Genomic and metabolomic Insights into Lipopeptide-Mediated antagonism and rhizosphere competence of Bacillus siamensis NB92 against Fusarium root rot in avocado
Year: 2026
Type: article
Abstract: Bacillus siamensis NB92, a rhizobacterium recovered from the avocado ( Persea americana Mill.) rhizosphere, exhibits strong antagonistic activity against the root-rot pathogen Fusarium sp. St7, achieving > 60 % hyphal growth inhibition in vitro , along with plant growth-promoting potential. To resolve the mechanistic drivers of these traits, we employed an integrative framework combining whole-genome sequencing, metabolomics (LC–MS and GC–MS), and phenotypic characterization. Genomic exploration using antiSMASH 8.0 with the detection strictness set to relaxed revealed 13 biosynthetic gene clusters (BGCs) associated with antimicrobial and biostimulatory metabolites, notably surfactin, fengycin, and bacillibactin—coupled with loci implicated in indole-3-acetic acid (IAA) and pyrroloquinoline quinone (PQQ) synthesis. These predictions were corroborated by metabolomic profiling, which identified characteristic mass signatures of lipopeptides and siderophores (putatively annotated at MSI Level 2 based on accurate mass matching), while headspace analysis tentatively annotated acetoin (∼91 % relative abundance) as the primary volatile organic compound, reported to elicit ISR-like responses in other plant systems. Beyond secondary metabolism, NB92 displayed extracellular lytic activities (e.g., protease and β-1,3-glucanase), siderophore production, IAA synthesis, and phosphate solubilization in qualitative plate assays. Mechanistic assays indicated that NB92 fermentation extracts suppress fungal hyphal extension, accompanied by loss of membrane integrity as evidenced by PI staining. Furthermore, avocado root exudates were found to stimulate bacterial swarming motility and biofilm formation, which may facilitate effective rhizosphere establishment—a trait evidenced by Bacillus population enrichment and improved seedling growth in pot trials. Collectively, this study characterizes a complementary biocontrol paradigm where direct antibiosis, enzymatic lysis, nutrient competition, and host-mediated signaling may operate in concert to suppress pathogen pressure and enhance host vigor. Consequently, B. siamensis NB92 represents a promising candidate for the biological management of avocado root rot.
Source: Biological Control
Institution: Baoshan University
Language: English
Subfield: Plant Science
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $3,390
OpenAlex ID: W7165625081