A call to arms: Mustering secondary metabolites for success and survival of an opportunistic pathogen

Aspergillus fumigatus biology, immunopathogenicity and drug resistance

Aspergillus fumigatus is a saprophytic fungus prevalent in the environment and capable of causing severe invasive infection in humans. This organism can use strategies such as molecule masking, immune response manipulation and gene expression alteration to evade host defences. Understanding these mechanisms is essential for developing effective diagnostics and therapies to improve patient outcomes in Aspergillus-related diseases. In this Review, we explore the biology and pathogenesis of A. fumigatus in the context of host biology and disease, highlighting virus-associated pulmonary aspergillosis, a newly identified condition that arises in patients with severe pulmonary viral infections. In the post-pandemic landscape, in which immunotherapy is gaining attention for managing severe infections, we examine the host immune responses that are critical for controlling invasive aspergillosis and how A. fumigatus circumvents these defences. Additionally, we address the emerging issue of azole resistance in A. fumigatus, emphasizing the urgent need for greater understanding in an era marked by increasing antimicrobial resistance. This Review provides timely insights necessary for developing new immunotherapeutic strategies against invasive aspergillosis.

Aspergillus fumigatus secondary metabolite pyripyropene is important for the dual biofilm formation with Pseudomonas aeruginosa

The human pathogenic fungus Aspergillus fumigatus establishes dual biofilm interactions in the lungs with the pathogenic bacterium Pseudomonas aeruginosa. Screening of 21 A. fumigatus null mutants revealed seven mutants (two G protein-coupled receptors, three mitogen-activated protein kinase receptors, a Gα protein, and one histidine kinase receptor) with reduced biofilm formation, specifically in the presence of P. aeruginosa. Transcriptional profiling and metabolomics analysis of secondary metabolites produced by one of these mutants, ΔgpaB (gpaB encodes a Gα protein), showed GpaB controls the production of several important metabolites for the dual biofilm interaction, including pyripyropene A, a potent inhibitor of mammalian acyl-CoA cholesterol acyltransferase. Deletion of pyr2, encoding a non-reducing polyketide synthase essential for pyripyropene biosynthesis, showed reduced A. fumigatus Δpyr2-P. aeruginosa biofilm growth, altered macrophage responses, and attenuated mouse virulence in a chemotherapeutic murine model. We identified pyripyropene as a novel player in the ecology and pathogenic interactions of this important human fungal pathogen.IMPORTANCEAspergillus fumigatus and Pseudomonas aeruginosa are two important human pathogens. Both organisms establish biofilm interactions in patients affected with chronic lung pulmonary infections, such as cystic fibrosis (CF) and chronic obstructive pulmonary disease. Colonization with A. fumigatus is associated with an increased risk of P. aeruginosa colonization in CF patients, and disease prognosis is poor when both pathogens are present. Here, we identified A. fumigatus genetic determinants important for the establishment of in vitro dual A. fumigatus-P. aeruginosa biofilm interactions. Among them, an A. fumigatus Gα protein GpaB is important for this interaction controlling the production of the secondary metabolite pyripyropene. We demonstrate that the lack of pyripyropene production decreases the dual biofilm interaction between the two species as well as the virulence of A. fumigatus in a chemotherapeutic murine model of aspergillosis. These results reveal a complete novel role for this secondary metabolite in the ecology and pathogenic interactions of this important human fungal pathogen.

Aspergillus fumigatus from Pathogenic Fungus to Unexplored Natural Treasure: Changing the Concept

The Aspergillus genus is one of the oldest known fungal genera. Its species can survive in extremely difficult environmental conditions and can affect plants, animals, and human health due to their pathogenic characteristics. Also, they represent an enormous chemical and biological repertoire. A. fumigatus is a fungal pathogen that has been thoroughly investigated due to its medical significance. Additionally, A. fumigatus has revealed a capacity to biosynthesize different classes of secondary metabolites such as alkaloids, terpenes, sterols, quinones, peptides, and benzophenones. Alkaloids are the most common type of secondary metabolites that A. fumigatus produces, and they have a variety of biological functions. This current study aimed to highlight the positive aspects of this fungus. The published research on the structures, biological functions, and biosynthesis of A. fumigatus's isolated metabolites were emphasized in this work. The current review comprised more than 400 compounds, with more than 145 references that were published between 1965 and August 2024. This review underscores the role of this fungus as a reservoir of bioactive compounds with antimicrobial, anticancer, anti-inflammatory, and agricultural applications.

Global transcriptome changes during growth of a novel Penicillium coffeae isolate on the wheat stripe rust fungus, Puccinia striiformis f. sp. tritici

Wheat stripe rust caused by the fungus Puccinia striiformis f. sp. tritici (Pst) is currently the most destructive disease of wheat. The major control methods which include the deployment of resistant wheat cultivars and application of chemical fungicides are losing efficiency as the fungus evolves. Natural antagonists of Pst may be an avenue for alternative and environmentally sustainable control of the disease in the field. Here we describe a novel fungus found growing on Pst pustules. We identified the fungus as a novel isolate of the plant endophyte Penicillium coffeae. We present a high-quality reference genome and a comparative transcriptomic analysis used to investigate how the fungus deploys its genes during growth amongst Pst spores. The gene content of the P. coffeae ANU01 genome is suggestive of a generalist that makes use of diverse substrates. An abundance of genes related to lipid, amino acid and carbohydrate metabolism indicate that P. coffeae ANU01 has evolved the ability to exploit nutrient stores in Pst urediniospores. P. coffeae ANU01 deploys a number of biosynthetic gene clusters during growth on Pst spores, potentially to inhibit urediniospores germination and halt defence responses. A number of genes encoding carbohydrate active enzymes are also highly upregulated, suggesting targeting and degradation of Pst urediniospores structures. Alongside carbohydrates, P. coffeae ANU01 appears to target spore lipids as a nutrient source, secreting several highly upregulated lipases. Our findings broaden the understanding of growth associated with rust spores as an evolutionary strategy and provide insight into the genes potentially required for this process.

Fungal Metabolomics: A Comprehensive Approach to Understanding Pathogenesis in Humans and Identifying Potential Therapeutics

Metabolomics has emerged as a transformative tool in the study of microbes, including pathogenic fungi, facilitating the identification of unique metabolic profiles that elucidate their pathogenic mechanisms, host interactions, and treatment resistance. This review highlights key applications of metabolomics in understanding fungal metabolites essential for human virulence, such as mycotoxins produced by various fungal species, including Aspergillus fumigatus (gliotoxin, fumagillins) and Candida species (phenylethyl alcohol, TCA cycle metabolites), and secondary metabolites that contribute to pathogenicity. It also explores the metabolic adaptations of fungi in relation to drug resistance and biofilm formation, revealing alterations in key metabolic pathways during infection, as seen in C. albicans and C. auris. Furthermore, metabolomics aids in deciphering host-pathogen interactions, showcasing how fungi like Cryptococcus neoformans and Candida modify host metabolism to promote survival and evade immune responses. The study of antifungal resistance mechanisms has also benefited from metabolomic approaches, identifying specific metabolite patterns that signify resistance, such as in Candida albicans and Candidozyma (Candida) auris, and informing new therapeutic strategies. The integration of metabolomics with other omics technologies is paving the way for a comprehensive understanding of fungal biology and pathogenesis. Such multi-omics approaches are crucial for discovering new therapeutic targets and developing innovative antifungal treatments. Thus, the purpose of this review is to provide an overview of how metabolomics is revolutionizing our understanding of fungal pathogenesis, drug resistance, and host interactions, and to highlight its potential for identifying new therapeutic targets and improving antifungal strategies.

Molecular characterization of gliotoxin synthesis in a biofilm model of Aspergillus fumigatus

Mycelial growth as biofilm structures and the activation of secondary metabolism leading to the release of low-molecular-weight molecules (known as secondary metabolites), are among the previously described strategies used by the filamentous fungi Aspergillus fumigatus to adapt and survive. Our study unveils that A. fumigatus strains can activate mechanisms linked to the production of gliotoxin, a crucial metabolite for Aspergillus, in the established in vitro biofilm model. Gliotoxin production exhibits strain- and time-dependent patterns and is associated -in a coordinated manner-with the expression levels of several genes involved in its regulation and synthesis. The transcriptional study of some of these genes by qPCR shows temporal inter-strain differences, which correlate with those obtained when evaluating the amounts of metabolites produced. Given that A. fumigatus forms biofilm structures within the site of infection, understanding the regulation of gliotoxin biosynthesis may have a role in the evolution of Aspergillus infection and guide diagnostic and treatment strategies.

Progress in the Study of Natural Antimicrobial Active Substances in Pseudomonas aeruginosa

The prevalence of antimicrobial resistance reduces the effectiveness of antimicrobial drugs in the prevention and treatment of infectious diseases caused by pathogens such as bacteria, fungi, and viruses. Microbial secondary metabolites have been recognized as important sources for new drug discovery and development, yielding a wide range of structurally novel and functionally diverse antimicrobial drugs for the treatment of a variety of diseases that are considered good producers of novel antimicrobial drugs. Bacteria produce a wide variety of antimicrobial compounds, and thus, antibiotics derived from natural products still dominate over purely synthetic antibiotics among the antimicrobial drugs developed and introduced over the last four decades. Among them, Pseudomonas aeruginosa secondary metabolites constitute a richly diverse source of antimicrobial substances with good antimicrobial activity. Therefore, they are regarded as an outstanding resource for finding novel bioactive compounds. The exploration of antimicrobial compounds among Pseudomonas aeruginosa metabolites plays an important role in drug development and biomedical research. Reports on the secondary metabolites of Pseudomonas aeruginosa, many of which are of pharmacological importance, hold great promise for the development of effective antimicrobial drugs against microbial infections by drug-resistant pathogens. In this review, we attempt to summarize published articles from the last twenty-five years (2000-2024) on antimicrobial secondary metabolites from Pseudomonas aeruginosa.

