Detection of metabolite induction in fungal co-cultures on solid media by high-throughput differential ultra-high pressure liquid chromatography-time-of-flight mass spectrometry fingerprinting

Unraveling the interaction of co-encapsulated Saccharomyces cerevisiae and Metarhizium brunneum in calcium alginate-based attract-and-kill beads

BACKGROUND

Attract-and-kill (AK) beads are biological, microbial insecticides developed as an alternative to synthetic soil insecticides. For wireworm control, beads are based on calcium alginate/starch co-encapsulating the carbon dioxide (CO2) producing yeast Saccharomyces cerevisiae H205 as the attract component, and the entomopathogenic fungus Metarhizium brunneum CB15-III as the kill component. However, the physicochemical processes inside beads during co-cultivation are still unclear. Here we reveal for the first time the spatiotemporal conditions of oxygen and pH inside AK beads measured with microelectrodes and describe the impact of S. cerevisiae on CO2 and conidia formation.

RESULTS

Measurements revealed a steep oxygen gradient already 2 days after co-encapsulation, with an internal hypoxic zone. Encapsulating either S. cerevisiae or M. brunneum already decreased the average pH from 5.5 to 4.7 and 4.6, respectively. However, on day 3, co-cultivation lead to temporal strong acidification of beads down to pH 3.6 which followed the maximum CO2 productivity and coincided with the maximum conidiation rate. Decreasing the yeast load decreased the total CO2 productivity to half, and the conidial production by 93%, while specific productivities normalized to 1% yeast load increased eight-fold and three-fold, respectively, with day 3 being an exception.

CONCLUSION

Our findings indicate a general beneficial interaction between M. brunneum and S. cerevisiae, but also suggest competition for resources. These findings will contribute to develop innovative co-formulations with maximum efficiency to save application rates and costs. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Monaspin B, a Novel Cyclohexyl-furan from Cocultivation of Monascus purpureus and Aspergillus oryzae, Exhibits Potent Antileukemic Activity

Natural products are a rich resource for the discovery of innovative drugs. Microbial cocultivation enables discovery of novel natural products through tandem enzymatic catalysis between different fungi. In this study, Monascus purpureus, as a food fermentation strain capable of producing abundant natural products, was chosen as an example of a cocultivation pair strain. Cocultivation screening revealed that M. purpureus and Aspergillus oryzae led to the production of two novel cyclohexyl-furans, Monaspins A and B. Optimization of the cocultivation mode and media enhanced the production of Monaspins A and B to 1.2 and 0.8 mg/L, respectively. Monaspins A and B were structurally elucidated by HR-ESI-MS and NMR. Furthermore, Monaspin B displayed potent antiproliferative activity against the leukemic HL-60 cell line by inducing apoptosis, with a half-maximal inhibitory concentration (IC50) of 160 nM. Moreover, in a mouse leukemia model, Monaspin B exhibited a promising in vivo antileukemic effect by reducing white blood cell, lymphocyte, and neutrophil counts. Collectively, these results indicate that Monaspin B is a promising candidate agent for leukemia therapy.

Structural diversity and biological activities of indole-diterpenoids from Penicillium janthinellum by co-culture with Paecilomyces formosus

Co-culturing the marine-derived fungi Penicillium janthinellium with Paecilomyces formosus led to the isolation of nine new indole-diterpenes, janthinellumines A-I (1-9), along with twelve known analogues (10-21). The chemical structures including their absolute configurations of them were assigned by the analysis of extensive spectroscopic data and calculated ECD and VCD methods. These indole-diterpenoids displayed extensive biological activities, including anti-influenza A virus, protein tyrosine phosphatase (PTP) inhibitory, and anti-Vibrio activities. Among them, the anti-influenza mechanism of compounds 1, 2, and 7 was further investigated using neuraminidase inhibitory assay, molecular docking, and reverse genetics methods, suggesting that 1, 2, and 7 could interact with Arg371 of the viral neuraminidase. The structure-activity relationship (SAR) of PTPs inhibitory activity for indole-diterpene derivatives (1, 2, 4, 5, 9-16, and 19-21) was also summarized.

Differential Volatile Organic Compound Expression in the Interaction of Daldinia eschscholtzii and Mycena citricolor

Fungi exhibit a wide range of ecological guilds, but those that live within the inner tissues of plants (also known as endophytes) are particularly relevant due to the benefits they sometimes provide to their hosts, such as herbivory deterrence, disease protection, and growth promotion. Recently, endophytes have gained interest as potential biocontrol agents against crop pathogens, for example, coffee plants (Coffea arabica). Published results from research performed in our laboratory showed that endophytic fungi isolated from wild Rubiaceae plants were effective in reducing the effects of the American leaf spot of coffee (Mycena citricolor). One of these isolates (GU11N) from the plant Randia grandifolia was identified as Daldinia eschscholtzii (Xylariales). Its antagonism mechanisms, effects, and chemistry against M. citricolor were investigated by analyzing its volatile profile alone and in the presence of the pathogen in contactless and dual culture assays. The experimental design involved direct sampling of agar plugs in vials for headspace (HS) and headspace solid-phase microextraction (HS-SPME) gas chromatography-mass spectrometry (GC-MS) analysis. Additionally, we used ultrahigh-performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS/MS) to identify nonvolatile compounds from organic extracts of the mycelia involved in the interaction. Results showed that more volatile compounds were identified using HS-SPME (39 components) than those by the HS technique (13 components), sharing only 12 compounds. Statistical tests suggest that D. eschscholtzii inhibited the growth of M. citricolor through the release of VOCs containing a combination of 1,8-dimethoxynapththalene and terpene compounds affecting M. citricolor pseudopilei. The damaging effects of 1,8-dimethoxynaphthalene were corroborated in an in vitro test against M. citricolor pseudopilei; scanning electron microscopy (SEM) photographs confirmed structural damage. After analyzing the UHPLC-HRMS/MS data, a predominance of fatty acid derivatives was found among the putatively identified compounds. However, a considerable proportion of features (37.3%) remained unannotated. In conclusion, our study suggests that D. eschscholtzii has potential as a biocontrol agent against M. citricolor and that 1,8-dimethoxynaphthalene contributes to the observed damage to the pathogen's reproductive structures.

