Fungal natural products-the mushroom perspective

Diversity of Agaricomycetes in southern South America and their bioactive natural products

Fungi have a unique metabolic plasticity allowing them to produce a wide range of natural products. Since the discovery of penicillin, an antibiotic of fungal origin, substantial efforts have been devoted globally to search for fungal-derived natural bioactive products. Andean region forests represent one of the few undisturbed ecosystems in the world with little human intervention. While these forests display a rich biological diversity, mycological and chemical studies in these environments have been scarce. This review aims to summarise all the efforts regarding the chemical or bioactivity analyses of Agaricomycetes (Basidiomycota) from southern South America environments. Overall, herein we report a total of 147 fungal species, 21 of them showing chemical characterisation and/or biological activity. In terms of chemical cores, furans, chlorinated phenol derivatives, polyenes, lactones, terpenes and himanimides have been reported. These natural products displayed a range of biological activities including antioxidant, antimicrobial, antifungal, neuroprotective and osteoclast-forming suppressing effects.

From the forest floor to the lab: Insights into the diversity and complexity of mushroom polyketide synthases

Mushroom-forming fungi exhibit a distinctive ecology, which is unsurprisingly also reflected in unique and divergent biosynthetic pathways. We review this phenomenon through the lens of the polyketide metabolism, where mushrooms often deviate from established principles and challenge conventional paradigms. This is evident not only by non-canonical enzyme architectures and functions but also by their propensity for multi-product synthases rather than single-product pathways. Nevertheless, mushrooms also feature many polyketides familiar from plants, bacteria, and fungi of their sister division Ascomycota, which, however, are the result of an independent evolution. In this regard, the captivating biosynthetic pathways of mushrooms might even help us understand the biological pressures that led to the simultaneous production of the same natural products (via convergent evolution, co-evolution, and/or metaevolution) and thus address the question of their raison d'être.

Psathrosterols C-E, highly conjugated ergosterol derivatives from Psathyrella rogueiana with anti-inflammatory and immunosuppressive activity

Three new ergosterols featuring with a highly conjugated ring system, psathrosterols C-E (1-3), have been isolated from the fungus Psathyrella rogueiana. The structures with the absolute configurations were elucidated by means of spectroscopic methods and single crystal X-ray diffraction. Compounds 1-3 exhibit inhibitory activity against NO production with IC50 values ranging from 8.4 to 21.8 μM. Compound 1 inhibits the LPS-induced proliferation of B lymphocyte cells with an IC50 value of 12.3 μM.

ent-Clavilactone J and Its Quinone Derivative, Meroterpenoids from the Fungus Resupinatus sp

Metabolites 1 and 2, isolated from cultures of the basidiomycete Resupinatus sp. BCC84615, collected in a tropical forest in northeastern Thailand, showed weak antibiotic activity against Bacillus subtilis and Staphylococcus aureus and cytotoxicity against cancer cell lines. Their planar structures were elucidated by high-resolution electrospray ionization mass spectrometry and NMR spectroscopy as clavilactone J, known from the basidiomycete Ampulloclitocybe clavipes, and its new 1,4-benzoquinone derivative. A detailed analysis of the ROESY correlations in 1 confirmed the recent revision of the relative configuration of clavilactone J. However, specific rotation and Cotton effects observed by electronic circular dichroism were contrary to those of the clavilactones; thus, we assigned a rare antipodal absolute configuration.

Dietary Oyster Mushroom (Pleurotus ostreatus) Waste Inhibits Experimentally Induced Eimeria tenella Challenge in Japanese Quails Model

The aim of this study was to investigate the potential of dietary 3% oyster mushroom (Pleurotus ostreatus) waste in enhancing the anticoccidial effects in broilers challenged with Eimeria tenella infection. The experiment involved a total of 600 Japanese quails, raised from one to thirty-five days of age, which were divided into four treatment groups. These included a negative control group that received a basal diet (BD) without any anticoccidial or antibiotic supplementation in the non-challenged birds (negative control, NC); a positive control (PC) group consisting of NC birds challenged with E. tenella; a group that received the BD with an anticoccidial drug (standard); and a group that received the BD supplemented with 3% waste from oyster mushrooms (3% Pleurotus ostreatus). The results showed that the feed intake, body weight gain, and feed efficiency were significantly lower in the PC (p < 0.05). However, the growth traits were similar in the standard and 3% Pleurotus ostreatus-treated groups. Similarly, there was no difference (p < 0.05) in the mortality rate, oocyst count in the feces, and lesion score between the standard and 3% Pleurotus ostreatus groups. Based on intestinal histology evaluation, the villi height and width were significantly higher in the standard and 3% Pleurotus ostreatus-treated groups compared to those of the PC (p < 0.01). In conclusion, it was found that 3% Pleurotus ostreatus effectively mitigated the low growth rate of Japanese quails induced by coccidial infection.

