Publications by authors named "Kerstin Voigt"

66 Publications

New Guaianolide Sesquiterpene Lactones and Other Constituents from Pyrethrum pulchrum.

Planta Med 2021 Aug 5. Epub 2021 Aug 5.

Mongolian National University of Medical Sciences, Ulaanbaatar, Mongolia.

is a rare Mongolian plant species that has been traditionally used as an ingredient in various remedies. Bioactivity-guided fractionation performed on the methanol extract of its aerial parts led to the isolation of 2 previously undescribed guaianolide-type sesquiterpene lactones, namely 1,10-epoxy-8-hydroxyguaia-3,11(13)-dien-6,12-olide (1: ) and 1,8,10-trihydroxyguaia-3,11(13)-dien-6,12-olide (2: ), along with the isolation or chromatographic identification of 11 compounds, arglabin (3: ), 3-hydroxycostunolide (4: ), isocostic acid (5: ), ()-9-(2-thienyl)-6-nonen-8-yn-3-ol (6: ), ()-9-(2-thienyl)-6-nonen-8-yn-3-ol (7: ), , , , -tetra-p-coumaroyl spermine (8: ), chlorogenic acid (9: ), 3,5-di--caffeoylquinic acid (10: ), 3,5-di--caffeoylquinic acid methyl ester (11: ), 3,4-di--caffeoylquinic acid (12: ), and tryptophan (13: ). Their structures were assigned based on spectroscopic and spectrometric data. The antimicrobial, antiproliferative and cytotoxic activities of selected compounds were evaluated. The new compounds showed weak to moderate antimicrobial activity. Arglabin (3: ), the major sesquiterpene lactone found in the methanol extract of , exhibited the highest activity against human cancer lines, while compound 1: also possesses significant antiproliferative activity against leukemia cells.
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http://dx.doi.org/10.1055/a-1554-2866DOI Listing
August 2021

Discovery of Novel (Backusellaceae, Mucorales) Isolated from Invertebrates and Toads in Cheongyang, Korea.

J Fungi (Basel) 2021 Jun 27;7(7). Epub 2021 Jun 27.

Environmental Microbiology Laboratory, Department of Agricultural Biological Chemistry, College of Agriculture & Life Sciences, Chonnam National University, Gwangju 61186, Korea.

Three novel fungal species, sp. nov., . sp. nov., and . sp. nov., as well as two new records, . and . , were found in Cheongyang, Korea, during an investigation of fungal species from invertebrates and toads. All species are described here using morphological characters and sequence data from internal transcribed spacer sequences of ribosomal DNA and large subunit of the ribosomal DNA. is different from other species by producing chlamydospores. can be distinguished from other species by producing abundant yeast-like cells.   is characterized by a variable (subglobose to oblong, applanate to oval, conical and ellipsoidal to pyriform) columellae and grows well at 37 °C. Multigene phylogenetic analyses of the combined ITS and LSU rDNA sequences data generated from maximum likelihood and MrBayes analyses indicate that , . , and . form distinct lineages in the family Backusellaceae. Detailed descriptions, illustrations, phylogenetic tree, and taxonomic key to the species present in Korea are provided.
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http://dx.doi.org/10.3390/jof7070513DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8303511PMC
June 2021

Expression Patterns in Reductive Iron Assimilation and Functional Consequences during Phagocytosis of , an Emerging Cause of Mucormycosis.

J Fungi (Basel) 2021 Apr 3;7(4). Epub 2021 Apr 3.

Jena Microbial Resource Collection, Leibniz Institute for Natural Product Research, and Infection Biology-Hans Knöll Institute (HKI), 07745 Jena, Germany.

Iron is an essential micronutrient for most organisms and fungi are no exception. Iron uptake by fungi is facilitated by receptor-mediated internalization of siderophores, heme and reductive iron assimilation (RIA). The RIA employs three protein groups: (i) the ferric reductases (Fre5 proteins), (ii) the multicopper ferroxidases (Fet3) and (iii) the high-affinity iron permeases (Ftr1). Phenotyping under different iron concentrations revealed detrimental effects on spore swelling and hyphal formation under iron depletion, but yeast-like morphology under iron excess. Since access to iron is limited during pathogenesis, pathogens are placed under stress due to nutrient limitations. To combat this, gene duplication and differential gene expression of key iron uptake genes are utilized to acquire iron against the deleterious effects of iron depletion. In the genome of the human pathogenic fungus , three, four and three copies were identified for , and genes, respectively. As in other fungi, and are syntenic and co-expressed in . Expression of , and genes is highly up-regulated during iron limitation (Fe-), but lower during iron excess (Fe+). Fe- dependent upregulation of gene expression takes place in II and III, I and II, as well as I and II suggesting a functional role in pathogenesis. The syntenic I- I gene pair is co-expressed during germination, whereas II- II is co-expressed during hyphal proliferation. I, II and IV were overexpressed in to represent high and moderate expression of intracellular transport of Fe3+, respectively. Challenge of macrophages with the yeast mutants revealed no obvious role for I, but possible functions of II and IVs in recognition by macrophages. RIA expression pattern was used for a new model of interaction between and macrophages.
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http://dx.doi.org/10.3390/jof7040272DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8065604PMC
April 2021

Direct Visualization of Fungal Burden in Filamentous Fungus-Infected Silkworms.

J Fungi (Basel) 2021 Feb 13;7(2). Epub 2021 Feb 13.

