Interactions with plant pathogens influence lipopeptides production and antimicrobial activity of Bacillus subtilis strain PTB185

Abstract

Bacillus subtilis has raised increasing interest because it is considered as a promising alternative to conventional pesticides for plant disease management. Production of lipopeptides (fengycin, iturin, surfactin) appears as one of the most important factors contributing to its biocontrol activity. In this study, we investigated the effect of different plant pathogens on the production of fengycin, iturin, and surfactin by B. subtilis strain PTB185. Confrontation assays conducted on agar showed that B. subtilis antagonistic activity and production of lipopeptides vary significantly (P ≤ 0.05) according to the pathogen tested. Autoclaved mycelia of plant pathogens were also shown to significantly influence the quantities of lipopeptides produced by B. subtilis in liquid culture. Fengycin and/or iturin were produced in significantly higher amounts in presence of mycelium of Botrytis cinerea, Mucor sp., Pythium ultimum, or Rhizoctonia solani while addition of mycelium in the medium did not significantly affect surfactin production as compared to the control. Bacteria grown in liquid medium amended with Mucor sp. mycelium caused a significantly higher reduction of mycelial growth of B. cinerea, R. solani, and Sclerotinia sclerotiorum as compared to the bacteria grown with no mycelium. This study shows the influence of autoclaved plant pathogen mycelium on B. subtilis antagonistic ability and fengycin/iturin production providing new insights into the optimisation of the culture medium to grow B. subtilis for biotechnological applications. It also provides additional evidence of effects of biotic interactions on the production of lipopeptides by B. subtilis.