Overall, Bacillus siamensis strain BACIII combines host-specific plant growth promotion with broad antifungal activity, supporting its potential for biological control in sustainable agriculture.
Abstract
Endophytic bacteria of the Bacillus subtilis species complex are known for plant growth promotion and antifungal activity, although strain-specific traits remain poorly understood. This study characterized the Bacillus siamensis strain BACIII, isolated from asymptomatic soybean roots in a charcoal rot-affected area, using whole-genome analysis and phenotypic assays. Genome sequencing identified BACIII as Bacillus siamensis and revealed a metabolically versatile genome containing twelve biosynthetic gene clusters linked to antimicrobial compounds such as difficidin, fengycin, and surfactin. Additionally, genomic islands associated with mobile elements, regulation, and stress response suggest adaptive potential. Inoculation with the BACIII strain significantly accelerated germination and increased early growth, biomass accumulation, and chlorophyll content in soybean and sunn hemp (p < 0.05), whereas no significant effects were observed in cotton or sunflower, indicating host-dependent responses. In vitro assays demonstrated consistent inhibition of several phytopathogenic fungi, including Sclerotinia sclerotiorum, Fusarium spp., and Macrophomina phaseolina, with variable intensity. Overall, BACIII combines host-specific plant growth promotion with broad antifungal activity, supporting its potential for biological control in sustainable agriculture.
The potential of P1 as a promising bioinoculant candidate for sustainable agriculture in the potato sector is demonstrated and the genome lacked major virulence factors and antimicrobial traits, supporting the non-pathogenic nature of the P1 strain.
Poonam Patel, K. Raval, Satyamitra Shekh et al.· Frontiers in Microbiology· 0 citations
Seed-associated microbiota are emerging as key determinants of early plant establishment and resilience, yet their functional potential in wheat remains underexplored. Here, we isolated and functionally characterized culturable bacterial endophytes from seeds of Triticum aestivum cvs. Saekeumkang, Baeggang, and Ariheuk to assess plant growth promotion and pathogen suppression. Sixteen bacterial strains, belonging to Pseudomonadota, Actinomycetota, and Bacillota, were identified using 16S rRNA gene sequencing. Functional assays revealed the high prevalence of plant growth-promoting traits, with all isolates producing indole-3-acetic acid and 56.25% exhibiting phosphate-solubilizing activity, whereas siderophore production was restricted to Pseudomonas poae WSSR12. Despite this apparent functional redundancy, in planta assays demonstrated strong strain-specific effects on seedling biomass. Neobacillus cucumis WSSR17 consistently induced the highest increase in fresh weight. In parallel, dual culture assays against multiple Fusarium pathogens revealed that only one isolate, Calidifontibacillus erzurumensis WSSR11, showed consistent antifungal activity across all tested Fusarium strains. Notably, isolates combining multiple functional traits did not always correspond to the strongest growth promotion, underscoring the importance of host-microbe compatibility and trait expression in planta. Collectively, these findings reveal a functionally diverse seed endophytic community with complementary roles in plant growth and disease suppression. We propose that rational selection and combination of complementary strains, particularly N. cucumis WSSR17 (growth promotion), C. erzurumensis WSSR11 (biocontrol), and P. poae WSSR12 (multifunctional nutrient mobilization) could enable the development of targeted, multi-strain bioinoculant strategies for wheat. This study advances our understanding of seed microbiome functionality and provides a foundation for microbiome-informed crop improvement.
B. velezensis BJ-1141 is a multifunctional bacterial strain with strong biocontrol efficacy and plant growth-promoting traits, supported by genomic evidence, and represents a promising candidate for sustainable crop disease management.
Yunyun Chen, Mei Liu, Wei Zhang et al.· Journal of Applied Microbiol...· 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
