Identification of antifungal lipopeptides from Bacillus subtilis Sh-17 targeting Fusarium oxysporum f. sp. lycopersici

Abstract Background This study addresses the critical issue of Fusarium wilt in tomatoes, caused by Fusarium oxysporum f. sp. lycopersici (FOL), a severe fungal pathogen responsible for global yield losses. Conventional control measures, such as resistant crop varieties and chemical fungicides, have limitations due to environmental concerns and the risk of pathogen resistance. As a sustainable alternative, this study aims to explore the biocontrol potential of the bacterial strain Sh-17, focusing on its lipopeptides (LPs) to effectively suppress FOL. Results This study demonstrated the antifungal capability of the Sh-17 strain, obtained from a tomato field, against FOL. Through 16S rDNA gene sequence analysis and phenotypic evaluation, Sh-17 was identified as Bacillus subtilis Sh-17. During the disease control assay using in vitro petri dishes, Sh-17 showed promising plant growth-promoting and disease-control capabilities in seedlings when tomato seeds were inoculated with both Sh-17 and FOL. Subsequently, the lipopeptide extract derived from Sh-17 showed strong antifungal properties in a dose-dependent manner, with complete inhibition of FOL at a concentration of 3500 µg mL−1. Furthermore, it was observed that LPs decreased the amount of ergosterol, which affects the stability and general structure of the plasma membrane. The genomic DNA of Sh-17 was subjected to PCR screening, which revealed the presence of genes responsible for the biosynthesis of antifungal LPs. Furthermore, LC–MS analysis identified distinct LPs, such as surfactins, fengycin, iturins, bacilysin, and bacillomycin derivatives in the crude LPs extract of Sh-17. Moreover, microscopic analyses (fluorescent/TEM) demonstrated morphological abnormalities and even death of the hyphae and spores of the phytopathogen upon its interaction with LPs. Conclusions B. subtilis Sh-17 exhibits strong antifungal properties against FOL and supports seedlings health by protecting them from pathogen infestation. The LPs produced by Sh-17 inhibit FOL growth in a dose-dependent manner by disrupting the pathogen’s cellular structures and proved to be an effective biocontrol agent against Fusarium wilt in tomatoes. Graphical abstract