Yeasts volatile organic compounds (VOCs) as potential growth enhancers and molds biocontrol agents of mushrooms mycelia.

Volatile organic compounds (VOCs) produced by yeasts can positively affect crops, acting as antifungals or biostimulants. In this study, Aureobasidium pullulans and Metschnikowia pulcherrima were evaluated as potential antagonists of Trichoderma spp., common fungal pathogen in mushroom cultivation. To assess the biocontrol ability and biostimulant properties of the selected yeast species, in vitro co-culture and VOCs exposure assays were conducted. In both assays, VOCs produced by Aureobasidium spp. showed the stronger antifungal activity with a growth inhibition up to 30 %. This result was further confirmed by the higher volatilome alcohol content revealed by solid phase microextraction-gas chromatography mass spectrometry (SPME/GC-MS). Overall, Aureobasidium strains can be potentially used as biocontrol agent in Pleorotus ostreatus and Cyclocybe cylindracea mycelial growth, without affecting their development as demonstrated by VOCs exposure assay and Fourier-transform infrared spectroscopy (FT-IR). Conversely, M. pulcherrima was characterized by a lower or absent antifungal properties and by a volatilome composition rich in isobutyl acetate, an ester often recognized as plant growth promoter. As confirmed by FT-IR, Lentinula mycelia exposed to M. pulcherrima VOCs showed a higher content of proteins and lipids, suggesting an improvement of some biochemical properties. Our study emphasizes that VOCs produced by specific yeast strains are potentially powerful alternative to synthetic fungicide in the vegetative growth of mushroom-forming fungi and also able to modify their biochemical composition.

Identification and fungicides sensitivity evaluation of the causal agent of cobweb disease on Lyophyllum decastes in China.

BACKGROUND: Cobweb disease is a fungal disease that commonly affects the cultivation and production of edible mushrooms, leading to serious yield and economic losses. It is considered a major fungal disease in the realm of edible mushrooms. The symptoms of cobweb disease were found during the cultivation of Lyophyllum decastes. This study aimed to identify the causative pathogen of cobweb disease and evaluate effective fungicides, providing valuable insights for field control and management of L. decastes cobweb disease. RESULTS: The causal agent of cobweb disease was isolated from samples infected and identified as Cladobotryum mycophilum based on morphological and cultural characteristics, as well as multi-locus phylogeny analysis (ITS, RPB1, RPB2, and TEF1-α). Pathogenicity tests further confirmed C. mycophilum as the responsible pathogen for this condition. Among the selected fungicides, Prochloraz-manganese chloride complex, Trifloxystrobin, tebuconazole, and Difenoconazole exhibited significant inhibitory effects on the pathogen's mycelium, with EC50 values of 0.076 µg/mL, 0.173 µg/mL, and 0.364 µg/mL, respectively. These fungicides can serve as references for future field control of cobweb disease in L. decastes. CONCLUSION: This study is the first report of C. mycophilum as the causing agent of cobweb disease in L. decastes in China. Notably, Prochloraz-manganese chloride complex demonstrated the strongest inhibitory efficacy against C. mycophilum.

Biological Synthesis of Bioactive Gold Nanoparticles from Inonotus obliquus for Dual Chemo-Photothermal Effects against Human Brain Cancer Cells.

The possibility for an ecologically friendly and simple production of gold nanoparticles (AuNPs) with Chaga mushroom (Inonotus obliquus) (Ch-AuNPs) is presented in this study. Chaga extract's reducing potential was evaluated at varied concentrations and temperatures. The nanoparticles synthesized were all under 20 nm in size, as measured by TEM, which is a commendable result for a spontaneous synthesis method utilizing a biological source. The Ch-AuNPs showed anti-cancer chemotherapeutic effects on human brain cancer cells which is attributed to the biofunctionalization of the AuNPs with Chaga bioactive components during the synthesis process. Further, the photothermal ablation capability of the as-prepared gold nanoparticles on human brain cancer cells was investigated. It was found that the NIR-laser induced thermal ablation of cancer cells was effective in eliminating over 80% of the cells. This research projects the Ch-AuNPs as promising, dual modal (chemo-photothermal) therapeutic candidates for anti-cancer applications.

TcTI, a Kunitz-type trypsin inhibitor from cocoa associated with defense against pathogens.