Strain heterogeneity in a non-pathogenic Aspergillus fungus highlights factors associated with virulence

Fungal pathogens exhibit extensive strain heterogeneity, including variation in virulence. Whether closely related non-pathogenic species also exhibit strain heterogeneity remains unknown. Here, we comprehensively characterized the pathogenic potentials (i.e., the ability to cause morbidity and mortality) of 16 diverse strains of Aspergillus fischeri, a non-pathogenic close relative of the major pathogen Aspergillus fumigatus. In vitro immune response assays and in vivo virulence assays using a mouse model of pulmonary aspergillosis showed that A. fischeri strains varied widely in their pathogenic potential. Furthermore, pangenome analyses suggest that A. fischeri genomic and phenotypic diversity is even greater. Genomic, transcriptomic, and metabolic profiling identified several pathways and secondary metabolites associated with variation in virulence. Notably, strain virulence was associated with the simultaneous presence of the secondary metabolites hexadehydroastechrome and gliotoxin. We submit that examining the pathogenic potentials of non-pathogenic close relatives is key for understanding the origins of fungal pathogenicity.

Genomic insights into the evolution of secondary metabolism of Escovopsis and its allies, specialized fungal symbionts of fungus-farming ants

The metabolic intimacy of symbiosis often demands the work of specialists. Natural products and defensive secondary metabolites can drive specificity by ensuring infection and propagation across host generations. But in contrast to bacteria, little is known about the diversity and distribution of natural product biosynthetic pathways among fungi and how they evolve to facilitate symbiosis and adaptation to their host environment. In this study, we define the secondary metabolism of Escovopsis and closely related genera, symbionts in the gardens of fungus-farming ants. We ask how the gain and loss of various biosynthetic pathways correspond to divergent lifestyles. Long-read sequencing allowed us to define the chromosomal features of representative Escovopsis strains, revealing highly reduced genomes composed of seven to eight chromosomes. The genomes are highly syntenic with macrosynteny decreasing with increasing phylogenetic distance, while maintaining a high degree of mesosynteny. An ancestral state reconstruction analysis of biosynthetic pathways revealed that, while many secondary metabolites are shared with non-ant-associated Sordariomycetes, 56 pathways are unique to the symbiotic genera. Reflecting adaptation to diverging ant agricultural systems, we observe that the stepwise acquisition of these pathways mirrors the ecological radiations of attine ants and the dynamic recruitment and replacement of their fungal cultivars. As different clades encode characteristic combinations of biosynthetic gene clusters, these delineating profiles provide important insights into the possible mechanisms underlying specificity between these symbionts and their fungal hosts. Collectively, our findings shed light on the evolutionary dynamic nature of secondary metabolism in Escovopsis and its allies, reflecting adaptation of the symbionts to an ancient agricultural system.IMPORTANCEMicrobial symbionts interact with their hosts and competitors through a remarkable array of secondary metabolites and natural products. Here, we highlight the highly streamlined genomic features of attine-associated fungal symbionts. The genomes of Escovopsis species, as well as species from other symbiont genera, many of which are common with the gardens of fungus-growing ants, are defined by seven chromosomes. Despite a high degree of metabolic conservation, we observe some variation in the symbionts' potential to produce secondary metabolites. As the phylogenetic distribution of the encoding biosynthetic gene clusters coincides with attine transitions in agricultural systems, we highlight the likely role of these metabolites in mediating adaptation by a group of highly specialized symbionts.

Pathogenicity is associated with population structure in a fungal pathogen of humans

Aspergillus flavus is a clinically and agriculturally important saprotrophic fungus responsible for severe human infections and extensive crop losses. We analyzed genomic data from 250 (95 clinical and 155 environmental) A. flavus isolates from 9 countries, including 70 newly sequenced clinical isolates, to examine population and pan-genome structure and their relationship to pathogenicity. We identified five A. flavus populations, including a new population, D, corresponding to distinct clades in the genome-wide phylogeny. Strikingly, > 75% of clinical isolates were from population D. Accessory genes, including genes within biosynthetic gene clusters, were significantly more common in some populations but rare in others. Population D was enriched for genes associated with zinc ion binding, lipid metabolism, and certain types of hydrolase activity. In contrast to the major human pathogen Aspergillus fumigatus, A. flavus pathogenicity in humans is strongly associated with population structure, making it a great system for investigating how population-specific genes contribute to pathogenicity.

Sirtuin E deacetylase is required for full virulence of Aspergillus fumigatus

Aspergillus fumigatus represents a public health problem due to the high mortality rate in immunosuppressed patients and the emergence of antifungal-resistant isolates. Protein acetylation is a crucial post-translational modification that controls gene expression and biological processes. The strategic manipulation of enzymes involved in protein acetylation has emerged as a promising therapeutic approach for addressing fungal infections. Sirtuins, NAD+-dependent lysine deacetylases, regulate protein acetylation and gene expression in eukaryotes. However, their role in the human pathogenic fungus A. fumigatus remains unclear. This study constructs six single knockout strains of A. fumigatus and a strain lacking all predicted sirtuins (SIRTKO). The mutant strains are viable under laboratory conditions, indicating that sirtuins are not essential genes. Phenotypic assays suggest sirtuins' involvement in cell wall integrity, secondary metabolite production, thermotolerance, and virulence. Deletion of sirE attenuates virulence in murine and Galleria mellonella infection models. The absence of SirE alters the acetylation status of proteins, including histones and non-histones, and triggers significant changes in the expression of genes associated with secondary metabolism, cell wall biosynthesis, and virulence factors. These findings encourage testing sirtuin inhibitors as potential therapeutic strategies to combat A. fumigatus infections or in combination therapy with available antifungals.

Fungal profile, levels of aflatoxin M1, exposure, and the risk characterization of local cheese 'wagashi' consumed in the Ho Municipality, Volta Region, Ghana

Wagashi is a West African type cottage cheese locally prepared from cow milk. Wagashi like other milk products, is prone to microbial contamination, particularly by fungi. Many of these fungal species produce mycotoxins which are of serious public health concern. This work aimed to update the mycoflora profile and determine the concentrations of aflatoxin M1 and its health risk characterization due to the consumption of wagashi. Culturing the wagashi on mycological media (Oxytetracycline Glucose Yeast Extract OGYE, Dichloran Rose Bengal Chloramphenicol DRBC) caused a de-novo growth of the quiescent spores at 28-30 °C for 5-7 days. The analysis of AFM1 levels in the samples was done using High-Performance Liquid Chromatography connected to a Fluorescence detector (HPLC-FLD). The exposure and risk assessment to the AFMI levels were determined using deterministic models prescribed by the European Food Safety Authority (EFSA). The fungal counts ranged between 2.36-4.30 log10 CFU/g. In total, thirteen (13) fungal species from eight (8) genera were isolated from all wagashi samples. They are; Fusarium oxysporum, Aspergillus flavus, Aspergillus niger, Fusarium verticillioides, Penicillium digitatum, Trichoderma harzianum, Aspergillus terreus, Rhodotorula mucilaginosa, Rhizopus stolonifer, Aspergillus fumigatus, Yeast sp., Mucor racemosus and Fusarium oligosporum belonging to the genera Fusarium, Aspergillus, Penicillium, Trichoderma, Rhodotorula, Rhizopus, Yeast, and Mucor. The AFM1 observed in the wagashi samples' analysis was low, ranging from 0.00 (Not Detected) ± 0.00 - 0.06 ± 0.002 µg/Kg. Risk assessments of AFM1 using deterministic models produced outcomes that ranged between 5.92 × 10-3- 0.14 ng/kg bw/day, 1.42 -44.35, 0-0.0323 ng aflatoxins/kg bw/day, and 1.51 × 10-3 - 9.69 × 10-4 cases/100,000 person/yr for estimated daily intake (EDI), margin of exposure (MOE), average potency, and cancer risks, respectively, for the age categories investigated. Fungal counts were interpreted as medium to high. It was also established that the consumption of wagashi may pose adverse health effects on all age categories in the selected zones of the study since all calculated MOE values were less than 100,000.

The evolution of the gliotoxin biosynthetic gene cluster in Penicillium fungi

Fungi biosynthesize diverse secondary metabolites, small organic bioactive molecules with key roles in fungal ecology. Fungal secondary metabolites are often encoded by physically clustered genes known as biosynthetic gene clusters (BGCs). Fungi in the genus Penicillium produce a cadre of secondary metabolites, some of which are useful (e.g. the antibiotic penicillin and the cholesterol-lowering drug mevastatin) and others harmful (e.g. the mycotoxin patulin and the immunosuppressant gliotoxin) to human affairs. Fungal genomes often also encode resistance genes that confer protection against toxic secondary metabolites. Some Penicillium species, such as Penicillium decumbens, are known to produce gliotoxin, a secondary metabolite with known immunosuppressant activity. To investigate the evolutionary conservation of homologs of the gliotoxin BGC and of genes involved in gliotoxin resistance in Penicillium, we analyzed 35 Penicillium genomes from 23 species. Homologous, lesser fragmented gliotoxin BGCs were found in 12 genomes, mostly fragmented remnants of the gliotoxin BGC were found in 21 genomes, whereas the remaining 2 Penicillium genomes lacked the gliotoxin BGC altogether. In contrast, broad conservation of homologs of resistance genes that reside outside the BGC across Penicillium genomes was observed. Evolutionary rate analysis revealed that BGCs with higher numbers of genes evolve slower than BGCs with few genes, suggestive of constraint and potential functional significance or more recent decay. Gene tree-species tree reconciliation analyses suggested that the history of homologs in the gliotoxin BGC across the genus Penicillium likely involved multiple duplications, losses, and horizontal gene transfers. Our analyses suggest that genes encoded in BGCs can have complex evolutionary histories and be retained in genomes long after the loss of secondary metabolite biosynthesis.

