Antifungal Metabolites Research Articles

GC-MS analysis of antifungal metabolites secreted by two potent endophytes Enterobacter cloacae and Achromobacter xylosoxidans

GC-MS analysis of antifungal metabolites secreted by two potent endophytes Enterobacter cloacae and Achromobacter xylosoxidans

Antifungal activity of a methanolic extract of Glycyrrhiza uralensis Fisch. root against Fusarium oxysporum and Phytophthora capsici

In the present study, we investigated the antifungal activity of a methanolic extract of Glycyrrhiza uralensisFisch. root, which inhibited the growth of the plant pathogens Fusarium oxysporum and Phytophthora capsici. The EC50 values of the G. uralensis Fisch. extract three, six, and nine days after treatment were 113.4, 150.6, and 191.4 μg/ml for F. oxysporum and 84.7, 148.6, and 190.1 μg/ml for P. capsici, respectively, and the antifungal activity exhibited a dose-dependent response. The MIC value of G. uralensis Fisch. extract was found to be 100, 200, and 400 μg/ml at three, six, and nine days after treatment for F. oxysporum. In contrast, for P. capsici, the MIC value was 50, 100, and 100 μg/ml at three, six, and nine days after treatment. After three days of incubation with 400 μg/ml G. uralensis Fisch. extract, the hyphae of F. oxysporum exhibited abnormalities and atrophy, leading to mycelial collapse. In contrast, the hyphae of P. capsici displayed swelling with increased branching. These results furnish valuable insights into the antifungal metabolites present in G. uralensis Fisch. extract, contributing to the development of environmentally friendly products aimed at controlling the growth of pathogenic fungi.

Antagonistic Activity of Macrolepiota sp. CS185 against Post-Harvest Fungi of Fig Fruits (Ficus carica L.)

Macrolepiota sp. CS185 is a basidiomycete with high potential as a biocontrol agent against various phytopathogenic fungi. Regardless of its pronounced potential as a post-harvest fungi biocontrol agent, its activity in tomato seedlings infected with Alternaria alternata has not been well studied. Thus, the present work aimed to evaluate the cultures and supernatants’ antagonistic activity against fig fruits’ post-harvest fungi and antifungal activity production kinetics. The culture antagonistic characteristics were assessed through multiple confrontations, the supernatant concentration effect, and the kinetics of antagonistic action. The multiple confrontations showed differences (p ≤ 0.05) among phytopathogens and over time, with Colletotrichum sp. 2 being the most susceptible. Based on the 9-day incubation profile, the treatment fractions supplemented with a 50% concentration of Macrolepiota sp. CS185 supernatants showed a higher inhibition percentage (%In). Except for Alternaria alternata 1 and 2, the rest of the isolates showed a similar decrease in antagonistic activity up to a certain extent over time. Among all tested strains, Colletotrichum sp. 2 was found with a higher susceptibility. Regarding the production kinetics of antagonistic activity, a triple interaction was observed between the phytopathogen, the age of the Macrolepiota sp. CS 185 culture, and incubation time. In addition, changes in the mycelium growth rate (p ≤ 0.05) along with the higher activity in the supernatants of 20 and 30 days were observed and suggested the production of multiple bioactive metabolites. These results indicate that Macrolepiota sp. CS185 produces antifungal metabolites at different times and could be a suitable candidate to control fig fruits’ post-harvest fungi issues.

Design and evaluation of semicarbazide-embeddedd stationary phases for liquid chromatography

Semicarbazide, as a derivative of urea, constitutes a great variety of functional molecules for different needs. Herein, novel stationary phases with an incorporated semicarbazide group were proposed. Using aliphatic (docosanoyl, C22) and aromatic (benzoyl, Bz) hydrazides, the semicarbazide-embedded ligands were synthesized before chemical modification of the silica gel, allowing for an accurate interpretation of the chromatographic properties of the corresponding packings. The new stationary phases were water-wettable, due to the presence of highly polar groups. In particular, Bz-semicarbazide (Bz-SCD) stationary phase was sufficiently hydrophilic to run in hydrophilic interaction (HILIC) mode, whilst the C22 (C22-SCD) equivalent, in spite of its reversed-phase nature, was markedly less hydrophobic than the referenced polar-embedded ones. The versatility of C22-SCD was demonstrated with a large selection of analytes, including geometric isomers and standard mixtures of polycyclic aromatic hydrocarbons, sulfonamides, sulfonylurea, substituted ureas, pyridines and carbamates, fat-soluble colorants, antifungal metabolites, angiotensin II receptor blockers and calcium channel blockers.

