Deciphering the biology and chemistry of the mutualistic partnership betweenBacillus velezensisand the arbuscular mycorrhizal fungusRhizophagus irregularis

Abstract

AbstractArbuscular mycorrhizal (AM) fungi (e.g.Rhizophagus irregularis) recruit specific bacterial species in their hyphosphere. However, the chemical interplay and the mutual benefit of this intricate partnership have not yet been investigated especially as it involves bacteria known as strong producers of antifungal compounds such asBacillus velezensis. Here, we show that the soil dwellingB. velezensismigrates along the hyphal network of the AM fungusR. irregularis, forming biofilms and inducing metabolic fluxes that contributes to host plant root colonization by the bacterium. During hyphosphere colonization,R. irregularismodulates the biosynthesis of specific lipopeptides and antimicrobial compounds inB. velezensisas a mechanism toward-off mycoparasitic fungi and bacteria to ensure stable coexistence. These mutual benefits are extended into a tripartite context via the provision of enhanced protection to the host plant through the induction of systemic resistance.