Metabolites from Lysobacter gummosus YMF3.00690 Against Meloidogyne javanica.

The strains in Lysobacter spp. have the potential to control plant-parasitic nematodes. In our experiment, L. gummosus YMF3.00690 showed antagonistic effects against plant root-knot nematode. Nine metabolites were isolated and identified from cultures of L. gummosus YMF3.00690, of which compound 1 was identified as a new metabolite tetrahydro-4,4,6-trimethyl-6-[(tetrahydro-6,6-dimethyl-2-oxo-4(1H)-pyrimidinylidene) methyl]-2(1H)-pyrimidinone. The activity assay showed that two compounds, 5-(hydroxymethyl)-1H-pyrrole-2-carbaldehyde (2) and 1H-pyrrole-2-carboxylic acid (3), had nematicidal activities against Meloidogyne javanica with mortalities of 69.93 and 90.54% at 400 ppm for 96 h, respectively. These two compounds were further tested for the inhibition activity of eggs hatching, and compound 3 showed a significant inhibition rate of 63.36% at 50 ppm for 48 h. In the chemotactic activity assay, three compounds (1 to 3) were found to have concentration-dependent chemotactic activity, of which compound 1 showed attractive activity. This experiment explored the active metabolites of L. gummosus YMF3.00690 against M. javanica and laid the foundation for biopesticide development.

DHXT1, a Virulence Factor of Dactylellina haptotyla, Regulates Pathogenicity by Participating in Trap Formation and Metabolite Synthesis.

The capsule-associated protein 10 gene (CAP10) is indispensable due to its involvement in pod formation and virulence maintenance in Cryptococcus neoformans. The function of the CAP10 gene in nematode-predatory fungi remains unreported. As a typical nematode-trapping fungus, Dactylellina haptotyla efficiently captures nematodes using adhesive knobs, which has potential applications in the biological control of plant-parasitic nematodes. In this study, we investigated the function of DHXT1 (a CAP10 homologous protein) in D. haptotyla-nematode interactions based on the disruption and overexpression of DHXT1, phenotypic analysis and metabolomic analysis. As a result, it was shown that the disruption of the DHXT1 gene causes a marked decrease in the number of adhesive knobs, and on the contrary, the overexpression of the DHXT1 gene causes a substantial increase in the number of adhesive knobs. Interestingly, the variety of metabolites increased with the disruption of the DHXT1 and decreased with the overexpression of the DHXT1 gene. The results suggest that DHXT1 effects pathogenicity through its involvement in adhesive knobs' formation and metabolite synthesis and serves as a key virulence factor in D. haptotyla.

Appressoria-Small but Incredibly Powerful Structures in Plant-Pathogen Interactions.

Plant-pathogenic fungi are responsible for many of the most severe crop diseases in the world and remain very challenging to control. Improving current protection strategies or designating new measures based on an overall understanding of molecular host-pathogen interaction mechanisms could be helpful for disease management. The attachment and penetration of the plant surface are the most important events among diverse plant-fungi interactions. Fungi evolved as small but incredibly powerful infection structure appressoria to facilitate attachment and penetration. Appressoria are indispensable for many diseases, such as rusts, powdery mildews, and blast diseases, as well as devastating oomycete diseases. Investigation into the formation of plant-pathogen appressoria contributes to improving the understanding of the molecular mechanisms of plant-pathogen interactions. Fungal host attachment is a vital step of fungal pathogenesis. Here, we review recent advances in the molecular mechanisms regulating the formation of appressoria. Additionally, some biocontrol agents were revealed to act on appressorium. The regulation of fungal adhesion during the infective process by acting on appressoria formation is expected to prevent the occurrence of crop disease caused by some pathogenic fungi.

Quassinoids from Twigs of Harrisonia perforata (Blanco) Merr and Their Anti-Parkinson's Disease Effect.

Six new C-20 and one new C-19 quassinoids, named perforalactones F-L (1-7), were isolated from twigs of Harrisonia perforata. Spectroscopic and X-ray crystallographic experiments were conducted to identify their structures. Through oxidative degradation of perforalactone B to perforaqussin A, the biogenetic process from C-25 quassinoid to C-20 via Baeyer-Villiger oxidation was proposed. Furthermore, the study evaluated the anti-Parkinson's disease potential of these C-20 quassinoids for the first time on 6-OHDA-induced PC12 cells and a Drosophila Parkinson's disease model of PINK1B9. Perforalactones G and I (2 and 4) showed a 10-15% increase in cell viability of the model cells at 50 µM, while compounds 2 and 4 (100 µM) significantly improved the climbing ability of PINK1B9 flies and increased the dopamine level in the brains and ATP content in the thoraces of the flies.