ZnO-S.cerevisiae: An effective growth promoter of Astragalus memeranaceus and nano-antifungal agent against Fusarium oxysporum

Astragalus memeranaceus has been widely used in health, and root rot is a common disease in its cultivation, which is caused by Fusarium oxysporum. ZnO- Saccharomyces. cerevisiae was synthesized and its antifungal activity against F.oxysporum was investigated in vitro and in vivo for the first time. It can directly inhibit pathogens by down-regulating physiological genes. In the plant experiment, the disease severity decreased in the ZnO-S.cerevisiae treated A.memeranaceus. Additionally, ZnO-S.cerevisiae increased the content of chlorophyll and Astragaloside IV, and improved the growth of A.memeranaceus seedlings. Furthermore, by analysis of muti-omic, activity of antioxidant enzymes and molecular docking, the obtained ZnO-S.cerevisiae could activate the antioxidant enzymes, improve antifungal metabolites and induce resistance genes in A.memeranaceus, indicating higher resistance of plants under biotic stresses. The multifunctional ZnO-S.cerevisiae with superior antifungal activity provides a promising alternative to the traditional antifungal agents and has great potential in plant protection.

Evaluation of Bacillus isolates as a biological control agents against soilborne phytopathogenic fungi.

Pesticides, used in agriculture to control plant diseases, pose risks to the environment and human health. To address this, there's a growing focus on biocontrol, using microorganisms instead of chemicals. In this study, we aimed to identify Bacillus isolates as potential biological control agents. We tested 1574 Bacillus isolates for antifungal effects against pathogens like Botrytis cinerea, Fusarium solani, and Rhizoctonia solani. Out of these, 77 isolates formed inhibition zones against all three pathogens. We then investigated their lytic enzyme activities (protease, chitinase, and chitosanase) and the production of antifungal metabolites (siderophore and hydrogen cyanide). Coagulase activity was also examined to estimate potential pathogenicity in humans and animals. After evaluating all mechanisms, 19 non-pathogenic Bacillus isolates with significant antifungal effects were chosen. Molecular identification revealed they belonged to B. subtilis (n = 19) strains. The 19 native Bacillus strains, demonstrating strong antifungal effects in vitro, have the potential to form the basis for biocontrol product development. This could address challenges in agricultural production, marking a crucial stride toward sustainable agriculture.

Efficacy of ergosterol peroxide obtained from the endophytic fungus Acrophialophora jodhpurensis against Rhizoctonia solani.

To investigate antifungal activity of the extract and major metabolite of the endophytic fungus Acrophialophora jodhpurensis (belonging to Chaetomiaceae) against crown and root rot caused by Rhizoctonia solani (teleomorph: Thanatephorus cucumeris), as an important pathogen of tomato. The endophytic fungus A. jodhpurensis, has high inhibitory effect against R. solani AG4-HG II in vitro and in vivo. The media conditions were optimized for production of the endophyte's metabolites. The highest amounts of secondary metabolites were produced at pH 7, 30°C temperature, and in the presence of 0.5% glucose, 0.033% sodium nitrate, and 1 gl-1 asparagine as the best carbon, nitrogen, and amino acid sources, respectively. The mycelia were extracted by methanol and the obtained extract was submitted to various chromatography techniques. Phytochemical analysis via thin-layer chromatography (TLC) and nuclear magnetic resonance (NMR) spectroscopy showed that ergosterol peroxide was the major component in the extract of this endophyte. Antifungal activities of the methanolic extract and ergosterol peroxide in the culture media were studied against R. solani. Minimum inhibitory concentrations of the extract and ergosterol peroxide against the pathogen were 600 and 150µg ml-1, respectively. Ergosterol peroxide revealed destructive effects on the pathogen structures in microscopic analyses and induced sclerotia production. Histochemical analyses revealed that it induced apoptosis in the mycelia of R. solani via superoxide production and cell death. Application of ergosterol peroxide in the leaf disc assay reduced the disease severity in tomato leaves. Antifungal metabolites produced by A. jodhpurensis, such as ergosterol peroxide, are capable of controlling destructive Rhizoctonia diseases on tomato.