Lessons on fruiting body morphogenesis from genomes and transcriptomes of Agaricomycetes

Fruiting bodies (sporocarps, sporophores or basidiomata) of mushroom-forming fungi (Agaricomycetes) are among the most complex structures produced by fungi. Unlike vegetative hyphae, fruiting bodies grow determinately and follow a genetically encoded developmental program that orchestrates their growth, tissue differentiation and sexual sporulation. In spite of more than a century of research, our understanding of the molecular details of fruiting body morphogenesis is still limited and a general synthesis on the genetics of this complex process is lacking. In this paper, we aim at a comprehensive identification of conserved genes related to fruiting body morphogenesis and distil novel functional hypotheses for functionally poorly characterised ones. As a result of this analysis, we report 921 conserved developmentally expressed gene families, only a few dozens of which have previously been reported to be involved in fruiting body development. Based on literature data, conserved expression patterns and functional annotations, we provide hypotheses on the potential role of these gene families in fruiting body development, yielding the most complete description of molecular processes in fruiting body morphogenesis to date. We discuss genes related to the initiation of fruiting, differentiation, growth, cell surface and cell wall, defence, transcriptional regulation as well as signal transduction. Based on these data we derive a general model of fruiting body development, which includes an early, proliferative phase that is mostly concerned with laying out the mushroom body plan (via cell division and differentiation), and a second phase of growth via cell expansion as well as meiotic events and sporulation. Altogether, our discussions cover 1 480 genes of Coprinopsis cinerea, and their orthologs in Agaricus bisporus, Cyclocybe aegerita, Armillaria ostoyae, Auriculariopsis ampla, Laccaria bicolor, Lentinula edodes, Lentinus tigrinus, Mycena kentingensis, Phanerochaete chrysosporium, Pleurotus ostreatus, and Schizophyllum commune, providing functional hypotheses for ~10 % of genes in the genomes of these species. Although experimental evidence for the role of these genes will need to be established in the future, our data provide a roadmap for guiding functional analyses of fruiting related genes in the Agaricomycetes. We anticipate that the gene compendium presented here, combined with developments in functional genomics approaches will contribute to uncovering the genetic bases of one of the most spectacular multicellular developmental processes in fungi. Citation: Nagy LG, Vonk PJ, Künzler M, Földi C, Virágh M, Ohm RA, Hennicke F, Bálint B, Csernetics Á, Hegedüs B, Hou Z, Liu XB, Nan S, M. Pareek M, Sahu N, Szathmári B, Varga T, Wu W, Yang X, Merényi Z (2023). Lessons on fruiting body morphogenesis from genomes and transcriptomes of Agaricomycetes. Studies in Mycology 104: 1-85. doi: 10.3114/sim.2022.104.01.

Cell-free synthesis of silver nanoparticles in spent media of different Aspergillus species

The recovery and valorization of metals and rare earth metals from wastewater are of great importance to prevent environmental pollution and recover valuable resources. Certain bacterial and fungal species are capable of removing metal ions from the environment by facilitating their reduction and precipitation. Even though the phenomenon is well documented, little is known about the mechanism. Therefore, we systematically investigated the influence of nitrogen sources, cultivation time, biomass, and protein concentration on silver reduction capacities of cell-free cultivation media (spent media) of Aspergillus niger, A. terreus, and A. oryzae. The spent medium of A. niger showed the highest silver reduction capacities with up to 15 μmol per milliliter spent medium when ammonium was used as the sole N-source. Silver ion reduction in the spent medium was not driven by enzymes and did not correlate with biomass concentration. Nearly full reduction capacity was reached after 2 days of incubation, long before the cessation of growth and onset of the stationary phase. The size of silver nanoparticles formed in the spent medium of A. niger was influenced by the nitrogen source, with silver nanoparticles formed in nitrate or ammonium-containing medium having an average diameter of 32 and 6 nm, respectively.

