P-309 - Bacterial metabolization of host-specific secondary metabolites

Plant roots are colonized by a diverse array of microbes, collectively known as the root microbiota. Plants shape the microbiota by secreting root exudates into the rhizosphere. Root exudates contain secondary metabolites that affect microbiota by semiochemical or toxic properties. Arabidopsis thaliana (Arabidopsis) and Zea mays (maize) exude secondary metabolites called coumarins and benzoxazinoids, respectively, and both alter their root microbiota composition and affect plant growth and health. Recently, our lab showed that various maize root bacteria could degrade the maize secondary metabolite MBOA, while selected non-host Arabidopsis bacteria did not. This finding suggests microbial adaptation to host-specific metabolites. To test whether adaptation to host-specific metabolites is common, we investigated the bacterial tolerance and metabolic capacity of host-specific metabolites using maize root bacteria and Arabidopsis bacteria. We monitored the growth of individual strains in the presence of Arabidopsis-derived coumarin scopoletin and followed compound degradation indirectly by scopoletin fluorescence. While most of the Arabidopsis bacteria and maize root bacteria did not metabolize scopoletin, a subset of Arabidopsis bacteria degraded scopoletin, which was confirmed by HPLC-MS analysis. We are using untargeted metabolite analysis to identify degradation products and comparative genomics to identify candidate degradation genes.