Genome-guided purification of high amounts of the siderophore ornibactin and detection of potentially novel burkholdine derivatives produced by Burkholderia catarinensis 89T.

The increased availability of genome sequences has enabled the development of valuable tools for the prediction and identification of bacterial natural products. Burkholderia catarinensis 89T produces siderophores and an unknown potent antifungal metabolite. The aim of this work was to identify and purify natural products of B. catarinensis 89T through a genome-guided approach. The analysis of B. catarinensis 89T genome revealed 16 clusters putatively related to secondary metabolism and antibiotics production. Of particular note was the identification of a nonribosomal peptide synthetase (NRPS) cluster related to the production of the siderophore ornibactin, a hybrid NRPS-polyketide synthase Type 1 cluster for the production of the antifungal glycolipopeptide burkholdine, and a gene cluster encoding homoserine lactones (HSL), probably involved in the regulation of both metabolites. We were able to purify high amounts of the ornibactin derivatives D/C6 and F/C8, while also detecting the derivative B/C4 in mass spectrometry investigations. A group of metabolites with molecular masses ranging from 1188 to 1272Da could be detected in MS experiments, which we postulate to be new burkholdine analogs produced by B. catarinensis. The comparison of B. catarinensis BGCs with other Bcc members corroborates the hypothesis that this bacterium could produce new derivatives of these metabolites. Moreover, the quorum sensing metabolites C6-HSL, C8-HSL, and 3OH-C8-HSL were observed in LC-MS/MS analysis. The new species B. catarinensis is a potential source of new bioactive secondary metabolites. Our results highlight the importance of genome-guided purification and identification of metabolites of biotechnological importance.

Improvement in Biocontrol Ability of Trichoderma Through Chemical Mutation and Gamma Irradiation for The Control of Soil Borne Pathogens

Biocontrol agent like Trichoderma viride was acclaimed as effective, eco-friendly and cheap, nullifying the ill effect of chemicals, These biocontrol agents are identified to act against on array of important soil borne plant pathogens viz.,Sclerotium rolfsii, Rhizoctonia bataticola and Fusarium oxysporum f. sp. ciceri etc.” Improvement in biocontrol ability of Trichoderma viride through mutation” was carried at Department of Plant Pathology, during 2019-2020. The antagonistic ability of a biocontrol agent was determined by its physiological state so that change in physiological or genetically conditions could alter the antagonism. Hence the genetic modification using mutagenesis offers the potential for producing improved bio-protection is likely to enhance their biocontrol capabilities against soil borne pathogen. Mutagenesis by chemical i.e. Ethyl Methyl Sulphonate (EMS) @ 100, 150, 200 and 250 µl/ml and time interval at 30, 45 and 60 minutes. The influence of gamma irradiation on improving production of antifungal metabolites and biological proficiency of the biocontrol agent against soil borne pathogen. Trichoderma viride were irradiated in different dose of gamma radiation (cobalt-60) @ 0, 20, 30, 40 and 50 k-rad. for induced mutation. Sixteen Trichoderma viride mutants were obtained after chemical mutagenesis and gamma irradiation and tested for their antagonistic activities in vitro. Morphological character of efficient mutants was tested up to six generation to check their stability. Among these, four stable mutants viz., TVME 2b, TVME 2c, TVME 3c and TVGM1 were proved as effective antagonists against Sclerotium rolfsii, Rhizoctonia bataticola and Fusarium oxysporum f.sp. ciceri basis of their maximum bioefficiency. Mutants TVME2b, TVME2c, TVME3c and TVGM1 exhibited the highest inhibition to mycelial growth of Sclerotium rolfsii with an inhibition percentage 64.76, 64.22, 63.08 and 62.93% respectively. Rhizoctonia bataticola was inhibited to the extent of 63.47, 60.87, 61.93 and 61.02% by relative mutants, while Fusarium oxysporum f. sp. ciceri was restricted and recorded 63.50, 62.88, 62.03 and 60.74% respectively. The highest chitinase enzyme units/mg of protein i.e. 0.64, 0.63, 0.63 and 0.62 was exerted in TVME2b, TVME2c, TVME3c and TVGM1 having respectively. However, TVME1c contains 0.37 enzyme units; it showed maximum ability against pathogens. hence present study proved that mutagenesis is the efficient tool for improving bioefficiency of Trichoderma viride, a biocontrol agent.

