(485e) Tracking Engineered Commensals to Understand Immune Suppression and Colonization in the Plant Root Microbiome

While many commensal bacteria in the rhizosphere microbiome carry immunogenic flagellin (flg22) epitopes that activate host innate immune responses, approximately 40% of strains have mechanisms to actively suppress or evade immunity. The functional consequences of this suppression and evasion for colonization and microbiome dynamics remain unclear.

Working in a plant microbiome system, we previously identified a conserved immune evasion mechanism among commensals in the order Xanthomonadales, involving a secreted protease, Immunosuppressive Subtilase A (IssA), that degrades immune-eliciting peptides such as flg22. To investigate how immune modulation influences microbial fitness and community composition, we are deploying a chromosomal DNA barcoding system to track colonization of wild-type and engineered strains in the rhizosphere. This approach allows us to assess whether immunosuppressive strains colonize more effectively than their non-suppressive counterparts and to evaluate their impact on plant microbiome structure.

This work connects molecular mechanisms of immune evasion with community structure in the plant microbiome and provides a platform for engineering microbial communities that support plant health. Similar immune suppression phenotypes and community dynamics may contribute to microbiome assembly in other host-microbiome systems.