A Timeline of Biosynthetic Gene Cluster Discovery in Aspergillus fumigatus: From Characterization to Future Perspectives

In 1999, the first biosynthetic gene cluster (BGC), synthesizing the virulence factor DHN melanin, was characterized in Aspergillus fumigatus. Since then, 19 additional BGCs have been linked to specific secondary metabolites (SMs) in this species. Here, we provide a comprehensive timeline of A. fumigatus BGC discovery and find that initial advances centered around the commonly expressed SMs where chemical structure informed rationale identification of the producing BGC (e.g., gliotoxin, fumigaclavine, fumitremorgin, pseurotin A, helvolic acid, fumiquinazoline). Further advances followed the transcriptional profiling of a ΔlaeA mutant, which aided in the identification of endocrocin, fumagillin, hexadehydroastechrome, trypacidin, and fumisoquin BGCs. These SMs and their precursors are the commonly produced metabolites in most A. fumigatus studies. Characterization of other BGC/SM pairs required additional efforts, such as induction treatments, including co-culture with bacteria (fumicycline/neosartoricin, fumigermin) or growth under copper starvation (fumivaline, fumicicolin). Finally, four BGC/SM pairs were discovered via overexpression technologies, including the use of heterologous hosts (fumicycline/neosartoricin, fumihopaside, sphingofungin, and sartorypyrone). Initial analysis of the two most studied A. fumigatus isolates, Af293 and A1160, suggested that both harbored ca. 34-36 BGCs. However, an examination of 264 available genomes of A. fumigatus shows up to 20 additional BGCs, with some strains showing considerable variations in BGC number and composition. These new BGCs present a new frontier in the future of secondary metabolism characterization in this important species.

Strain heterogeneity in a non-pathogenic fungus highlights factors contributing to virulence

Fungal pathogens exhibit extensive strain heterogeneity, including variation in virulence. Whether closely related non-pathogenic species also exhibit strain heterogeneity remains unknown. Here, we comprehensively characterized the pathogenic potentials (i.e., the ability to cause morbidity and mortality) of 16 diverse strains of Aspergillus fischeri, a non-pathogenic close relative of the major pathogen Aspergillus fumigatus. In vitro immune response assays and in vivo virulence assays using a mouse model of pulmonary aspergillosis showed that A. fischeri strains varied widely in their pathogenic potential. Furthermore, pangenome analyses suggest that A. fischeri genomic and phenotypic diversity is even greater. Genomic, transcriptomic, and metabolomic profiling identified several pathways and secondary metabolites associated with variation in virulence. Notably, strain virulence was associated with the simultaneous presence of the secondary metabolites hexadehydroastechrome and gliotoxin. We submit that examining the pathogenic potentials of non-pathogenic close relatives is key for understanding the origins of fungal pathogenicity.

Genomic, transcriptomic, and ecological diversity of Penicillium species in cheese rind microbiomes

Although Penicillium molds can have significant impacts on agricultural, industrial, and biomedical systems, the ecological roles of Penicillium species in many microbiomes are not well characterized. Here we utilized a collection of 35 Penicillium strains isolated from cheese rinds to broadly investigate the genomic potential for secondary metabolism in cheese-associated Penicillium species, the impact of Penicillium on bacterial community assembly, and mechanisms of Penicillium-bacteria interactions. Using antiSMASH, we identified 1558 biosynthetic gene clusters, 406 of which were mapped to known pathways, including several mycotoxins and antimicrobial compounds. By measuring bacterial abundance and fungal mRNA expression when culturing representative Penicillium strains with a cheese rind bacterial community, we observed divergent impacts of different Penicillium strains, from strong inhibitors of bacterial growth to those with no impact on bacterial growth or community composition. Through differential mRNA expression analyses, Penicillium strains demonstrated limited differential gene expression in response to the bacterial community. We identified a few shared responses between the eight tested Penicillium strains, primarily upregulation of nutrient metabolic pathways, but we did not identify a conserved fungal response to growth in a multispecies community. These results in tandem suggest high variation among cheese-associated Penicillium species in their ability to shape bacterial community development and highlight important ecological diversity within this iconic genus.

Role of the osaA Gene in Aspergillus fumigatus Development, Secondary Metabolism and Virulence

Aspergillus fumigatus is the leading cause of aspergillosis, associated with high mortality rates, particularly in immunocompromised individuals. In search of novel genetic targets against aspergillosis, we studied the WOPR transcription factor OsaA. The deletion of the osaA gene resulted in colony growth reduction. Conidiation is also influenced by osaA; both osaA deletion and overexpression resulted in a decrease in spore production. Wild-type expression levels of osaA are necessary for the expression of the conidiation regulatory genes brlA, abaA, and wetA. In addition, osaA is necessary for normal cell wall integrity. Furthermore, the deletion of osaA resulted in a reduction in the ability of A. fumigatus to adhere to surfaces, decreased thermotolerance, as well as increased sensitivity to oxidative stress. Metabolomics analysis indicated that osaA deletion or overexpression led to alterations in the production of multiple secondary metabolites, including gliotoxin. This was accompanied by changes in the expression of genes in the corresponding secondary metabolite gene clusters. These effects could be, at least in part, due to the observed reduction in the expression levels of the veA and laeA global regulators when the osaA locus was altered. Importantly, our study shows that osaA is indispensable for virulence in both neutropenic and corticosteroid-immunosuppressed mouse models.

Aspergillus fumigatus mitogen-activated protein kinase MpkA is involved in gliotoxin production and self-protection

Aspergillus fumigatus is a saprophytic fungus that can cause a variety of human diseases known as aspergillosis. Mycotoxin gliotoxin (GT) production is important for its virulence and must be tightly regulated to avoid excess production and toxicity to the fungus. GT self-protection by GliT oxidoreductase and GtmA methyltransferase activities is related to the subcellular localization of these enzymes and how GT can be sequestered from the cytoplasm to avoid increased cell damage. Here, we show that GliT:GFP and GtmA:GFP are localized in the cytoplasm and in vacuoles during GT production. The Mitogen-Activated Protein kinase MpkA is essential for GT production and self-protection, interacts physically with GliT and GtmA and it is necessary for their regulation and subsequent presence in the vacuoles. The sensor histidine kinase SlnASln1 is important for modulation of MpkA phosphorylation. Our work emphasizes the importance of MpkA and compartmentalization of cellular events for GT production and self-defense.

Pleiotropic functions of SscA on the asexual spore of the human pathogenic fungus Aspergillus fumigatus

Asexual spores, called conidia, are key reproductive fungal particles that enable survival in harsh environmental conditions or host systems. The conidia can infect humans, animals, and plants to cause various fungal diseases. Transcription factors, including VosA, WetA, and SscA, have key roles in conidia formation and long-term survival in Aspergillus nidulans. Herein, we report the pleiotropic functions of SscA in the conidia of the human pathogen A. fumigatus. The deletion of sscA increased conidia formation despite decreased fungal growth. Absence of sscA impaired long-term survival and reduced spore resistance to various stresses, including heat, UV, and oxidation. Transcriptomic analyses showed that SscA involved the mRNA expression of cell wall organisation-related genes. Importantly, the sscA deletion mutant conidia contained an increased amount of β-glucan and chitin compared to wild type conidia. In addition, conidial gliotoxin production was decreased in the sscA deletion strain. Overall, SscA has pleiotropic roles in conidia formation, maturation and dormancy and mycotoxin production in A. fumigatus.

The Metabolite Profiling of Aspergillus fumigatus KMM4631 and Its Co-Cultures with Other Marine Fungi

An Aspergillus fumigatus KMM 4631 strain was previously isolated from a Pacific soft coral Sinularia sp. sample and was found to be a source of a number of bioactive secondary metabolites. The aims of this work are the confirmation of this strain' identification based on ITS, BenA, CaM, and RPB2 regions/gene sequences and the investigation of secondary metabolite profiles of Aspergillus fumigatus KMM 4631 culture and its co-cultures with Penicillium hispanicum KMM 4689, Amphichorda sp. KMM 4639, Penicillium sp. KMM 4672, and Asteromyces cruciatus KMM 4696 from the Collection of Marine Microorganisms (PIBOC FEB RAS, Vladivostok, Russia). Moreover, the DPPH-radical scavenging activity, urease inhibition, and cytotoxicity of joint fungal cultures' extracts on HepG2 cells were tested. The detailed UPLC MS qTOF investigation resulted in the identification and annotation of indolediketopiperazine, quinazoline, and tryptoquivaline-related alkaloids as well as a number of polyketides (totally 20 compounds) in the extract of Aspergillus fumigatus KMM 4631. The metabolite profiles of the co-cultures of A. fumigatus with Penicillium hispanicum, Penicillium sp., and Amphichorda sp. were similar to those of Penicillium hispanicum, Penicillium sp., and Amphichorda sp. monocultures. The metabolite profile of the co-culture of A. fumigatus with Asteromyces cruciatus differed from that of each monoculture and may be more promising for the isolation of new compounds.

