Jul 2026· Journal of Agricultural and Food Chemistry· 0 citations· 64 references
Medicine
TL;DR
An engineered strain is constructed by overexpressing the transcriptional regulator OmpR, which significantly enhanced nematicidal activity against Meloidogyne incognita J2s and increased secondary metabolite production, providing a promising engineered strain and lead compounds for developing novel microbial nematicides.
Abstract
The development of green alternatives to chemical nematicides is an urgent need in sustainable agriculture. This study constructed an engineered strain, LG209, by overexpressing the transcriptional regulator OmpR, which significantly enhanced nematicidal activity against Meloidogyne incognita J2s and increased secondary metabolite production. From its fermentation broth, 20 compounds were isolated, including a new naphthoquinone derivative. Notably, phenylacetic acid (3), 2-(4-methoxyphenyl)acetic acid (5), and 9H-carbazole (18) exhibited strong nematicidal activity, with LC50 values of 52.34, 88.52, and 15.18 μg/mL at 96 h, respectively. These compounds induced ROS burst and lipid peroxidation, leading to necrotic cell death in nematodes. Additionally, certain indole derivatives modulated nematode chemotaxis. In soil trials, LG209 fermentation broth achieved 68.9% control efficacy against root-knot nematode in tomato, surpassing the wild-type strain. This work provides a promising engineered strain and lead compounds for developing novel microbial nematicides.
Postharvest blue mold in apples caused by Penicillium expansum poses a great risk to food safety. Here, we report on a phytopathogen targeted enrichment strategy that led to the isolation of an endophytic biocontrol agent (BCA), Bacillus subtilis 507, with strong antagonism against P. expansum. Using a unique dual application approach that combines both live BCA and its crude metabolites (Bac + CM), our result showed an enhanced efficacy. Relative to the control, the disease incidence of blue mold in apples was reduced by 45.95% and lesion diameter was limited to 19.18 mm. Untargeted metabolomics identified bioactive compounds, including 3-phenyllactic acid, pipecolic acid, and spermine, suggesting direct antifungal activity and host based modulation. The mechanistic investigations showed that Bac + CM inhibited spore germination up to 37.3%, and depletion of ergosterol with 97.09% cellular membrane leakage. Fungal hyphal deformation and structural collapse were confirmed by SEM. The BCA rapidly colonized apple fruit wounds and surfaces up to 9.4 log10CFU and reduced natural decay to 5.13% without affecting fruit quality. This study presents a combined, metabolite-enhanced biocontrol strategy that positions B. subtilis 507 as a promising candidate for sustainable management of postharvest food diseases such as blue mold in apples.
Aasia Muhammed Jamiu, Asuama Kwasi Yeboah, Qu Xin Yue et al.· Journal of food microbiology· 0 citations
The phytopathogen Fusarium oxysporum threatens global food security, necessitating sustainable biocontrol alternatives to chemical fungicides. Here, we employed an OSMAC-driven dual-layer fast screening (DLFS) approach to identify Streptomyces sp. OUC-HL1638 as a potent antagonist. Through integrated NMR-based lipopeptide signature mapping and LC-MS-assisted NRPS gene mining, we efficiently targeted and isolated two stendomycins (1 and 2). These compounds exhibited potent in vitro antifungal activity (MIC = 1 μM), outperforming hymexazol by 1000-fold, and effectively controlled F. oxysporum infection in radish seedlings and postharvest cherry tomatoes without phytotoxicity. The producing strain intrinsically balances stendomycin production with low plant toxicity and sustains production under high-salinity and alkaline conditions, indicating potential for saline-alkaline agriculture. This work establishes an efficient pipeline for green fungicide discovery and highlights the promise of stendomycins and strain OUC-HL1638 as sustainable biocontrol agents for crop protection.
Jingyi Lyu, Hu Chen, Junjie Liu et al.· Journal of Agricultural and...· 0 citations
Bacterial wilt caused by Ralstonia solanacearum is a destructive soil-borne disease affecting numerous crops worldwide. Although synthetic pesticides and antibiotics are commonly used for disease management, their excessive application has raised concerns regarding environmental pollution, human health risks, and the emergence of antibiotic-resistant pathogens. As a sustainable alternative, rhizosphere microorganisms have gained attention as potential biocontrol agents. In our previous study, strain JCK-8401 exhibited strong antibacterial activity against R. solanacearum. In the present study, its biocontrol potential was comprehensively characterized through analyses of physiological and biochemical traits, antagonistic activity against phytopathogens, induction of salicylic acid (SA)-mediated defense responses using Arabidopsis thaliana PR1::GUS reporter line, and in vivo suppression of tomato bacterial wilt. Based on 16S rRNA sequence analysis, JCK-8401 was identified as Streptomyces virginiae. The strain utilized diverse carbon sources and produced hydrolytic enzymes and indole-3-acetic acid. Furthermore, it exhibited antibacterial activity against various phytopathogenic bacteria and oomycetes, though it lacked antifungal activity. Both cell suspension and culture filtrate of the strain induced GUS expression, indicating activation of the SA-mediated defense pathway. In vivo assay demonstrated that seed treatment with JCK-8401 achieved 96.40% control efficacy against tomato bacterial wilt. Additionally, pretreatment with diluted culture filtrates (250-, 500-, and 1000-fold) effectively suppressed disease incidence regardless of the application method, strongly suggesting the activation of induced systemic resistance. Overall, Streptomyces virginiae JCK-8401 is a highly promising, multifunctional biocontrol agent for managing soil-borne diseases through a synergistic combination of antibiosis, bioinoculation, and the induction of host plant defense responses.
