University of Lausanne Lausanne, Vaud, SWITZERLAND
Legume plants have evolved endosymbiotic relationships with nitrogen-fixing rhizobia bacteria within specialized root organs called nodules. For decades, it was believed that only rhizobia colonized these structures, while the presence of other bacteria was considered incidental. In recent years, multiple studies indicate that various bacterial species, including Pseudomonas, frequently co-colonize nodules alongside rhizobia. However, the prevalence and potential functions of these non-rhizobial bacteria remain largely unknown. Our team investigates how Pseudomonas influence symbiosis though interactions with both the host plant and rhizobia. We have evidence that nodule-associated Pseudomonas are not pathogenic but can trigger immune responses in the host. Additionally, they produce specific antimicrobials that suppress ineffective rhizobia while sparing beneficial strains, ultimately shaping root colonization and nodule formation. In my presentation I will provide evidence suggesting a more intricate interaction between Pseudomonas, the legume host, and rhizobia than previously shown. These findings challenge the traditional view of root nodule symbiosis as a binary interaction between host and a single bacterial partner.