The novel spore-specific regulator SscA controls Aspergillus conidiogenesis

IMPORTANCE

Filamentous fungi produce myriads of asexual spores, which are the main reproductive particles that act as infectious or allergenic agents. Although the serial of asexual sporogenesis is coordinated by various genetic regulators, there remain uncharacterized transcription factors in Aspergillus. To understand the underlying mechanism of spore formation, integrity, and viability, we have performed comparative transcriptomic analyses on three Aspergillus species and found a spore-specific transcription factor, SscA. SscA has a major role in conidial formation, maturation and dormancy, and germination in Aspergillus nidulans. Functional studies indicate that SscA coordinates conidial wall integrity, amino acid production, and secondary metabolism in A. nidulans conidia. Furthermore, the roles of SscA are conserved in other Aspergillus species. Our findings that the SscA has broad functions in Aspergillus conidia will help to understand the conidiogenesis of Aspergillus species.

A heterologous expression platform in Aspergillus nidulans for the elucidation of cryptic secondary metabolism biosynthetic gene clusters: discovery of the Aspergillus fumigatus sartorypyrone biosynthetic pathway

Aspergillus fumigatus is a serious human pathogen causing life-threatening Aspergillosis in immunocompromised patients. Secondary metabolites (SMs) play an important role in pathogenesis, but the products of many SM biosynthetic gene clusters (BGCs) remain unknown. In this study, we have developed a heterologous expression platform in Aspergillus nidulans, using a newly created genetic dereplication strain, to express a previously unknown BGC from A. fumigatus and determine its products. The BGC produces sartorypyrones, and we have named it the spy BGC. Analysis of targeted gene deletions by HRESIMS, NMR, and microcrystal electron diffraction (MicroED) enabled us to identify 12 products from the spy BGC. Seven of the compounds have not been isolated previously. We also individually expressed the polyketide synthase (PKS) gene spyA and demonstrated that it produces the polyketide triacetic acid lactone (TAL), a potentially important biorenewable platform chemical. Our data have allowed us to propose a biosynthetic pathway for sartorypyrones and related natural products. This work highlights the potential of using the A. nidulans heterologous expression platform to uncover cryptic BGCs from A. fumigatus and other species, despite the complexity of their secondary metabolomes.

A glimpse into the fungal metabolomic abyss: Novel network analysis reveals relationships between exogenous compounds and their outputs

Fungal specialized metabolites are a major source of beneficial compounds that are routinely isolated, characterized, and manufactured as pharmaceuticals, agrochemical agents, and industrial chemicals. The production of these metabolites is encoded by biosynthetic gene clusters that are often silent under standard growth conditions. There are limited resources for characterizing the direct link between abiotic stimuli and metabolite production. Herein, we introduce a network analysis-based, data-driven algorithm comprising two routes to characterize the production of specialized fungal metabolites triggered by different exogenous compounds: the direct route and the auxiliary route. Both routes elucidate the influence of treatments on the production of specialized metabolites from experimental data. The direct route determines known and putative metabolites induced by treatments and provides additional insight over traditional comparison methods. The auxiliary route is specific for discovering unknown analytes, and further identification can be curated through online bioinformatic resources. We validated our algorithm by applying chitooligosaccharides and lipids at two different temperatures to the fungal pathogen Aspergillus fumigatus. After liquid chromatography-mass spectrometry quantification of significantly produced analytes, we used network centrality measures to rank the treatments' ability to elucidate these analytes and confirmed their identity through fragmentation patterns or in silico spiking with commercially available standards. Later, we examined the transcriptional regulation of these metabolites through real-time quantitative polymerase chain reaction. Our data-driven techniques can complement existing metabolomic network analysis by providing an approach to track the influence of any exogenous stimuli on metabolite production. Our experimental-based algorithm can overcome the bottlenecks in elucidating novel fungal compounds used in drug discovery.

Deacetylation by sirtuins is important for Aspergillus fumigatus pathogenesis and virulence

Protein acetylation is a crucial post-translational modification that controls gene expression and a variety of biological processes. Sirtuins, a prominent class of NAD + -dependent lysine deacetylases, serve as key regulators of protein acetylation and gene expression in eukaryotes. In this study, six single knockout strains of fungal pathogen Aspergillus fumigatus were constructed, in addition to a strain lacking all predicted sirtuins (SIRTKO). Phenotypic assays suggest that sirtuins are involved in cell wall integrity, secondary metabolite production, thermotolerance, and virulence. AfsirE deletion resulted in attenuation of virulence, as demonstrated in murine and Galleria infection models. The absence of AfSirE leads to altered acetylation status of proteins, including histones and non-histones, resulting in significant changes in the expression of genes associated with secondary metabolism, cell wall biosynthesis, and virulence factors. These findings encourage testing sirtuin inhibitors as potential therapeutic strategies to combat A. fumigatus infections or in combination therapy with available antifungals.

Melanin precursors mediated adaption to temperature changes in fungus and animal via inhibition of lipid-mediated ferroptosis

The discovery of biological activities of natural products plays a vital part in drug development. The mechanism by which organisms respond to temperature changes via biosynthesis of natural products remained largely cryptic. A thermophilic fungus under cold stress turned black and accumulated a polyketide metabolite 1 and lipid mass. Deficiency in 1 caused melanin loss and accumulated extra lipid mass, unexpectedly leading to seriously damaged mitochondria diagnostic for ferroptosis. Further analysis revealed that lipid mass induced by cold stress intensively increased ferroptosis risk and 1 functioned as cell wall reinforcer against mass lipid accumulation and as reactive oxygen species scavenger against lipid peroxidation. We also found that melanin in mice lowered lipid level but enhanced animal resistance to cold stress. Treatment with melanin precursors significantly increased mouse cell survival rate under cold stress. Our results unveiled a metabolite-lipid-ferroptosis-cold relationship, which provided mechanistic insights into the functions of most common metabolites and into diseases related to cold stress. These findings opened a perspective for developing anti-cold and anti-ferroptosis therapeutics and agents.

The Transcriptome Response to Azole Compounds in Aspergillus fumigatus Shows Differential Gene Expression across Pathways Essential for Azole Resistance and Cell Survival

The opportunistic pathogen Aspergillus fumigatus is found on all continents and thrives in soil and agricultural environments. Its ability to readily adapt to novel environments and to produce billions of spores led to the spread of azole-resistant A. fumigatus across the globe, posing a threat to many immunocompromised patients, including critically ill patients with severe influenza or COVID-19. In our study, we sought to compare the adaptational response to azoles from A. fumigatus isolates that differ in azole susceptibility and genetic background. To gain more insight into how short-term adaptation to stressful azole compounds is managed through gene expression, we conducted an RNA-sequencing study on the response of A. fumigatus to itraconazole and the newest clinically approved azole, isavuconazole. We observed many similarities in ergosterol biosynthesis up-regulation across isolates, with the exception of the pan-azole-resistant isolate, which showed very little differential regulation in comparison to other isolates. Additionally, we found differential regulation of membrane efflux transporters, secondary metabolites, iron metabolism, and various stress response and cell signaling mechanisms.

New Anti-Hypoxic Metabolites from Co-Culture of Marine-Derived Fungi Aspergillus carneus KMM 4638 and Amphichorda sp. KMM 4639

The KMM 4639 strain was identified as Amphichorda sp. based on two molecular genetic markers: ITS and β-tubulin regions. Chemical investigation of co-culture marine-derived fungi Amphichorda sp. KMM 4639 and Aspergillus carneus KMM 4638 led to the identification of five new quinazolinone alkaloids felicarnezolines A-E (1-5), a new highly oxygenated chromene derivative oxirapentyn M (6) and five previously reported related compounds. Their structures were established using spectroscopic methods and by comparison with related known compounds. The isolated compounds showed low cytotoxicity against human prostate and breast cancer cells but felicarnezoline B (2) protected rat cardiomyocytes H9c2 and human neuroblastoma SH-SY5Y cells against CoCl₂-induced damage.

Mutational Analysis of Aspergillus fumigatus Volatile Oxylipins in a Drosophila Eclosion Assay

Aspergillus fumigatus is a ubiquitous opportunistic pathogen. We have previously reported that volatile organic compounds (VOCs) produced by A. fumigatus cause delays in metamorphosis, morphological abnormalities, and death in a Drosophila melanogaster eclosion model. Here, we developed A. fumigatus deletion mutants with blocked oxylipin biosynthesis pathways (∆ppoABC) and then exposed the third instar larvae of D. melanogaster to a shared atmosphere with either A. fumigatus wild-type or oxylipin mutant cultures for 15 days. Fly larvae exposed to VOCs from wild-type A. fumigatus strains exhibited delays in metamorphosis and toxicity, while larvae exposed to VOCs from the ∆ppoABC mutant displayed fewer morphogenic delays and higher eclosion rates than the controls. In general, when fungi were pre-grown at 37 °C, the effects of the VOCs they produced were more pronounced than when they were pre-grown at 25 °C. GC-MS analysis revealed that the wild-type A. fumigatus Af293 produced more abundant VOCs at higher concentrations than the oxylipin-deficient strain Af293∆ppoABC did. The major VOCs detected from wild-type Af293 and its triple mutant included isopentyl alcohol, isobutyl alcohol, 2-methylbutanal, acetoin, and 1-octen-3-ol. Unexpectedly, compared to wild-type flies, the eclosion tests yielded far fewer differences in metamorphosis or viability when flies with immune-deficient genotypes were exposed to VOCs from either wild-type or ∆ppoABC oxylipin mutants. In particular, the toxigenic effects of Aspergillus VOCs were not observed in mutant flies deficient in the Toll (spz6) pathway. These data indicate that the innate immune system of Drosophila mediates the toxicity of fungal volatiles, especially via the Toll pathway.

