P-376 - Rhizosphere Burkholderia reduces methane emissions by enriching methanotrophs

Methane is a potent greenhouse gas and its emission from rice paddies is a significant contributor to global warming. Silicate fertilizer (SF), derived from blast furnace slag, has been shown to reduce methane emissions in paddy fields, yet its precise mechanism of action remains poorly understood. SF treatment promotes methanotroph growth, leading to significant methane mitigation. In this study, we identified Burkholderia vietnamiensis as a key rhizosphere bacterial taxa enriched by this treatment. Metagenomic analysis revealed that SF application reshaped the rhizosphere microbiome, enriching B. vietnamiensis and methanotrophic genera such as Methylocaldum and Methylococcus. Greenhouse experiments demonstrated that inoculating paddy soil with B. vietnamiensis strain HU01 alone enhanced methanotroph activity, which significantly reduced methane emissions. To uncover the underlying mechanisms, in vitro and in silico analyses showed that B. vietnamiensis supports the growth of the methanotroph Methylococcus geothermalis, by supplying low molecular weight, heat-stable metabolites such as L-glutamate and cobalamin. Our study provides direct evidence that enrichment of a single bacterial species in the rhizosphere mitigates methane emissions by promoting methanotroph activity through metabolite exchange. Thus, B. vietnamiensis represents a sustainable, microbial-based alternative to chemical fertilizers for reducing methane emissions.