Protease inhibitors (PIs) are important biotechnological tools of interest in agriculture. Usually they are the first proteins to be activated in plant-induced resistance against pathogens. Therefore, the aim of this study was to characterize a Theobroma cacao trypsin inhibitor called TcTI. The ORF has 740 bp encoding a protein with 219 amino acids, molecular weight of approximately 23 kDa. rTcTI was expressed in the soluble fraction of Escherichia coli strain Rosetta [DE3]. The purified His-Tag rTcTI showed inhibitory activity against commercial porcine trypsin. The kinetic model demonstrated that rTcTI is a competitive inhibitor, with a Ki value of 4.08 × 10-7 mol L-1. The thermostability analysis of rTcTI showed that 100% inhibitory activity was retained up to 60 °C and that at 70-80 °C, inhibitory activity remained above 50%. Circular dichroism analysis indicated that the protein is rich in loop structures and ß-conformations. Furthermore, in vivo assays against Helicoverpa armigera larvae were also performed with rTcTI in 0.1 mg mL-1 spray solutions on leaf surfaces, which reduced larval growth by 70% compared to the control treatment. Trials with cocoa plants infected with Mp showed a greater accumulation of TcTI in resistant varieties of T. cacao, so this regulation may be associated with different isoforms of TcTI. This inhibitor has biochemical characteristics suitable for biotechnological applications as well as in resistance studies of T. cacao and other crops.

Multimodal Molecular Imaging and Identification of Bacterial Toxins Causing Mushroom Soft Rot and Cavity Disease.

Soft rot disease of edible mushrooms leads to rapid degeneration of fungal tissue and thus severely affects farming productivity worldwide. The bacterial mushroom pathogen Burkholderia gladioli pv. agaricicola has been identified as the cause. Yet, little is known about the molecular basis of the infection, the spatial distribution and the biological role of antifungal agents and toxins involved in this infectious disease. We combine genome mining, metabolic profiling, MALDI-Imaging and UV Raman spectroscopy, to detect, identify and visualize a complex of chemical mediators and toxins produced by the pathogen during the infection process, including toxoflavin, caryoynencin, and sinapigladioside. Furthermore, targeted gene knockouts and in vitro assays link antifungal agents to prevalent symptoms of soft rot, mushroom browning, and impaired mycelium growth. Comparisons of related pathogenic, mutualistic and environmental Burkholderia spp. indicate that the arsenal of antifungal agents may have paved the way for ancestral bacteria to colonize niches where frequent, antagonistic interactions with fungi occur. Our findings not only demonstrate the power of label-free, in vivo detection of polyyne virulence factors by Raman imaging, but may also inspire new approaches to disease control.

Burkholderia perseverans sp. nov., a bacterium isolated from the Restinga ecosystem, is a producer of volatile and diffusible compounds that inhibit plant pathogens.

Gram-negative, aerobic, rod-shaped, non-spore-forming, motile bacteria, designated CBAS 719 T, CBAS 732 and CBAS 720 were isolated from leaf litter samples, collected in Espírito Santo State, Brazil, in 2008. Sequences of the 16S rRNA, gyrB, lepA and recA genes showed that these strains grouped with Burkholderia plantarii LMG 9035 T, Burkholderia gladioli LMG 2216 T and Burkholderia glumae LMG 2196 T in a clade of phytopathogenic Burkholderia species. Digital DNA-DNA hybridization experiments and ANI analyses demonstrated that strain CBAS 719 T represents a novel species in this lineage that is very closely related with B. plantarii. The genome sequence of the type strain is 7.57 Mbp and its G + C content is 69.01 mol%. The absence of growth on TSA medium supplemented with 3% (w/v) NaCl, citrate assimilation, ß-galactosidase (PNPG) activity, and of lipase C14 activity differentiated strain CBAS 719 T from B. plantarii LMG 9035 T, its nearest phylogenetic neighbor. Its predominant fatty acid components were C16:0, C18:1 ω7c, cyclo-C17:0 and summed feature 3 (C16:1 ω7c and/or C15:0 iso 2-OH). Based on these genotypic and phenotypic characteristics, the strains CBAS 719 T, CBAS 732 and CBAS 720 are classified in a novel Burkholderia species, for which the name Burkholderia perseverans sp. nov. is proposed. The type strain is CBAS 719 T (= LMG 31557 T = INN12T).