Evaluation of Effectiveness of a Novel Multicomponent Mycotoxins Detoxification Agent in the Presence of AFB1 and T-2 Toxin on Broiler Chicks

This experimental study was conducted to determine the ability of a novel mycotoxins detoxification agent (MR) at a concentration of 0.2% to reduce the toxicity of aflatoxin B1 (AFB1) or T-2 toxin, alone or in combination, and to examine its effect on performance, pathohistological changes (PH) and the residue of these toxins in the tissues of broiler chicks. A total of 96 broiler chicks were divided into eight equal groups: group C, which served as control (without any additives); group MR, which received the novel detoxification agent (supplemented with 0.2%); group E-I (0.1 mg AFB1/kg of diet); group E-II (0.1 mg AFB1/kg of diet + MR 0.2%); group E-III (0.5 mg T-2 toxin/kg of diet); group E-IV (0.5 mg T-2 toxin/kg of diet + 0.2% MR); group E-V (combination of 0.1 mg AFB1/kg, 0.5 mg T-2 toxin/kg of diet); and group E-VI (combination of 0.1 mg AFB1/kg, 0.5 mg T-2 toxin + 0.2% MR). Results indicate that feeds containing AFB1 and T-2 toxin, alone or in combination, adversely affected the health and performance of poultry. However, the addition of MR to diets containing AFB1 and T-2 toxin singly and in combination exerted a positive effect on body weight, feed intake, weight gain, feed efficiency and microscopic lesions in visceral organs. Residual concentration of AFB1 in liver samples was significantly (p < 0.05) decreased when chicks were fed diets supplemented with 0.2% of MR.

Regulation of pseurotin A biosynthesis by GliZ and zinc in Aspergillus fumigatus

Recently, we reported that zinc regulates gliotoxin biosynthesis via ZafA, which is a zinc-responsive transcriptional activator. From an HPLC analysis of culture media of Aspergillus fumigatus, we found a trend of decreasing gliotoxin production but increasing pseurotin A and fumagillin production in proportion to the zinc concentration. The expression of the genes involved in pseurotin A biosynthesis was upregulated under high zinc concentrations. Furthermore, upregulated expression of pseurotin A biosynthetic genes and higher production of pseurotin A were observed in the zafA deletion strain. Interestingly, the deletion of gliZ, a transcriptional activator of gliotoxin biosynthesis genes, resulted in upregulated expression of pseurotin A biosynthetic genes and increased production of pseurotin A. We detected upregulation of fumR expression in the gliZ and zafA deletion mutants. The overexpression of gliZ observed in the zafA deletion mutant resulted in the failure of the mutant to increase pseurotin A production, which is a phenotype of the zafA deletion mutant. These results suggest that ZafA sequentially regulates pseurotin A biosynthesis through GliZ. Finally, we found through a murine virulence test that the gliZ and fumR double-deletion mutants showed a delayed death rate compared with the single-deletion mutants of either gliZ or fumR. Taken together, these results suggested that the biosynthesis of gliotoxin and pseurotin A are regulated in opposite ways by zinc utilization and that each secondary metabolite is synthesized when the synthesis of another secondary metabolite fails to protect it against the defense system of the host.

Siderophore-Based Noninvasive Differentiation of Aspergillus fumigatus Colonization and Invasion in Pulmonary Aspergillosis

Germination from conidia to hyphae and hyphal propagation of Aspergillus fumigatus are the key pathogenic steps in the development of invasive pulmonary aspergillosis (IPA). By applying in vitro observations in a clinical study of 13 patients diagnosed with probable IPA, here, we show that the transition from colonization to the A. fumigatus invasive stage is accompanied by the secretion of triacetylfusarinine C (TafC), triacetylfusarinine B (TafB), and ferricrocin (Fc) siderophores into urine, with strikingly better sensitivity performance than serum sampling. The best-performing index, the TafC/creatinine index, with a median value of 17.2, provided 92.3% detection sensitivity (95% confidence interval [CI], 64.0 to 99.8%) and 100% specificity (95% CI, 84.6 to 100%), i.e., substantially better than the corresponding indications provided by galactomannan (GM) and β-d-glucan (BDG) serology. For the same patient cohort, the serum GM and BDG sensitivities were 46.2 and 76.9%, respectively, and their specificities were 86.4 and 63.6%, respectively. The time-dependent specific appearance of siderophores in the host's urine represents an impactful clinical diagnostic advantage in the early discrimination of invasive aspergillosis from colonization. A favorable concentration of TafC in a clinical specimen distant from a deep infection site enables the noninvasive sampling of patients suffering from IPA. IMPORTANCE The importance of this research lies in the demonstration that siderophore analysis can distinguish between asymptomatic colonization and invasive pulmonary aspergillosis. We found clear associations between phases of fungal development, from conidial germination to the proliferative stage of invasive aspergillosis, and changes in secondary metabolite secretion. The critical extracellular fungal metabolites triacetylfusarinines C and B are produced during the polarized germination or postpolarized growth phase and reflect the morphological status of the proliferating pathogen. False positivity in Aspergillus diagnostics is minimized as mammalian cells do not synthesize Aspergillus siderophore or mycotoxin molecules.

The evolution of the gliotoxin biosynthetic gene cluster in Penicillium fungi

Fungi biosynthesize a diversity of secondary metabolites, small organic bioactive molecules that play diverse roles in fungal ecology. Fungal secondary metabolites are often encoded by physically clustered sets of genes known as biosynthetic gene clusters (BGCs). Fungi in the genus Penicillium produce diverse secondary metabolites that have been both useful (e.g., the antibiotic penicillin and the cholesterol-lowering drug mevastatin) and harmful (e.g., the mycotoxin patulin and the immunosuppressant gliotoxin) to human affairs. BGCs often also encode resistance genes that confer self-protection to the secondary metabolite-producing fungus. Some Penicillium species, such as Penicillium lilacinoechinulatum and Penicillium decumbens, are known to produce gliotoxin, a secondary metabolite with known immunosuppressant activity; however, an evolutionary characterization of the BGC responsible for gliotoxin biosynthesis among Penicillium species is lacking. Here, we examine the conservation of genes involved in gliotoxin biosynthesis and resistance in 35 Penicillium genomes from 23 species. We found homologous, less fragmented gliotoxin BGCs in 12 genomes, mostly fragmented remnants of the gliotoxin BGC in 21 genomes, whereas the remaining two Penicillium genomes lacked the gliotoxin BGC altogether. In contrast, we observed broad conservation of homologs of resistance genes that reside outside the BGC across Penicillium genomes. Evolutionary rate analysis revealed that BGCs with higher numbers of genes evolve slower than BGCs with few genes. Even though the gliotoxin BGC is fragmented to varying degrees in nearly all genomes examined, ancestral state reconstruction suggests that the ancestor of Penicillium species possessed the gliotoxin BGC. Our analyses suggest that genes that are part of BGCs can be retained in genomes long after the loss of secondary metabolite biosynthesis.

The Toll pathway mediates Drosophila resilience to Aspergillus mycotoxins through specific Bomanins

Host defense against infections encompasses both resistance, which targets microorganisms for neutralization or elimination, and resilience/disease tolerance, which allows the host to withstand/tolerate pathogens and repair damages. In Drosophila, the Toll signaling pathway is thought to mediate resistance against fungal infections by regulating the secretion of antimicrobial peptides, potentially including Bomanins. We find that Aspergillus fumigatus kills Drosophila Toll pathway mutants without invasion because its dissemination is blocked by melanization, suggesting a role for Toll in host defense distinct from resistance. We report that mutants affecting the Toll pathway or the 55C Bomanin locus are susceptible to the injection of two Aspergillus mycotoxins, restrictocin and verruculogen. The vulnerability of 55C deletion mutants to these mycotoxins is rescued by the overexpression of Bomanins specific to each challenge. Mechanistically, flies in which BomS6 is expressed in the nervous system exhibit an enhanced recovery from the tremors induced by injected verruculogen and display improved survival. Thus, innate immunity also protects the host against the action of microbial toxins through secreted peptides and thereby increases its resilience to infection.

Genomic and Phenotypic Trait Variation of the Opportunistic Human Pathogen Aspergillus flavus and Its Close Relatives

Fungal diseases affect millions of humans annually, yet fungal pathogens remain understudied. The mold Aspergillus flavus can cause both aspergillosis and fungal keratitis infections, but closely related species are not considered clinically relevant. To study the evolution of A. flavus pathogenicity, we examined genomic and phenotypic traits of two strains of A. flavus and three closely related species, Aspergillus arachidicola (two strains), Aspergillus parasiticus (two strains), and Aspergillus nomiae (one strain). We identified >3,000 orthologous proteins unique to A. flavus, including seven biosynthetic gene clusters present in A. flavus strains and absent in the three nonpathogens. We characterized secondary metabolite production for all seven strains under two clinically relevant conditions, temperature and salt concentration. Temperature impacted metabolite production in all species, whereas salinity did not affect production of any species. Strains of the same species produced different metabolites. Growth under stress conditions revealed additional heterogeneity within species. Using the invertebrate fungal disease model Galleria mellonella, we found virulence of strains of the same species varied widely; A. flavus strains were not more virulent than strains of the nonpathogens. In a murine model of fungal keratitis, we observed significantly lower disease severity and corneal thickness for A. arachidicola compared to other species at 48 h postinfection, but not at 72 h. Our work identifies variations in key phenotypic, chemical, and genomic attributes between A. flavus and its nonpathogenic relatives and reveals extensive strain heterogeneity in virulence that does not correspond to the currently established clinical relevance of these species. IMPORTANCE Aspergillus flavus is a filamentous fungus that causes opportunistic human infections, such as aspergillosis and fungal keratitis, but its close relatives are considered nonpathogenic. To begin understanding how this difference in pathogenicity evolved, we characterized variation in infection-relevant genomic, chemical, and phenotypic traits between strains of A. flavus and its relatives. We found extensive variation (or strain heterogeneity) within the pathogenic A. flavus as well as within its close relatives, suggesting that strain-level differences may play a major role in the ability of these fungi to cause disease. Surprisingly, we also found that the virulence of strains from species not considered to be pathogens was similar to that of A. flavus in both invertebrate and murine models of disease. These results contrast with previous studies on Aspergillus fumigatus, another major pathogen in the genus, for which significant differences in infection-relevant chemical and phenotypic traits are observed between closely related pathogenic and nonpathogenic species.