Computation-aided studies related to the induction of specialized metabolite biosynthesis in microbial co-cultures: An introductory overview

Co-cultivation is an effective method of inducing the production of specialized metabolites (SMs) in microbial strains. By mimicking the ecological interactions that take place in natural environment, this approach enables to trigger the biosynthesis of molecules which are not formed under monoculture conditions. Importantly, microbial co-cultivation may lead to the discovery of novel chemical entities of pharmaceutical interest. The experimental efforts aimed at the induction of SMs are greatly facilitated by computational techniques. The aim of this overview is to highlight the relevance of computational methods for the investigation of SM induction via microbial co-cultivation. The concepts related to the induction of SMs in microbial co-cultures are briefly introduced by addressing four areas associated with the SM induction workflows, namely the detection of SMs formed exclusively under co-culture conditions, the annotation of induced SMs, the identification of SM producer strains, and the optimization of fermentation conditions. The computational infrastructure associated with these areas, including the tools of multivariate data analysis, molecular networking, genome mining and mathematical optimization, is discussed in relation to the experimental results described in recent literature. The perspective on the future developments in the field, mainly in relation to the microbiome-related research, is also provided.

Protective and Therapeutic Effects of Lactic Acid Bacteria against Aflatoxin B1 Toxicity to Rat Organs

BACKGROUND

Aflatoxin (AF), a metabolite of Aspergillus flavus, is injurious to vital body organs. The bacterial defense against such mycotoxins has attracted significant attention. Lactic acid bacteria (LAB) are known to ameliorate AF toxicity.

METHODS

Thirty adult male rats were divided into six groups (five each) to perform the experiments. The control (Co) group was fed a basal diet and water. Each of the following periods lasted 21 days: the milk (MK) group orally received milk (500 µL); LAB suspension (500 µL) containing 10⁷ cfu/mL was orally provided to the LAB group; AF (0.5 mg/kg) was orally given to the AF group; and a combination of AF and LAB was administered to the AF + LAB group. The AF/LAB group was initially given AF for 21 days, followed by LAB for the same period. Finally, the rats were dissected to retrieve blood and tissue samples for hematological, biochemical, and histological studies.

RESULTS

The results revealed a significant decrease in RBCs, lymphocytes, total proteins, eosinophil count, albumin, and uric acid, whereas the levels of WBCs, monocytes, neutrophils, creatinine, urea, aspartate aminotransferase, alkaline phosphatase, alanine aminotransferase, lactate dehydrogenase, and creatinine kinase significantly increased in the AF group in comparison to the control group. The histological examination of the AF group revealed necrosis and apoptosis of the kidney's glomeruli and renal tubules, nuclei vacuolization and apoptosis of hepatocytes, congestion of the liver's dilated portal vein, lymphoid depletion in the white pulp, localized hemorrhages, hemosiderin pigment deposition in the spleen, and vacuolization of seminiferous tubules with a complete loss of testis spermatogenic cells. Meanwhile, protective and therapeutic LAB administration in AF-treated rats improved the hematological, biochemical, and histological changes.

CONCLUSIONS

The study revealed LAB-based amelioration to AFB1-induced disruptions of the kidney, liver, spleen, and testis by inhibiting tissue damage. The therapeutic effects of LAB were comparatively more pronounced than the protective effects.

Enhancing chemical and biological diversity by co-cultivation

In natural product research, microbial metabolites have tremendous potential to provide new therapeutic agents since extremely diverse chemical structures can be found in the nearly infinite microbial population. Conventionally, these specialized metabolites are screened by single-strain cultures. However, owing to the lack of biotic and abiotic interactions in monocultures, the growth conditions are significantly different from those encountered in a natural environment and result in less diversity and the frequent re-isolation of known compounds. In the last decade, several methods have been developed to eventually understand the physiological conditions under which cryptic microbial genes are activated in an attempt to stimulate their biosynthesis and elicit the production of hitherto unexpressed chemical diversity. Among those, co-cultivation is one of the most efficient ways to induce silenced pathways, mimicking the competitive microbial environment for the production and holistic regulation of metabolites, and has become a golden methodology for metabolome expansion. It does not require previous knowledge of the signaling mechanism and genome nor any special equipment for cultivation and data interpretation. Several reviews have shown the potential of co-cultivation to produce new biologically active leads. However, only a few studies have detailed experimental, analytical, and microbiological strategies for efficiently inducing bioactive molecules by co-culture. Therefore, we reviewed studies applying co-culture to induce secondary metabolite pathways to provide insights into experimental variables compatible with high-throughput analytical procedures. Mixed-fermentation publications from 1978 to 2022 were assessed regarding types of co-culture set-ups, metabolic induction, and interaction effects.

Deciphering interactions between the marine dinoflagellate Prorocentrum lima and the fungus Aspergillus pseudoglaucus

The comprehension of microbial interactions is one of the key challenges in marine microbial ecology. This study focused on exploring chemical interactions between the toxic dinoflagellate Prorocentrum lima and a filamentous fungal species, Aspergillus pseudoglaucus, which has been isolated from the microalgal culture. Such interspecies interactions are expected to occur even though they were rarely studied. Here, a co-culture system was designed in a dedicated microscale marine-like condition. This system allowed to explore microalgal-fungal physical and metabolic interactions in presence and absence of the bacterial consortium. Microscopic observation showed an unusual physical contact between the fungal mycelium and dinoflagellate cells. To delineate specialized metabolome alterations during microalgal-fungal co-culture metabolomes were monitored by high-performance liquid chromatography coupled to high-resolution mass spectrometry. In-depth multivariate statistical analysis using dedicated approaches highlighted (1) the metabolic alterations associated with microalgal-fungal co-culture, and (2) the impact of associated bacteria in microalgal metabolome response to fungal interaction. Unfortunately, only a very low number of highlighted features were fully characterized. However, an up-regulation of the dinoflagellate toxins okadaic acid and dinophysistoxin 1 was observed during co-culture in supernatants. Such results highlight the importance to consider microalgal-fungal interactions in the study of parameters regulating toxin production.

How to Completely Squeeze a Fungus-Advanced Genome Mining Tools for Novel Bioactive Substances

Fungal species have the capability of producing an overwhelming diversity of bioactive substances that can have beneficial but also detrimental effects on human health. These so-called secondary metabolites naturally serve as antimicrobial "weapon systems", signaling molecules or developmental effectors for fungi and hence are produced only under very specific environmental conditions or stages in their life cycle. However, as these complex conditions are difficult or even impossible to mimic in laboratory settings, only a small fraction of the true chemical diversity of fungi is known so far. This also implies that a large space for potentially new pharmaceuticals remains unexplored. We here present an overview on current developments in advanced methods that can be used to explore this chemical space. We focus on genetic and genomic methods, how to detect genes that harbor the blueprints for the production of these compounds (i.e., biosynthetic gene clusters, BGCs), and ways to activate these silent chromosomal regions. We provide an in-depth view of the chromatin-level regulation of BGCs and of the potential to use the CRISPR/Cas technology as an activation tool.

