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.
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Claims 11
Claim · model-written summary
NB92 inhibited Fusarium hyphal growth by over 60% in vitro.
- Taxon
- avocado
Persea americanae0 - Interactor
- Fusarium sp. St7e0pathogen
- Second interactor
- Bacillus siamensis NB92Bacillus siamensise0biocontrol_agent
- Outcome
- Fusarium sp. St7, achieving > 60 % hyphal growth inhibitione0
- Value
- > 60 %e0
- Setting
- in vitroe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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”
Claim · model-written summary
NB92 genome analysis identified 13 biosynthetic gene clusters.
- Taxon
- avocadoPersea americanat0
- Interactor
- Bacillus siamensis NB92Bacillus siamensist0biocontrol_agent
- Outcome
- biosynthetic gene clusters (BGCs)e0
- Value
- 13 biosynthetic gene clusterse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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”
t0“Bacillus siamensis NB92 against Fusarium root rot in avocado”
Claim · model-written summary
Metabolomics putatively identified lipopeptide and siderophore signatures.
- Taxon
- avocadoPersea americanat0
- Outcome
- mass signatures of lipopeptides and siderophorese0
- Qualifier
- putatively annotated at MSI Level 2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“metabolomic profiling, which identified characteristic mass signatures of lipopeptides and siderophores (putatively annotated at MSI Level 2 based on accurate mass matching)”
t0“avocado”
Claim · model-written summary
Acetoin was tentatively annotated as the main volatile at about 91% relative abundance.
- Taxon
- avocadoPersea americanat0
- Outcome
- acetoine0
- Value
- ∼91 % relative abundancee0
- Qualifier
- tentatively annotatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“headspace analysis tentatively annotated acetoin (∼91 % relative abundance) as the primary volatile organic compound”
t0“avocado”
Claim · model-written summary
NB92 showed lytic activities, siderophore production, IAA synthesis and phosphate solubilization.
- Taxon
- avocadoPersea americanat0
- Interactor
- NB92e0biocontrol_agent
- Outcome
- extracellular lytic activities (e.g., protease and β-1,3-glucanase), siderophore production, IAA synthesis, and phosphate solubilizatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NB92 displayed extracellular lytic activities (e.g., protease and β-1,3-glucanase), siderophore production, IAA synthesis, and phosphate solubilization in qualitative plate assays”
t0“avocado”
Claim · model-written summary
NB92 fermentation extracts suppressed fungal hyphal extension.
- Taxon
- avocadoPersea americanat0
- Treatment
- NB92 fermentation extractse0
- Second interactor
- NB92e0biocontrol_agent
- Outcome
- fungal hyphal extensione0
- Direction
- suppresse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NB92 fermentation extracts suppress fungal hyphal extension, accompanied by loss of membrane integrity as evidenced by PI staining”
t0“avocado”
t1“Fusarium root rot”
e1“root-rot pathogen Fusarium sp. St7”
Claim · model-written summary
NB92 extracts caused fungal membrane integrity loss.
- Taxon
- avocadoPersea americanat0
- Outcome
- loss of membrane integritye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“loss of membrane integrity as evidenced by PI staining”
t0“avocado”
t1“Fusarium root rot”
e1“root-rot pathogen Fusarium sp. St7”
Claim · model-written summary
Avocado root exudates stimulated NB92 swarming motility and biofilm formation.
- Taxon
- avocadoPersea americanae0
- Treatment
- avocado root exudatese0
- Interactor
- Bacillus siamensis NB92Bacillus siamensist0biocontrol_agent
- Outcome
- bacterial swarming motility and biofilm formatione0
- Direction
- stimulatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“avocado root exudates were found to stimulate bacterial swarming motility and biofilm formation”
t0“Bacillus siamensis NB92”
Claim · model-written summary
Pot trials showed Bacillus population enrichment.
- Taxon
- avocadoPersea americanat0
- Interactor
- Bacilluse0biocontrol_agent
- Outcome
- Bacillus population enrichmente0
- Setting
- pot trialse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Bacillus population enrichment and improved seedling growth in pot trials”
t0“avocado”
Claim · model-written summary
Pot trials showed improved avocado seedling growth.
- Taxon
- avocadoPersea americanat0
- Outcome
- seedling growthe0
- Direction
- improvede0
- Setting
- pot trialse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Bacillus population enrichment and improved seedling growth in pot trials”
t0“avocado”
Claim · model-written summary
The authors propose NB92 as a candidate for avocado root rot management.
- Taxon
- avocadoPersea americanae0
- Interactor
- B. siamensis NB92Bacillus siamensise0biocontrol_agent
- Outcome
- biological management of avocado root rote0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“B. siamensis NB92 represents a promising candidate for the biological management of avocado root rot”
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See all 9 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.