Interaction between arbuscular mycorrhizal fungi and bacteria

Plants, arbuscular mycorrhizal (AM) fungi and soil bacteria form a continuum and coexist stably in ecosystems. Resource availability can affect the mutualistic relationship between plants and AM fungi, but it is unclear how it affects the reciprocal cooperation between AM fungi and bacteria. Here, we used the in vitro culture system to explore the reciprocal cooperation between an AM fungus and a phosphate-solubilizing bacterium (PSB) and reveal the underlying mechanisms mediated by environmental phosphorus (P) availability. Under low inorganic P availability, the reciprocal cooperation between AM fungus and PSB materialized by carbon (C)-P exchange, was strengthened, accompanied by the activation of multiple C metabolism and P transport and regulation pathways of both parters. Conversely, under high inorganic P availability, AM fungi directly absorbed and stored excess P, which slowed down the exchange for C with plants and accompanied by the activation of only P transport and regulation pathways without activating any C metabolism pathway, thereby weakening the reciprocal cooperation with PSB.