Bioremediation of organic/heavy metal contaminants by mixed cultures of microorganisms: A review

Although microbial remediation has been widely used in the bioremediation of various contaminants, in practical applications of biological remediation, pure cultures of microorganisms are seriously limited by their adaptability, efficiency, and capacity to handle multiple contaminants. Mixed cultures of microorganisms involve the symbiosis of two or more microorganisms. Such cultures exhibit a collection of the characteristics of each microorganism species or strain, showing enormous potential in the bioremediation of organic or heavy metal pollutants. The present review focuses on the mixed cultures of microorganisms, demonstrating its importance and summarizing the advantages of mixed cultures of microorganisms in bioremediation. Furthermore, the internal and external relations of mixed culture microorganisms were analyzed with respect to their involvement in the removal process to elucidate the underlying mechanisms.

Fungal-fungal co-culture: a primer for generating chemical diversity

Covering: 2002 to 2020In their natural environment, fungi must compete for resources. It has been hypothesized that this competition likely induces the biosynthesis of secondary metabolites for defence. In a quest to discover new chemical diversity from fungal cultures, a growing trend has been to recapitulate this competitive environment in the laboratory, essentially growing fungi in co-culture. This review covers fungal-fungal co-culture studies beginning with the first literature report in 2002. Since then, there has been a growing number of new secondary metabolites reported as a result of fungal co-culture studies. Specifically, this review discusses and provides insights into (1) rationale for pairing fungal strains, (2) ways to grow fungi for co-culture, (3) different approaches to screening fungal co-cultures for chemical diversity, (4) determining the secondary metabolite-producing strain, and (5) final thoughts regarding the fungal-fungal co-culture approach. Our goal is to provide a set of practical strategies for fungal co-culture studies to generate unique chemical diversity that the natural products research community can utilize.

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.

Metabolic Potential of Epichloë Endophytes for Host Grass Fungal Disease Resistance

Asexual species of the genus Epichloë (Clavicipitaceae, Ascomycota) form endosymbiotic associations with Pooidae grasses. This association is important both ecologically and to the pasture and turf industries, as the endophytic fungi confer a multitude of benefits to their host plant that improve competitive ability and performance such as growth promotion, abiotic stress tolerance, pest deterrence and increased host disease resistance. Biotic stress tolerance conferred by the production of bioprotective metabolites has a critical role in an industry context. While the known antimammalian and insecticidal toxins are well characterized due to their impact on livestock welfare, antimicrobial metabolites are less studied. Both pasture and turf grasses are challenged by many phytopathogenic diseases that result in significant economic losses and impact livestock health. Further investigations of Epichloë endophytes as natural biocontrol agents can be conducted on strains that are safe for animals. With the additional benefits of possessing host disease resistance, these strains would increase their commercial importance. Field reports have indicated that pasture grasses associated with Epichloë endophytes are superior in resisting fungal pathogens. However, only a few antifungal compounds have been identified and chemically characterized, and these from sexual (pathogenic) Epichloë species, rather than those utilized to enhance performance in turf and pasture industries. This review provides insight into the various strategies reported in identifying antifungal activity from Epichloë endophytes and, where described, the associated antifungal metabolites responsible for the activity.

Genomic and Metabolomic Insights into Secondary Metabolites of the Novel Bacillus halotolerans Hil4, an Endophyte with Promising Antagonistic Activity against Gray Mold and Plant Growth Promoting Potential

The endophytic bacterial strain Hil4 was isolated from leaves of the medicinal plant Hypericum hircinum. It exhibited antifungal activity against Botrytis cinerea and a plethora of plant growth promoting traits in vitro. Whole genome sequencing revealed that it belongs to Bacillus halotolerans and possesses numerous secondary metabolite biosynthetic gene clusters and genes involved in plant growth promotion, colonization, and plant defense elicitation. The Mojavensin cluster was present in the genome, making this strain novel among plant-associated B. halotolerans strains. Extracts of secreted agar-diffusible compounds from single culture secretome extracts and dual cultures with B. cinerea were bioactive and had the same antifungal pattern on TLC plates after bioautography. UHPLC-HRMS analysis of the single culture secretome extract putatively annotated the consecutively produced antimicrobial substances and ISR elicitors. The isolate also proved efficient in minimizing the severity of gray mold post-harvest disease on table grape berries, as well as cherry tomatoes. Finally, it positively influenced the growth of Arabidopsis thaliana Col-0 and Solanum lycopersicum var. Chondrokatsari Messinias after seed biopriming in vitro. Overall, these results indicate that the B. halotolerans strain Hil4 is a promising novel plant growth promoting and biocontrol agent, and can be used in future research for the development of biostimulants and/or biological control agents.

Evaluation of the Antibacterial Activity of Crude Extracts Obtained From Cultivation of Native Endophytic Fungi Belonging to a Tropical Montane Rainforest in Colombia

Bioactive secondary metabolite production from endophytic fungi has gained a recurring research focus in recent decades as these microorganisms represent an unexplored biological niche for their diverse biotechnological potential. Despite this focus, studies involving tropical endophytes remain scarce, particularly those isolated from medicinal plants of these ecosystems. In addition, the state of the art of the pharmaceutical industry has experienced stagnation in the past 30years, which has pushed pathogenic infections to get one step ahead, resulting in the development of resistance to existing treatments. Here, five fungal endophytes were isolated from the medicinal plant Otoba gracilipes (Myristicaceae), which corresponded to the genera Xylaria and Diaporthe, and screened to demonstrate the promissory potential of these microorganisms for producing bioactive secondary metabolites with broad-spectrum antibacterial activities. Thus, the evaluation of crude organic extracts obtained from the mycelia and exhaust medium allowed the elucidation of Xylaria sp. and Diaporthe endophytica potential toward providing crude extracellular extracts with promising bioactivities against reference strains of Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923), according to the determined half-maximum inhibitory concentration (IC₅₀) with values down to 3.91 and 10.50mg/ml against each pathogen, respectively. Follow-up studies provided insights into the polarity nature of bioactive compounds in the crude extracts through bioactivity guided fractionation using a polymeric resin absorbent alternative extraction procedure. In addition, evaluation of the co-culturing methods demonstrated how this strategy can enhance endophytes biosynthetic capacity and improve their antibacterial potential with a 10-fold decrease in the IC₅₀ values against both pathogens compared to the obtained values in the preliminary evaluations of Xylaria sp. and D. endophytica crude extracts. These results support the potential of Colombian native biodiversity to provide new approaches concerning the global emergence of antibiotics resistance and future production of undiscovered compounds different from the currently used antibiotics classes and simultaneously call for the value of preserving native habitats due to their promising ecosystemic applications in the biotechnological and pharmaceutical industries.

