Mutually beneficial interactions between bacteria and Arabidopsis promote phosphorus nutrition and growth.

It remains unknown whether plants establish mutualistic relationships with any bacteria to cope with phosphorus (P) limitation. We characterized root-bacterial microbiome members to show that many of them may cooperate with Arabidopsis to promote seedling P nutrition and growth. In-depth analyses uncovered an intricate interaction between Arabidopsis and Acinetobacter bacteria during P deficiency. Instead of a direct role in P-mining, malate secreted by P-deprived roots acts as a call-for-help signal that recruits bacteria to the rhizoplane, where Acinetobacter adopt a mutualistic lifestyle and utilize host-derived nutrients to robustly mobilize P normally inaccessible to plants. The rhizoplane, but not the surrounding space, served as a hotspot for P acquisition by both plants and bacteria. The interaction occurred in the context of a bacterial community and in P-impoverished soil. Our work reveals a mutualistic strategy between bacteria and a non-mycorrhizal plant that promotes P nutrition.