Proteomic and metabolomic analysis reveals that Amycolatopsis sp. BX17 synthesizes antifungal metabolites against Fusarium graminearum through the shikimate pathway

Soil-isolated Amycolatopsis sp. BX17 releases antifungal extracellular metabolites, capable of antagonizing the phytopathogenic fungus Fusarium graminearum and protecting maize plants from fungus colonization. A metabolomic analysis was performed to identify the extracellular metabolites produced by this strain. Also, a shot-gun proteomic analysis of axenic BX17 strain cultures was conducted using tandem mass spectrometry, and identified 1821 proteins of which 1039 were classified according to their biological function by KEGG. Results showed that central carbon metabolism, genetic information processing, environmental information processing, and amino acid metabolism were the most enriched pathways. Furthermore, an essential set of proteins was found related to the metabolism of terpenoids and polyketides. Overall, 20 compounds were found, and echinosporin identified in the global profile by MSE analysis. This evidence suggests that Amycolatopsis BX17 synthesize this antifungal molecule by converting of shikimate to chorismate. Our results advance our understanding of the mechanisms of bioactive compounds production in Amycolatopsis, and the metabolic machinery involved.

Alternaria brassicicola’ya karşı Trans-cinnamic Asit ve Xenorhabdus szentirmaii’nin Antifungal Metabolitlerinin Kullanım Potansiyellerinin Araştırılması

The, antifungal activities of trans-cinamic acid (TCA) and cell-free supernatant (CFS) of X. szentirmaii were evaluated against Alternaria brassicicola that cause Black spot disease. The results showed that TCA was more suppressive than CFS of X. szentirmaii in the control of A. brassicicola. In petri assays, the highest suppressive effect on spore germination was in TCA treatments compared to CFS of X. szentirmaii. Moreover, no germ tube elongation was observed in any of tested concentrations (0.25%, 0.50%, 1%, 2%) of TCA. The highest level of mycelial growth inhibitions (100% and 92%) were exhibited by TCA (2%) and TCA (1%), respectively. The curative and protective activity of TCA on disease severity of A. brassicicola were also evaluated on broccoli plants. In the curative activity assays, disease severities were 71.00%, 56.33% and 54.03% for control, TCA (1%) and TCA (2%), respectively. Whereas in the protective activity, TCA (2%) suppressed the disease severity significantly greater than TCA (1%). The disease severity of A. brassicicola after TCA application on broccoli plants was 25.21% and 17.37% for TCA (1%) and TCA (2%) respectively. Similar data were obtained in the efficacy of TCA on A. brassicicola. In the curative activity assays, TCA (1%) and TCA (2%) exhibited the efficacy with rates of 20.57% and 23.02%, respectively. However, TCA (2%) showed significantly higher efficacy than TCA (1%) in the protective activity. The current study provides that TCA has a great potential to suppress A. brassicicola and can be a good alternative to synthetic fungicides.

Revalorization of beer brewing waste as an antifungal ingredient for bread biopreservation

This study assesses the potential revalorization of beer bagasse (BB), an important food industry waste, as antifungal ingredient in bread, by lactic acid bacterial (LAB) fermentation of this food waste. Initially, in vitro studies of the metabolite and antifungal activity were performed for the preparation of a microbial culture medium for the LAB. The culture medium with a 20% BB was determined as the optimal for the bacterial growth. Therefore, bread was prepared with a 5% and 10% (w/w) of a dried powder of this fermented culture medium as ingredient. The fermentation and heat treatment during baking did not compromise the antifungal metabolites in the bread. In the trials of the augment of the shelf-life the bread with a 10% concentration of the ingredient extended the shelf life of the bread by a 1 day and 3 days against Aspergillus flavus and Penicillium commune, respectively, compared to a regular bred. When studying the mycotoxin production in the bread the addition of the ingredient at a 10% concentration resulted in an 86% reduction in aflatoxin concentration compared to the control bread. Moreover, this ingredient did not importantly deteriorate the technological parameters of the bread.

