Integrative genomic and phenotypic analyses reveal broad-spectrum antifungal activity and biocontrol potential in Bacillus ayatagriensis.

The Caatinga biome represents an important reservoir of microbial biodiversity that remains largely unexplored for the development of agricultural bioinputs. In this study, genomic analyses and phenotypic assays were integrated to investigate the biocontrol potential of two Bacillus strains isolated from this environment. Phylogenomic analyses identified the isolates as Bacillus subtilis BSS.245 and Bacillus ayatagriensis BSS.246. The genomes comprised 4.10 and 4.01 Mb, with GC contents of 43.67% and 46.58%, encoding 4,077 and 3,852 genes, respectively. Genome mining revealed biosynthesis-related gene clusters associated with the production of antimicrobial metabolites, including bacilysin, bacillibactin, fengycin, and surfactin. B. ayatagriensis BSS.246 exclusively harbored clusters for macrolactin H and difficidin biosynthesis, compounds widely recognized for their antimicrobial activity. Genes potentially involved in plant growth promotion, stress adaptation, and plant-microbe interactions were also identified. Phenotypic assays demonstrated tolerance to reduced water availability, salinity, and elevated temperature in both strains, as well as exopolysaccharide production. Both strains exhibited broad-spectrum antifungal activity against Alternaria, Colletotrichum, Corynespora, Fusarium, Lasiodiplodia, Macrophomina, Rhizoctonia, and Sclerotinia species, with mycelial growth inhibition ranging from 58.04% to 100.00%. To our knowledge, this study provides the first experimental evidence of the antifungal potential of B. ayatagriensis, expanding the current knowledge of this recently described species. These findings identify both strains as promising agricultural microbial resources and provide a basis for further evaluation of their potential for phytopathogen management and plant-associated applications.