Secretions Induce Shifts in Macrolactin Composition and Reduction in Antimicrobial Activity of BNC5.

, a pathogen causing bacterial wilt, threatens global crop production, necessitating sustainable biocontrol solutions. is a promising biocontrol agent, but the mechanisms of its interaction with are not well understood. This study investigates the effects of secretions on the growth, metabolite production, and antimicrobial properties of BNC5. Untargeted metabolomics revealed increases in two known macrolactins (A and M), six novel macrolactins (BA1-6), and one novel polyketide (BAP1), along with decreases in 7--malonyl macrolactin A and a new macrolactin, BA7, following exposure to the secretions. Real-time polymerase chain reaction showed a downregulation of the tailoring enzyme gene . The reduced antimicrobial activity in the exposed extracts (78 vs 39-78 μg mL in unexposed extracts) is likely due to diminished macrolactin efficacy in macrolactin fractions from the exposed (512-1024 μg mL) compared to those from the unexposed samples (4 μg mL). Supported by tomato pot experiments, these results suggest that applying extracts prior to introducing live bacteria may enhance the management of in severely affected fields, providing a sustainable alternative to chemical pesticides.