Morin Induces Melanogenesis via Activation of MAPK Signaling Pathways in B16F10 Mouse Melanoma Cells.

Morin is a well-known flavonoid, and has been reported to have various properties, such as anti-cell death, antioxidant, and anti-inflammatory properties. Although studies on the biochemical and biological actions of morin have been reported, the melanin biosynthesis effects and molecular mechanisms are unknown. In this study, we first found that morin has the effect of enhancing melanin biosynthesis in B16F10 mouse melanoma cells, and analyzed the molecular mechanism. In this study, we examined the effects of morin on the melanin contents and tyrosinase activity, as well as the protein expression levels of the melanogenic enzymes TRP-1, TRP-2, and microphtalmia-associated transcription factor (MITF) in B16F10 mouse melanoma cells. Morin showed no cytotoxicity in the concentration range of 5-100 µM, and significantly increased the intracellular tyrosinase activity and melanin contents. In mechanism analysis, morin increased the protein expression of TRP-1, TRP-2, and MITF associated with melanogenesis. Furthermore, morin increased phosphorylated ERK and p38 at the early time, and decreased phosphorylated ERK after 12 h. The results suggest that morin enhances melanin synthesis through the MAPK signaling pathways in B16F10 mouse melanoma cells.

Sugars in an aqueous extract of the spent substrate of the mushroom Hypsizygus marmoreus induce defense responses in rice.

Plant defense responses are activated by various exogenous stimuli. We found that an aqueous extract of spent mushroom substrate used for the cultivation of Hypsizygus marmoreus induced defense responses in rice. Fractionation of the spent mushroom substrate extract indicated that the compounds responsible for this induction were neutral and hydrophilic molecules with molecular weights lower than 3 kDa. Compounds with these characteristics, namely glucose, fructose, and sucrose, were detected in the extract at concentrations of 17.4, 3.3, and 1.6 mM, respectively, and the treatment of rice leaves with these sugars induced defense responses. Furthermore, microarray analysis indicated that the genes involved in defense responses were commonly activated by the treatment of leaves with spent mushroom substrate extract and glucose. These findings indicate that the induction of defense responses by treatment with spent mushroom substrate extract is, at least in part, attributable to the sugar constituents of the extract.

Simultaneous determination of spirodiclofen, spiromesifen, and spirotetramat and their relevant metabolites in edible fungi using ultra-performance liquid chromatography/tandem mass spectrometry.

A fast, sensitive, and reliable analytical method was developed and validated for simultaneous identification and quantification of spirodiclofen, spiromesifen, and spirotetramat and their relevant metabolites in edible fungi by ultra-performance liquid chromatography/tandem mass spectrometry (UHPLC-MS/MS). First, sample extraction was done with acetonitrile containing 1% formic acid followed by phase separation with the addition of MgSO4:NaOAc. Then, the supernatant was purified by primary secondary amine (PSA), octadecylsilane (C18), and graphitized carbon black (GCB). The linearities of the calibrations for all analytes were excellent (R2 ≥ 0.9953). Acceptable recoveries (74.5-106.4%) for all analytes were obtained with good intra- and inter- relative standard deviations of less than 14.5%. The limit of quantification (LOQs) for all analytes was 10 µg kg-1. For accurate quantification, matrix-matched calibration curve was applied to normalize the matrix effect. The results indicated that the method was suitable for detecting the three acaricides and their relevant metabolites in edible fungi.

Investigation on mycelial growth requirements of Cantharellus cibarius under laboratory conditions.

The golden chanterelle represents one of the commonly found, edible mushrooms that is highly valued in various cuisines. The present study focused on assessing the requirements of Cantharellus cibarius such as pH, temperature, as well as the carbon and nitrogen sources for mycelial growth. Optimization of the growth parameters was carried out by one-factor-at-a-time method. The optimal pH and temperature were determined to be 6.0 and 22.5 °C, respectively. Among the various carbon sources studied, sucrose at a concentration of 2% gave maximum mycelial growth and proved to be the most suitable one. Amongst the nitrogen sources studied, peptone, ammonium sulphate, and sodium nitrate, gave the maximum mycelial growth at an optimized concentration of 0.5%. In the presence of beef extract and yeast extract, a change in colony pigmentation from yellow to dark grey was observed. Finally, the carbon to nitrogen ratio of 2:0.5 proved to be optimal for mycelial growth. This study is the first report on the optimisation of in vitro growth requirements of C. cibarius.