Diversity and Biosynthetic Potential of Fungi Isolated from St. John's Island, Singapore

Adaptation to a wide variety of habitats allows fungi to develop unique abilities to produce diverse secondary metabolites with diverse bioactivities. In this study, 30 Ascomycetes fungi isolated from St. John's Island, Singapore were investigated for their general biosynthetic potential and their ability to produce antimicrobial secondary metabolites (SMs). All the 30 fungal isolates belong to the Phylum Ascomycota and are distributed into 6 orders and 18 genera with Order Hypocreales having the highest number of representative (37%). Screening for polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS) genes using degenerate PCR led to the identification of 23 polyketide synthases (PKSs) and 5 nonribosomal peptide synthetases (NRPSs) grouped into nine distinct clades based on their reduction capabilities. Some of the identified PKSs genes share high similarities between species and known reference genes, suggesting the possibility of conserved biosynthesis of closely related compounds from different fungi. Fungal extracts were tested for their antimicrobial activity against S. aureus, Methicillin-resistant S. aureus (MRSA), and Candida albicans. Bioassay-guided fractionation of the active constituents from two promising isolates resulted in the isolation of seven compounds: Penilumamides A, D, and E from strain F4335 and xanthomegnin, viomellein, pretrichodermamide C and vioxanthin from strain F7180. Vioxanthin exhibited the best antibacterial activity with IC50 values of 3.0 μM and 1.6 μM against S. aureus and MRSA respectively. Viomellein revealed weak antiproliferative activity against A549 cells with an IC50 of 42 μM. The results from this study give valuable insights into the diversity and biosynthetic potential of fungi from this unique habitat and forms a background for an in-depth analysis of the biosynthetic capability of selected strains of interest with the aim of discovering novel fungal natural products.

Production and Functionalities of Specialized Metabolites from Different Organic Sources

Medicinal plants are rich sources of specialized metabolites that are of great importance to plants, animals, and humans. The usefulness of active biological compounds cuts across different fields, such as agriculture, forestry, food processing and packaging, biofuels, biocatalysts, and environmental remediation. In recent years, research has shifted toward the use of microbes, especially endophytes (bacteria, fungi, and viruses), and the combination of these organisms with other alternatives to optimize the production and regulation of these compounds. This review reinforces the production of specialized metabolites, especially by plants and microorganisms, and the effectiveness of microorganisms in increasing the production/concentration of these compounds in plants. The study also highlights the functions of these compounds in plants and their applications in various fields. New research areas that should be explored to produce and regulate these compounds, especially in plants and microbes, have been identified. Methods involving molecular studies are yet to be fully explored, and next-generation sequencing possesses an interesting and reliable approach.

Cyclohumulanoid Sesquiterpenes Induced by the Noncompetitive Coculture of Phellinus orientoasiaticus and Xylodon flaviporus

Microbial cocultivation has been applied as a strategy to induce the biosynthesis of specialized metabolites. However, most previous studies have focused on competitive interactions between test strains. During our LC-MS-based chemical screening of randomized cocultures of Basidiomycetous fungi, we discovered that the coculture of Phellinus orientoasiaticus (Hymenochaetaceae) and Xylodon flaviporus (Schizoporaceae) induces multiple metabolites, although they did not show any competitive morphology. Targeted isolation yielded three new sesquiterpenes (1-3) along with five known analogues (4-8). The structures of the isolates were determined by MS and NMR experiments as well as electronic circular dichroism analysis. LC-MS analysis suggested that cyclohumulanoids of illudane-, sterpurane-, and tremulane-type scaffolds (1-7) were produced by P. orientoasiaticus, whereas a drimane-type sesquiterpene (8) was produced by X. flaviporus. None of the isolates exhibited antifungal activity or cytotoxicity, and compounds 1-7 exhibited NO production of LPS-treated RAW276.4 cells in a range of 15.9% to 38.0% at 100 μM.

Genetic sequence analysis and characterization of bioactive compounds in mushroom-forming fungi

Mushroom-forming fungi produce unique bioactive compounds that have potential applications as medicines, supplements, and agrochemicals. Thus, it is necessary to clarify the biosynthetic pathways of these compounds using genome and transcriptome analyses. This review introduces some of our research on bioactive compounds isolated from mushrooms, as well as genetic analysis with next-generation sequencing.