Advances in the Study of Metabolomics and Metabolites in Some Species Interactions.

In the natural environment, interactions between species are a common natural phenomena. The mechanisms of interaction between different species are mainly studied using genomic, transcriptomic, proteomic, and metabolomic techniques. Metabolomics is a crucial part of system biology and is based on precision instrument analysis. In the last decade, the emerging field of metabolomics has received extensive attention. Metabolomics not only provides a qualitative and quantitative method for studying the mechanisms of interactions between different species, but also helps clarify the mechanisms of defense between the host and pathogen, and to explore new metabolites with various biological activities. This review focuses on the methods and progress of interspecies metabolomics. Additionally, the prospects and challenges of interspecies metabolomics are discussed.

Vib-PT, an Aromatic Prenyltransferase Involved in the Biosynthesis of Vibralactone from Stereum vibrans.

Vibralactone, a hybrid compound derived from phenols and a prenyl group, is a strong pancreatic lipase inhibitor with a rare fused bicyclic ß-lactone skeleton. Recently, a researcher reported a vibralactone derivative (compound C1) that caused inhibition of pancreatic lipase with a half-maximal inhibitory concentration of 14 nM determined by structure-based optimization, suggesting a potential candidate as a new antiobesity treatment. In the present study, we sought to identify the main gene encoding prenyltransferase in Stereum vibrans, which is responsible for the prenylation of phenol leading to vibralactone synthesis. Two RNA silencing transformants of the identified gene (vib-PT) were obtained through Agrobacterium tumefaciens-mediated transformation. Compared to wild-type strains, the transformants showed a decrease in vib-PT expression ranging from 11.0 to 56.0% at 5, 10, and 15 days in reverse transcription-quantitative PCR analysis, along with a reduction in primary vibralactone production of 37 to 64% at 15 and 21 days, respectively, as determined using ultra-high-performance liquid chromatography-mass spectrometry analysis. A soluble and enzymatically active fusion Vib-PT protein was obtained by expressing vib-PT in Escherichia coli, and the enzyme's optimal reaction conditions and catalytic efficiency (Km /kcat) were determined. In vitro experiments established that Vib-PT catalyzed the C-prenylation at C-3 of 4-hydroxy-benzaldehyde and the O-prenylation at the 4-hydroxy of 4-hydroxy-benzenemethanol in the presence of dimethylallyl diphosphate. Moreover, Vib-PT shows promiscuity toward aromatic compounds and prenyl donors.IMPORTANCE Vibralactone is a lead compound with a novel skeleton structure that shows strong inhibitory activity against pancreatic lipase. Vibralactone is not encoded by the genome directly but rather is synthesized from phenol, followed by prenylation and other enzyme reactions. Here, we used an RNA silencing approach to identify and characterize a prenyltransferase in a basidiomycete species that is responsible for the synthesis of vibralactone. The identified gene, vib-PT, was expressed in Escherichia coli to obtain a soluble and enzymatically active fusion Vib-PT protein. In vitro characterization of the enzyme demonstrated the catalytic mechanism of prenylation and broad substrate range for different aromatic acceptors and prenyl donors. These characteristics highlight the possibility of Vib-PT to generate prenylated derivatives of aromatics and other compounds as improved bioactive agents or potential prodrugs.

Griseaketides A-D, New Aromatic Polyketides from the Pathogenic Fungus Magnaporthe grisea.

Magnaporthe grisea is the causal agent of rice blast disease, which is the most serious disease of cultivated rice. Aromatic polyketides are its typical metabolites and are involved in the infection process. In the search for novel lead compounds, chemical investigation of the fungus M. grisea M639 has led to the isolation of four new aromatic polyketides (salicylaldehyde skeleton bearing an unsaturated side chain), griseaketides A-D (1-4), as well as 15 known compounds (5-19). The structures of the new compounds were elucidated on the basis of extensive spectroscopic analyses, including HR-MS, 2D NMR. Compound 12 showed prominent activity that killed 94.5% of C. elegans at 400 ppm and 66.9% at 200 ppm over 24 h. This is the first report describing the nematicidal activity of this type aromatic polyketide.