Genomic Analysis and Secondary Metabolites Production of the Endophytic Bacillus velezensis Bvel1: A Biocontrol Agent against Botrytis cinerea Causing Bunch Rot in Post-Harvest Table Grapes

Botrytis bunch rot caused by Botrytis cinerea is one of the most economically significant post-harvest diseases of grapes. In the present study, we showed that the bacterial strain Bvel1 is phylogenetically affiliated to Bacillus velezensis species. The strain Bvel1 and its secreted metabolites exerted an antifungal activity, under in vitro conditions, against B. cinerea. UHPLC-HRMS chemical analysis revealed that iturin A2, surfactin-C13 and -C15, oxydifficidin, bacillibactin, L-dihydroanticapsin, and azelaic acid were among the metabolites secreted by Bvel1. Treatment of wounded grape berries with Bacillus sp. Bvel1 cell culture was effective for controlling grey mold ingress and expansion in vivo. The effectiveness of this biological control agent was a function of the cell culture concentration of the antagonist applied, while preventive treatment proved to be more effective compared to curative. The strain Bvel1 exhibited an adequate colonization efficiency in wounded grapes. The whole-genome phylogeny, combined with ANI and dDDH analyses, provided compelling evidence that the strain Bvel1 should be taxonomically classified as Bacillus velezensis. Genome mining approaches showed that the strain Bvel1 harbors 13 antimicrobial biosynthetic gene clusters, including iturin A, fengycin, surfactin, bacilysin, difficidin, bacillaene, and bacillibactin. The results provide new insights into the understanding of the endophytic Bacillus velezensis Bvel1 biocontrol mechanism against post-harvest fungal pathogens, including bunch rot disease in grape berries.

Elicitation of Streptomyces lunalinharesii secondary metabolism through co-cultivation with Rhizoctonia solani

The concern regarding the emergence of phytopathogens strains which are resistant to conventional agrochemicals has given support to the search for alternatives on the use of chemical pesticides in agriculture. In this context, microorganisms are considered as promising sources of useful natural compounds and actinobacteria are particularly relevant since they are known to produce several bioactive metabolites. The objective of this work was to investigate the production of secondary metabolites with antifungal activity by a strain of the actinobacteria Streptomyces lunalinharesii (A54A) under axenic conditions and in co-cultivation with the phytopathogen Rhizoctonia solani. Tests to evaluate antifungal activity of the extracts indicated the presence of diffusable molecules capable of inhibiting the growth of R. solani produced by S. lunalinharesii, especially when in the presence of the fungus during fermentation. Metabolomic analyzes allowed the putative annotation of the bioactive compounds desferrioxamine E and anisomycin, in addition to the evaluation of the metabolic profile of the isolate when grown in axenic mode and in co-cultivation, while statistical analyzes enabled the comparison of such profiles and the identification of metabolites produced in greater relative quantities in the elicitation condition. Such methodologies provided the selection of unknown features with high bioactive potential for dereplication, and several metabolites of S. lunalinharesii possibly represent novel compounds.

Are bio-based and biodegradable microplastics impacting for blue mussel (Mytilus edulis)?

The substitution of petrochemical plastics by bio-based and biodegradable plastics are in need of an evaluation for the potential toxic impacts that they can have on marine wildlife. This study aims to assess the toxicological effects of polylactic acid microparticles at two concentrations, 10 and 100 μg/L, during 8 days on the blue mussel, Mytilus edulis. No significant oxidative stress (catalase, glutathione-S-transferase and superoxide dismutase activities), neurotoxicity (acetylcholinesterase), or immunotoxicity (lysosomal membrane stability and acid phosphatase activity) were detectable. The multivariate analysis of metabolomic data allowed us to differentiate the individuals according to the exposure. From the loading plot of OPLS-DA, 48 ions down-regulated in the individuals exposed to microplastics. They were identified based on HRMS data as glycerophospholipids.

Endophytic Bacteria Bacillus subtilis, Isolated from Zea mays, as Potential Biocontrol Agent against Botrytis cinerea

Simple Summary

Plant–microorganism associations date back more than 400 million years. Plants host microorganisms that establish many different relationships with them, some negative and others very positive for both organisms. A type of this relationship is established with microorganisms that live inside them, known as endophytic microorganisms; they can include bacteria, yeasts, and fungi. In this study, we isolate endophytic bacteria from maize plants, and we characterize them in order to check their potential for being used as biocontrol agents against Botrytis cinerea, one of the most important phytopathogenic fungi in the world. The endophytic bacteria showed this antagonistic effect during in vitro assay and also during in vivo assay in Phaseolus vulgaris. At the same time, they showed the capacity for promoting growth in Zea mays plants.

Abstract

Plant diseases are one of the main factors responsible for food loss in the world, and 20–40% of such loss is caused by pathogenic infections. Botrytis cinerea is the most widely studied necrotrophic phytopathogenic fungus. It is responsible for incalculable economic losses due to the large number of host plants affected. Today, B. cinerea is controlled mainly by synthetic fungicides whose frequent application increases risk of resistance, thus making them unsustainable in terms of the environment and human health. In the search for new alternatives for the biocontrol of this pathogen, the use of endophytic microorganisms and their metabolites has gained momentum in recent years. In this work, we isolated endophytic bacteria from Zea mays cultivated in Colombia. Several strains of Bacillus subtilis, isolated and characterized in this work, exhibited growth inhibition against B. cinerea of more than 40% in in vitro cultures. These strains were characterized by studying several of their biochemical properties, such as production of lipopeptides, potassium solubilization, proteolytic and amylolytic capacity, production of siderophores, biofilm assays, and so on. We also analyzed: (i) its capacity to promote maize growth (Zea mays) in vivo, and (ii) its capacity to biocontrol B. cinerea during in vivo infection in plants (Phaseolus vulgaris).

Advances in antibiotic drug discovery: reducing the barriers for antibiotic development

Antibiotic drug discovery has been an essential field of research since the early 1900s, but the threat from infectious bacteria has only increased over the decades because of the emergence of widespread multidrug resistance. In this review, we discuss the recent advances in natural product, computational and medicinal chemistry that have reinvigorated the field of antibiotic drug discovery while giving perspective on how easily, both in cost and in expertise, these methods can be implemented by other researchers with the goal of increasing the number of scientists contributing to this public health crisis.

New approaches for antituberculosis leads from Actinobacteria

Bioactive metabolites derived from the phylum Actinobacteria represent many of the existing antimicrobial drugs. Compared with other bacterial pathogens, direct preliminary screening by diffusion assays is a limiting factor against Mycobacterium tuberculosis (Mtb) and different methodologies have been used to improve the search for new molecules. However, the concern remains that most of the previously discovered molecules replicate by conventional procedures. The combination of multidisciplinary approaches with new technologies could advance the discovery of new leads against Mtb like considering the unexplored Actinobacteria jointly with selective and integrative procedures.

