A patho-symbiotic bacteria in legume plants

Atypical rhizobia trigger nodulation and pathogenesis on the same legume hosts

The emergence of commensalism and mutualism often derives from ancestral parasitism. However, in the case of rhizobium-legume interactions, bacterial strains displaying both pathogenic and nodulation features on a single host have not been described yet. In a study published in Nature Communication, the SYMUNITY team directed by P. Ratet (IPS2), in collaboration with the LIPME (INRAE Toulouse) and the stratup iMean, has isolated and characterized such a bacterium (Ensifer adhaerens T4) from Medicago nodules. On the same legume plant, the T4 strain can induce ineffective, non-nitrogen-fixing nodules in a highly competitive way, and behave as a harsh parasite triggering plant death. The T4 strain showed this dual behavior on multiple legume species, the output of the interaction depending on the developmental stage of the plant. This study also showed that beyond the T4 strain, other E. adhaerens strains such as T173 harbor such dual patho-symbiotic behavior. Overall, these bacteria might represent a missing link between ancestral pathogens and nodulating rhizobia.

Procedure used to trap Medicago littoralis nodule endophytes and to validate the Koch’s postulate. The three behaviors (endophyte, symbiotic, or pathogenic) of the T4 strain, depending of the plant developmental stage, are indicated at the bottom of the scheme.

21/11/2024