T6SS-mediated competition by <i>Stenotrophomonas rhizophila</i> shapes seed-borne bacterial communities and seed-to-seedling transmission dynamics

The high prevalence of the type VI secretion system (T6SS) in seed-borne bacteria supports the importance of T6SS-mediated competition for seed microbiota assembly. <i>In vitro</i>, <i>S. rhizophila</i> CFBP13503 T6SS exerts a strong impact on bacterial community dynamics. The susceptibility to the T6SS increases with the phylogenetic and metabolic proximities of bacteria to CFBP13503, suggesting the influence of interspecies trophic patterns in T6SS-mediated competitions. <i>In planta</i> and in soil, CFBP13503 T6SS influences specific bacterial taxa, leading to shifts in bacterial interactions and distinct community dynamics. T6SS-mediated competition plays a pivotal role in shaping seed bacterial communities and the dynamics of seed-to-seedling transitions.