Mind the mushroom: natural product biosynthetic genes and enzymes of Basidiomycota

Covering: up to September 2020 Mushroom-forming fungi of the division Basidiomycota have traditionally been recognised as prolific producers of structurally diverse and often bioactive secondary metabolites, using the methods of chemistry for research. Over the past decade, -omics technologies were applied on these fungi, and sophisticated heterologous gene expression platforms emerged, which have boosted research into the genetic and biochemical basis of the biosyntheses. This review provides an overview on experimentally confirmed natural product biosyntheses of basidiomycete polyketides, amino acid-derived products, terpenoids, and volatiles. We also present challenges and solutions particular to natural product research with these fungi. 222 references are cited.

Cytochrome P450 enzymes in fungal natural product biosynthesis

Covering: 2015 to the end of 2020 Fungal-derived polyketides, non-ribosomal peptides, terpenoids and their hybrids contribute significantly to the chemical space of total natural products. Cytochrome P450 enzymes play essential roles in fungal natural product biosynthesis with their broad substrate scope, great catalytic versatility and high frequency of involvement. Due to the membrane-bound nature, the functional and mechanistic understandings for fungal P450s have been limited for quite a long time. However, recent technical advances, such as the efficient and precise genome editing techniques and the development of several filamentous fungal strains as heterologous P450 expression hosts, have led to remarkable achievements in fungal P450 studies. Here, we provide a comprehensive review to cover the most recent progresses from 2015 to 2020 on catalytic functions and mechanisms, research methodologies and remaining challenges in the fast-growing field of fungal natural product biosynthetic P450s.

Agaricus subrufescens and Pleurotus ostreatus mushrooms as alternative additives to antibiotics in diets for broilers challenged with Eimeria spp

1. The effect of A. subrufescens and P. ostreatus mushrooms as an alternative to antibiotics (avilamycin or monensin sodium) on performance, intestinal morphometry, immunity, and biochemical profile of broilers challenged with Eimeria spp. was studied from 1 to 42 d old. A total of 900 male Cobb® broiler chicks were distributed, according to a completely randomised design, into five treatments with six replicates each.2. The treatments consisted of: negative control (NC) - basal diet (BD) with no anticoccidial or antibiotic (non-challenged birds); negative control challenged (NCC) - NC fed to Eimeria spp. challenged birds; BD with 0.2% A. subrufescens inclusion for challenged birds (As), BD with 0.2% P. ostreatus inclusion for challenged birds (Po); and a positive control - BD with anticoccidial and antibiotic inclusion for challenged birds (ATB).3. At 11 d.o., the birds were each inoculated orally with 1 ml solution containing 2 × 10⁵ sporulated oocysts/ml Eimeria acervulina and 2 × 10⁴ sporulated oocysts/ml E. maxima and E. tenella.4. Birds subjected to Eimeria spp. challenge up to 21 d of age had greater crypt depth, indicating that the presence of undesirable microorganisms had an effect on cell proliferation.5. At 21 d old, the birds receiving ATB had higher average weight gain (AWG), feed intake (AFI), and feed conversion ratio (FCR) compared to those fed diets supplemented with mushrooms (As or Po). For the total rearing period (42 days), the birds that received ATB had higher AWG and AFI (P < 0.001) compared to those that received As or Po diets. Feeding avilamycin did not affect (P = 0.0676) FCR compared to the As or Po diet groups.6. From the morphometric and blood analyses there were no differences between broilers fed ATB, Po or As diets in either rearing periods. However, Po and As supplementation lowered blood triglyceride levels. At 21d there was a difference (P < 0.05) for MCV and haemoglobin, in which the mushrooms were similar to the antibiotic. At 42 d, there was a difference (P < 0.05) in haematocrit, erythrocyte, MCV, H: L, protein and albumin variables, in which the use of mushrooms was similar to the positive control, demonstrating that both (mushrooms and antibiotics) promoted a certain improvement in the health of the chickens.7. A. subrufescens and P. ostreatus can be used in broiler diets without compromising intestinal or haematological status, however, these ingredients did not result in improvements in performance.

