Phenotypic and Genomic Insights Into Bacillus spp. and Peribacillus spp. of Spanish Olive Groves With...

Spore-forming organisms are an integral component of the rhizosphere, providing plants with significant advantages. Previous studies determined the antimicrobial activity of the olive sporobiota, identifying five candidates of particular relevance, belonging to the Bacillus subtilis, Peribacillus simplex and Bacillus cereus clade. This study aimed to determine their biotechnological properties, safety aspects, spore structure and resistance, and interaction with the environment through a combined microbiological and genomic approach. We report on the ability of these strains to produce hydrolytic and surface-active enzymes and provide evidence for differences in population behaviour through the formation of strong sessile or floating biofilms. Electron microscopic analysis revealed for the first time the presence of an exosporium layer in olive sporobiota isolates belonging to the P. simplex and B. cereus clade, including numerous pili-like structures on the latter. Spores showed significant differences in their resistance to wet heat, oxidising agents, and UV exposure. Whole genome sequencing of isolate Peribacillus frigoritolerans yielded information on its antimicrobial compound biosynthesis and environmental safety. Overall, our findings provide insights into the phenotypic, morphological and genetic variations of spore-formers from Spanish olive groves, which can be useful for the development of bioactive compounds in sustainable agriculture.