Isolation of lipopeptide antibiotics from <i>Bacillus siamensis</i>: a potential biocontrol agent for <i>Fusarium graminearum</i>

Abstract

Fusarium head blight (FHB), a destructive fungal disease that can cause damage to various crops and reduce yield and quality, is primarily caused by several species of the soil-borne fungal genus Fusarium, which produce mycotoxins that contaminate grains and may cause various severe chronic diseases in humans and livestock. In recent years, Bacillus spp. have been reported to be good producers of antifungal antibiotics against FHB. This study aimed to explore the potential role of a newly identified Bacillus strain, designated as CU-XJ-9, against FHB. This strain, which was isolated from traditional Chinese fermented food, was identified as Bacillus siamensis and confirmed to produce lipopeptide biosurfactants, which according to the analysis by quadrupole time-of-flight tandem mass spectrometry (Q-TOF-MS/MS) may belong to the iturin lipopeptide family. At 100 μg/mL, the isolated antifungal compounds completely inhibited conidial germination. Observation of the effects of the isolated antifungal compounds on the mycelia of F. graminearum by scanning electron microscopy revealed obvious nodes in the middle of the mycelia and destroyed mycelial structures, and these changes became more pronounced with increasing dose. Overall, this study provides important information regarding the ability of Bacillus siamensis to produce lipopeptide biosurfactants, which showed significant antagonistic activity against F. graminearum.