Interdisciplinary Center for Clinical Research Laboratory, Department of Internal Medicine II, Würzburg University Hospital, 97080 Würzburg, Germany.

Invasive fungal infections (IFIs) are difficult to diagnose and to treat and, despite several available antifungal drugs, cause high mortality rates. In the past decades, the incidence of IFIs has continuously increased. More recently, SARS-CoV-2-associated lethal IFIs have been reported worldwide in critically ill patients. Combating IFIs requires a more profound understanding of fungal pathogenicity to facilitate the development of novel antifungal strategies. Animal models are indispensable for studying fungal infections and to develop new antifungals. However, using mammalian animal models faces various hurdles including ethical issues and high costs, which makes large-scale infection experiments extremely challenging. To overcome these limitations, we optimized an invertebrate model and introduced a simple calcofluor white (CW) staining protocol to macroscopically and microscopically monitor disease progression in silkworms () infected with the human pathogenic filamentous fungi and . This advanced silkworm infection model could validate knockout mutants with either attenuated, strongly attenuated or unchanged virulence. Finally, CW staining allowed us to efficiently visualize antifungal treatment outcomes in infected silkworms. Conclusively, we here present a powerful animal model combined with a straightforward staining protocol to expedite large-scale in vivo research of fungal pathogenicity and to investigate novel antifungal candidates.
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http://dx.doi.org/10.3390/jof7020136DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7918154PMC
February 2021

The impact of episporic modification of on virulence and interaction with phagocytes.

Comput Struct Biotechnol J 2021 20;19:880-896. Epub 2021 Jan 20.

Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI), Jena, Germany.

Fungal infections caused by the ancient lineage Mucorales are emerging and increasingly reported in humans. Comprehensive surveys on promising attributes from a multitude of possible virulence factors are limited and so far, focused on and . This study addresses a systematic approach to monitor phagocytosis after physical and enzymatic modification of the outer spore wall of , one of the major causative agents of mucormycosis. Episporic modifications were performed and their consequences on phagocytosis, intracellular survival and virulence by murine alveolar macrophages and in an invertebrate infection model were elucidated. While depletion of lipids did not affect the phagocytosis of both strains, delipidation led to attenuation of LCA strain but appears to be dispensable for infection with LCV strain in the settings used in this study. Combined glucano-proteolytic treatment was necessary to achieve a significant decrease of virulence of the LCV strain in during maintenance of the full potential for spore germination as shown by a novel automated germination assay. Proteolytic and glucanolytic treatments largely increased phagocytosis compared to alive resting and swollen spores. Whilst resting spores barely (1-2%) fuse to lysosomes after invagination in to phagosomes, spore trypsinization led to a 10-fold increase of phagolysosomal fusion as measured by intracellular acidification. This is the first report of a polyphasic measurement of the consequences of episporic modification of a mucormycotic pathogen in spore germination, spore surface ultrastructure, phagocytosis, stimulation of Toll-like receptors (TLRs), phagolysosomal fusion and intracellular acidification, apoptosis, generation of reactive oxygen species (ROS) and virulence.
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http://dx.doi.org/10.1016/j.csbj.2021.01.023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7851798PMC
January 2021

Human mucosal-associated invariant T cells respond to Mucorales species in a MR1-dependent manner.

Med Mycol 2021 May;59(5):505-509

Klinik für Innere Medizin II, Abteilung für Hämatologie und Internistische Onkologie, Universitätsklinikum Jena, Jena, Germany.

Activation of mucosal-associated invariant T cells (MAIT cells) by certain bacteria, viruses, and yeast is well studied, but the activation potential of filamentous moulds from the order Mucorales is not known. Here, we show a rapid response of human MAIT cells against the Mucorales species Mucor circinelloides, Rhizopus arrhizus, and Rhizopus microsporus. This activation included upregulation of CD69 and degranulation marked by increased CD107a expression, while intracellular perforin and granzyme A expression were reduced. Furthermore, blocking of the antigen-presenting molecule major histocompatibility complex class I-related abrogated MAIT cell activation demonstrating a T cell receptor-dependent stimulation by Mucorales.
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http://dx.doi.org/10.1093/mmy/myaa103DOI Listing
May 2021

Iron Assimilation during Emerging Infections Caused by Opportunistic Fungi with emphasis on Mucorales and the Development of Antifungal Resistance.

Genes (Basel) 2020 10 30;11(11). Epub 2020 Oct 30.

Jena Microbial Resource Collection, Leibniz Institute for Natural Product Research, and Infection Biology-Hans Knöll Institute, Jena, Adolf-Reichwein-Straße 23, 07745 Jena, Germany.

Iron is a key transition metal required by most microorganisms and is prominently utilised in the transfer of electrons during metabolic reactions. The acquisition of iron is essential and becomes a crucial pathogenic event for opportunistic fungi. Iron is not readily available in the natural environment as it exists in its insoluble ferric form, i.e., in oxides and hydroxides. During infection, the host iron is bound to proteins such as transferrin, ferritin, and haemoglobin. As such, access to iron is one of the major hurdles that fungal pathogens must overcome in an immunocompromised host. Thus, these opportunistic fungi utilise three major iron acquisition systems to overcome this limiting factor for growth and proliferation. To date, numerous iron acquisition pathways have been fully characterised, with key components of these systems having major roles in virulence. Most recently, proteins involved in these pathways have been linked to the development of antifungal resistance. Here, we provide a detailed review of our current knowledge of iron acquisition in opportunistic fungi, and the role iron may have on the development of resistance to antifungals with emphasis on species of the fungal basal lineage order Mucorales, the causative agents of mucormycosis.
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http://dx.doi.org/10.3390/genes11111296DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7693903PMC
October 2020

Host Immune Defense upon Fungal Infections with Mucorales: Pathogen-Immune Cell Interactions as Drivers of Inflammatory Responses.