Deleterious action of azadirachtin against the mutualistic fungus of leaf-cutting ants.

Leaf-cutting ants have a beneficial and obligatory relationship with the fungus that they grow. This mutualism allowed the evolutionary success of these ants. The great defoliation capacity of these insects, which often exceeds the level of tolerable economic damage, includes them as severe pests in many cultures. However, given the close relationship between these two agents of mutualism, it is expected that an impact on the fungus will reflect on the performance of the colony as a whole. Therefore, the effect of azadirachtin on the development, and the macronutrient composition of Leucoagaricus gongylophorus was evaluated. Azadirachtin reduced the final fungal mass at the end of treatment at all concentrations tested, but did not reduce the final growth area. A reduction in the amount of hyphae produced with increasing azadirachtin concentration was also observed. Regarding macronutrients, the compound did not affect their total amount in the fungus. Thus, it is observed that azadirachtin did not alter the composition of L. gongylophorus macronutrients, but inhibited its growth by reducing the number of hyphae produced. This reduction reflects directly on the amount of nutrients offered to the workers and the queen and may improve the management of these insects.

Biodegradation of atrazine and ligninolytic enzyme production by basidiomycete strains.

BACKGROUND: Atrazine is one of the most widespread chlorinated herbicides, leaving large bulks in soils and groundwater. The biodegradation of atrazine by bacteria is well described, but many aspects of the fungal metabolism of this compound remain unclear. Thus, we investigated the toxicity and degradation of atrazine by 13 rainforest basidiomycete strains. RESULTS: In liquid medium, Pluteus cubensis SXS320, Gloelophyllum striatum MCA7, and Agaricales MCA17 removed 30, 37, and 38%, respectively, of initial 25 mg L- 1 of the herbicide within 20 days. Deficiency of nitrogen drove atrazine degradation by Pluteus cubensis SXS320; this strain removed 30% of atrazine within 20 days in a culture medium with 2.5 mM of N, raising three metabolites; in a medium with 25 mM of N, only 21% of initial atrazine were removed after 40 days, and two metabolites appeared in culture extracts. This is the first report of such different outcomes linked to nitrogen availability during the biodegradation of atrazine by basidiomycetes. The herbicide also induced synthesis and secretion of extracellular laccases by Datronia caperata MCA5, Pycnoporus sanguineus MCA16, and Polyporus tenuiculus MCA11. Laccase levels produced by of P. tenuiculus MCA11 were 13.3-fold superior in the contaminated medium than in control; the possible role of this enzyme on atrazine biodegradation was evaluated, considering the strong induction and the removal of 13.9% of the herbicide in vivo. Although 88% of initial laccase activity remained after 6 h, no evidence of in vitro degradation was observed, even though ABTS was present as mediator. CONCLUSIONS: This study revealed a high potential for atrazine biodegradation among tropical basidiomycete strains. Further investigations, focusing on less explored ligninolytic enzymes and cell-bound mechanisms, could enlighten key aspects of the atrazine fungal metabolism and the role of the nitrogen in the process.

Indole alkaloid derivatives as building blocks of natural products from Bacillus thuringiensis and Bacillus velezensis and their antibacterial and antifungal activity study.

Six known indole alkaloid derivatives have been isolated for the first time from Bacillus thuringiensis and Bacillus velezensis strains, all of them as building blocks for the synthesis of larger natural products. Their structure was elucidated by a complete spectroscopy. Their biological activities were tested against some Gram-positive and Gram-negative bacteria and three phytopathogenic fungi which cause diseases in important crops, such as Moniliophthora roreri, the causal agent of cacao disease. The results indicated that some compounds had modest antibacterial activity; however, some of them had strong antifungal activity against the probed fungi. This antifungal activity of these compounds has not been reported.

Melatonin enhances the cadmium tolerance of mushrooms through antioxidant-related metabolites and enzymes.

