P-375 - Rhizobacteria orchestrate indirect methane reduction and disease suppression in rice

Methane is a potent greenhouse gas contributing to global warming. In paddy soils, a major source of methane emission, anaerobic methanogens produce methane, which is oxidized by aerobic methanotrophs. While microbe-based bioreagents offer promise for methane reduction, the direct application of methanotrophs is limited by bulk cultivation challenges. In this study, 1,920 heterotrophic bacteria were isolated from the rice rhizosphere to identify helper bacteria that promote methanotroph growth for eco-friendly methane mitigation. Growth-promoting effects were assessed using a high-throughput screening system targeting bacterial metabolites. Among the isolates, several bacterial genera exhibited the potent effect, increasing methanotroph growth. In paddy soil trials, bacterial treatment reduced methane emissions while increasing methanotroph abundance. In silico analysis suggested that rhizobacteria potentially promotes methanotrophs by supplying some primary metabolites. Furthermore, applying these metabolites to plant roots significantly alleviated bacterial blight symptoms by upregulating genes involved in induced systemic resistance. These findings highlight rhizobacteria as a promising bioreagent for methane mitigation and rice disease resistance enhancement.