Marc Stadler

The sooty moulds

Sooty moulds are a remarkable, but poorly understood group of fungi. They coat fruits and leaves superficially with black mycelia, which reduces photosynthesis rates of host plants. Few researchers have, however, tried to quantify their economic importance. Sooty moulds have been well-studied at the morphological level, but they are poorly represented in a natural classification based on phylogeny. Representatives are presently known in Antennulariellaceae, Capnodiaceae, Chaetothyriaceae, Coccodiniaceae, Euantennariaceae, Metacapnodiaceae and Trichomeriaceae and several miscellaneous genera. However, molecular data is available for only five families. Most sooty mould colonies comprise numerous species and thus it is hard to confirm relationships between genera or sexual and asexual states. Future studies need to obtain single spore isolates of species to test their phylogenetic affinities and linkages between morphs. Next generation sequencing has shown sooty mould colonies to contain many more fungal species than expected, but it is not clear which species are dominant or active in the communities. They are more common in tropical, subtropical and warm temperate regions and thus their prevalence in temperate regions is likely to increase with global warming. Sooty moulds are rarely parasitized by fungicolous taxa and these may have biocontrol potential. They apparently grow in extreme environments and may be xerophilic. This needs testing as xerophilic taxa may be of interest for industrial applications. Sooty moulds grow on sugars and appear to out-compete typical “weed” fungi and bacteria. They may produce antibiotics for this purpose and their biochemical potential for obtaining novel bioactive compounds for medical application is underexplored.

Bioactive metabolites from macrofungi: ethnopharmacology, biological activities and chemistry

Exploration of natural sources for novel bioactive compounds has been an emerging field of medicine over the past decades, providing drugs or lead compounds of considerable therapeutic potential. This research has provided exciting evidence on the isolation of microbe-derived metabolites having prospective biological activities. Mushrooms have been valued as traditional sources of natural bioactive compounds for many centuries and have been targeted as promising therapeutic agents. Many novel biologically active compounds have been reported as a result of research on medicinal mushrooms. In this review, we compile the information on bioactive structure-elucidated metabolites from macrofungi discovered over the last decade and highlight their unique chemical diversity and potential benefits to novel drug discovery. The main emphasis is on their anti-Alzheimer, anti-diabetic, anti-malarial, anti-microbial, anti-oxidant, anti-tumor, anti-viral and hypocholesterolemic activities which are important medicinal targets in terms of drug discovery today. Moreover, the reader’s attention is brought to focus on mushroom products and food supplements available in the market with claimed biological activities and potential human health benefits.

Synthetic Biotechnology to Study and Engineer Ribosomal Bottromycin Biosynthesis

Bottromycins represent a promising class of antibiotics binding to the therapeutically unexploited A-site of the bacterial ribosome. By inhibiting translation they are active against clinically important pathogens, such as vancomycin-resistant Enterococci. Structurally, bottromycins are heavily modified peptides exhibiting various unusual biosynthetic features. To set the stage for compound modification and yield optimization, we identified the biosynthetic gene cluster, used synthetic biotechnology approaches to establish and improve heterologous production, and generated analogs by pathway genetic engineering. We unambiguously identified three radical SAM methyltransferase-encoding genes required for various methylations at unactivated carbons yielding tert-butyl valine, methyl-proline, and β-methyl-phenylalanine residues, plus a gene involved in aspartate methyl-ester formation. Evidence for the formation of the exo-thiazole unit and for a macrocyclodehydration mechanism leading to amidine ring formation is provided.

Families of Sordariomycetes

Sordariomycetes is one of the largest classes of Ascomycota that comprises a highly diverse range of fungi characterized mainly by perithecial ascomata and inoperculate unitunicate asci. The class includes many important plant pathogens, as well as endophytes, saprobes, epiphytes, coprophilous and fungicolous, lichenized or lichenicolous taxa. They occur in terrestrial, freshwater and marine habitats worldwide. This paper reviews the 107 families of the class Sordariomycetes and provides a modified backbone tree based on phylogenetic analysis of four combined loci, with a maximum five representative taxa from each family, where available. This paper brings together for the first time, since Barrs’ 1990 Prodromus, descriptions, notes on the history, and plates or illustrations of type or representative taxa of each family, a list of accepted genera, including asexual genera and a key to these taxa of Sordariomycetes. Delineation of taxa is supported where possible by molecular data. The outline is based on literature to the end of 2015 and the Sordariomycetes now comprises six subclasses, 32 orders, 105 families and 1331 genera. The family Obryzaceae and Pleurotremataceae are excluded from the class.