J Fungi (Basel) 2020 Sep 17;6(3). Epub 2020 Sep 17.

Jena Microbial Resource Collection, Leibniz Institute for Natural Product Research and Infection Biology-Hans Knöll Institute (HKI), 07745 Jena, Germany.

During the last few decades, mucormycosis has emerged as one of the most common fungal infections, following candidiasis and aspergillosis. The fungal order responsible for causing mucormycosis is the Mucorales. The main hallmarks of this infection include the invasion of blood vessels, infarction, thrombosis, and tissue necrosis, which are exhibited at the latest stages of the infection. Therefore, the diagnosis is often delayed, and the rapid progression of the infection severely endangers the life of people suffering from diabetes mellitus, hematological malignancies, or organ transplantation. Given the fact that mortality rates for mucormycosis range from 40 to 80%, early diagnosis and novel therapeutic strategies are urgently needed to battle the infection. However, compared to other fungal infections, little is known about the host immune response against Mucorales and the influence of inflammatory processes on the resolution of the infection. Hence, in this review, we summarized our current understanding of the interplay among pro-inflammatory cytokines, chemokines, and the host-immune cells in response to mucoralean fungi, as well as their potential use for immunotherapies.
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http://dx.doi.org/10.3390/jof6030173DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7557740PMC
September 2020

Functional surface proteomic profiling reveals the host heat-shock protein A8 as a mediator of Lichtheimia corymbifera recognition by murine alveolar macrophages.

Environ Microbiol 2020 09 21;22(9):3722-3740. Epub 2020 Jul 21.

Jena Microbial Resource Collection, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI), Jena, Germany.

Mucormycosis is an emergent, fatal fungal infection of humans and warm-blooded animals caused by species of the order Mucorales. Immune cells of the innate immune system serve as the first line of defence against inhaled spores. Alveolar macrophages were challenged with the mucoralean fungus Lichtheimia corymbifera and subjected to biotinylation and streptavidin enrichment procedures followed by LC-MS/MS analyses. A total of 28 host proteins enriched for binding to macrophage-L. corymbifera interaction. Among those, the HSP70-family protein Hspa8 was found to be predominantly responsive to living and heat-killed spores of a virulent and an attenuated strain of L. corymbifera. Confocal scanning laser microscopy of infected macrophages revealed colocalization of Hspa8 with phagocytosed spores of L. corymbifera. The amount of detectable Hspa8 was dependent on the multiplicity of infection. Incubation of alveolar macrophages with an anti-Hspa8 antibody prior to infection reduced their capability to phagocytose spores of L. corymbifera. In contrast, anti-Hspa8 antibodies did not abrogate the phagocytosis of Aspergillus fumigatus conidia by macrophages. These results suggest an important contribution of the heat-shock family protein Hspa8 in the recognition of spores of the mucoralean fungus L. corymbifera by host alveolar macrophages and define a potential immunomodulatory therapeutic target.
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http://dx.doi.org/10.1111/1462-2920.15140DOI Listing
September 2020

Quantitative Impact of Cell Membrane Fluorescence Labeling on Phagocytosis Measurements in Confrontation Assays.

Front Microbiol 2020 5;11:1193. Epub 2020 Jun 5.

Applied Systems Biology, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute, Jena, Germany.

Phagocytosis is series of steps where the pathogens and the immune cells interact during an invasion. This starts with the adhesion process between the host and pathogen cells, and is followed by the engulfment of the pathogens. Many analytical methods that are applied to characterize phagocytosis based on imaging the host-pathogen confrontation assays rely on the fluorescence labeling of cells. However, the potential effect of the membrane labeling on the quantitative results of the confrontation assays has not been studied in detail. In this study, we determine whether the fluorescence labeling processes themselves influence the results of the phagocytosis measurements. Here, alveolar macrophages, which form one of the most important compartments of the innate immune system, were used as an example of host cells, whereas and that cause aspergillosis and mucormycosis, respectively, were studied as examples for pathogens. At first, our study investigated the importance of the sequence of steps of the fixation process when preparing the confrontation assay sample for microscopy studies. Here we showed that applying the fixation agent before the counter-staining causes miscalculations during the determination of the phagocytic measures. Furthermore, we also found that staining the macrophages with various concentrations of DID, as a typical membrane label, in most cases altered the capability of macrophages to phagocytose FITC-stained and spores in comparison with unlabeled macrophages. This effect of the DID staining showed a differential character dependent upon the labeling status and the specific type of pathogen. Moreover, labeling the spores of and with FITC increased the phagocytic measures during confrontation with unlabeled macrophages when compared to label-free spores. Overall, our study confirms that the staining process itself may significantly manipulate the quantitative outcome of the confrontation assay. As a result of our study, we also developed a user-friendly image analysis tool that analyses confrontation assays both with and without fluorescence labeling of the host cells and of the pathogens. Our image analysis algorithm saves experimental work effort and time, provides more precise results when calculating the phagocytic measures, and delivers a convenient analysis tool for the biologists to monitor host-pathogen interactions as they happen without the artifacts that fluorescence labeling imposes on biological interactions.
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http://dx.doi.org/10.3389/fmicb.2020.01193DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7289966PMC
June 2020

Microbiomes in an acidic rock-water cave system.