Study of the effect of bacteria of the genus <i>Pseudomonas</i> on the growth and toxin production of the fungus <i>Fusarium graminearum</i> <i>in vitro</i>

Aim. To study the potential of bacteria strains P. chlororaphis BZR 245‐F and Pseudomonas sp. BZR 523‐2 to inhibit the growth of Fusarium ear blight pathogens through the example of the fungus F. graminearum and to reduce the accumulation of deoxynivalenol (DON) and zearalenone (ZEN) in vitro. Materials and Methods. Antifungal metabolites of Pseudomonas bacteria were analysed by thin layer chromatography and bioautography. An experiment on the effect of liquid culture and supernatant of bacteria on the growth and toxin production of the fungus F. graminearum in vitro was carried out on wheat grain. Analysis of grain for mycotoxins was carried out by HPLC‐HRMS. Results. The ability of strains P. chlororaphis BZR 245‐F and Pseudomonas sp. BZR 523‐2 to produce antifungal metabolites was found, while inhibiting the growth of the fungus F. graminearum 60318 in vitro. The content of DON decreases both under the action of the liquid culture and supernatant of P. chlororaphis BZR 245‐F bacteria by 60 % and 70 %, respectively, and the liquid culture and supernatant of Pseudomonas sp. BZR 523‐2 bacteria by 75 % and 90 %, respectively. The accumulation of ZEN is also significantly suppressed under the influence of liquid cultures and supernatants of bacterial strains. The amount of ZEN decreases under the influence of liquid culture and supernatant of P. chlororaphis BZR 245‐F bacteria by 80 % and 95 %, respectively. Liquid culture and supernatant of Pseudomonas sp. BZR 523‐2 bacteria inhibited the accumulation of ZEN by 60 % and 84 %, respectively. Conclusion. The results obtained through the study of the effect of liquid cultures and supernatants of P. chlororaphis BZR 245‐F and Pseudomonas sp. BZR 523‐2 strains on the growth and toxin production of the fungus F. graminearum 60318 in vitro allow us to consider these strains as potential producers of effective biofungicides against toxin‐producing fungi. Further studies of these bacterial strains in vitro and in vivo on plants are needed.

Mass multiplication of native rhizospheric bacteria on cheaply available organic substrates and their plant growth promotion potentiality on cowpea

The intensive agricultural system results into considerable environmental damage and its inevitable effects on various environmental and ecological factors. Known for their role in the natural disease-suppressiveness of particular soil, Fluorescent pseudomonads are a genus of root-associated bacteria that may colonise the roots of agricultural plants and create antifungal metabolites, making them a viable alternative to the use of chemical fungicides. The successful application of Fluorescent pseudomonads as bioinoculants depends to a great extent on their capability to establish roots and to contend with indigenous microbiome in the rhizosphere. Because of various limitations, variations in the bio control agents are bound to occur in different agro-climatic regions, so it is advisable to choose native bio control agents. In the present investigation, a comprehensive effort was undertaken to check the growth of Pseudomonas aeruginosa (GP-8), which was found to be much lesser in aqueous extracts of cow dung, vermicompost and groundnut cake as compared to the growth of GP-8 (Pseudomonas aeruginosa) in nutrient broth media. The enrichment of Nitrogen and other supplementary nutrients may be required for the development of low cost indigenous media from cheaply available substrates for commercial mass production of Pseudomonas aeruginosa (GP-8) and also a field level screening trial was undertaken with efficient native Fluorescent pseudomonads solely or in consortia for improvement of plant health and management of soil borne pathogens as well as to develop a culture media with cheap and readily available substrate sources for mass production of Fluorescent pseudomonads strains. In the present study, it was found that shoot length and root length of native Fluorescent pseudomonads inoculated cowpea plants were significantly increased as compared with those of the control plants both at 30 and 60 days after sowing.