Cystobactamids: Myxobacterial Topoisomerase Inhibitors Exhibiting Potent Antibacterial Activity

The development of new antibiotics faces a severe crisis inter alia owing to a lack of innovative chemical scaffolds with activities against Gram-negative and multiresistant pathogens. Herein, we report highly potent novel antibacterial compounds, the myxobacteria-derived cystobactamids 1-3, which were isolated from Cystobacter sp. and show minimum inhibitory concentrations in the low μg mL(-1) range. We describe the isolation and structure elucidation of three congeners as well as the identification and annotation of their biosynthetic gene cluster. By studying the self-resistance mechanism in the natural producer organism, the molecular targets were identified as bacterial type IIa topoisomerases. As quinolones are largely exhausted as a template for new type II topoisomerase inhibitors, the cystobactamids offer exciting alternatives to generate novel antibiotics using medicinal chemistry and biosynthetic engineering.

Towards unraveling relationships in Xylariomycetidae (Sordariomycetes)

The classification of subclass Xylariomycetidae is revisited with additional collections and phylogeny based on novel rDNA sequence data. Phylogenetic inferences are provided and are based on analysis of 115 sequence data, including new data for 27 strains. An updated outline to the subclass is presented based on the phylogenies and comprises two orders, 18 families and 222 genera. An account of each order, family and genus in the subclass is given. We accept the orders Amphisphaeriales and Xylariales based on morphological and phylogenetic evidence. Amphisphaeriales comprises Amphisphaeriaceae, Bartaliniaceae fam. nov., Clypeosphaeriaceae, Discosiaceae fam. nov., Pestalotiopsidaceae fam. nov. and Phlogicylindriaceae fam. nov. Xylariales comprises Apiosporaceae, Cainiaceae, Coniocessiaceae, Diatrypaceae, Graphostromataceae (doubtful), Hyponectriaceae, Iodosphaeriaceae, Lopadostomaceae fam. nov., Melogrammataceae, Pseudomassariaceae fam. nov., Vialaeaceae and Xylariaceae. The new genera and species introduced are Arthrinium hyphopodii, A. subglobosa, Cainia anthoxanthis, Ciferriascosea gen. nov., C. fluctamurum, C. rectamurum, Discosia neofraxinea, D. pseudopleurochaeta, Hyalotiella rubi, Seimatosporium cornii, S. ficeae, S. vitis and Truncatella spartii.

A polyphasic taxonomy of Daldinia (Xylariaceae)

For a monograph based on a polythetic concept, several thousands of herbarium specimens, and several hundreds of freshly collected and cultured specimens of Daldinia and allied Xylariaceae, originating from around the world, were studied for morphological traits, including by SEM, and chemically by HPLC profiles using UV-visible and mass spectrometric detection. Emphasis was given to tropical material, and importantly, ancient specimens, including as many types as possible, were tracked and studied to review earlier taxonomic concepts. An epitype of D. eschscholtzii was selected as representative of the morphochemotype that is most widely distributed in the tropics. Six new species of Daldinia from the tropics and the southern Hemisphere are described. Daldinia asphalatum is resurrected, and D. cudonia is regarded as its synonym. In addition, the following binomials are epi-, iso-, neo- and/or lectotypified: Daldinia asphalatum, D. caldariorum, D. clavata, D. cuprea, D. durissima, D. eschscholtzii, D. grandis, D. loculata, and D. vernicosa. Annellosporium and Versiomyces are regarded as synonyms of Daldinia. Many new synonymies in Daldinia are proposed, and some previously published names are rejected. In total, 47 taxa in Daldinia are recognised and a key is provided. Their biogeography, chorology, and ecology, as well as the importance of their secondary metabolites, are also discussed. The previous definition of the genus is emended. The species concept is based mainly on morphological and other phenotype-derived characters because, despite diligent search, no molecular data or cultures of several of the accepted species could be obtained. Daldinia is segregated into five major groups, based on phenotypic characteristics. Some unnamed but aberrant specimens were not found in good condition and are therefore not formally described as new species. However, they are illustrated in detail in a hope that this will facilitate the discovery of fresh material in future. A preliminary molecular phylogeny based on 5.8S/ITS nrDNA including numerous representatives of all hitherto described taxa for which cultures are extant, was found basically in agreement with the above mentioned segregation of the genus, based on morphological and chemotaxonomic evidence. In the rDNA based phylogenetic tree, Daldinia appears clearly distinct from members of the genera Annulohypoxylon and Hypoxylon; nevertheless, representatives of small genera of predominantly tropical origin (Entonaema, Phylacia, Ruwenzoria, Rhopalostroma, Thamnomyces) appear to have evolved from daldinioid ancestors and are nested inside the Daldinia clade. Interestingly, these findings correlate with chemotaxonomic characters to a great extent, especially regarding the distribution of marker metabolites in their mycelial cultures. Hence, the current study revealed for the first time that fungal secondary metabolite profiles can have taxonomic value beyond the species rank and even coincide with phylogenetic data. Taxonomic novelties: Daldinia andina sp. nov., D. australis sp. nov., D. hausknechtii sp. nov., D. rehmii sp. nov., D. starbaeckii sp. nov., D. theissenii sp. nov., D. cahuchosa comb. nov., D. nemorosa comb. nov.