Fungal evolution: cellular, genomic and metabolic complexity

The question of how phenotypic and genomic complexity are inter-related and how they are shaped through evolution is a central question in biology that historically has been approached from the perspective of animals and plants. In recent years, however, fungi have emerged as a promising alternative system to address such questions. Key to their ecological success, fungi present a broad and diverse range of phenotypic traits. Fungal cells can adopt many different shapes, often within a single species, providing them with great adaptive potential. Fungal cellular organizations span from unicellular forms to complex, macroscopic multicellularity, with multiple transitions to higher or lower levels of cellular complexity occurring throughout the evolutionary history of fungi. Similarly, fungal genomes are very diverse in their architecture. Deep changes in genome organization can occur very quickly, and these phenomena are known to mediate rapid adaptations to environmental changes. Finally, the biochemical complexity of fungi is huge, particularly with regard to their secondary metabolites, chemical products that mediate many aspects of fungal biology, including ecological interactions. Herein, we explore how the interplay of these cellular, genomic and metabolic traits mediates the emergence of complex phenotypes, and how this complexity is shaped throughout the evolutionary history of Fungi.

Biosynthetic gene clusters and the evolution of fungal chemodiversity

Covering: up to 2019Fungi produce a remarkable diversity of secondary metabolites: small, bioactive molecules not required for growth but which are essential to their ecological interactions with other organisms. Genes that participate in the same secondary metabolic pathway typically reside next to each other in fungal genomes and form biosynthetic gene clusters (BGCs). By synthesizing state-of-the-art knowledge on the evolution of BGCs in fungi, we propose that fungal chemodiversity stems from three molecular evolutionary processes involving BGCs: functional divergence, horizontal transfer, and de novo assembly. We provide examples of how these processes have contributed to the generation of fungal chemodiversity, discuss their relative importance, and outline major, outstanding questions in the field.

Comparing “Leaf-to-Root”, “Nose-to-Tail” and Other Efficient Food Utilization Options from a Consumer Perspective

The efficient use of natural raw materials is a key element of sustainable development and is also gaining importance in the food sector. Consumers are increasingly realizing that food is too valuable to be used only partially. However, consumer acceptance is an important precondition for establishing efficient food utilization options. A total of 470 German consumers were surveyed through an online-questionnaire where they had to evaluate three options each for the efficient use of plant-based foods as well as animal-based foods with respect to eight different criteria. The results show that the six options differed significantly regarding consumer acceptance. The efficient use of plant-based foods (especially non-standard fruits/vegetables and the “leaf-to-root” principle) was more accepted than the efficient utilization of animal-based foods. Furthermore, it can be seen that options using the by-products in a natural form were considered more acceptable than those which subject the by-products to some form of processing. These results provide an insight into the views of consumers on food waste reduction strategies, which are frequently debated in the sustainability discussion.

Ascomycete Aspergillus oryzae Is an Efficient Expression Host for Production of Basidiomycete Terpenes by Using Genomic DNA Sequences

Basidiomycete fungi are an attractive resource for biologically active natural products for use in pharmaceutically relevant compounds. Recently, genome projects on mushroom fungi have provided a great deal of biosynthetic gene cluster information. However, functional analyses of the gene clusters for natural products were largely unexplored because of the difficulty of cDNA preparation and lack of gene manipulation tools for basidiomycete fungi. To develop a versatile host for basidiomycete genes, we examined gene expression using genomic DNA sequences in the robust ascomycete host Aspergillus oryzae, which is frequently used for the production of metabolites from filamentous fungi. Exhaustive expression of 30 terpene synthase genes from the basidiomycetes Clitopilus pseudo-pinsitus and Stereum hirsutum showed two splicing patterns, i.e., completely spliced cDNAs giving terpenes (15 cases) and mostly spliced cDNAs, indicating that A. oryzae correctly spliced most introns at the predicted positions and lengths. The mostly spliced cDNAs were expressed after PCR-based removal of introns, resulting in the successful production of terpenes (14 cases). During this study, we observed relatively frequent mispredictions in the automated program. Hence, the complementary use of A. oryzae expression and automated prediction will be a powerful tool for genome mining.IMPORTANCE The recent large influx of genome sequences from basidiomycetes, which are prolific producers of bioactive natural products, may provide opportunities to develop novel drug candidates. The development of a reliable expression system is essential for the genome mining of natural products because of the lack of a tractable host for heterologous expression of basidiomycete genes. For this purpose, we applied the ascomycete Aspergillus oryzae system for the direct expression of fungal natural product biosynthetic genes from genomic DNA. Using this system, 29 sesquiterpene synthase genes and diterpene biosynthetic genes for bioactive pleuromutilin were successfully expressed. Together with the use of computational tools for intron prediction, this Aspergillus oryzae system represents a practical method for the production of basidiomycete natural products.