Many wild mushroom species are known to immune heavy metals. However, the mechanism by which this occurs remains largely unsolved. Melatonin (MT) has been proven to play an important defensive role against various abiotic stresses in plants and animals. This study reports on the presence of MT in edible fungi and its role in the response to cadmium (Cd)-induced stress. We found that melatonin was widely distributed in all experimental species and could also relieve Cd-induced damage in the Volvariella volvacea. Comparative metabolic and proteome analyses reveal that tryptophan/proline/tyrosine metabolism, the citrate cycle, nitrogen and glutathione metabolism, and oxidation-reduction processes were enriched after Cd and/or MT addition, indicating an antioxidant mechanism was aroused. Finally, different MT and cadmium treatments were studied for their effects on the expression and activity of oxidation-related enzymes (superoxide dismutase, catalase, peroxidase, etc), which further verified the ameliorative influence of MT on Cd-induced oxidative stress.

Gloeostereum cimri, a novel shelf fungus isolated from a human pulmonary cyst.

Filamentous basidiomycetes are uncommon agents of human diseases, despite their ubiquitous presence in the environment. We present a case of symptomatic pulmonary infection in a 38-year-old male with cough and fever; a thin-walled cyst in the posterior left upper pulmonary lobe was revealed by radiography. A non-sporulating fungus was isolated from sputum and biopsy material from the cyst. ITS and LSU sequences placed the fungus phylogenetically in Agaricales, family Cyphellaceae, and identified it as a member of shelf fungi in Gloeostereum, but without identity to any known species. The new species is described as Gloeostereum cimri. The clinical strain showed high MIC to voriconazole (>8 µg/ml) but had low MIC to amphotericin B (0.5 µg/ml).

Evaluation of Phenolic Compound Toxicity Using a Bioluminescent Assay with the Fungus Gerronema viridilucens.

Basidiomycetes (phylum Basidiomycota) are filamentous fungi characterized by the exogenous formation of spores on a club-shaped cell called a basidium that are often formed on complex fruiting bodies (mushrooms). Many basidiomycetes serve an important role in recycling lignocellulosic material to higher trophic levels, and some show symbiotic relationships with plants. All known bioluminescent fungi are mushroom-forming basidiomycetes in the order Agaricales. Hence, the disruption of the basidiomycete community can entirely compromise the carbon cycle in nature from fungi to higher trophic levels. The fungus Gerronema viridilucens was used in the present study to investigate the toxicity of a phenolic compound series based on the inhibition of its bioluminescence. The median effect concentration (EC50) obtained from curves of bioluminescence inhibition versus log [phenolic compound] showed that 2,4,6-trichlorophenol was the most toxic compound in the series. The log EC50 values of all phenolic compounds were then used for the prediction of their toxicity. The univariate correlation of log EC50 values obtained from 6 different phenolic compounds was stronger with the dissociation constant (pKa ) than with 1-octanol/water partition coefficient (KOW ). Nevertheless, the toxicity can be better predicted by using both parameters, suggesting that the phenol-driven uncoupling of fungus mitochondrial adenosine triphosphate synthesis is the origin of phenolic compound toxicity to the test fungus. Environ Toxicol Chem 2020;39:1558-1565. © 2020 SETAC.

Biochemical characterization and inhibition of the alternative oxidase enzyme from the fungal phytopathogen Moniliophthora perniciosa.

Moniliophthora perniciosa is a fungal pathogen and causal agent of the witches' broom disease of cocoa, a threat to the chocolate industry and to the economic and social security in cocoa-planting countries. The membrane-bound enzyme alternative oxidase (MpAOX) is crucial for pathogen survival; however a lack of information on the biochemical properties of MpAOX hinders the development of novel fungicides. In this study, we purified and characterised recombinant MpAOX in dose-response assays with activators and inhibitors, followed by a kinetic characterization both in an aqueous environment and in physiologically-relevant proteoliposomes. We present structure-activity relationships of AOX inhibitors such as colletochlorin B and analogues which, aided by an MpAOX structural model, indicates key residues for protein-inhibitor interaction. We also discuss the importance of the correct hydrophobic environment for MpAOX enzymatic activity. We envisage that such results will guide the future development of AOX-targeting antifungal agents against M. perniciosa, an important outcome for the chocolate industry.

