Surfactin stimulated by root molecular patterns acts as a key driver of Bacillus-plant mutualistic interaction

Bacillus velezensis is a rhizospheric bacteria well studied for its role in plant protection against pathogen ingress. Bacillus biocontrol potential directly relies on its ability to produce a wide range of bioactive secondary metabolites (BSMs). If the mechanisms of plant protection have been widely studied in the past years, the way Bacillus communicates with the host plant and establishes in the rhizosphere remains elusive. Here we show that early in planta production of the lipopeptide surfactin is quantitatively and qualitatively stimulated by plant triggers including root exudates and plant cell wall polymers. On one hand, early surfactin production favors Bacillus implementation in the rhizosphere whereas on the other hand, it acts as an elicitor to activate plant immunity. Thus, evolution of Bacillus in close connection with it host lead to an optimization of surfactin production that became a shared good between both partners.