Biochemical characterization of TyrA dehydrogenases from Saccharomyces cerevisiae (Ascomycota) and Pleurotus ostreatus (Basidiomycota)

L-Tyrosine is an aromatic amino acid necessary for protein synthesis in all living organisms and a precursor of secondary (specialized) metabolites. In fungi, tyrosine-derived compounds are associated with virulence and defense (i.e. melanin production). However, how tyrosine is produced in fungi is not fully understood. Generally, tyrosine can be synthesized via two pathways: by prephenate dehydrogenase (TyrA_p/PDH), a pathway found in most bacteria, or by arogenate dehydrogenase (TyrA_a/ADH), a pathway found mainly in plants. Both enzymes require the cofactor NAD⁺ or NADP⁺ and typically are strongly feedback inhibited by tyrosine. Here, we biochemically characterized two TyrA enzymes from two distantly related fungi in the Ascomycota and Basidiomycota, Saccharomyces cerevisiae (ScTyrA/TYR1) and Pleurotus ostreatus (PoTyrA), respectively. We found that both enzymes favor the prephenate substrate and NAD⁺ cofactor in vitro. Interestingly, while PoTyrA was strongly inhibited by tyrosine, ScTyrA exhibited relaxed sensitivity to tyrosine inhibition. We further mutated ScTyrA at the amino acid residue that was previously shown to be involved in the substrate specificity of plant TyrAs; however, no changes in its substrate specificity were observed, suggesting that a different mechanism is involved in the TyrA substrate specificity of fungal TyrAs. The current findings provide foundational knowledge to further understand and engineer tyrosine-derived specialized pathways in fungi.

Onge RP, Tang Y, Hillenmeyer ME. HEx: A heterologous expression platform for the discovery of fungal natural products

For decades, fungi have been a source of U.S. Food and Drug Administration-approved natural products such as penicillin, cyclosporine, and the statins. Recent breakthroughs in DNA sequencing suggest that millions of fungal species exist on Earth, with each genome encoding pathways capable of generating as many as dozens of natural products. However, the majority of encoded molecules are difficult or impossible to access because the organisms are uncultivable or the genes are transcriptionally silent. To overcome this bottleneck in natural product discovery, we developed the HEx (Heterologous EXpression) synthetic biology platform for rapid, scalable expression of fungal biosynthetic genes and their encoded metabolites in Saccharomyces cerevisiae. We applied this platform to 41 fungal biosynthetic gene clusters from diverse fungal species from around the world, 22 of which produced detectable compounds. These included novel compounds with unexpected biosynthetic origins, particularly from poorly studied species. This result establishes the HEx platform for rapid discovery of natural products from any fungal species, even those that are uncultivable, and opens the door to discovery of the next generation of natural products.

Lepistatins A-C, chlorinated sesquiterpenes from the cultured basidiomycete Lepista sordida

Three new chlorinated sesquiterpenes, named lepistatins A-C, were isolated from the culture broth of Basidiomycete Lepista sordida. The structures were determined by the analysis of spectroscopic data including HREIMS and 1D and 2D NMR. The absolute configuration of lepistatin B was determined by comparing the specific rotation and circular dichroism spectrum with those of known structurally related compounds bearing the same chiral carbon. The structures of lepistatins A-C feature the indanone core structure, but differ from other indanone-containing sesquiterpenes of fungal origin by the alkyl substitution pattern. This indicates that lepistatins A-C probably possess a new sesquiterpene scaffold derived from the common precursor, trans-humulyl cation, by an alternative cyclization.

Enzymatic Synthesis of Psilocybin

Psilocybin is the psychotropic tryptamine-derived natural product of Psilocybe carpophores, the so-called "magic mushrooms". Although its structure has been known for 60 years, the enzymatic basis of its biosynthesis has remained obscure. We characterized four psilocybin biosynthesis enzymes, namely i) PsiD, which represents a new class of fungal l-tryptophan decarboxylases, ii) PsiK, which catalyzes the phosphotransfer step, iii) the methyltransferase PsiM, catalyzing iterative N-methyl transfer as the terminal biosynthetic step, and iv) PsiH, a monooxygenase. In a combined PsiD/PsiK/PsiM reaction, psilocybin was synthesized enzymatically in a step-economic route from 4-hydroxy-l-tryptophan. Given the renewed pharmaceutical interest in psilocybin, our results may lay the foundation for its biotechnological production.