Exogenous l-ascorbic acid regulates the antioxidant system to increase the regeneration of damaged mycelia and induce the development of fruiting bodies in Hypsizygus marmoreus.

Hypsizygus marmoreus is an important commercial edible fungus, but the lack of basic studies on this fungus has hindered further development of its commercial value. In this study, we found that the treatment of damaged vegetative mycelia with 1 mM l-ascorbic acid (ASA) significantly increased the antioxidant enzyme activities (GPX, GR, CAT and SOD) and antioxidant contents (GSH and ASA) and reduced the ROS levels (H2O2 and O2-) in mechanically damaged mycelia. Additionally, this treatment increased mycelial biomass. At the reproductive stage, our results demonstrated that the treatment of damaged H. marmoreus mycelia with 2.24 mM ASA significantly increased the antioxidant enzyme activities (GPX, GR, GST, TRXR and CAT), endogenous ASA contents and GSH/GSSG ratios in different developmental stages and significantly decreased the MDA and H2O2 contents. Furthermore, this study showed that the expression levels of the antioxidant enzyme genes were consistent with the enzyme activities. Damaged mycelia treated with ASA regenerated 2-3 d earlier than the control group and showed significantly enhanced fruiting body production. These results suggested that exogenous ASA regulated mycelia intracellular ASA content to increase mycelial antioxidant abilities, induce the regeneration of damaged mycelia and regulate the development of fruiting bodies in H. marmoreus.

Dillapiole in Piper holtonii as an Inhibitor of the Symbiotic Fungus Leucoagaricus gongylophorus of Leaf-Cutting Ants.

Plants of the Piperaceae family are studied for their diverse secondary metabolism with a vast array of compounds that act as chemical defense agents against herbivores. Of all the agricultural pests, the management of insects is a highly significant challenge in the Neotropics, and ants of the Attini tribe pose a major problem. Due to their symbiotic association with the fungus Leucoagaricus gongylophorus (Möller) Singer (Agaricaceae), the species of Atta and Acromyrmex have exhaustive foraging activity which has intensified as deforestation and monoculture farming have increased. The control of leaf-cutting ants is still carried out with synthetic products with negative consequences to the environment and human health. In search for natural and sustainable alternatives to synthetic pesticides, Piper holtonii C. DC. was selected among other plant species after field observations of the foraging activity of Atta cephalotes, which revealed that P. holtonii was never chosen by ants. In vitro evaluation of an ethanol extract of the leaves of P. holtonii resulted in promising inhibitory activity (IC50 102 ppm) against L. gongylophorus. Subsequently, bioassay-guided fractionation led to the isolation of the phenylpropanoid dillapiole, which was also detected in the essential oil. This compound demonstrated inhibition of the fungus with an IC50 of 38 ppm. Considering the symbiotic relationship between the Attini ants and L. gongylophorus, the negative effect on the survival of one of the organisms will affect the survival of the other, so dillapiole or standardized essential oil extracts of P. holtonii containing this active principle could be a unique and useful source as a control agent for leaf cutting-ants.

Comprehensive profiling of the VOCs of Trichoderma longibrachiatum EF5 while interacting with Sclerotium rolfsii and Macrophomina phaseolina.

Trichoderma longibrachiatum EF5 is an endophytic fungal antagonist of rice. It is used for the control of soil-borne fungal pathogens-Sclerotium rolfsii and Macrophomina phaseolina. We demonstrate that T. longibrachiatum EF5 inhibits the growth of these pathogens on direct interaction as well as via the production of the microbial volatile organic compounds (mVOCs). The mVOCs reduced mycelial growth and inhibited the production of sclerotia by altering the mycelial structure. We profiled 138 mVOCs, when T. longibrachiatum EF5 interacted with the two pathogens. During these interactions, several compounds are up- or downregulated by T. longibrachiatum EF5, including longifolene, caryophyllene,1-Butanol 2-methyl, cedrene, and cuprenene. These compounds are involved in the biosynthetic pathways of the sesquiterpenoid and alkane, and the degradation pathway of trimethylamine. We provide an insight into the multiple modes by which T. longibrachiatum EF5 exerts antagonistic actions, such as hyperparasitism, competitions, and antibiosis via mVOCs. In contrast to their antimicrobial properties, these metabolites could also promote plant growth.