FEMS Microbiol Lett 2019 07;366(13)

Institute of Microbiology, Microbial Communication, Friedrich Schiller University Jena, Neugasse 25, D-07743 Jena, Germany.

Belowground ecosystems are accessible by mining, where a specific microbial community can be discovered. The biodiversity of a former alum mine rich in carbon, but with a low pH of 2.6-3.7, was evaluated by DNA- and cultivation-dependent methods using samples of the black slate rock material, secondary mineralization phases and seepage water. Pyrite oxidation within the low-grade metamorphic Silurian black slate established high concentrations of Fe and $\rm{SO}_4^{2-}$ forming the extreme conditions visible with acidophilic and Fe-oxidizing microorganisms. In addition, an unexpected predominance of fungi in this C-rich and acidic cave ecosystem, including high numbers of Mucoromycota and Mortierellomycota, was detected. Therefore, fungal cultures were obtained, mainly from the secondary mineral phases that are iron phosphates. Hence, the fungi might well have been involved in phosphate mobilization there. The rock material itself is rich in organic carbon that can be used by oxidase activity. The cultivation setup mimicked the cave conditions (low temperature, low pH, oxic conditions), with one oligotrophic and one medium rich in nutrients that allowed for isolation of different fungal (and eutrophic bacterial) groups. The acidic conditions prevented the occurrence of many basidiomycetes, while the isolated fungi could survive these adverse conditions.
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http://dx.doi.org/10.1093/femsle/fnz167DOI Listing
July 2019

The geographical region of origin determines the phagocytic vulnerability of Lichtheimia strains.

Environ Microbiol 2019 12 5;21(12):4563-4581. Epub 2019 Aug 5.

Institute of Microbiology, Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany.

Mucormycoses are life-threatening infections that affect patients suffering from immune deficiencies. We performed phagocytosis assays confronting various strains of Lichtheimia species with alveolar macrophages, which form the first line of defence of the innate immune system. To investigate 17 strains from four different continents in a comparative fashion, transmitted light and confocal fluorescence microscopy was applied in combination with automated image analysis. This interdisciplinary approach enabled the objective and quantitative processing of the big volume of image data. Applying machine-learning supported methods, a spontaneous clustering of the strains was revealed in the space of phagocytic measures. This clustering was not driven by measures of fungal morphology but rather by the geographical origin of the fungal strains. Our study illustrates the crucial contribution of machine-learning supported automated image analysis to the qualitative discovery and quantitative comparison of major factors affecting host-pathogen interactions. We found that the phagocytic vulnerability of Lichtheimia species depends on their geographical origin, where strains within each geographic region behaved similarly, but strongly differed amongst the regions. Based on this clustering, we were able to also classify clinical isolates with regard to their potential geographical origin.
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http://dx.doi.org/10.1111/1462-2920.14752DOI Listing
December 2019

Author Correction: Arylmethylamino steroids as antiparasitic agents.

Nat Commun 2019 Jul 8;10(1):2997. Epub 2019 Jul 8.

Biochemistry and Molecular Biology, Interdisciplinary Research Centre, Justus Liebig University Giessen, Heinrich Buff Ring 26-32, 35392, Giessen, Germany.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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http://dx.doi.org/10.1038/s41467-019-11018-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6614475PMC
July 2019

A Revised Species Concept for Opportunistic Species Reveals Species-Specific Antifungal Susceptibility Profiles.

Antimicrob Agents Chemother 2019 08 25;63(8). Epub 2019 Jul 25.

German National Reference Center for Invasive Fungal Infections, Leibniz Institute for Natural Product Research and Infection Biology-Hans Knöll Institute, Jena, Germany

Recently, the species concept of opportunistic and its relatives has been revised, resulting in the recognition of its classical formae as independent species and the description of new species. In this study, we used isolates of all clinically relevant species and performed susceptibility testing using the EUCAST reference method to identify potential species-specific susceptibility patterns. susceptibility profiles of 101 mucoralean strains belonging to the genus (72), the closely related species (3), (12), (10), and (4) to six antifungals (amphotericin B, natamycin, terbinafine, isavuconazole, itraconazole, and posaconazole) were determined. The most active drug for all Mucorales was amphotericin B. Antifungal susceptibility profiles of pathogenic species were specific for isavuconazole, itraconazole, and posaconazole. The species formerly united in showed clear differences in their antifungal susceptibilities. , , ( f. ), and exhibited high MICs to all azoles tested. presented high MICs for isavuconazole and posaconazole, and and showed high MICs for isavuconazole. MIC values of spp. for posaconazole, isavuconazole, and itraconazole were high compared to those for and the Lichtheimiaceae ( and ). Molecular identification combined with susceptibility testing is recommended for species, especially if azoles are applied in treatment.
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http://dx.doi.org/10.1128/AAC.00653-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6658771PMC
August 2019

Noursamycins, Chlorinated Cyclohexapeptides Identified from Molecular Networking of Streptomyces noursei NTR-SR4.

