P-387 - The relationship between Xylella fastidiosa and microbiome

Xylella fastidiosa is the causal agent of important crop diseases and is transmitted by xylem sap-feeding insects. The bacterium colonizes xylem vessels and can persist with a commensal or pathogen lifestyle in more than 500 plant species. Recent studies suggest that the microbiome composition shows signs of dysbiosis in Xff-infected plants. How X. fastidiosa interacts with the host’s microbiome remains unclear. In our study, we use Arabidopsis thaliana and its derived L-SPHERE microbiome collection as the experimental models. To investigate the impact of Xff on the structure of the A. thaliana microbiome, we developed a method for infecting A. thaliana with Xff under gnotobiotic conditions. Amplicon-based 16s rRNA sequencing showed that the composition of L-SPHERE’s 62 SynCom was altered by Xff, with a higher abundance of Bacteroidetes isolates. None of the Bacteroidetes isolates exhibited immunomodulatory activity. In vitro confrontation assay showed that Bacteroidetes isolates exhibited an inhibitory effect against Xff growth. Interestingly, xff shows increased biofilm formation when grown in the presence of supernatant of Bacteroidetes isolates. Colonization of individual and combined Bacteroidetes did not affect Xff load in A. thaliana at the point of Xff inoculation. Current experiments will clarify whether Xff forms biofilms in plants in response to Bacteroidetes and whether Bacteriodetes can colonize the xylem.