Mushroom-Derived Indole Alkaloids

Mushrooms are known to produce over 140 natural products bearing an indole heterocycle. In this review, the isolation of these mushroom-derived indole alkaloids is discussed, along with their associated biological activities.

Purification, characterization, and antitumor activity of a novel glucan from the fruiting bodies of Coriolus Versicolor

Cancer is one of the most common causes of deaths worldwide. Herein, we report an efficient natural anticancer glucan (CVG) extracted from Coriolus Versicolar (CV). CVG was extracted by the hot water extraction method followed by ethanol precipitation and purified using gas exclusion chromatography. Structural analysis revealed that CVG has a linear α-glucan chain composed of only (1→ 6)-α-D-Glcp. The antitumor activity of CVG on Sarcoma-180 cells was investigated in vitro and in vivo. Mice were treated with three doses of CVG (40, 100, 200 mg/kg body weight) for 9 days. Tumor weight, relative spleen, thymus weight, and lymphocyte proliferation were studied. A significant increase (P< 0.01) in relative spleen and thymus weight and a decrease (P< 0.01) in tumor weight at the doses of 100 and 200 mg/kg were observed. The results obtained demonstrate CVG has antitumor activity towards Sarcoma-180 cells by its immunomodulation activity.

Monochlorinated calocerins A-D and 9-oxostrobilurin derivatives from the basidiomycete Favolaschia calocera

Eight previously undescribed compounds were isolated and characterised from the supernatant and mycelium of a culture of the basidiomycete Favolaschia calocera originating from Kakamega equatorial rainforest in Kenya. These were: 9- oxostrobilurins A, G, K and I and the four monochlorinated calocerins A, B, C and D. The calocerins extend our knowledge of halogenated compounds obtained from natural sources. Four further known compounds were also identified: strobilurin G, favolon, pterulinic acid and 2,3 -dihydro-1-benzoxepin derivative. The four oxostrobilurins exhibited prominent antifungal and cytotoxic activities while the four calocerins only showed cytotoxic activity.

Biologically Active Secondary Metabolites from the Fungi

Many Fungi have a well-developed secondary metabolism. The diversity of fungal species and the diversification of biosynthetic gene clusters underscores a nearly limitless potential for metabolic variation and an untapped resource for drug discovery and synthetic biology. Much of the ecological success of the filamentous fungi in colonizing the planet is owed to their ability to deploy their secondary metabolites in concert with their penetrative and absorptive mode of life. Fungal secondary metabolites exhibit biological activities that have been developed into life-saving medicines and agrochemicals. Toxic metabolites, known as mycotoxins, contaminate human and livestock food and indoor environments. Secondary metabolites are determinants of fungal diseases of humans, animals, and plants. Secondary metabolites exhibit a staggering variation in chemical structures and biological activities, yet their biosynthetic pathways share a number of key characteristics. The genes encoding cooperative steps of a biosynthetic pathway tend to be located contiguously on the chromosome in coregulated gene clusters. Advances in genome sequencing, computational tools, and analytical chemistry are enabling the rapid connection of gene clusters with their metabolic products. At least three fungal drug precursors, penicillin K and V, mycophenolic acid, and pleuromutilin, have been produced by synthetic reconstruction and expression of respective gene clusters in heterologous hosts. This review summarizes general aspects of fungal secondary metabolism and recent developments in our understanding of how and why fungi make secondary metabolites, how these molecules are produced, and how their biosynthetic genes are distributed across the Fungi. The breadth of fungal secondary metabolite diversity is highlighted by recent information on the biosynthesis of important fungus-derived metabolites that have contributed to human health and agriculture and that have negatively impacted crops, food distribution, and human environments.

Pyristriatins A and B: Pyridino-Cyathane Antibiotics from the Basidiomycete Cyathus cf. striatus

Two novel pyridino-cyathane diterpenoids, pyristriatins A and B (1 and 2), together with striatin C (3) were isolated from cultures of Cyathus cf. striatus, a basidiomycete that was found during a field trip in northern Thailand. The pyristriatins showed antimicrobial effects against Gram-positive bacteria and fungi. The isolation, structure elucidation, relative configuration, and biological and cytotoxic activity are described. Their structures were assigned by HRMS and NMR spectroscopy. We also describe the first 2D NMR assignment of striatin C. Pyristriatins A and B are the first cyathane natural products featuring a pyridine ring.