J Nat Prod 2019 06 7;82(6):1478-1486. Epub 2019 Jun 7.

Technische Universität Berlin, Institut für Chemie , Straße des 17. Juni 124 , 10623 Berlin , Germany.

The noursamycins A-F are chlorinated cyclic hexapeptides, which were identified and isolated from the strain Streptomyces noursei NTR-SR4 overexpressing a LuxR-like transcriptional activator. The molecules were structurally characterized by mass spectrometric analyses and 1D and 2D NMR spectroscopic techniques. The enzymatic machinery involved in the biosynthesis of these peptides is represented by a modular nonribosomal peptide synthetase (NRPS), and the corresponding gene cluster was identified in the S. noursei genome. The latter suggested the biosynthetic pathway for the noursamycins. Spectral networking analysis uncovered noursamycin derivatives that were later found to result from a relaxed substrate specificity of the A and A adenylation domains of the NRPS. The stereochemistry of the amino acid constituents of the noursamycins was resolved by chemical derivatization, subsequent enantiomer analytics by GC-EIMS, and in silico data analyses. Noursamycins A and B exhibited antibacterial activity against Gram-positive and Gram-negative bacteria, while no apparent cytotoxicity was observed.
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http://dx.doi.org/10.1021/acs.jnatprod.8b00967DOI Listing
June 2019

Pathogenicity patterns of mucormycosis: epidemiology, interaction with immune cells and virulence factors.

Med Mycol 2019 Apr;57(Supplement_2):S245-S256

Jena Microbial Resource Collection, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute, Adolf-Reichwein-Strasse 23, 07745 Jena, Germany.

Fungi of the basal lineage order Mucorales are able to cause infections in animals and humans. Mucormycosis is a well-known, life-threatening disease especially in patients with a compromised immune system. The rate of mortality and morbidity caused by mucormycosis has increased rapidly during the last decades, especially in developing countries. The systematic, phylogenetic, and epidemiological distributions of mucoralean fungi are addressed in relation to infection in immunocompromised patients. The review highlights the current achievements in (i) diagnostics and management of mucormycosis, (ii) the study of the interaction of Mucorales with cells of the innate immune system, (iii) the assessment of the virulence of Mucorales in vertebrate and invertebrate infection models, and (iv) the determination of virulence factors that are key players in the infection process, for example, high-affinity iron permease (FTR1), spore coat protein (CotH), alkaline Rhizopus protease enzyme (ARP), ADP-ribosylation factor (ARF), dihydrolipoyl dehydrogenase, calcineurin (CaN), serine and aspartate proteases (SAPs). The present mini-review attempts to increase the awareness of these difficult-to-manage fungal infections and to encourage research in the detection of ligands and receptors as potential diagnostic parameters and drug targets.
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http://dx.doi.org/10.1093/mmy/myz011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6394756PMC
April 2019

Anaerobic fungal communities differ along the horse digestive tract.

Fungal Biol 2019 03 27;123(3):240-246. Epub 2018 Dec 27.

Institute of Animal Physiology and Genetics, CAS, Vídeňská 1083, Prague 14220, Czech Republic. Electronic address:

Anaerobic fungi are potent fibre degrading microbes in the equine hindgut, yet our understanding of their diversity and community structure is limited to date. In this preliminary work, using a clone library approach we studied the diversity of anaerobic fungi along six segments of the horse hindgut: caecum, right ventral colon (RVC), left ventral colon (LVC), left dorsal colon (LDC), right dorsal colon (RDC) and rectum. Of the 647 ITS1 clones, 61.7 % were assigned to genus level groups that are so far without any cultured representatives, and 38.0 % were assigned to the cultivated genera Neocallimastix (35.1 %), Orpinomyces (2.3 %), and Anaeromyces (0.6 %). AL1 dominated the group of uncultured anaerobic fungi, particularly in the RVC (88 %) and LDC (97 %). Sequences from the LSU clone library analysis of the LDC, however, split into two distinct phylogenetic clusters with low sequence identity to Caecomyces sp. (94-96 %) and Liebetanzomyces sp. (92 %) respectively. Sequences belonging to cultured Neocallimastix spp. dominated in LVC (81 %) and rectum (75.5 %). Quantification of anaerobic fungi showed significantly higher concentrations in RVC and RDC compared to other segments, which influenced the interpretation of the changes in anaerobic fungal diversity along the horse hindgut. These preliminary findings require further investigation.
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http://dx.doi.org/10.1016/j.funbio.2018.12.004DOI Listing
March 2019

Formation of Nudicaulins In Vivo and In Vitro and the Biomimetic Synthesis and Bioactivity of -Methylated Nudicaulin Derivatives.

Molecules 2018 Dec 18;23(12). Epub 2018 Dec 18.

Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, D-07745 Jena, Germany.

Nudicaulins are yellow flower pigments accounting for the color of the petals of (Papaveraceae). These glucosidic compounds belong to the small group of indole/flavonoid hybrid alkaloids. Here we describe in vivo and in vitro experiments which substantiate the strongly pH-dependent conversion of pelargonidin glucosides to nudicaulins as the final biosynthetic step of these alkaloids. Furthermore, we report the first synthesis of nudicaulin aglycon derivatives, starting with quercetin and ending up at the biomimetic fusion of a permethylated anthocyanidin with indole. A small library of nudicaulin derivatives with differently substituted indole units was prepared, and the antimicrobial, antiproliferative and cell toxicity data of the new compounds were determined. The synthetic procedure is considered suitable for preparing nudicaulin derivatives which are structurally modified in the indole and/or the polyphenolic part of the molecule and may have optimized pharmacological activities.
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http://dx.doi.org/10.3390/molecules23123357DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6320756PMC
December 2018

Comparative Study on Alternative Splicing in Human Fungal Pathogens Suggests Its Involvement During Host Invasion.

