Activation dynamics and assembly of root zone soil bacterial communities in response to stress-associated phytohormones.

Plants can "cry for help" to recruit supportive microbiome members during stress, but the precise signals a plant uses to activate and assemble these microorganisms remain unclear. We evaluated the activation dynamics of root zone soil bacteria in response to phytohormones produced when plants are stressed, hypothesizing that responsive taxa could support plant resilience. We conducted a mesocosm experiment using root zone soil collected from the planted fields of two crops: the annual legume common bean ( IMPORTANCE: Global food security is a pressing societal challenge that has been exacerbated by climate change and other anthropogenic stressors on the environment. Microbial bioinoculants are a promising solution for improving crop health and resilience, but ensuring their persistence and activation in the field remains a significant challenge. This study examined how dormant root-zone-associated bacteria reactivate after exposure to the plant stress hormones abscisic acid and salicylic acid. The experiment revealed that certain bacterial taxa could reactivate in response to these plant stress signals and persist for at least 2 weeks. This work advances our understanding of the potential cues for reactivating beneficial plant-associated microbes and supports the goal of developing microbial solutions for sustainable agriculture.