publications, 2019-03-01)
      Total synthesis of cystobactamid 920-1 and its epimer has allowed an unambiguous assignment of the relative and absolute configuration of the natural product. A careful structural analysis of each isomer using both NMR and computational techniques also prompted a constitutional revision of the structures originally reported for cystobactamids 920-1 and 920-2, and has provided further insight into the unique conformational preferences of the cystobactamid family
    • Cytochalasans Act as Inhibitors of Biofilm Formation of Staphylococcus Aureus.

      Yuyama, Kamila Tomoko; Wendt, Lucile; Surup, Frank; Kretz, Robin; Chepkirui, Clara; Wittstein, Kathrin; Boonlarppradab, Chollaratt; Wongkanoun, Sarunyou; Luangsa-Ard, Jennifer; Stadler, Marc; et al. (MPDI, 2018-10-30)
      During the course of our ongoing work to discover new inhibitors of biofilm formation of Staphylococcus aureus from fungal sources, we observed biofilm inhibition by cytochalasans isolated from cultures of the ascomycete Hypoxylon fragiforme for the first time. Two new compounds were purified by a bioassay-guided fractionation procedure; their structures were elucidated subsequently by nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HR-MS). This unexpected finding prompted us to test further cytochalasans from other fungi and from commercial sources for comparison. Out of 21 cytochalasans, 13 showed significant inhibition of Staphylococcus aureus biofilm formation at subtoxic levels. These findings indicate the potential of cytochalasans as biofilm inhibitors for the first time, also because the minimum inhibitory concentrations (MIC) are independent of the anti-biofilm activities. However, cytochalasans are known to be inhibitors of actin, making some of them very toxic for eukaryotic cells. Since the chemical structures of the tested compounds were rather diverse, the inclusion of additional derivatives, as well as the evaluation of their selectivity against mammalian cells vs. the bacterium, will be necessary as next step in order to develop structure-activity relationships and identify the optimal candidates for development of an anti-biofilm agent. View Full-Text
    • Cytotoxic, anti-biofilm and antimicrobial polyketides from the plant associated fungus Chaetosphaeronema achilleae.

      Narmani, Abolfazl; Teponno, Rémy Bertrand; Helaly, Soleiman E; Arzanlou, Mahdi; Stadler, Marc; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Elsevier, 2019-10-23)
      From extracts of the plant associated fungus Chaetosphaeronema achilleae collected in Iran, a previously unreported isoindolinone named chaetosisoindolinone (1) and a previously undescribed indanone named chaetosindanone (2) were isolated in addition to five known metabolites, 2-(2-acetyl-3,5-dihydroxyphenyl) acetic acid (3), vulculic acid (4), 2-(2-acetyl-3-hydroxy-5-methoxyphenyl)acetic acid (5), curvulin (6), and curvulol (7). Their structures were elucidated on the basis of extensive spectroscopic analysis and high-resolution mass spectrometry. The isolated compounds were tested for their antimicrobial, anti-biofilm, and nematicidal activities. Compound 2 exhibited cytotoxicity against the human breast adenocarcinoma MCF-7 cells with an IC50 value of 1.5 μg/mL. Furthermore, compounds 4 and 7 almost completely inhibited biofilm formation in Staphylococcus aureus at 256 μg/mL. Weak antimicrobial activities were also observed for some of the isolated compounds against Mucor hiemalis, Rhodoturula glutinis, Chromobacterium violaceum, and Staphylococcus aureus.
    • Cytotoxic, antimicrobial and antiviral secondary metabolites produced by the plant pathogenic fungus Cytospora sp. CCTU A309.

      Narmani, Abolfazl; Teponno, Rémy Bertrand; Arzanlou, Mahdi; Surup, Frank; Helaly, Soleiman E; Wittstein, Kathrin; Praditya, Dimas F; Babai-Ahari, Asadollah; Steinmann, Eike; Stadler, Marc; et al. (Elsevier, 2019-04-01)
      Chemical analysis of extracts from cultures of the plant pathogenic fungus Cytospora sp. strain CCTU A309 collected in Iran led to the isolation of two previously unreported heptanedioic acid derivatives namely (2R,3S) 2-hydroxy-3-phenyl-4-oxoheptanedioic acid (1) and (2S,3S) 2-hydroxy-3-phenyl-4-oxoheptanedioic acid (2) as diastereomers, four previously undescribed prenylated p-terphenyl quinones 3-6 in addition to five known metabolites. Their structures were elucidated on the basis of extensive spectroscopic analysis and high-resolution mass spectrometry. For metabolites 1 and 2, the absolute configurations at C-2 were deduced from comparison of the 1H NMR difference of their (S)- and (R)-phenylglycine methyl ester derivatives while the relative configurations were tentatively assigned by a J-based analysis and confirmed by comparison of 13C chemical shifts to literature data. The isolated compounds were tested for their cytotoxic, antimicrobial (including biofilm inhibition), antiviral, and nematicidal activities. While only moderate antimicrobial effects were observed, the terphenyl quinone derivatives 3-6 and leucomelone (10) exhibited significant cytotoxicity against the mouse fibroblast L929 and cervix carcinoma KB-3-1 cell lines with IC50 values ranging from 2.4 to 26 μg/mL. Furthermore, metabolites 4-6 showed interesting antiviral activity against hepatitis C virus (HCV).