Front Microbiol 2018 2;9:2313. Epub 2018 Oct 2.

Research Group PiDOMICS, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute, Jena, Germany.

Alternative splicing (AS) is an important regulatory mechanism in eukaryotes but only little is known about its impact in fungi. Human fungal pathogens are of high clinical interest causing recurrent or life-threatening infections. AS can be well-investigated genome-wide and quantitatively with the powerful technology of RNA-Seq. Here, we systematically studied AS in human fungal pathogens based on RNA-Seq data. To do so, we investigated its effect in seven fungi during conditions simulating infection processes and during stress. Genes undergoing AS are species-specific and act independently from differentially expressed genes pointing to an independent mechanism to change abundance and functionality. species stand out with a low number of introns with higher and more varying lengths and more alternative splice sites. Moreover, we identified a functional difference between response to host and other stress conditions: During stress, AS affects more genes and is involved in diverse regulatory functions. In contrast, during response-to-host conditions, genes undergoing AS have membrane functionalities and might be involved in the interaction with the host. We assume that AS plays a crucial regulatory role in pathogenic fungi and is important in both response to host and stress conditions.
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http://dx.doi.org/10.3389/fmicb.2018.02313DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6176087PMC
October 2018

Novel insight into the reaction of nitro, nitroso and hydroxylamino benzothiazinones and of benzoxacinones with Mycobacterium tuberculosis DprE1.

Sci Rep 2018 09 7;8(1):13473. Epub 2018 Sep 7.

Platform Technology & Science, GlaxoSmithKline, Gunnels Wood Road, Stevenage, SG1 2NY, United Kingdom.

Nitro-substituted 1,3-benzothiazinones (nitro-BTZs) are mechanism-based covalent inhibitors of Mycobacterium tuberculosis decaprenylphosphoryl-β-D-ribose-2'-oxidase (DprE1) with strong antimycobacterial properties. We prepared a number of oxidized and reduced forms of nitro-BTZs to probe the mechanism of inactivation of the enzyme and to identify opportunities for further chemistry. The kinetics of inactivation of DprE1 was examined using an enzymatic assay that monitored reaction progress up to 100 min, permitting compound ranking according to k/K values. The side-chain at the 2-position and heteroatom identity at the 1-position of the BTZs were found to be important for inhibitory activity. We obtained crystal structures with several compounds covalently bound. The data suggest that steps upstream from the covalent end-points are likely the key determinants of potency and reactivity. The results of protein mass spectrometry using a 7-chloro-nitro-BTZ suggest that nucleophilic reactions at the 7-position do not operate and support a previously proposed mechanism in which BTZ activation by a reduced flavin intermediate is required. Unexpectedly, a hydroxylamino-BTZ showed time-dependent inhibition and mass spectrometry corroborated that this hydroxylamino-BTZ is a mechanism-based suicide inhibitor of DprE1. With this BTZ derivative, we propose a new covalent mechanism of inhibition of DprE1 that takes advantage of the oxidation cycle of the enzyme.
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http://dx.doi.org/10.1038/s41598-018-31316-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6128881PMC
September 2018

Early Diverging Insect-Pathogenic Fungi of the Order Entomophthorales Possess Diverse and Unique Subtilisin-Like Serine Proteases.

G3 (Bethesda) 2018 10 3;8(10):3311-3319. Epub 2018 Oct 3.

Section for Organismal Biology, Department of Plant and Environmental Sciences, University of Copenhagen, Denmark

Insect-pathogenic fungi use subtilisin-like serine proteases (SLSPs) to degrade chitin-associated proteins in the insect procuticle. Most insect-pathogenic fungi in the order Hypocreales (Ascomycota) are generalist species with a broad host-range, and most species possess a high number of SLSPs. The other major clade of insect-pathogenic fungi is part of the subphylum Entomophthoromycotina (Zoopagomycota, formerly Zygomycota) which consists of high host-specificity insect-pathogenic fungi that naturally only infect a single or very few host species. The extent to which insect-pathogenic fungi in the order Entomophthorales rely on SLSPs is unknown. Here we take advantage of recently available transcriptomic and genomic datasets from four genera within Entomophthoromycotina: the saprobic or opportunistic pathogens , , , , and the host-specific insect pathogens and , specific pathogens of house flies () and wood ants (), respectively. In total 154 SLSP from six fungi in the subphylum Entomophthoromycotina were identified: (n = 22), (n = 6), (n = 60), (n = 18), (n = 36), and (n = 12). A unique group of 11 SLSPs was discovered in the genomes of the obligate biotrophic fungi , and the saprobic human pathogen that loosely resembles bacillopeptidase F-like SLSPs. Phylogenetics and protein domain analysis show this class represents a unique group of SLSPs so far only observed among Bacteria, Oomycetes and early diverging fungi such as Cryptomycota, Microsporidia, and Entomophthoromycotina. This group of SLSPs is missing in the sister fungal lineages of Kickxellomycotina and the fungal phyla Mucoromyocta, Ascomycota and Basidiomycota fungi suggesting interesting gene loss patterns.
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http://dx.doi.org/10.1534/g3.118.200656DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6169396PMC
October 2018

Phylogenetic and Phylogenomic Definition of Species.

