The soil microorganism Bacillus amyloliquefaciens N3-8 shows potential as a biocontrol agent against the pathogen Burkholderia pseudomallei and its effect on rice plantation.

Burkholderia pseudomallei is a saprophytic bacterium responsible for melioidosis in humans and animals. In this study, Bacillus amyloliquefaciens N3-8 was applied as a biocontrol agent on sterile soil spiked with 107 colony-forming unit (CFU) per gram of B. pseudomallei p37 at two ratios: 1:10,000 and 1:100,000 CFU/g soil. Both treatments significantly reduced B. pseudomallei by 4-5 logs within 4 weeks. A subsequent experiment applied the 1:10,000 ratio to 10 kg of natural soil in a pot containing 102-103 CFU/g of B. pseudomallei alongside rice cultivation. Bacterial counts, rice yield, soil physicochemical factors, and microbial populations were monitored. B. pseudomallei was undetectable in biocontrol-treated soil by day 14 but reappeared by day 30, eventually matching the levels in control soil, suggesting interference by native microbial communities. No significant differences between the control and biocontrol treatments were observed in rice yield or soil physicochemical properties. Metataxonomic analysis revealed 17 bacterial phyla across all samples, with no significant differences in the overall microbial community structure between treatments at any time point. On the other hand, significant changes in microbial beta-diversity over time within the same soil treatments suggest that temporal dynamics, rather than the biocontrol treatment, drive shifts in microbial community structure. This study highlights the potential of B. amyloliquefaciens N3-8 as a biocontrol agent against B. pseudomallei on a pot scale with a rice plantation. For effective control of the pathogen, repeated applications in a rice field trial are necessary to ensure sustained management while being mindful not to disrupt the soil microbial balance.IMPORTANCEBacillus amyloliquefaciens N3-8 has been used in soil as a biocontrol agent against Burkholderia pseudomallei, a bacterium pathogenic to humans and animals, where it has shown no significant effects on soil physicochemical properties, rice yield, and bacterial community structure. However, long-term treatments are needed to achieve sustainable control, and critical management is required to avoid disturbing the microbial balance in the soil.