Role of symbiosis in the discovery of novel antibiotics

Antibiotic resistance has been an ongoing challenge that has emerged almost immediately after the initial discovery of antibiotics and requires the development of innovative new antibiotics and antibiotic combinations that can effectively mitigate the development of resistance. More than 35,000 people die each year from antibiotic resistant infections in just the United States. This signifies the importance of identifying other alternatives to antibiotics for which resistance has developed. Virtually, all currently used antibiotics can trace their genesis to soil derived bacteria and fungi. The bacteria and fungi involved in symbiosis is an area that still remains widely unexplored for the discovery and development of new antibiotics. This brief review focuses on the challenges and opportunities in the application of symbiotic microbes and also provides an interesting platform that links natural product chemistry with evolutionary biology and ecology.

Mining the Metabolome and the Agricultural and Pharmaceutical Potential of Sea Foam-Derived Fungi

Sea foam harbors a diverse range of fungal spores with biological and ecological relevance in marine environments. Fungi are known as the producers of secondary metabolites that are used in health and agricultural sectors, however the potentials of sea foam-derived fungi have remained unexplored. In this study, organic extracts of six foam-derived fungal isolates belonging to the genera Penicillium, Cladosporium, Emericellopsis and Plectosphaerella were investigated for their antimicrobial activity against plant and human pathogens and anticancer activity. In parallel, an untargeted metabolomics study using UPLC-QToF–MS/MS-based molecular networking (MN) was performed to unlock their chemical inventory. Penicillium strains were identified as the most prolific producers of compounds with an average of 165 parent ions per strain. In total, 49 known mycotoxins and functional metabolites were annotated to specific and ubiquitous parent ions, revealing considerable chemical diversity. This allowed the identification of putative new derivatives, such as a new analog of the antimicrobial tetrapeptide, fungisporin. Regarding bioactivity, the Penicillium sp. isolate 31.68F1B showed a strong and broad-spectrum activity against seven plant and human pathogens, with the phytopathogen Magnaporthe oryzae and the human pathogen Candida albicans being the most susceptible (IC₅₀ values 2.2 and 6.3 µg/mL, respectively). This is the first study mining the metabolome of the sea foam-derived fungi by MS/MS-based molecular networking, and assessing their biological activities against phytopathogens.

Design of Fungal Co-Cultivation Based on Comparative Metabolomics and Bioactivity for Discovery of Marine Fungal Agrochemicals

Microbial co-cultivation is employed for awakening silent biosynthetic gene clusters (BGCs) to enhance chemical diversity. However, the selection of appropriate partners for co-cultivation remains a challenge. Furthermore, competitive interactions involving the suppression of BGCs or upregulation of known, functional metabolite(s) during co-cultivation efforts is also common. Herein, we performed an alternative approach for targeted selection of the best co-cultivation pair. Eight marine sediment-derived fungi were classified as strong or weak, based on their anti-phytopathogenic potency. The fungi were co-cultured systematically and analyzed for their chemical profiles and anti-phytopathogenic activity. Based on enhanced bioactivity and a significantly different metabolite profile including the appearance of a co-culture specific cluster, the co-culture of Plenodomus influorescens (strong) and Pyrenochaeta nobilis (weak) was prioritized for chemical investigation. Large-scale co-cultivation resulted in isolation of five polyketide type compounds: two 12-membered macrolides, dendrodolide E (1) and its new analog dendrodolide N (2), as well as two rare azaphilones spiciferinone (3) and its new analog 8a-hydroxy-spiciferinone (4). A well-known bis-naphtho-γ-pyrone type mycotoxin, cephalochromin (5), whose production was specifically enhanced in the co-culture, was also isolated. Chemical structures of compounds 1-5 were elucidated by NMR, HRMS and [] analyses. Compound 5 showed the strongest anti-phytopathogenic activity against Xanthomonas campestris and Phytophthora infestans with IC₅₀ values of 0.9 and 1.7 µg/mL, respectively.

Expanding the chemical diversity through microorganisms co-culture: Current status and outlook

Natural products (NPs) are considered as a cornerstone for the generation of bioactive leads in drug discovery programs. However, one of the major limitations of NP drug discovery program is "rediscovery" of known compounds, thereby hindering the rate of drug discovery efficiency. Therefore, in recent years, to overcome these limitations, a great deal of attention has been drawn towards understanding the role of microorganisms' co-culture in inducing novel chemical entities. Such induction could be related to activation of genes which might be silent or expressed at very low levels (below detection limit) in pure-strain cultures under normal laboratory conditions. In this review, chemical diversity of compounds isolated from microbial co-cultures, is discussed. For this purpose, chemodiversity has been represented as a chemical-structure network based on the "Tanimoto Structural Similarity Index". This highlights the huge structural diversity induced by microbial co-culture. In addition, the current trends in microbial co-culture research are highlighted. Finally, the current challenges (1 - induction monitoring, 2 - reproducibility, 3 - growth time effect and 4 - up-scaling for isolation purposes) are discussed. The information in this review will support researchers to design microbial co-culture strategies for future research efforts. In addition, guidelines for co-culture induction reporting are also provided to strengthen future reporting in this NP field.

Extractable impurities from fluoropolymer-based membrane filters - interference in high-throughput, untargeted analysis

The removal of particles using fluoropolymer-based membrane filters is usually done so to prolong the life span of an analytical column, prevent hardware damage, and reduce signal suppression. Ironically, these membrane filters tend to leach impurities into the samples as the samples are filtered through them. These impurities have the potential to affect the researcher's interpretation in high-throughput, non-targeted analysis. In this study, extractable impurities from different brands of fluoropolymer-based membrane filters present in the filtrate filtered using the said filters were investigated. The results demonstrated that different brand membrane filters and materials tend to elute vastly different numbers of impurities. There were instances whereby the extractable impurities persisted in both the membrane filter and the filtrate despite the filter being pre-conditioned (up to 3 times). Principle component analysis revealed that filtrates at different purge intervals are distant from the unfiltered samples. Pre-conditioning of the PTFE membrane filters could potentially reduce the number of extractable impurities across the tested brands. PVDF filtrates, however, tend to co-cluster with their respective brands, thus suggesting that dissimilarity persists in brands following conditioning. As such, pre-conditioning of the PTFE membrane filters should be encouraged so as to reduce false positive results, while the use of PVDF membrane filters for mass-spectrometry-based untargeted analysis is not advisable as extractable impurities would still persist after 3 rounds of conditioning. Neither the use of different filter brands, nor the use of different filter materials in a sample batch are encouraged as different membrane materials or brands could potentially elute varying impurities.