G3 (Bethesda) 2018 05 31;8(6):2007-2018. Epub 2018 May 31.

North Florida Research and Educational Center, University of Florida, Quincy, Florida, 32351.

Phylogenomic approaches have the potential to improve confidence about the inter-relationships of species in the order Mucorales within the fungal tree of life. species are especially important as plant and animal pathogens and bioindustrial fermenters for food and metabolite production. A dataset of 192 orthologous genes was used to construct a phylogenetic tree of 21 strains, classified into four species isolated from habitats of industrial, medical and environmental importance. The phylogeny indicates that the genus consists of three major clades, with as the basal species and the sister lineage to and two closely related species and A comparative analysis of the mating type locus across reveals that its structure is flexible even between different species in the same genus, but shows similarities between and other mucoralean fungi. The topology of single-gene phylogenies built for two genes involved in mating is similar to the phylogenomic tree. Comparison of the total length of the genome assemblies showed that genome size varies by as much as threefold within a species and is driven by changes in transposable element copy numbers and genome duplications.
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http://dx.doi.org/10.1534/g3.118.200235DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5982828PMC
May 2018

Phylogenetic Status of Two Undescribed Zygomycete Species from Korea: and .

Mycobiology 2017 Dec 31;45(4):344-352. Epub 2017 Dec 31.

Division of Food Technology, Biotechnology and Agrochemistry, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 61186, Korea.

During a survey of fungal diversity of the order Mucorales, three zygomycete isolates, CNUFC-YR113-1, CNUFC-KNU16-7, and CNUFC-BS1-1 were isolated from freshwater and soil samples in Korea. The strains were analyzed both morphologically and phylogenetically based on internal transcribed spacer and 28S rDNA gene sequences. Based on their morphology and phylogeny, the CNUFC-YR113-1 and CNUFC-KNU16-7 isolates were identified as , and CNUFC-BS1-1 was identified as . To the best of our knowledge, the species and , belonging to an undiscovered taxon, have not been previously described in Korea.
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http://dx.doi.org/10.5941/MYCO.2017.45.4.344DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5780366PMC
December 2017

Harnessing fungal nonribosomal cyclodepsipeptide synthetases for mechanistic insights and tailored engineering.

Chem Sci 2017 Nov 25;8(11):7834-7843. Epub 2017 Sep 25.

Fachgebiet Biologische Chemie , Institut für Chemie , Technische Universität Berlin , Strasse des 17. Juni 124 , 10623 Berlin , Germany . Email:

Nonribosomal peptide synthetases represent potential platforms for the design and engineering of structurally complex peptides. While previous focus has been centred mainly on bacterial systems, fungal synthetases assembling drugs like the antifungal echinocandins, the antibacterial cephalosporins or the anthelmintic cyclodepsipeptide (CDP) PF1022 await in-depth exploitation. As various mechanistic features of fungal CDP biosynthesis are only partly understood, effective engineering of NRPSs has been severely hampered. By combining protein truncation, expression and combinatorial swapping, we assigned important functional segments of fungal CDP synthetases and assessed their biosynthetic capabilities. Hence, artificial assembly line components comprising of up to three different synthetases were generated. Using as a heterologous expression host, we obtained new-to-nature octa-enniatin (4 mg L) and octa-beauvericin (10.8 mg L), as well as high titers of the hybrid CDP hexa-bassianolide (1.3 g L) with an engineered ring size. The hybrid compounds showed up to 12-fold enhanced antiparasitic activity against and compared to the reference drugs miltefosine and benznidazole, respectively. Our findings thus contribute to a rational engineering of iterative nonribosomal assembly lines.
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http://dx.doi.org/10.1039/c7sc03093bDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5674221PMC
November 2017

Ketoacidosis alone does not predispose to mucormycosis by Lichtheimia in a murine pulmonary infection model.

Virulence 2017 11 24;8(8):1657-1667. Epub 2017 Aug 24.

a Research Group Microbial Immunology, Leibniz Institute for Natural Product Research and Infection Biology, Hans-Knöll-Institute (HKI) , Jena , Germany.

Mucormycosis is a rare fungal infection; however, the number of cases increased during the last decades. The main risk factors are immunosuppression and uncontrolled diabetes mellitus. Although Lichtheimia species represent a common cause of mucormycosis in Europe, virulence and pathogenesis of this genus has not been investigated in detail yet. Using murine pulmonary infection models, we found that immunosuppression is essential for establishment of infection. The disease was characterized by necrosis, angioinvasion, thrombosis, and the lethal course of infection was associated with systemic activation of platelets. Furthermore, dissemination to internal organs was frequently observed. While the virulence potential of individual L. corymbifera and L. ramosa isolates differed, pathogenicity of both species was comparable. Although ketoacidosis promoted Rhizopus infection in mice, it did not predispose mice to infection with Lichtheimia in the absence of additional immunosuppression. This might partially explain the dominance of Rhizopus as cause of mucormycosis in countries with high prevalence of ketoacidotic patients.
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http://dx.doi.org/10.1080/21505594.2017.1360460DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5810507PMC
November 2017

A tale of four kingdoms - isoxazolin-5-one- and 3-nitropropanoic acid-derived natural products.