Production of bioactive secondary metabolites in the fruit bodies of macrofungi as a response to injury

The conversion of secondary metabolites as a response to injury in fruit bodies of 121 species of Ascomycetes and Basidiomycetes was investigated. Extracts of intact and injured specimens were compared by analysis with TLC, and by assaying their antifungal (against Nematospora coryli), antibacterial (against Bacillus brevis) and nematicidal (against Caenorhabditis elegans) activities. Significant conversions induced by injury were observed (by TLC comparison) in the extracts of 66 species. For 37 of these the extract of the injured specimen showed higher bioactivity. Of the remaining 55 species, in which no changes between the extracts of intact and injured fruit bodies were observed, 30 were found to contain bioactive compounds. The possibility that these findings reflect the presence of chemical defence systems in mushrooms, mediated by enzymatic conversions activated by physical injury, is discussed.

The Xylariaceae as model example for a unified nomenclature following the “One Fungus-One Name” (1F1N) concept

The introduction of a One Fungus-One Name (1F1N) concept has led to intensive discussions among taxonomists. Based on the Xylariaceae, a hyperdiverse family of Ascomycota with over 1300 species, the advantages and pitfalls of these nomenclatural changes and their consequences for taxonomy and applied mycology are discussed. Historically, in the Xylariaceae, an 1F1N concept had already been realised: the types of all important genera are conserved. Most teleomorphs were discovered long before the anamorphic states and the latter did not receive separate names, hence no drastic taxonomic changes are expected. The new nomenclature calls for abandonment of some ill-defined anamorph genera, such as Muscodor. Other anamorph genera will be retained because their names refer to morphological symplesiomorphies that occur in several teleomorph genera. Various important taxa are only known from ancient specimens, and no DNA-based data are available. Much work still remains to be done to recollect these fungi, select epitypes, and settle their phylogenetic relationships. Until then, we recommend that taxonomic changes be applied at the suprageneric ranks whenever possible to maintain nomenclatural stability.

Genomic and transcriptomic analysis of the endophytic fungus Pestalotiopsis fici reveals its lifestyle and high potential for synthesis of natural products

BackgroundIn recent years, the genus Pestalotiopsis is receiving increasing attention, not only because of its economic impact as a plant pathogen but also as a commonly isolated endophyte which is an important source of bioactive natural products. Pestalotiopsis fici Steyaert W106-1/CGMCC3.15140 as an endophyte of tea produces numerous novel secondary metabolites, including chloropupukeananin, a derivative of chlorinated pupukeanane that is first discovered in fungi. Some of them might be important as the drug leads for future pharmaceutics.ResultsHere, we report the genome sequence of the endophytic fungus of tea Pestalotiopsis fici W106-1/CGMCC3.15140. The abundant carbohydrate-active enzymes especially significantly expanding pectinases allow the fungus to utilize the limited intercellular nutrients within the host plants, suggesting adaptation of the fungus to endophytic lifestyle. The P. fici genome encodes a rich set of secondary metabolite synthesis genes, including 27 polyketide synthases (PKSs), 12 non-ribosomal peptide synthases (NRPSs), five dimethylallyl tryptophan synthases, four putative PKS-like enzymes, 15 putative NRPS-like enzymes, 15 terpenoid synthases, seven terpenoid cyclases, seven fatty-acid synthases, and five hybrids of PKS-NRPS. The majority of these core enzymes distributed into 74 secondary metabolite clusters. The putative Diels-Alderase genes have undergone expansion.ConclusionThe significant expansion of pectinase encoding genes provides essential insight in the life strategy of endophytes, and richness of gene clusters for secondary metabolites reveals high potential of natural products of endophytic fungi.