[Two new lactone derivatives from an endophyte Diaporthe sp. XZ-07 cultivated on Camptotheca acuminata].

To study the secondary metabolites and their cytotoxic activities of an endophytic fungus Diaporthe sp. XZ-07cultivated on Camptotheca acuminata. Colum chromatography by RP-18, Sephadex LH-20 and silica gel was used to isolate and purify the chemical constituent. Two new compounds were isolatedand identified as 5-((E)-1,4,5-trihydroxyhex-2-enyl)furan-2(5H)-one(1)and(5Z)-5-(2,3,4,5-tetrahydroxyhexylidene)furan-2(5H)-one(2)by spectroscopic analysis. Cytotoxic activities were evaluated by MTT method. Compound 1 showed strong inhibitory activity against Human cervical carcinoma cell line Hela, and compound 2 showed strong inhibitory activity against breast cancer cell line MCF-7, Human neuroblastoma SH-SY5Y and Lewis lung carcinoma cells 3LL.

Pestalpolyols A-D, Cytotoxic Polyketides from Pestalotiopsis sp. cr013.

Four novel polyketides, named pestalpolyols A (1), B (2), C (3), and D (4), were isolated from solid fermentation products of Pestalotiopsis sp. cr013. Their structures were elucidated by extensive spectroscopic methods, including 1D and 2D nuclear magnetic resonance and high-resolution electrospray ionization mass spectrometry experiments, and the absolute configuration was confirmed by single-crystal X-ray diffraction analysis using the anomalous scattering of Cu Kα radiation. The inhibitory activities of compounds 1, 2, and 4 against five human tumor lines were tested in vitro, and showed IC50 values 2.3-31.2 µM.

Two new phenol derivatives from Stereum hirsutum FP-91666.

Two new phenol derivatives, 2-(3-methyl-2-buten-1-yl)-4-methoxyethyl-phenol (1) and 5-hydroxy-4-(hydroxymethyl)-2-(3-methylbut-2-en-1-yl)cyclohex-4-en-1-one (2), together with eight known compounds consisting of phenol derivatives (3 and 4), niacinamide (5), and five ergosta type compounds (6-10), were isolated from solid fermentation products of Stereum hirsutum FP-91666. Two new structures were elucidated by extensive spectroscopic methods, including 1D NMR and 2D NMR, and HR-EI-MS experiments.

Diterpenoids from the Endophytic Fungus Botryosphaeria sp. P483 of the Chinese Herbal Medicine Huperzia serrata.

Two new tetranorlabdane diterpenoids, named botryosphaerins G (1) and H (2), were isolated from the solid fermentation products of Botryosphaeria sp. P483 along with seven known tetranorlabdane diterpenes (3-9). Their structures were elucidated by extensive analysis, including 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). Their absolute configuration was confirmed by single-crystal X-ray diffraction analyses using the anomalous scattering of Cu Kα radiation. All of the isolated compounds were tested for activity against phytopathogenic fungi and nematodes. Compounds 2 and 3 showed antifungal activity and compound 2 showed weak nematicidal activity.

Cis-3-Indoleacrylic Acid: A Nematicidal Compound from Streptomyces youssoufiensis YMF3.862 as V-ATPase Inhibitor on Meloidogyne incognita.

The application of the bionematicides derived from microorganisms and their secondary metabolites represents a promising strategy for managing root-knot nematodes. In this study, a nematicidal compound, cis-3-indoleacrylic acid, was isolated from Streptomyces youssoufiensis YMF3.862. This compound caused Meloidogyne incognita juveniles to have swollen bodies with apparent cracks on the cuticle surface. The LC50 value of cis-3-indoleacrylic acid against juveniles was 16.31 µg/mL 24 h of post-treatment. Cis-3-indoleacrylic acid at 20 µg/mL significantly inhibited V-ATPase expression and remarkably decreased enzyme activity by 84.41%. As an inhibitor of V-ATPase, cis-3-indoleacrylic acid caused significant H+ accumulation in nematode bodies, resulting in lower intracellular pH values and higher extracellular pH values of M. incognita. Application of 50 µg/mL cis-3-indoleacrylic acid generated a 71.06% control efficiency against M. incognita on tomatoes. The combination results of this study indicated that cis-3-indoleacrylic acid can be developed as a natural nematicide for controlling M. incognita.

Secondary metabolites and their bioactivities from Paecilomyces gunnii YMF1.00003.