From genomics to metabolomics, moving toward an integrated strategy for the discovery of fungal secondary metabolites

Fungal secondary metabolites are defined by bioactive properties that ensure adaptation of the fungus to its environment. Although some of these natural products are promising sources of new lead compounds especially for the pharmaceutical industry, others pose risks to human and animal health. The identification of secondary metabolites is critical to assessing both the utility and risks of these compounds. Since fungi present biological specificities different from other microorganisms, this review covers the different strategies specifically used in fungal studies to perform this critical identification. Strategies focused on the direct detection of the secondary metabolites are firstly reported. Particularly, advances in high-throughput untargeted metabolomics have led to the generation of large datasets whose exploitation and interpretation generally require bioinformatics tools. Then, the genome-based methods used to study the entire fungal metabolic potential are reported. Transcriptomic and proteomic tools used in the discovery of fungal secondary metabolites are presented as links between genomic methods and metabolomic experiments. Finally, the influence of the culture environment on the synthesis of secondary metabolites by fungi is highlighted as a major factor to consider in research on fungal secondary metabolites. Through this review, we seek to emphasize that the discovery of natural products should integrate all of these valuable tools. Attention is also drawn to emerging technologies that will certainly revolutionize fungal research and to the use of computational tools that are necessary but whose results should be interpreted carefully.

Restoring the Taxol biosynthetic machinery of Aspergillus terreus by Podocarpus gracilior Pilger microbiome, with retrieving the ribosome biogenesis proteins of WD40 superfamily

Attenuating the Taxol yield of Aspergillus terreus with the subculturing and storage were the technical challenges that prevent this fungus to be a novel platform for industrial Taxol production. Thus, the objective of this study was to unravel the metabolic machineries of A. terreus associated with attenuation of Taxol productivity, and their restoring potency upon cocultivation with the Podocarpus gracilior microbiome. The Taxol yield of A. terreus was drastically reduced with the fungal subculturing. At the 10th subculture, the yield of Taxol was reduced by four folds (78.2 µg/l) comparing to the original culture (268 µg/l), as authenticated from silencing of molecular expression of the Taxol-rate limiting enzymes (GGPPS, TDS, DBAT and BAPT) by qPCR analyses. The visual fading of A. terreus conidial pigmentation with the subculturing, revealing the biosynthetic correlation of melanin and Taxol. The level of intracellular acetyl-CoA influx was reduced sequentially with the fungal subculturing, rationalizing the decreasing on Taxol and melanin yields. Fascinatingly, the Taxol biosynthetic machinery and cellular acetyl-CoA of A. terreus have been completely restored upon addition of 3% surface sterilized leaves of P. gracilior, suggesting the implantation of plant microbiome on re-triggering the molecular machinery of Taxol biosynthesis, their transcriptional factors, and/or increasing the influx of Acetyl-CoA. The expression of the proteins of 74.4, 68.2, 37.1 kDa were exponentially suppressed with A. terreus subculturing, and strongly restored upon addition of P. gracilior leaves, ensuring their profoundly correlation with the molecular expression of Taxol biosynthetic genes. From the proteomic analysis, the restored proteins 74.4 kDa of A. terreus upon addition of P. gracilior leaves were annotated as ribosome biogenesis proteins YTM and microtubule-assembly proteins that belong to WD40 superfamily. Thus, further ongoing studies for molecular cloning and expression of these genes with strong promotors in A. terreus, have been initiated, to construct a novel platform of metabolically stable A. terreus for sustainable Taxol production. Attenuating the Taxol yield of A. terreus with the multiple-culturing and storage might be due to the reduction on main influx of acetyl-CoA, or downregulation of ribosome biogenesis proteins that belong to WD40 protein superfamily.

Co-Culture Systems for the Production of Secondary Metabolites: Current and Future Prospects

Microorganisms are the great sources of Natural Products (NPs); these are imperative to their survival apart from conferring competitiveness amongst each other within their environmental niches. Primary and secondary metabolites are the two major classes of NPs that help in cell development, where antimicrobial activity is closely linked with secondary metabolites. To capitalize on the effects of secondary metabolites, co-culture methods have been often used to develop an artificial microbial community that promotes the action of these metabolites. Different analytical techniques will subsequently be employed based on the metabolite specificity and sensitivity to further enhance the metabolite induction. Liquid Chromatography-Mass Spectrometry (LC-MS) and Gas Chromatography (GC)-MS are commonly used for metabolite separation while Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS) have been used as tools to elucidate the structure of compounds. This review intends to discuss current systems in use for co-culture in addition to its advantages, with discourse into the investigation of specific techniques in use for the detailed study of secondary metabolites. Further advancements and focus on co-culture technologies are required to fully realize the massive potential in synthetic biological systems.

Using UHPLC-MS Profiling for the Discovery of New Dihydro-β-Agarofurans from Australian Celastraceae Plant Extracts

An analytical method using UHPLC-MS was developed and applied to 16 crude CH₂Cl₂ extracts from Australian Celastraceae plants; the endemic plant materials were accessed from Griffith University’s NatureBank resource and included bark, fruit, leaf, root, twig and mixed samples, all of which were collected from Queensland, Australia. The generated UHPLC-MS data were analysed and dereplicated using the scientific databases Dictionary of Natural Products and SciFinder Scholar in order to potentially identify new dihydro-β-agarofurans from local Celastraceae plants. These investigations led to the large-scale extraction and isolation work on a prioritised fruit sample that belonged to the rainforest plant Denhamia celastroides. Chemical investigations resulted in the purification of four new natural products, denhaminols O–R (1–4), along with the related and known compound, denhaminol G (5). The structures of all the new compounds were determined via detailed analysis of NMR and MS data.

Mapping the Fungal Battlefield: Using in situ Chemistry and Deletion Mutants to Monitor Interspecific Chemical Interactions Between Fungi

Fungi grow in competitive environments, and to cope, they have evolved strategies, such as the ability to produce a wide range of secondary metabolites. This begs two related questions. First, how do secondary metabolites influence fungal ecology and interspecific interactions? Second, can these interspecific interactions provide a way to “see” how fungi respond, chemically, within a competitive environment? To evaluate these, and to gain insight into the secondary metabolic arsenal fungi possess, we co-cultured Aspergillus fischeri, a genetically tractable fungus that produces a suite of mycotoxins, with Xylaria cubensis, a fungus that produces the fungistatic compound and FDA-approved drug, griseofulvin. To monitor and characterize fungal chemistry in situ, we used the droplet-liquid microjunction-surface sampling probe (droplet probe). The droplet probe makes a microextraction at defined locations on the surface of the co-culture, followed by analysis of the secondary metabolite profile via liquid chromatography-mass spectrometry. Using this, we mapped and compared the spatial profiles of secondary metabolites from both fungi in monoculture versus co-culture. X. cubensis predominantly biosynthesized griseofulvin and dechlorogriseofulvin in monoculture. In contrast, under co-culture conditions a deadlock was formed between the two fungi, and X. cubensis biosynthesized the same two secondary metabolites, along with dechloro-5′-hydroxygriseofulvin and 5′-hydroxygriseofulvin, all of which have fungistatic properties, as well as mycotoxins like cytochalasin D and cytochalasin C. In contrast, in co-culture, A. fischeri increased the production of the mycotoxins fumitremorgin B and verruculogen, but otherwise remained unchanged relative to its monoculture. To evaluate that secondary metabolites play an important role in defense and territory establishment, we co-cultured A. fischeri lacking the master regulator of secondary metabolism laeA with X. cubensis. We found that the reduced secondary metabolite biosynthesis of the ΔlaeA strain of A. fischeri eliminated the organism’s ability to compete in co-culture and led to its displacement by X. cubensis. These results demonstrate the potential of in situ chemical analysis and deletion mutant approaches for shedding light on the ecological roles of secondary metabolites and how they influence fungal ecological strategies; co-culturing may also stimulate the biosynthesis of secondary metabolites that are not produced in monoculture in the laboratory.

