Surfactin and fengycin B extracted from Bacillus pumilus W-7 provide protection against potato late blight via distinct and synergistic mechanisms

Potato late blight caused by Phytophthora infestans is one of the most serious plant diseases worldwide. Cyclic lipopeptides (CLPs) extracted from Bacillus strains exhibit a promising effect in the biocontrol of a variety of phytopathogens. However, the specific inhibitory effects and underlying mechanisms of CLPs against P. infestans are poorly understood. In this study, we showed that Bacillus pumilus W-7 can inhibit the growth of P. infestans mycelium. Two metabolites from W-7, surfactin and fengycin B, were identified using MS/MS. Fengycin B inhibited mycelium growth by inducing mycelium deformations, oxidative damage, and mitochondrial dysfunction. Surfactin induced potato plant defense responses by increasing the expression of the biocontrol genes (pod, pal, and cat) and their enzyme activities (POD, PAL, and CAT). Also, surfactin and fengycin B could exhibit a synergistic inhibitory effect on P. infestans. Taken together, our findings indicate that B. pumilus W-7 and its CLPs are potential environmentally friendly and effective biocontrol agents for the preservation of potato crops. KEY POINTS: • Lipopeptides of surfactin and fengycin B are extracted from Bacillus pumilus W-7. • Fengycin B inhibits Phytophthora infestans mycelium growth in a direct manner. • Surfactin induces potato plant defense responses to control late blight.

Keywords: Bacillus pumilus; Fengycin B; Inhibition; Phytophthora infestans; Potato late blight; Surfactin.