Four new polyketides (1-4) and seven known compounds (5-11) including three polyketides and four sterols were isolated from the fermented extracts of Paecilomyces gunnii YMF1.00003. The new chemical structures were determined through the analysis of the nuclear magnetic resonance and high-resolution electrospray ionization mass spectrometry, and their configurations were subsequently confirmed by nuclear overhauser effect spectroscopy, the calculated electronic circular dichroism (ECD) spectra, and quantum chemical calculations of the NMR data (qcc NMR). Based on the results of pre-activity screening and compound structure target prediction, certain metabolites were assayed to evaluate their cytotoxic and protein kinase Cα inhibitory activities. Results indicated that 3ß-hydroxy-7α-methoxy-5α,6α-epoxy-8(14),22E-dien-ergosta (8) exhibited potent cytotoxic activity, with half-maximal inhibitory concentration values of 3.00 ± 0.27 to 15.69 ± 0.61 µM against five tumor cells, respectively. The new compound gunniiol A (1) showed weak cytotoxic activity at a concentration of 40 µM. At a concentration of 20 µg/mL, compounds 1, 6, and 7 exhibited protein kinase Cα inhibition by 43.63, 40.93, and 57.66%, respectively. This study is the first to report steroids demonstrating good cytotoxicity and polyketides exhibiting inhibitory activity against protein kinase Cα from the extracts of P. gunnii.

PD-Like Pathogenesis in Caenorhabditis elegans Intestinally Infected with Nocardia farcinica and the Underlying Molecular Mechanisms.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the abnormal aggregation of α-synuclein (α-syn) and the loss of dopaminergic neurons. Although microbial infection has been implicated in the pathogenesis of PD, the associated virulence factors and the underlying molecular mechanisms require further elucidation. Here, we found that intestinal infection with Nocardia farcinica induced a series of PD-like symptoms in Caenorhabditis elegans, such as the accelerated degeneration of dopaminergic neurons, impaired locomotion capacity, and enhanced α-syn aggregation, through the disturbance of mitochondrial functions. To identify the potential virulence factors involved in these effects, we knocked out the nbtB/C and nbtS genes in N. farcinica, which are localized in the gene clusters responsible for nocobactin biosynthesis. The deletion of either gene partially rescued the degenerative effects of wild-type N. farcinica on dopaminergic neurons by attenuating mitochondrial dysfunction. LC-MS analysis further identified a decrease in the abundance of several siderophores in the two mutants, including nocobactin NA-a, nocobactin NA-b, and nocardimicin B. Collectively, our results demonstrated that intestinal N. farcinica infection in C. elegans facilitates PD-like pathogenesis and provides novel evidence for the involvement of pathogenic bacteria in neurodegenerative diseases via non-neuroinvasive mechanisms.

Intergenerational epigenetic inheritance mediated by MYS-2/MOF in the pathogenesis of Alzheimer's disease.

Although autosomal-dominant inheritance is believed an important cause of familial clustering Alzheimer's disease (FAD), it covers only a small proportion of FAD incidence, and so we investigated epigenetic memory as an alternative mechanism to contribute for intergenerational AD pathogenesis. Our data in vivo showed that mys-2 of Caenorhabditis elegans that encodes a putative MYST acetyltransferase responsible for H4K16 acetylation modulated AD occurrence. The phenotypic improvements in the parent generation caused by mys-2 disfunction were passed to their progeny due to epigenetic memory, which resulted in similar H4K16ac levels among the candidate target genes of MYS-2 and similar gene expression patterns of the AD-related pathways. Furthermore, the ROS/CDK-5/ATM pathway functioned as an upstream activator of MYS-2. Our study indicated that MYS-2/MOF could be inherited intergenerationally via epigenetic mechanisms in C. elegans and mammalian cell of AD model, providing a new insight into our understanding of the etiology and inheritance of FAD.

Exploring the nematicidal mechanisms and control efficiencies of oxalic acid producing Aspergillus tubingensis WF01 against root-knot nematodes.

