Climate change continues to threaten the world's coral reefs, which support at least a quarter of all marine life. Though probiotics have been shown to rehabilitate corals in aquarium experiments, demonstrating the efficacy of such microbial therapy in the ocean is difficult. In a study published in the journal Cell Reports on Sept. 3, researchers establish that both live probiotic and inactivated postbiotic treatments improve coral health—while the animals are under thermal stress during a natural marine heat wave.