Lipo-Chitooligosaccharides Induce Specialized Fungal Metabolite Profiles That Modulate Bacterial Growth

Lipo-chitooligosaccharides (LCOs) are historically known for their role as microbial-derived signaling molecules that shape plant symbiosis with beneficial rhizobia or mycorrhizal fungi. Recent studies showing that LCOs are widespread across the fungal kingdom have raised questions about the ecological function of these compounds in organisms that do not form symbiotic relationships with plants. To elucidate the ecological function of these compounds, we investigate the metabolomic response of the ubiquitous human pathogen Aspergillus fumigatus to LCOs. Our metabolomics data revealed that exogenous application of various types of LCOs to A. fumigatus resulted in significant shifts in the fungal metabolic profile, with marked changes in the production of specialized metabolites known to mediate ecological interactions. Using network analyses, we identify specific types of LCOs with the most significant effect on the abundance of known metabolites. Extracts of several LCO-induced metabolic profiles significantly impact the growth rates of diverse bacterial species. These findings suggest that LCOs may play an important role in the competitive dynamics of non-plant-symbiotic fungi and bacteria. This study identifies specific metabolomic profiles induced by these ubiquitously produced chemicals and creates a foundation for future studies into the potential roles of LCOs as modulators of interkingdom competition. IMPORTANCE The activation of silent biosynthetic gene clusters (BGC) for the identification and characterization of novel fungal secondary metabolites is a perpetual motion in natural product discoveries. Here, we demonstrated that one of the best-studied symbiosis signaling compounds, lipo-chitooligosaccharides (LCOs), play a role in activating some of these BGCs, resulting in the production of known, putative, and unknown metabolites with biological activities. This collection of metabolites induced by LCOs differentially modulate bacterial growth, while the LCO standards do not convey the same effect. These findings create a paradigm shift showing that LCOs have a more prominent role outside of host recognition of symbiotic microbes. Importantly, our work demonstrates that fungi use LCOs to produce a variety of metabolites with biological activity, which can be a potential source of bio-stimulants, pesticides, or pharmaceuticals.

Production of Natural Pigments by Penicillium brevicompactum Using Agro-Industrial Byproducts

The demand for natural pigments for industrial applications has significantly increased. Penicillium brevicompactum was recently reported as a promising pigments producer using submerged fermentation and a synthetic culture medium containing lactose. In this work, pigment production by P. brevicompactum was studied under different fermentation conditions, namely, submerged fermentation with free (SmF) and immobilized mycelium (SmFi), and solid-state fermentation (SSF). The potential of culture media composed of agro-industrial byproducts (cheese-whey (CW) and corn steep liquor (CSL)) was investigated for the first time as low-cost alternatives to pigment production by P. brevicompactum. The fungus showed great adaptability to the different culture media and types of fermentation, being able to synthesize pigments under all the tested conditions. A culture medium composed of 34.6 g/L of CW and 8 g/L of CSL proved to be the most suitable alternative to the synthetic medium, especially under SmF and SmFi. Our data also show that different mixtures of pigments (yellow, orange, and red) can be produced depending on the medium composition and the type of fermentation. Additionally, the immobilization and reuse of biomass to produce pigments by P. brevicompactum were demonstrated for the first time, suggesting the possibility of operating under repeated batch mode at an industrial scale.

Breathing can be dangerous: Opportunistic fungal pathogens and the diverse community of the small mammal lung mycobiome

Human lung mycobiome studies typically sample bronchoalveolar lavage or sputum, potentially overlooking fungi embedded in tissues. Employing ultra-frozen lung tissues from biorepositories, we obtained fungal ribosomal RNA ITS2 sequences from 199 small mammals across 39 species. We documented diverse fungi, including common environmental fungi such as Penicillium and Aspergillus, associates of the human mycobiome such as Malassezia and Candida, and others specifically adapted for lungs (Coccidioides, Blastomyces, and Pneumocystis). Pneumocystis sequences were detected in 83% of the samples and generally exhibited phylogenetic congruence with hosts. Among sequences from diverse opportunistic pathogens in the Onygenales, species of Coccidioides occurred in 12% of samples and species of Blastomyces in 85% of samples. Coccidioides sequences occurred in 14 mammalian species. The presence of neither Coccidioides nor Aspergillus fumigatus correlated with substantial shifts in the overall mycobiome, although there was some indication that fungal communities might be influenced by high levels of A. fumigatus. Although members of the Onygenales were common in lung samples (92%), they are not common in environmental surveys. Our results indicate that Pneumocystis and certain Onygenales are common commensal members of the lung mycobiome. These results provide new insights into the biology of lung-inhabiting fungi and flag small mammals as potential reservoirs for emerging fungal pathogens.

RimO (SrrB) is required for carbon starvation signaling and production of secondary metabolites in Aspergillus nidulans

Depending on the prevailing environmental, developmental and nutritional conditions, fungi activate biosynthetic gene clusters (BGCs) to produce condition-specific secondary metabolites (SMs). For activation, global chromatin-based de-repression must be integrated with pathway-specific induction signals. Here we describe a new global regulator needed to activate starvation-induced SMs. In our transcriptome dataset, we found locus AN7572 strongly transcribed solely under conditions of starvation-induced SM production. The predicted AN7572 protein is most similar to the stress and nutritional regulator Rim15 of Saccharomyces cerevisiae, and to STK-12 of Neurospora crassa. Based on this similarity and on stress and nutritional response phenotypes of A. nidulans knock-out and overexpression strains, AN7572 is designated rimO. In relation to SM production, we found that RimO is required for the activation of starvation-induced BGCs, including the sterigmatocystin (ST) gene cluster. Here, RimO regulates the pathway-specific transcription factor AflR both at the transcriptional and post-translational level. At the transcriptional level, RimO mediates aflR induction following carbon starvation and at the post-translational level, RimO is required for nuclear accumulation of the AflR protein. Genome-wide transcriptional profiling showed that cells lacking rimO fail to adapt to carbon starvation that, in the wild type, leads to down-regulation of genes involved in basic metabolism, membrane biogenesis and growth. Consistently, strains overexpressing rimO are more resistant to oxidative and osmotic stress, largely insensitive to glucose repression and strongly overproduce several SMs. Our data indicate that RimO is a positive regulator within the SM and stress response network, but this requires nutrient depletion that triggers both, rimO gene transcription and activation of the RimO protein.

Distinct Cohorts of Aspergillus fumigatus Transcription Factors Are Required for Epithelial Damage Occurring via Contact- or Soluble Effector-Mediated Mechanisms

Damage to the lung epithelium is a unifying feature of disease caused by the saprophytic fungus Aspergillus fumigatus. However, the mechanistic basis and the regulatory control of such damage is poorly characterized. Previous studies have identified A. fumigatus mediated pathogenesis as occurring at early (≤ 16 hours) or late (>16 hours) phases of the fungal interaction with epithelial cells, and respectively involve direct contact with the host cell or the action of soluble factors produced by mature fungal hyphae. Both early and late phases of epithelial damage have been shown to be subject to genetic regulation by the pH-responsive transcription factor PacC. This study sought to determine whether other transcriptional regulators play a role in modulating epithelial damage. In particular, whether the early and late phases of epithelial damage are governed by same or distinct regulators. Furthermore, whether processes such as spore uptake and hyphal adhesion, that have previously been documented to promote epithelial damage, are governed by the same cohorts of epithelial regulators. Using 479 strains from the recently constructed library of A. fumigatus transcription factor null mutants, two high-throughput screens assessing epithelial cell detachment and epithelial cell lysis were conducted. A total of 17 transcription factor mutants were found to exhibit reproducible deficits in epithelial damage causation. Of these, 10 mutants were defective in causing early phase damage via epithelial detachment and 8 mutants were defective in causing late phase damage via epithelial lysis. Remarkably only one transcription factor, PacC, was required for causation of both phases of epithelial damage. The 17 mutants exhibited varied and often unique phenotypic profiles with respect to fitness, epithelial adhesion, cell wall defects, and rates of spore uptake by epithelial cells. Strikingly, 9 out of 10 mutants deficient in causing early phase damage also exhibited reduced rates of hyphal extension, and culture supernatants of 7 out of 8 mutants deficient in late phase damage were significantly less cytotoxic. Our study delivers the first high-level overview of A. fumigatus regulatory genes governing lung epithelial damage, suggesting highly coordinated genetic orchestration of host-damaging activities that govern epithelial damage in both space and time.