Plant Metabolomics: Evaluation of Different Extraction Parameters for Nontargeted UPLC-ESI-QTOF-Mass Spectrometry at the Example of White Asparagus officinalis

The extraction of metabolites turns out to be one of the most important key factors for nontargeted metabolomics approaches as this step can significantly affects the informative value of the successive measurements. Compared to metabolomics experiments of various matrices of bacterial or mammalian origins, there are only few studies, which focus on different extraction methods for plant metabolomics analyses. In this study, various solvent extraction compositions were compared and assessed using an UPLC-ESI-QTOF-MS strategy. Exemplary, white asparagus ( Asparagus officinalis) were employed as a low-fat-, low-protein-, high-water-content model commodity with the objective of designing an optimal nontargeted extraction protocol for polar and nonpolar metabolites. Furthermore, the influence of acid addition, mechanical cell disruption methods (ball mill, ultrasonic bath, vortex mixer), and extract stability have been systematically scrutinized too. The different extraction protocols were compared based on sum of features, sum of peak intensities, sum of peak areas, as well as by analyzing individual signals of as many different substance groups as possible to obtain a maximum overview.

A Class 1 Histone Deacetylase as Major Regulator of Secondary Metabolite Production in Aspergillus nidulans

An outstanding feature of filamentous fungi is their ability to produce a wide variety of small bioactive molecules that contribute to their survival, fitness, and pathogenicity. The vast collection of these so-called secondary metabolites (SMs) includes molecules that play a role in virulence, protect fungi from environmental damage, act as toxins or antibiotics that harm host tissues, or hinder microbial competitors for food sources. Many of these compounds are used in medical treatment; however, biosynthetic genes for the production of these natural products are arranged in compact clusters that are commonly silent under growth conditions routinely used in laboratories. Consequently, a wide arsenal of yet unknown fungal metabolites is waiting to be discovered. Here, we describe the effects of deletion of hosA, one of four classical histone deacetylase (HDAC) genes in Aspergillus nidulans; we show that HosA acts as a major regulator of SMs in Aspergillus with converse regulatory effects depending on the metabolite gene cluster examined. Co-inhibition of all classical enzymes by the pan HDAC inhibitor trichostatin A and the analysis of HDAC double mutants indicate that HosA is able to override known regulatory effects of other HDACs such as the class 2 type enzyme HdaA. Chromatin immunoprecipitation analysis revealed a direct correlation between hosA deletion, the acetylation status of H4 and the regulation of SM cluster genes, whereas H3 hyper-acetylation could not be detected in all the upregulated SM clusters examined. Our data suggest that HosA has inductive effects on SM production in addition to its classical role as a repressor via deacetylation of histones. Moreover, a genome wide transcriptome analysis revealed that in addition to SMs, expression of several other important protein categories such as enzymes of the carbohydrate metabolism or proteins involved in disease, virulence, and defense are significantly affected by the deletion of HosA.

Bacillus amyloliquefaciens induces production of a novel blennolide K in coculture of Setophoma terrestris

AIMS

The discovery of known bioactive chemical leads from microbial monocultures hinders the efficiency of drug discovery programmes. Therefore, in recent years, the use of fungal-bacterial coculture experiments has gained considerable attention due to their ability to generate new bioactive leads. In this work, fungal strain Setophoma terrestris was cocultured with Bacillus amyloliquifaciens to discover novel bioactive compounds.

MATERIALS AND METHODS

The bioactive methanolic coculture extract was chosen for the isolation of compounds by chromatographic methods. The isolated compounds were characterized by NMR and mass spectrometric techniques.

CONCLUSION

Coculture extract has resulted in the production of five blennolides. The novel compound, blennolide K was found active against PC-3 (prostate) and MCF-7 (breast) cell lines with an IC₅₀ value of 3·7 ± 0·6 and 4·8 ± 0·4 μmol l^-1 respectively. Furthermore, the nuclear morphology study in PC-3 cells after treatment with blennolide K, demonstrated chromatin condensation, formation of apoptotic bodies and shrinkage of cells.

SIGNIFICANCE AND IMPACT OF THE STUDY

To our knowledge, only few studies have reported the induction of bioactive compounds by coculture having long-distance inhibition morphology. This is principally due to the low occurrences of such morphology. Our study demonstrates the impact of coculture on production of new chemical leads in drug discovery programmes.

Self-resistance guided genome mining uncovers new topoisomerase inhibitors from myxobacteria

There is astounding discrepancy between the genome-inscribed production capacity and the set of known secondary metabolite classes from many microorganisms as detected under laboratory cultivation conditions. Genome-mining techniques are meant to fill this gap, but in order to favor discovery of structurally novel as well as bioactive compounds it is crucial to amend genomics-based strategies with selective filtering principles. In this study, we followed a self-resistance guided approach aiming at the discovery of inhibitors of topoisomerase, known as valid target in both cancer and antibiotic therapy. A common host self-defense mechanism against such inhibitors in bacteria is mediated by so-called pentapeptide repeat proteins (PRP). Genes encoding the biosynthetic machinery for production of an alleged topoisomerase inhibitor were found on the basis of their collocation adjacent to a predicted PRP in the genome of the myxobacterium Pyxidicoccus fallax An d48, but to date no matching compound has been reported from this bacterium. Activation of this peculiar polyketide synthase type-II gene cluster in the native host as well as its heterologous expression led to the structure elucidation of new natural products that were named pyxidicyclines and provided an insight into their biosynthesis. Subsequent topoisomerase inhibition assays showed strong affinity to - and inhibition of - unwinding topoisomerases such as E. coli topoisomerase IV and human topoisomerase I by pyxidicyclines as well as precise selectivity, since E. coli topoisomerase II (gyrase) was not inhibited at concentrations up to 50 μg ml-1.