Background and aims: Root-knot nematodes (RKN; Meloidogyne spp.) are among the highly prevalent and significantly detrimental pathogens that cause severe economic and yield losses in crops. Currently, control of RKN primarily relies on the application of chemical nematicides but it has environmental and public health concerns, which open new doors for alternative methods in the form of biological control. Methods: In this study, we investigated the nematicidal and attractive activities of an endophytic strain WF01 against Meloidogyne incognita in concentration-dependent experiments. The active nematicidal metabolite was extracted in the WF01 crude extract through the Sephadex column, and its structure was identified by nuclear magnetic resonance and mass spectrometry data. Results: The strain WF01 was identified as Aspergillus tubingensis based on morphological and molecular characteristics. The nematicidal and attractive metabolite of A. tubingensis WF01 was identified as oxalic acid (OA), which showed solid nematicidal activity against M. incognita, having LC50 of 27.48 µg ml-1. The Nsy-1 of AWC and Odr-7 of AWA were the primary neuron genes for Caenorhabditis elegans to detect OA. Under greenhouse, WF01 broth and 200 µg ml-1 OA could effectively suppress the disease caused by M. incognita on tomatoes respectively with control efficiency (CE) of 62.5% and 70.83%, and promote plant growth. In the field, WF01-WP and 8% OA-WP formulations showed moderate CEs of 51.25%-61.47% against RKN in tomato and tobacco. The combined application of WF01 and OA resulted in excellent CEs of 66.83% and 69.34% toward RKN in tomato and tobacco, respectively. Furthermore, the application of WF01 broth or OA significantly suppressed the infection of J2s in tomatoes by upregulating the expression levels of the genes (PAL, C4H, HCT, and F5H) related to lignin synthesis, and strengthened root lignification. Conclusion: Altogether, our results demonstrated that A. tubingensis WF01 exhibited multiple weapons to control RKN mediated by producing OA to lure and kill RKN in a concentration-dependent manner and strengthen root lignification. This fungus could serve as an environmental bio-nematicide for managing the diseases caused by RKN.

Secondary Metabolites from the Nematode-Trapping Fungus Dactylellina haptotyla YMF1.03409.

As a representative nematode-trapping fungus, Dactylellina haptotyla can capture and kill nematodes by producing traps, known as adhesive knobs. In this paper, the strain of D. haptotyla YMF1.03409 was studied by means of medium screening, fermentation, and purification and identification of crude extracts. Eighteen compounds were obtained from D. haptotyla YMF1.03409, including two new metabolites, nosporins C (1) and D (2). The known metabolites were identified to be 3-chloro-4-methoxybenzaldehyde (3), 3-chloro-4-methoxybenzoic acid (4), 2-chloro-1-methoxy-4-(methoxymethyl)benzene (5), 3-hydroxy-3-methyloxindole (6), nicotinic acid (7), succinic acid (8), 3,4-dihydroxybutanoic acid (9), 5'-O-methyladenosine (10), uridine (11), 2'-deoxyuridine (12), thymidine (13), 3-(phenylmethyl)-2,5-morpholinedione (14), methyl-ß-D-glucopyranoside (15), 1,2-benzenedicarboxylic acid bis(2-methyl heptyl) ester (16), ß-sitosterol (17), and 3ß,6α-diol-stigmastane (18). The bioactive assay showed that these compounds had no obvious nematicidal activity against the nematodes Meloidogyne incognita and Panagrellus redivivus.

The metabolite alpha-ketobutyrate extends lifespan by promoting peroxisomal function in C. elegans.

Metabolism is intimately linked to aging. There is a growing number of studies showing that endogenous metabolites may delay aging and improve healthspan. Through the analysis of existing transcriptome data, we discover a link between activation of the transsulfuration pathway and a transcriptional program involved in peroxisome function and biogenesis in long-lived glp-1(e2141ts) mutant Caenorhabditis elegans worms. Subsequently, we show that supplementation with α-ketobutyrate, an intermediate of the transsulfuration pathway, extends lifespan in wild-type worms. Alpha-ketobutyrate augments the production of NAD+ via the lactate dehydrogenase LDH-1, leading to SIR-2.1/SIRT1-mediated enhanced peroxisome function and biogenesis, along with a concomitant increase in the expression of acox-1.2/ACOX1 in the peroxisomal fatty acid ß-oxidation pathway. ACOX-1.2/ACOX1 promotes H2O2 formation, thereby resulting in activation of SKN-1/NRF2. This transcription factor in turn extends the lifespan of worms by driving expression of autophagic and lysosomal genes. Finally, we show that α-ketobutyrate also delays the cellular senescence in fibroblast cells through the SIRT1-ACOX1-H2O2-NRF2 pathway. This finding uncovers a previously unknown role for α-ketobutyrate in organismal lifespan and healthspan by coordinating the NAD+-SIRT1 signaling and peroxisomal function.

