P-306 - Tracking bacterial population dynamics within the phyllosphere microbiome using Wild-type Isogenic Standardized Hybrid (WISH)-tags

The phyllosphere, comprising the leaf-dominated aerial parts of plants, hosts diverse bacterial communities which substantially impact the growth and health of the host. While plant microbiomes consistently establish into similar structural patterns, the population dynamics underlying community assembly remain largely unexplored. To address this knowledge gap, we developed a genomic barcoding system – WISH-tags (Wild-type Isogenic Standardized Hybrid-tags) – to distinguish bacterial subpopulations in a microbiota context. These barcodes were introduced into a set of ecologically relevant strains from the At-LSPHERE, a representative collection of strains isolated from wild Arabidopsis plants. Using gnotobiotic Arabidopsis systems and synthetic communities, we tracked bacterial populations and investigated priority effects. We observed that different bacterial strains exhibit distinct inherent capacities to overcome the plant barriers during colonization. We also found that late-introduced populations are accommodated proportionally to their presence at the inoculation timepoint. This approach enhances our ability to predict bacterial establishment patterns and contributes to the rational design of beneficial plant microbiomes.