Material cycling in plant-associated bacteria by metagenome analysis

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We investigated bacterial communities in paddy rice with low (LN), standard (SN) levels of N fertilizer application. Metagenome analysis suggested shifts of bacterial communities between LN and SN root microbiomes. The abundances of functional genes for methane oxidation were significantly increased in LN root microbiome. Plants have mutualistic symbiotic relationships with microorganisms by CCaMK. We examined the effect of an OsCCaMK mutant (NE1115). The CH4 flux of NE1115 in the LN field was significantly higher than that of WT, although no difference was observed in the SN field. qPCR and 13C/15N isotopic determinations suggested that CH4 oxidation and N2 fixation were simultaneously activated in the root of WT rice in the LN field, and both processes are likely controlled by OsCCaMK. Metaproteome and CARD-FISH analyses demonstrated that both processes are mediated by type II methanotrophs inhabiting the vascular bundles and epidermal cells of the rice roots.