Secondary Metabolites Produced during Aspergillus fumigatus and Pseudomonas aeruginosa Biofilm Formation

In cystic fibrosis (CF), mucus plaques are formed in the patient's lungs, creating a hypoxic condition and a propitious environment for colonization and persistence of many microorganisms. There is clinical evidence showing that Aspergillus fumigatus can cocolonize CF patients with Pseudomonas aeruginosa, which has been associated with lung function decline. P. aeruginosa produces several compounds with inhibitory and antibiofilm effects against A. fumigatus in vitro; however, little is known about the fungal compounds produced in counterattack. Here, we annotated fungal and bacterial secondary metabolites (SM) produced in mixed biofilms under normoxia and hypoxia conditions. We detected nine SM produced by P. aeruginosa. Phenazines and different analogs of pyoverdin were the main compounds produced by P. aeruginosa, and their secretion levels were increased by the fungal presence. The roles of the two operons responsible for phenazine production (phzA1 and phzA2) were also investigated, and mutants lacking one of those operons were able to produce partial sets of phenazines. We detected a total of 20 SM secreted by A. fumigatus either in monoculture or in coculture with P. aeruginosa. All these compounds were secreted during biofilm formation in either normoxia or hypoxia. However, only eight compounds (demethoxyfumitremorgin C, fumitremorgin, ferrichrome, ferricrocin, triacetylfusigen, gliotoxin, gliotoxin E, and pyripyropene A) were detected during biofilm formation by the coculture of A. fumigatus and P. aeruginosa under normoxia and hypoxia conditions. Overall, we showed how diverse SM secretion is during A. fumigatus and P. aeruginosa mixed culture and how this can affect biofilm formation in normoxia and hypoxia. IMPORTANCE The interaction between Pseudomonas aeruginosa and Aspergillus fumigatus has been well characterized in vitro. In this scenario, the bacterium exerts a strong inhibitory effect against the fungus. However, little is known about the metabolites produced by the fungus to counterattack the bacteria. Our work aimed to annotate secondary metabolites (SM) secreted during coculture between P. aeruginosa and A. fumigatus during biofilm formation in both normoxia and hypoxia. The bacterium produces several different types of phenazines and pyoverdins in response to presence of the fungus. In contrast, we were able to annotate 29 metabolites produced during A. fumigatus biofilm formation, but only 8 compounds were detected during biofilm formation by the coculture of A. fumigatus and P. aeruginosa upon either normoxia or hypoxia. In conclusion, we detected many SM secreted during A. fumigatus and P. aeruginosa biofilm formation. This analysis provides several opportunities to understand the interactions between these two species.

Extensive non-coding sequence divergence between the major human pathogen Aspergillus fumigatus and its relatives

Invasive aspergillosis is a deadly fungal disease; more than 400,000 patients are infected worldwide each year and the mortality rate can be as high as 50-95%. Of the ~450 species in the genus Aspergillus only a few are known to be clinically relevant, with the major pathogen Aspergillus fumigatus being responsible for ~50% of all invasive mold infections. Genomic comparisons between A. fumigatus and other Aspergillus species have historically focused on protein-coding regions. However, most A. fumigatus genes, including those that modulate its virulence, are also present in other pathogenic and non-pathogenic closely related species. Our hypothesis is that differential gene regulation - mediated through the non-coding regions upstream of genes' first codon - contributes to A. fumigatus pathogenicity. To begin testing this, we compared non-coding regions upstream of the first codon of single-copy orthologous genes from the two A. fumigatus reference strains Af293 and A1163 and eight closely related Aspergillus section Fumigati species. We found that these non-coding regions showed extensive sequence variation and lack of homology across species. By examining the evolutionary rates of both protein-coding and non-coding regions in a subset of orthologous genes with highly conserved non-coding regions across the phylogeny, we identified 418 genes, including 25 genes known to modulate A. fumigatus virulence, whose non-coding regions exhibit a different rate of evolution in A. fumigatus. Examination of sequence alignments of these non-coding regions revealed numerous instances of insertions, deletions, and other types of mutations of at least a few nucleotides in A. fumigatus compared to its close relatives. These results show that closely related Aspergillus species that vary greatly in their pathogenicity exhibit extensive non-coding sequence variation and identify numerous changes in non-coding regions of A. fumigatus genes known to contribute to virulence.

Dynamic description of temporal changes of gut microbiota in broilers

The diversity of bacteria and fungi in the gut microbiota of commercial broilers that raised in cages from hatch to the end of the production cycle were examined by an analysis of 3,592 and 3,899 amplicon sequence variants (ASVs), respectively. More than 90% sequences in bacterial communities were related to Firmicutes and Proteobacteria. More than 90% sequences in fungal communities were related to Ascomycota, Basidiomycota, and Glomeromycota. A statistical analysis of the microbiota composition succession showed that age was one of the main factors affecting the intestinal microbial communities of broilers. The increasingly complex community succession of transient microbiota occurred along with an increase of age. This dynamic change was observed to be similar between bacteria and fungi. The gut microbiota had a special structure in the first 3 d after birth of broiler. The microbiota structure was quite stable in the period of rapid skeletal growth (d 14–21), and then changed significantly in the period of rapid gaining weight (d 35–42), thus indicating the composition of gut microbiota in broilers had unique structures at different developmental stages. We observed that several bacteria and fungi occupied key functions in the gut microbiota of broilers, suggesting that the gut homeostasis of broilers might be affected by losses of bacteria and fungi via altering interactions between microbiota. This study aimed to provide a data basis for manipulating the microbiota at different developmental stages, in order to improve production and the intestinal health of broilers.

Evolution of the human pathogenic lifestyle in fungi

Fungal pathogens cause more than a billion human infections every year, resulting in more than 1.6 million deaths annually. Understanding the natural history and evolutionary ecology of fungi is helping us understand how disease-relevant traits have repeatedly evolved. Different types and mechanisms of genetic variation have contributed to the evolution of fungal pathogenicity and specific genetic differences distinguish pathogens from non-pathogens. Insights into the traits, genetic elements, and genetic and ecological mechanisms that contribute to the evolution of fungal pathogenicity are crucial for developing strategies to both predict emergence of fungal pathogens and develop drugs to combat them.

Population genomics confirms acquisition of drug-resistant Aspergillus fumigatus infection by humans from the environment

Infections caused by the fungal pathogen Aspergillus fumigatus are increasingly resistant to first-line azole antifungal drugs. However, despite its clinical importance, little is known about how susceptible patients acquire infection from drug-resistant genotypes in the environment. Here, we present a population genomic analysis of 218 A. fumigatus isolates from across the UK and Ireland (comprising 153 clinical isolates from 143 patients and 65 environmental isolates). First, phylogenomic analysis shows strong genetic structuring into two clades (A and B) with little interclade recombination and the majority of environmental azole resistance found within clade A. Second, we show occurrences where azole-resistant isolates of near-identical genotypes were obtained from both environmental and clinical sources, indicating with high confidence the infection of patients with resistant isolates transmitted from the environment. Third, genome-wide scans identified selective sweeps across multiple regions indicating a polygenic basis to the trait in some genetic backgrounds. These signatures of positive selection are seen for loci containing the canonical genes encoding fungicide resistance in the ergosterol biosynthetic pathway, while other regions under selection have no defined function. Lastly, pan-genome analysis identified genes linked to azole resistance and previously unknown resistance mechanisms. Understanding the environmental drivers and genetic basis of evolving fungal drug resistance needs urgent attention, especially in light of increasing numbers of patients with severe viral respiratory tract infections who are susceptible to opportunistic fungal superinfections.

Mycobiota profile, phenology, and potential toxicogenic and pathogenic species associated with stored groundnuts (Arachis hypogaea L.) from the Volta Region, Ghana

This study updates the mycobiota resident in groundnut seeds, their phenology during storage with the view to ascertain their occurrence, potential toxigenic species, and pathologically important species in the stored samples. The moisture content of the seeds ranged from 5.7% to 6.5% within the stipulated safe moisture content of 8% for extension of shelf life. Culturing the seeds on mycological media (Sabouraud's Dextrose Agar SDA; Oxytetracycline Glucose Yeast Extract OGYE, Potato Dextrose Agar, PDA) caused a de novo growth of the quiescent spores at 28-30°C for 7-14 days. Fungal population counts on the three media ranged from 2.01 to 2.16 log10 CFU/g samples to a final 6-month count of 1.67-2.60 log10 CFU/g. Eighteen different fungal species belonging to ten genera were encountered on the media, namely Aspergillus, Cladosporium, Curvularia, Fusarium, Penicillium, Trichoderma, Rhizopus, Rhodotorula, Sporendonema, and Paecilomyces. Aspergillus spp. (A. niger, A. flavus, A. fumigatus, and A. terreus) were the most frequently isolated, followed by Fusarium species (F. oxysporum, F. solani, and F. verticillioides), Trichoderma (T. harzianum and T. viride), Rhizopus spp (R. oligosporus and R. stolonifer), and Penicillium verrucosum. The species which were seed borne (A. niger, A. flavus, A. terreus, A. fumigatus, F. solani, F. verticillioides, T. viride, C. herbarum, and Curvularia lunata) were isolated on both surface sterilized and non-surface sterilized seeds. The phenology of the encountered fungal species generally followed five patterns. The most frequently isolated Aspergillus niger, A. flavus, and A. fumigatus predominated throughout the 6 months sampling period, while A. ustus and A. terreus appeared sporadically and disappeared. The early colonizers (R. oligosporus, R. stolonifer, and Paecilomyces) could not be isolated after 2-3 months owing presumably to stronger antibiosis competition from the Aspergillus species. The most predominant Aspergillus species initially constituted 36%-48% of the total population but declined to 10%-36% in 6 months. Mycobiota encountered with mycotoxigenic potential and human health importance were A. niger, A. flavus, A. fumigatus, F. verticillioides, and Penicillium verrucosum. Other species of pathological importance to plants were Curvularia lunata and Fusarium oxysporum. The practical implications of these findings are discussed.

