Ability of Different Bacteria from Grapevine to Colonize Arabidopsis thaliana Plants

This study investigates the impact of inoculating seeds with bacterial endophytes isolated from Vitis amurensis Rupr. on endophytic community composition in Arabidopsis thaliana (L.) Heynh. Ten bacterial isolates of the genera Agrobacterium, Bacillus, Curtobacterium, Erwinia, Frondihabitans, Gordonia, Pantoea, Pseudomonas, Sphingomonas, and Xanthomonas were applied to seeds and some visible phenotypic effects were observed on plant growth after two weeks. High-throughput sequencing of 16S rRNA revealed that the native endophytic microbiome of A. thaliana was dominated by Gammaproteobacteria, Actinomycetes, Bacteroidia, and Alphaproteobacteria. The key families were Microscillaceae, Chitinophagaceae, Rhizobiaceae, Rhodanobacteraceae, Nocardioi-daceae, Nocardiaceae, Xanthomonadaceae, Devosiaceae, Microbacteriaceae, Crocinitomi-caceae, Pseudomonadaceae, Solimonadaceae, Comamonadaceae, Caulobacteraceae, and Micrococcaceae. Arabidopsis seed inoculation with Agrobacterium sp. R8SCh-B12, Curtobacterium sp. P7SA-B3, and Gordonia aichiensis P6PL2 significantly reduced alpha diversity (Shannon index) and altered beta diversity relative to controls, indicating strong community restructuring. These three isolates, along with Pseudomonas sp. R8SCh-B2, Sphingomonas sp. RA62c-B5, Xanthomonas sp. R7SCh-B6, and Bacillus velezensis AMR25, successfully colonized the plant tissues, as evidenced by significant increases in genus-specific amplicon sequence variants, ASVs (up to 17,820-fold for Curtobacterium sp. ASV33). In contrast, Pantoea sp. P7SCH-B5, Erwinia sp. R8SCh-B3, and Frondihabitans sp. RA62c-B2 failed to colonize A. thaliana, despite being applied to the seeds, suggesting the existence of mechanisms restraining colonization. These findings demonstrate that only a subset of grapevine-derived endophytes can effectively colonize A. thaliana, and that successful colonization correlates with significant shifts in the native microbiome, even in the absence of overt phenotypic changes. This emphasizes the importance of strain-specific compatibility in plant-endophyte interactions. Thus, we report the first descriptions of several novel endophytes that colonized Arabidopsis plants and establish a convenient model to investigate plant-bacterial interactions.