L. T. Nguyen, A. Park, H. Le et al.· Plant Pathology Journal· 0 citations
Bacillus thuringiensis is the most widely used microbial bioinsecticide; however, only a few strains possess additional traits such as plant growth promotion and biocontrol potential. This study characterized 25 B. thuringiensis isolates obtained from soil and infected insect cadavers to identify multifunctional strains with insecticidal and plant growth‐promoting (PGP) properties. Microscopic examination revealed diverse parasporal crystal morphologies, while 16S rRNA sequencing confirmed their identity with 99%–100% similarity to reference strains. Enzymatic profiling showed protease activity in 24 strains and lipase activity in 21 strains, whereas all isolates produced lecithinase and chitinase. All strains produced indole‐3‐acetic acid (11.22–31.87 µg mL−1) and ammonia (26.74–77.68 µg mL−1), while phosphate solubilization and siderophore production were observed in 21 and 11 strains, respectively. Bioassays against Spodoptera frugiperda identified five highly virulent strains causing more than 90% larval mortality. Among these, NBAIR Bt25 showed the highest efficacy, causing 92% mortality within 96 h with an LC50 of 39.75 µg mL−1. PCR analysis revealed that NBAIR Bt25 carries multiple pesticidal genes (cry1A, cry1D, cry1E, cry1I, cry2A, and vip3A). Paper towel and glasshouse assays demonstrated that strain NBAIR Bt25 significantly enhanced shoot growth and secondary root development. Overall, NBAIR Bt25 emerged as a promising multifunctional strain with strong insecticidal activity, plant growth‐promoting ability, and biocontrol potential, making it a suitable candidate for sustainable pest management and climate‐smart agriculture.
Manjunatha Channappa, Aditya Kukreti, L. Manjunath et al.· Journal of Basic Microbiolog...· 0 citations
Endophytic bacteria represent a promising, sustainable alternative to synthetic agrochemicals for plant disease management by actively antagonizing phytopathogens and stimulating host immune responses. Despite its traditional use as an antimicrobial remedy, Wedelia chinensis remains underexplored as a source of beneficial endophytes. This study aimed to isolate and screen endophytic bacteria from W. chinensis for their antifungal activity against Fusarium oxysporum. Among 14 endophytic isolates, Bacillus subtilis LS1-5 showed the strongest antifungal activity by dual culture assay. Its cell-free culture filtrate effectively inhibited fungal spore germination by 91.3% at a 20% concentration. Crucially, B. subtilis LS1-5 produced several extracellular enzymes, including cellulase, amylase, chitinase, pectinase, gelatinase, lipase, and protease. Furthermore, the LS1-5 strain exhibited a broad array of plant growth-promoting and environmental resilience traits. Notably, it synthesized indole-3-acetic acid (IAA) at 2.11 ± 0.27 µg/mL in an LB medium without L-tryptophan, significantly promoted a 34.19% increase in root elongation, and demonstrated remarkable tolerance to extreme conditions, including high salinity (11% NaCl) and broad pH levels ranging from 6 to 12. Additionally, volatile organic compounds (VOCs) emitted by LS1-5 significantly inhibited the severe bacterial pathogens Xanthomonas oryzae (45.83%) and Xanthomonas citri (47.99%). These findings highlight B. subtilis LS1-5 as a highly effective candidate for biological control and sustainable agricultural applications.
D. Nguyen, Dong Tang Vien, Ngoc-Minh Truong Bui et al.· IOP Conference Series: Earth...· 0 citations
This study introduces L. aquatilis strain MC3 as an emerging candidate for bioinoculant development and one of the first reports for identification of L. aquatilis as multifunctional PGPR from Himalayan ecosystems.
S. Devi, Riya Chandel, D. Thakur et al.· Frontiers in Systems Biology· 0 citations