Glandular trichomes as a source of antifungal metabolites in a karyologically characterized population of Argyrochosma flava: Morphology and histochemistry

Argyrochosma, a xeric-adapted fern genus mostly from the New World, includes both farinose and non-farinose species. The yellow farina appears to be a synapomorphy of A. flava. The aims of this research were to study the morphology, location, distribution, and density of glandular trichomes; perform a histochemical analysis of the farina secretion; evaluate the biological activity of farinas against phytopathogenic fungi; and characterize the species genetically by making chromosome counts and building the karyotype of A. flava. Usual methods in plant anatomy and histochemistry were performed. Minimum Inhibitory Concentrations (MICs) and Minimum Fungicidal Concentrations (MFCs) of farina against four phytopathogenic fungi were determined by the broth microdilution technique. Chromosome counts and karyotyping metaphase plates were obtained from fiddleheads. The distribution of glandular trichomes in pinnules changes along the ontogenetic development of the frond. The histochemical study of the trichomes revealed the complex nature of the secreted material, including flavonoids and terpenes along with other metabolites. The farina was active against the four pathogenic fungi evaluated, with MICs between 31.25 and 125 μg/mL showing the highest inhibition for Monilinia fructicola. Botrytis cinerea displayed a MIC value of only one-fold dilutions more than the commercial fungicide Carbendazim. Cytogenetically, the base number proposed for the genus is x = 27, which is derived from aneuploidy of x = 29. The genus has diploid and tetraploid forms. The results obtained support the important role of glandular trichomes and farinous exudate secretion in the protection against phytopathogenic fungi. The obtained chromosome numbers support the taxonomic placement of A. flava.

Functional Characterization and Localization of Plant-Growth Promoting Bacteria Grown Under Stressful Conditions.

Various bacterial species are associated with plant roots. However, symbiotic and free-living plant growth-promoting bacteria (PGPB) can only help plants to grow and develop under normal and stressful conditions. Several biochemical and in vitro assays were previously designed to differentiate between the PGPB and other plant-associated bacterial strains. This chapter describes and summarizes some of these assays and proposes a strategy to screen for PGPB. To determine the involvement of the PGPB in abiotic stress tolerance, assays for the ability to produce 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, ammonium, gibberellic acid (GA), indole acetic acid (IAA), and microbial volatile organic compounds (mVOCs) are described in this chapter. Additionally, assays to show the capacity to solubilize micronutrients such as potassium, phosphorus, and zinc by bacteria were also summarized in this chapter. To determine the contribution of the PGPB in biotic stress tolerance in plants, Fe-siderophore, hydrogen cyanide, and antibiotic and antifungal metabolites production assays were described. Moreover, assays to investigate the growth-promotion activities of a bacterium strain on plants, using the gnotobiotic root elongation, in vitro, and pots assays, were explained. Finally, an assay for the localization of endophytic bacterium in plant tissues was also presented in this chapter. Although the assays described in this chapter can give evidence of the nature of the mechanism behind the PGPB actions, other unknown growth-promoting means are yet to decipher, and until then, new methodologies will be developed.

Antifeedant, Antifungal Cryptic Polyketides with Six Structural Frameworks from Tea Endophyte Daldinia eschscholtzii Propelled by the Antagonistic Coculture with Phytopathogen Colletotrichum pseudomajus and Different Culture Methods.

The antagonistic coculture with tea phytopathogen Colletotrichum pseudomajus induces antifungal cryptic metabolites from isogenesis endophyte Daldinia eschscholtzii against tea phytopathogens. Sixteen new polyketides with six structural frameworks including ten cryptic ones, named coldaldols A-C (1-3), collediol (5), and daldinrins A-L (10-20 and 23), were found from the coculture of C. pseudomajus and D. eschscholtzii by different culture methods. The unique framework of compounds 11 and 12 featured a benzopyran-C7 polyketone hybrid, and compounds 13-16 were characterized by the novel benzopyran dimer. The structures were determined mainly by spectroscopic methods, including extensive one-dimensional (1D), two-dimensional (2D) NMR, high resolution electrospray ionisation mass spectroscopy (HRESIMS), ECD calculation, and single-crystal X-ray diffraction. The configuration of acyclic compounds 5 and 18 were determined by application of the universal NMR database. Most compounds showed significant antifungal activities against the tea pathogens C. pseudomajus and Alternaria sp. with MICs of 1-8 μg/mL. Compound 12 had stronger antifungal activity than that of positive drug nystatin. The ether bond at C-4 of the benzopyran derivative increased the antifungal activity. Compounds 4-9 and 11-23 showed antifeedant activities against silkworms with feeding deterrence indices of 15-100% at the concentration of 50 μg/cm2.