Biotechnological potential of microbial consortia and future perspectives

Design of a microbial consortium is a newly emerging field that enables researchers to extend the frontiers of biotechnology from a pure culture to mixed cultures. A microbial consortium enables microbes to use a broad range of carbon sources. It provides microbes with robustness in response to environmental stress factors. Microbes in a consortium can perform complex functions that are impossible for a single organism. With advancement of technology, it is now possible to understand microbial interaction mechanism and construct consortia. Microbial consortia can be classified in terms of their construction, modes of interaction, and functions. Here we discuss different trends in the study of microbial functions and interactions, including single-cell genomics (SCG), microfluidics, fluorescent imaging, and membrane separation. Community profile studies using polymerase chain-reaction denaturing gradient gel electrophoresis (PCR-DGGE), amplified ribosomal DNA restriction analysis (ARDRA), and terminal restriction fragment-length polymorphism (T-RFLP) are also reviewed. We also provide a few examples of their possible applications in areas of biopolymers, bioenergy, biochemicals, and bioremediation.

Development of an analytical method for identification of Aspergillus flavus based on chemical markers using HPLC-MS

Aspergillus flavus is a filamentous fungus found in nature and characterized by the production of bright and colourful colonies. It grows on different substrates, producing secondary metabolites and, if present in foodstuffs, can be a source of health problems for humans and animals, as well as causing economic losses. Traditional methods for fungal identification are based on morphological characteristics, requiring specialists and being very time-consuming. The development of analytical alternatives might have advantages such as greater efficiency, more reproducibility and be less time-consuming. Thus, a qualitative analytical method to detect Aspergillus flavus in food samples, based on the identification of fungal chemical markers by HPLC-MS, was developed. The method comprises methanol extraction followed by HPLC-MS analysis, and was able to identify 14 fungus secondary metabolites, namely aflatoxin B1, aflatoxin G1, aspergillic acid, aspyrone, betaine, chrysogine, deacetyl parasiticolide A, flufuran, gregatin B, hydroxysydonic acid, nicotinic acid, phomaligin A, spinulosin and terrein.

Molecular inter-kingdom interactions of endophytes isolated from Lychnophora ericoides

The importance of microbial natural products has been widely demonstrated in the search for new antibiotics. However, the functional role of microbial metabolites in nature remains to be deciphered. Several natural products are known to mediate microbial interactions through metabolic exchange. One approach to investigate metabolic exchange in the laboratory is through microbial interactions. Here, we describe the chemical study of selected endophytes isolated from the Brazilian medicinal plant Lychnophora ericoides by pairwise inter-kingdom interactions in order to correlate the impact of co-cultivation to their metabolic profiles. Combining mass spectrometry tools and NMR analyses, a total of 29 compounds were identified. These compounds are members of polyene macrocycles, pyrroloindole alkaloids, angucyclines, and leupeptins chemical families. Two of the identified compounds correspond to a new fungal metabolite (29) and a new actinobacterial angucycline-derivative (23). Our results revealed a substantial arsenal of small molecules induced by microbial interactions, as we begin to unravel the complexity of microbial interactions associated with endophytic systems.

Metabolomic differential analysis of interspecific interactions among white rot fungi Trametes versicolor, Dichomitus squalens and Pleurotus ostreatus

Interspecific fungal antagonism occurred commonly in the interaction zone of different white rot fungi. This competitive interaction could markedly influence the metabolic pathway of intracellular metabolites, which was associated with the fungal morphology change and growth restriction. So far, it remains unknown on intracellular metabolite regulation during fungal competitive interaction. Herein, we performed the metabolomic analysis of the in vivo metabolite changes during competitive interaction between each two of the three white rot fungi Trametes versicolor, Pleurotus ostreatus and Dichomitus squalens and identified differential metabolites in the interaction zone compared to each two isolates. Many metabolites in the carnitine, lipid, ethylene and trehalose metabolic pathways were significantly up-regulated. These metabolic pathways are all involved in defensive response to abiotic and/or biotic stressful condition.

Symbiosis-inspired approaches to antibiotic discovery

Covering: 2010 up to 2017Life on Earth is characterized by a remarkable abundance of symbiotic and highly refined relationships among life forms. Defined as any kind of close, long-term association between two organisms, symbioses can be mutualistic, commensalistic or parasitic. Historically speaking, selective pressures have shaped symbioses in which one organism (typically a bacterium or fungus) generates bioactive small molecules that impact the host (and possibly other symbionts); the symbiosis is driven fundamentally by the genetic machineries available to the small molecule producer. The human microbiome is now integral to the most recent chapter in animal-microbe symbiosis studies and plant-microbe symbioses have significantly advanced our understanding of natural products biosynthesis; this also is the case for studies of fungal-microbe symbioses. However, much less is known about microbe-microbe systems involving interspecies interactions. Microbe-derived small molecules (i.e. antibiotics and quorum sensing molecules, etc.) have been shown to regulate transcription in microbes within the same environmental niche, suggesting interspecies interactions whereas, intraspecies interactions, such as those that exploit autoinducing small molecules, also modulate gene expression based on environmental cues. We, and others, contend that symbioses provide almost unlimited opportunities for the discovery of new bioactive compounds whose activities and applications have been evolutionarily optimized. Particularly intriguing is the possibility that environmental effectors can guide laboratory expression of secondary metabolites from "orphan", or silent, biosynthetic gene clusters (BGCs). Notably, many of the studies summarized here result from advances in "omics" technologies and highlight how symbioses have given rise to new anti-bacterial and antifungal natural products now being discovered.

Stable Isotope-Assisted Evaluation of Different Extraction Solvents for Untargeted Metabolomics of Plants

The evaluation of extraction protocols for untargeted metabolomics approaches is still difficult. We have applied a novel stable isotope-assisted workflow for untargeted LC-HRMS-based plant metabolomics , which allows for the first time every detected feature to be considered for method evaluation. The efficiency and complementarity of commonly used extraction solvents, namely 1 + 3 (v/v) mixtures of water and selected organic solvents (methanol, acetonitrile or methanol/acetonitrile 1 + 1 (v/v)), with and without the addition of 0.1% (v/v) formic acid were compared. Four different wheat organs were sampled, extracted and analysed by LC-HRMS. Data evaluation was performed with the in-house-developed MetExtract II software and R. With all tested solvents a total of 871 metabolites were extracted in ear, 785 in stem, 733 in leaf and 517 in root samples, respectively. Between 48% (stem) and 57% (ear) of the metabolites detected in a particular organ were found with all extraction mixtures, and 127 of 996 metabolites were consistently shared between all extraction agent/organ combinations. In aqueous methanol, acidification with formic acid led to pronounced pH dependency regarding the precision of metabolite abundance and the number of detectable metabolites, whereas extracts of acetonitrile-containing mixtures were less affected. Moreover, methanol and acetonitrile have been found to be complementary with respect to extraction efficiency. Interestingly, the beneficial properties of both solvents can be combined by the use of a water-methanol-acetonitrile mixture for global metabolite extraction instead of aqueous methanol or aqueous acetonitrile alone.