Nat Prod Rep 2017 04;34(4):343-360

Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.

Covering up to September 2016This review reports on natural compounds that derive from the isoxazolinone ring as well as the 3-nitropropanoic acid (3-NPA) moiety. These structural elements occur in compounds that have been identified in plants, insects, bacteria and fungi. In particular, plants belonging to the family of legumes produce such compounds. In the case of insects, isoxazolin-5-one and 3-NPA derivatives were found in leaf beetles of the subtribe Chrysomelina. A number of these natural products have been synthesized so far. In the case of the single compound 3-NPA, several synthetic strategies have been reported and some of the most efficient routes are reviewed. The toxicity of 3-NPA results from its ability to bind covalently to the catalytic center of succinate dehydrogenase causing irreversible inhibition of mitochondrial respiration. As a motif that is produced by many species of plants, leaf beetles and fungi, different detoxification mechanisms for 3-NPA have evolved in different species. These mechanisms are based on amide formation of 3-NPA with amino acids, reduction to β-alanine, ester formation or oxidation to malonic acid semialdehyde. The biosynthetic pathways of 3-NPA and isoxazolin-5-one moieties have been studied in fungi, plants and leaf beetles. In the case of fungi, 3-NPA derives from aspartate, while leaf beetles use essential amino acids such as valine as ultimate precursors. In the case of plants, it is supposed that malonate serves as a precursor of 3-NPA, as indicated by feeding of C-labeled precursors to Indigofera spicata. In other leguminous plants it is suggested that asparagine is incorporated into compounds that derive from isoxazolin-5-one, which was indicated by C-labeled compounds as well. In the case of leaf beetles it was demonstrated that detection of radioactivity after C-labeling from a few precursors is not sufficient to unravel biosynthetic pathways.
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http://dx.doi.org/10.1039/c6np00122jDOI Listing
April 2017

Arylmethylamino steroids as antiparasitic agents.

Nat Commun 2017 02 17;8:14478. Epub 2017 Feb 17.

Biochemistry and Molecular Biology, Interdisciplinary Research Centre, Justus Liebig University Giessen, Heinrich Buff Ring 26-32, 35392 Giessen, Germany.

In search of antiparasitic agents, we here identify arylmethylamino steroids as potent compounds and characterize more than 60 derivatives. The lead compound 1o is fast acting and highly active against intraerythrocytic stages of chloroquine-sensitive and resistant Plasmodium falciparum parasites (IC 1-5 nM) as well as against gametocytes. In P. berghei-infected mice, oral administration of 1o drastically reduces parasitaemia and cures the animals. Furthermore, 1o efficiently blocks parasite transmission from mice to mosquitoes. The steroid compounds show low cytotoxicity in mammalian cells and do not induce acute toxicity symptoms in mice. Moreover, 1o has a remarkable activity against the blood-feeding trematode parasite Schistosoma mansoni. The steroid and the hydroxyarylmethylamino moieties are essential for antimalarial activity supporting a chelate-based quinone methide mechanism involving metal or haem bioactivation. This study identifies chemical scaffolds that are rapidly internalized into blood-feeding parasites.
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http://dx.doi.org/10.1038/ncomms14478DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5321741PMC
February 2017

The tip and hidden part of the iceberg: Proteinogenic and non-proteinogenic aliphatic amino acids.

Biochim Biophys Acta Gen Subj 2017 Jan 20;1861(1 Pt A):3258-3269. Epub 2016 Aug 20.

Dept. of Bioinformatics, University of Jena, Ernst-Abbe-Pl. 2, 07743 Jena, Germany. Electronic address:

Background: Amino acids are the essential building blocks of proteins and, therefore, living organisms. While the focus often lies on the canonical or proteinogenic amino acids, there is also a large number of non-canonical amino acids to explore. Some of them are part of toxins or antibiotics in fungi, bacteria or animals (e.g. sponges). Some others operate at the translational level like an "undercover agent".

Scope Of Review: Here we give an overview of natural aliphatic amino acids, up to a side chain length of five carbons, without rings and with an unmodified backbone, and have a closer look on each of them. Some of them are dehydro amino acids with double or even triple bonds. Moreover, we outline mathematical methods for enumerating the complete list of all potential aliphatic amino acids of a given chain length. This should be of interest for synthetic biology.

Major Conclusions: Most non-proteinogenic amino acids are found within fungi, with particularly many produced by Amanita species as defence chemicals. Several are incorporated into peptide antibiotics. Some of the amino acids occur due to broad substrate specificity of the branched-chain amino acid synthesis pathways. A large variety of amino acids were also found in the Murchison meteorite.

General Significance: Non-proteinogenic amino acids are of interest for numerous medical applications: discovery of new antibiotics, support in designing synthetic antibiotics, improvement of protein and peptide pharmaceuticals by avoiding incorporation of non-canonical amino acids, study of toxic cyanobacteria and other applications.
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http://dx.doi.org/10.1016/j.bbagen.2016.08.008DOI Listing
January 2017

Chemical Composition and Antimicrobial Activity of Populus nigra Shoot Resin.

Nat Prod Commun 2016 Jul;11(7):989-992

The chemical composition of Populus nigra shoot resin has been investigated by chromatographic and spectroscopic methods. The analyses resulted in identification of 19 known compounds. The resin exhibited low activity against selected microorganisms.
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July 2016
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