<i>Pseudomonadota</i> bridge cross-trophic interactions to suppress plant pathogens

Trait-mediated interactions across trophic levels drive trophic cascades in macroecological systems, yet their relevance in microbially dominated soil ecosystems remains underexplored. We combined a regional field survey with controlled experiments using a defined 122-strain synthetic bacterial community and bacterivorous nematodes to test whether faunal predation reorganizes root-associated microbiomes to suppress soilborne disease. Field observations showed that sites with stronger nematode-Pseudomonadota associations had lower bacterial wilt incidence. In controlled experiments, nematode predation selectively enriched Pseudomonadota in the rhizosphere and reduced Ralstonia solanacearum populations and disease incidence. Preferential grazing drove this enrichment: Pseudomonadota constituted over 95% of sequences in nematode guts, and focal taxa showed moderate antagonism, small cell size, and high metabolic activity. Together, these results identify Pseudomonadota as key bridging taxa in cross-trophic interactions. Trait-linked responses to predation contribute to pathogen suppression and suggest a biocontrol framework that integrates microbial traits with trophic connectivity.