Discovery of antifungal secondary metabolites from an intestinal fungus Fusarium sp.

Intestinal fungi, which are important parts of the gut microbiota, have the ability to produce specialized metabolites that significantly contribute to maintaining the balance of the gut microbiota and promoting the health of the host organism. In the present study, two new glycosides, including fusintespyrone A (1) and cerevisterolside A (4), as well as ten known compounds were isolated from the intestinal fungus Fusarium sp. LE06. The structures of the new compounds were elucidated by a combination of spectroscopic methods, such as mass spectrometry (MS) and nuclear magnetic resonance (NMR), along with chemical reactions and calculations of NMR and ECD spectra. Compounds 1-3 showed significant growth inhibition against Aspergillus fumigatus, Fusarium oxysporum, and Verticillium dahliae with MIC values in the range of 1.56-6.25 μg ml-1.

The Identity, Virulence, and Antifungal Effects of the Didymellacesous Fungi Associated with the Rapeseed Blackleg Pathogen Leptosphaeria biglobosa.

Eight fungal strains (P1 to P8) were isolated from rapeseed stems (Brassica napus) infected with the blackleg pathogen Leptosphaeria biglobosa (Lb). They formed pycnidia with similar morphology to those of Lb, and thus were considered as Lb relatives (LbRs). The species-level identification of these strains was performed. Their virulence on rapeseed and efficacy in the suppression of Lb infection were determined, and the biocontrol potential and biocontrol mechanisms of strain P2 were investigated. The results showed that the LbRs belong to two teleomorphic genera in the family Didymellaceae, Didymella for P1 to P7 and Boeremia for P8. Pathogenicity tests on rapeseed cotyledons and stems indicated the LbRs were weakly virulent compared to L. biglobosa. Co-inoculation assays on rapeseed cotyledons demonstrated that P1 to P7 (especially P1 to P4) had a suppressive effect on Lb infection, whereas P8 had a marginal effect on infection by L. biglobosa. Moreover, D. macrostoma P2 displayed a more aggressive behavior than L. biglobosa in the endophytic colonization of healthy rapeseed cotyledons. Cultures of P2 in potato dextrose broth (PDB) and pycnidiospore mucilages exuded from P2 pycnidia showed antifungal activity to L. biglobosa. Further leaf assays revealed that antifungal metabolites (AM) of strain P2 from PDB cultures effectively suppressed infection by L. biglobosa, Botrytis cinerea (gray mold), and Sclerotinia sclerotiorum (white mold). An antifungal metabolite, namely penicillither, was purified and identified from PDB cultures and detected in pycnidiospore mucilages of strain P2. This study suggests that the LbRs are a repertoire for screening biocontrol agents (BCAs) against rapeseed diseases, and D. macrostoma P2 is a multi-functional BCA, a penicillither producer, and an endophyte.

Antifungal Effect of Bacillus velezensis ZN-S10 against Plant Pathogen Colletotrichum changpingense and Its Inhibition Mechanism

In order to optimize crop production and mitigate the adverse impacts associated with the utilization of chemical agents, it is necessary to explore new biocontrol agents. Bacillus velezensis has been widely studied as a biocontrol agent because of its efficient and ecofriendly plant disease control mechanisms. This study shows that the strain ZN-S10 effectively reduces the area of leaf spots caused by the pathogen Colletotrichum changpingense ZAFU0163-1, which affects conidia production and germination, inhibits mycelium growth, and induces mycelium deformation. In antifungal experiments with crude extracts, we observed a delay in the cell cycle of conidia, which may be responsible for the inhibition of conidial germination. Among the bioactive metabolites detected through integrated LC-MS- and GC-MS-based untargeted metabolomics, 7-O-Succinyl macrolactin A, telocinobufagin, and surfactin A may be the main antifungal metabolites of strain ZN-S10. The presence of 7-O-Succinyl macrolactin A could explain the cell damage in germ tubes. This is the first report of telocinobufagin detected in B. velezensis. These results are significant for understanding the inhibitory mechanisms employed by B. velezensis and should serve as a reference in the production of biocontrol agents.