Bacillus velezensis Bac-9, isolated from kefir, possesses antifungal activity and improves resistance of tomato plant against whitefly Bemisia tabaci

Abstract

Background: The Bacillus genus comprises spore-forming, Gram-positive bacteria widely recognized for their capacity to produce bioactive compounds with antimicrobial properties. This activity is primarily attributed to the synthesis of diverse molecules, including peptides, non-ribosomal peptides, and polyketides, which exhibit inhibitory effects against various pathogens. Bacillus species are ubiquitous and highly diverse, encompassing strains with significant biotechnological potential. Results: Bac-9 is a bacterial strain belonging to Bacillus genus isolated from kefir in Escárcega, Campeche, México. This strain exhibits strong antifungal activity against Fusarium equiseti, F. solani, Curvularia sp. and the oomycete, Phytophthora capsici. The genome comprises 4,059,427 bp, with a total of 4,195 coding sequences and a GC content of 46.3%. A total of 21 biosynthetic gene clusters were identified: 55% were non-ribosomal peptides (NRPs), 36% were polyketides (PKs) and 9% were NRP + PK hybrids. This bacterium produces compounds with insecticidal properties, such as thietane and acenaphthylene, which were detected by GC-MS. In tomato plants, different Bac-9 extracts activate genes involved in defense against insects and pathogens, including genes associated with the biosynthesis of jasmonic acid and salicylic acid. In addition, the extracts reduce oviposition by the whitefly Bemisia tabaci in Lycopersicon esculentum. Conclusion: This study offers valuable insights into bioactive compounds with potential for the biological control of phytopathogens and whiteflies. Overall, the bacterium emerges as a promising candidate for use in biological control strategies.