Laxitextines A and B, Cyathane Xylosides from the Tropical Fungus Laxitextum incrustatum

Bioassay-guided fractionation of the mycelial extract of a basidiomycete culture collected in Kenya led to the isolation of two new cyathane diterpenoids named laxitextines A (1) and B (2). The producer strain was characterized by detailed taxonomic studies based on rDNA using the 5.8S gene region, the internal transcribed spacer 2 (ITS2), and part of the large subunit that identified the fungus as Laxitextum incrustatum. The structures of 1 and 2 were elucidated by NMR spectroscopic and mass spectrometric analyses. Both compounds exhibited moderate activities against Gram-positive bacteria Bacillus subtilis (DSM 10), Staphylococcus aureus (DSM 346), and methicillin-resistant Staph. aureus (DSM 1182). The two compounds also showed variable antiproliferative activities against mouse fibroblast (L929) and selected human cell lines (breast cancer MCF-7, epidermoid carcinoma A431, and umbilical vein endothelial HUVEC). The IC50 values with respect to the MCF-7 cell line for compounds 1 and 2 were 2.3 and 2.0 μM, respectively.

Exploitation of Fungal Biodiversity for Discovery of Novel Antibiotics

Fungi were among the first sources for antibiotics. The discovery and development of the penicillin-type and cephalosporin-type β-lactams and their synthetic versions were transformative in emergence of the modern pharmaceutical industry. They remain some of the most important antibiotics, even 70 years after their discovery. Meanwhile, thousands of fungal metabolites have been discovered, yet these metabolites have only contributed a few additional compounds that have entered clinical development. Substantial expansion in fungal biodiversity assessment along with the availability of modern "-OMICS" technology and revolutionary developments in fungal biotechnology have been made in the last 15 years subsequent to the exit of most of the big Pharma companies from the field of novel antibiotics discovery. Therefore, the timing seems opportune to revisit these fascinating chemically rich organisms as a reservoir of small-molecule templates for lead discovery. This review will describe ongoing interdisciplinary scenarios in which specialists in fungal biology collaborate with chemists, pharmacologists and biochemical and process engineers in order to reveal and make new antibiotics. The utility of a pre-selection process based on phylogenetic data and distribution of secondary metabolite encoding gene cluster will be highlighted. Examples of novel bioactive metabolites from fungi derived from special ecological groups and new phylogenetic lineages will also be discussed.

New Structural Templates for Clinically Validated and Novel Targets in Antimicrobial Drug Research and Development

The development of bacterial resistance against current antibiotic drugs necessitates a continuous renewal of the arsenal of efficacious drugs. This imperative has not been met by the output of antibiotic research and development of the past decades for various reasons, including the declining efforts of large pharma companies in this area. Moreover, the majority of novel antibiotics are chemical derivatives of existing structures that represent mostly step innovations, implying that the available chemical space may be exhausted. This review negates this impression by showcasing recent achievements in lead finding and optimization of antibiotics that have novel or unexplored chemical structures. Not surprisingly, many of the novel structural templates like teixobactins, lysocin, griselimycin, or the albicidin/cystobactamid pair were discovered from natural sources. Additional compounds were obtained from the screening of synthetic libraries and chemical synthesis, including the gyrase-inhibiting NTBI's and spiropyrimidinetrione, the tarocin and targocil inhibitors of wall teichoic acid synthesis, or the boronates and diazabicyclo[3.2.1]octane as novel β-lactamase inhibitors. A motif that is common to most clinically validated antibiotics is that they address hotspots in complex biosynthetic machineries, whose functioning is essential for the bacterial cell. Therefore, an introduction to the biological targets-cell wall synthesis, topoisomerases, the DNA sliding clamp, and membrane-bound electron transport-is given for each of the leads presented here.

Deconins A-E: Cuparenic and Mevalonic or Propionic Acid Conjugates from the Basidiomycete Deconica sp. 471

Bioassay-guided fractionation of antibacterial extracts from cultures of a basidiomycete from Northern Thailand, which represents a new species of the genus Deconica, yielded the terpenoid deconin A (1), whose structure was elucidated by spectral methods (NMR, HRMS) as a cuparenic/mevalonic acid conjugate. The absolute configuration of 1 was determined after saponification and comparison of specific rotations of the resulting cuparenic acid and mevalonolactone with authentic standards and literature data. Six minor congeners (2-7) were isolated and identified, and their antimicrobial and cytotoxic effects are reported. Compounds 1-4 are the first natural products featuring an unmodified mevalonic acid residue as a building block.