2-Furoic acid associated with the infection of nematodes by Dactylellina haptotyla and its biocontrol potential on plant root-knot nematodes.

Dactylellina haptotyla is a typical nematode-trapping fungus that has garnered the attention of many scholars for its highly effective lethal potential for nematodes. Secondary metabolites play an important role in D. haptotyla-nematode interactions, but which metabolites perform which function remains unclear. We report the metabolic functions based on high-quality, chromosome-level genome assembly of wild D. haptotyla YMF1.03409. The results indicate that a large variety of secondary metabolites and their biosynthetic genes were significantly upregulated during the nematode-trapping stage. In parallel, we identified that 2-furoic acid was specifically produced during nematode trapping by D. haptotyla YMF1.03409 and isolated it from fermentation production. 2-Furoic acid demonstrated strong nematicidal activity with an LD50 value of 55.05 µg/mL against Meloidogyne incognita at 48 h. Furthermore, the pot experiment showed that the number of galls of tomato root was significantly reduced in the experimental group treated with 2-furoic acid. The considerable increase in the 2-furoic acid content during the infection process and its virulent nematicidal activity revealed an essential synergistic effect during the process of nematode-trapping fungal infection. IMPORTANCE Dactylellina haptotyla have significant application potential in nematode biocontrol. In this study, we determined the chromosome-level genome sequence of D. haptotyla YMF1.03409 by long-read sequencing technology. Comparative genomic analysis identified a series of pathogenesis-related genes and revealed significant gene family contraction events during the evolution of D. haptotyla YMF1.03409. Combining transcriptomic and metabolomic data as well as in vitro activity test results, a compound with important application potential in nematode biocontrol, 2-furoic acid, was identified. Our result expanded the genetic resource of D. haptotyla and identified a previously unreported nematicidal small molecule, which provides new options for the development of plant biocontrol agents.

Ethanol mediates the interaction between Caenorhabditis elegans and the nematophagous fungus Purpureocillium lavendulum.

Accurately recognizing pathogens by the host is vital for initiating appropriate immune response against infecting microorganisms. Caenorhabditis elegans has no known receptor to recognize pathogen-associated molecular pattern. However, recent studies showed that nematodes have a strong specificity for transcriptomes infected by different pathogens, indicating that they can identify different pathogenic microorganisms. However, the mechanism(s) for such specificity remains largely unknown. In this study, we showed that the nematophagous fungus Purpureocillium lavendulum can infect the intestinal tract of the nematode C. elegans and the infection led to the accumulation of reactive oxygen species (ROS) in the infected intestinal tract, which suppressed fungal growth. Co-transcriptional analysis revealed that fungal genes related to anaerobic respiration and ethanol production were up-regulated during infection. Meanwhile, the ethanol dehydrogenase Sodh-1 in C. elegans was also up-regulated. Together, these results suggested that the infecting fungi encounter hypoxia stress in the nematode gut and that ethanol may play a role in the host-pathogen interaction. Ethanol production in vitro during fungal cultivation in hypoxia conditions was confirmed by gas chromatography-mass spectrometry. Direct treatment of C. elegans with ethanol elevated the sodh-1 expression and ROS accumulation while repressing a series of immunity genes that were also repressed during fungal infection. Mutation of sodh-1 in C. elegans blocked ROS accumulation and increased the nematode's susceptibility to fungal infection. Our study revealed a new recognition and antifungal mechanism in C. elegans. The novel mechanism of ethanol-mediated interaction between the fungus and nematode provides new insights into fungal pathogenesis and for developing alternative biocontrol of pathogenic nematodes by nematophagous fungi. IMPORTANCE Nematodes are among the most abundant animals on our planet. Many of them are parasites in animals and plants and cause human and animal health problems as well as agricultural losses. Studying the interaction of nematodes and their microbial pathogens is of great importance for the biocontrol of animal and plant parasitic nematodes. In this study, we found that the model nematode Caenorhabditis elegans can recognize its fungal pathogen, the nematophagous fungus Purpureocillium lavendulum, through fungal-produced ethanol. Then the nematode elevated the reactive oxygen species production in the gut to inhibit fungal growth in an ethanol dehydrogenase-dependent manner. With this mechanism, novel biocontrol strategies may be developed targeting the ethanol receptor or metabolic pathway of nematodes. Meanwhile, as a volatile organic compound, ethanol should be taken seriously as a vector molecule in the microbial-host interaction in nature.