Work clothes as a vector for microorganisms: Accumulation, transport, and resuspension of microorganisms as demonstrated for waste collection workers

Work clothes may act as a vector for the transport of microorganisms leading to second-hand exposure; however, this has not been studied in work environments. We investigated whether microorganisms accumulate on workers' clothes in environments with elevated microbial exposures, and whether they are transported with the clothes and subsequently resuspended to the air. To study this, we selected waste collection workers and potential transport of bacteria and fungi to waste truck cabs via clothes, and compared the microbial communities within truck cabs, in waste collection workers' personal exposure, and on clean T-shirts worn by the workers. Microbial communities were also investigated for the presence of potentially harmful microorganisms. Results showed that microorganisms accumulated in large quantities (GM = 3.69 × 10⁵ CFU/m²/h for bacteria, GM = 8.29 × 10⁴ CFU/m²/h for fungi) on workers' clothes. The concentrations and species composition of airborne fungi in the truck cabs correlated significantly with the accumulation and composition of fungi on clothes and correlated to concentrations (a trend) and species composition of their personal exposures. The same patterns were not found for bacteria, indicating that work clothes to a lesser degree act as a vector for bacteria under waste collection workers' working conditions compared to fungi. Several pathogenic or allergenic microorganisms were present, e.g.: Klebsiella oxytoca, K. pneumoniae, Proteus mirabilis, Providencia rettgeri, Pseudomonas aeruginosa, and Aspergillus fumigatus, A. glaucus, A. nidulans, A. niger, and various Penicillium species. The potential 'take-home' exposure to these microorganisms are of most concern for immunocompromised or atopic individuals or people with open wounds or cuts. In conclusion, the large accumulation of microorganisms on workers' clothes combined with the overlap between fungal species for the different sample types, and the presence of pathogenic and allergenic microorganisms forms the basis for encouragement of good clothing hygiene during and post working hours.

Exposure to the Pseudomonas aeruginosa secretome alters the proteome and secondary metabolite production of Aspergillus fumigatus

The fungal pathogen Aspergillus fumigatus is frequently cultured from the sputum of cystic fibrosis (CF) patients along with the bacterium Pseudomonas aeruginosa. A. fumigatus secretes a range of secondary metabolites, and one of these, gliotoxin, has inhibitory effects on the host immune response. The effect of P. aeruginosa culture filtrate (CuF) on fungal growth and gliotoxin production was investigated. Exposure of A. fumigatus hyphae to P. aeruginosa cells induced increased production of gliotoxin and a decrease in fungal growth. In contrast, exposure of A. fumigatus hyphae to P. aeruginosa CuF led to increased growth and decreased gliotoxin production. Quantitative proteomic analysis was used to characterize the proteomic response of A. fumigatus upon exposure to P. aeruginosa CuF. Changes in the profile of proteins involved in secondary metabolite biosynthesis (e.g. gliotoxin, fumagillin, pseurotin A), and changes to the abundance of proteins involved in oxidative stress (e.g. formate dehydrogenase) and detoxification (e.g. thioredoxin reductase) were observed, indicating that the bacterial secretome had a profound effect on the fungal proteome. Alterations in the abundance of proteins involved in detoxification and oxidative stress highlight the ability of A. fumigatus to differentially regulate protein synthesis in response to environmental stresses imposed by competitors such as P. aeruginosa. Such responses may ultimately have serious detrimental effects on the host.

Host-mycobiome metabolic interactions in health and disease

Fungal communities (mycobiome) have an important role in sustaining the resilience of complex microbial communities and maintenance of homeostasis. The mycobiome remains relatively unexplored compared to the bacteriome despite increasing evidence highlighting their contribution to host-microbiome interactions in health and disease. Despite being a small proportion of the total species, fungi constitute a large proportion of the biomass within the human microbiome and thus serve as a potential target for metabolic reprogramming in pathogenesis and disease mechanism. Metabolites produced by fungi shape host niches, induce immune tolerance and changes in their levels prelude changes associated with metabolic diseases and cancer. Given the complexity of microbial interactions, studying the metabolic interplay of the mycobiome with both host and microbiome is a demanding but crucial task. However, genome-scale modelling and synthetic biology can provide an integrative platform that allows elucidation of the multifaceted interactions between mycobiome, microbiome and host. The inferences gained from understanding mycobiome interplay with other organisms can delineate the key role of the mycobiome in pathophysiology and reveal its role in human disease.

Regulation of gliotoxin biosynthesis and protection in Aspergillus species

Aspergillus fumigatus causes a range of human and animal diseases collectively known as aspergillosis. A. fumigatus possesses and expresses a range of genetic determinants of virulence, which facilitate colonisation and disease progression, including the secretion of mycotoxins. Gliotoxin (GT) is the best studied A. fumigatus mycotoxin with a wide range of known toxic effects that impair human immune cell function. GT is also highly toxic to A. fumigatus and this fungus has evolved self-protection mechanisms that include (i) the GT efflux pump GliA, (ii) the GT neutralising enzyme GliT, and (iii) the negative regulation of GT biosynthesis by the bis-thiomethyltransferase GtmA. The transcription factor (TF) RglT is the main regulator of GliT and this GT protection mechanism also occurs in the non-GT producing fungus A. nidulans. However, the A. nidulans genome does not encode GtmA and GliA. This work aimed at analysing the transcriptional response to exogenous GT in A. fumigatus and A. nidulans, two distantly related Aspergillus species, and to identify additional components required for GT protection. RNA-sequencing shows a highly different transcriptional response to exogenous GT with the RglT-dependent regulon also significantly differing between A. fumigatus and A. nidulans. However, we were able to observe homologs whose expression pattern was similar in both species (43 RglT-independent and 11 RglT-dependent). Based on this approach, we identified a novel RglT-dependent methyltranferase, MtrA, involved in GT protection. Taking into consideration the occurrence of RglT-independent modulated genes, we screened an A. fumigatus deletion library of 484 transcription factors (TFs) for sensitivity to GT and identified 15 TFs important for GT self-protection. Of these, the TF KojR, which is essential for kojic acid biosynthesis in Aspergillus oryzae, was also essential for virulence and GT biosynthesis in A. fumigatus, and for GT protection in A. fumigatus, A. nidulans, and A. oryzae. KojR regulates rglT, gliT, gliJ expression and sulfur metabolism in Aspergillus species. Together, this study identified conserved components required for GT protection in Aspergillus species.

A. fumigatus secretes mycotoxins that are essential for its virulence and pathogenicity. Gliotoxin (GT) is a sulfur-containing mycotoxin, which is known to impair several aspects of the human immune response. GT is also toxic to different fungal species, which have evolved several GT protection strategies. To further decipher these responses, we used transcriptional profiling aiming to compare the response to GT in the GT producer A. fumigatus and the GT non-producer A. nidulans. This analysis allowed us to identify additional genes with a potential role in GT protection. We also identified 15 transcription factors (TFs) encoded in the A. fumigatus genome that are important for conferring resistance to exogenous gliotoxin. One of these TFs, KojR, which is essential for A. oryzae kojic acid production, is also important for virulence in A. fumigatus and GT protection in A. fumigatus, A. nidulans and A. oryzae. KojR regulates the expression of genes important for gliotoxin biosynthesis and protection, and sulfur metabolism. Together, this work identified conserved components required for gliotoxin protection in Aspergillus species.

Comprehensive Guide to Extracting and Expressing Fungal Secondary Metabolites with Aspergillus fumigatus as a Case Study

Fungal secondary metabolites (SMs) have captured the interest of natural products researchers in academia and industry for decades. In recent years, the high rediscovery rate of previously characterized metabolites is making it increasingly difficult to uncover novel compounds. Additionally, the vast majority of fungal SMs reside in genetically intractable fungi or are silent under normal laboratory conditions in genetically tractable fungi. The fungal natural products community has broadly overcome these barriers by altering the physical growth conditions of the fungus and heterologous/homologous expression of biosynthetic gene cluster regulators or proteins. The protocols described here summarize vital methodologies needed when researching SM production in fungi. We also summarize the growth conditions, genetic backgrounds, and extraction protocols for every published SM in Aspergillus fumigatus, enabling readers to easily replicate the production of previously characterized SMs. Readers will also be equipped with the tools for developing their own strategy for expressing and extracting SMs from their given fungus or a suitable heterologous model system. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Making glycerol stocks from spore suspensions Alternate Protocol 1: Creating glycerol stocks from non-sporulating filamentous fungi Basic Protocol 2: Activating spore-suspension glycerol stocks Basic Protocol 3: Extracting secondary metabolites from Aspergillus spp grown on solid medium Alternate Protocol 2: Extracting secondary metabolites from Aspergillus spp using ethyl acetate Alternate Protocol 3: High-volume metabolite extraction using ethyl acetate Alternate Protocol 4: Extracting secondary metabolites from Aspergillus spp in liquid medium Support Protocol: Creating an overlay culture Basic Protocol 4: Extracting DNA from filamentous fungi Basic Protocol 5: Creating a DNA construct with double-joint PCR Alternate Protocol 5: Creating a DNA construct with yeast recombineering Basic Protocol 6: Transformation of Aspergillus spp Basic Protocol 7: Co-culturing fungi and bacteria for extraction of secondary metabolites.