Molecular systematics, microevolution and phylogeography of plant-associated Proteobacteria.

Participants: Claudia Silva, Lourdes Lloret, Ernesto Ormeño, Esperanza Martínez-Romero, Valeria Souza(IE-UNAM), Luis Eguiarte (IE-UNAM) and Pablo Vinuesa.

We are studying diverse aspects of the molecular systematics, evolutionary biology and biogeography of plant-associated bacteria, using state of the art phylogenetic inference methods combined with population genetic approaches. The inferences are based on multilocus sequence analyses from large collections of isolates obtained from different hosts and geographic origins.

Our recent works on these issues using rhizobia associated with different legume tribes have shown that taking this evolutionary approach is not only suitable, but very effective to delineate bacterial species. We are implementing such methods in molecular systematic and taxonomic studies of different groups of rhizobia. These approaches have also shown that all the species that we have studied so far have a very broad geographic distribution, often displaying different symbiotic ecotypes or biovarieties in different ecosystems. Recombination and migration apparently have a very strong impact on shaping the population genetic structure of diverse rhizobial species. (Fig.5 and 6)

Fig. 5. Native acacias from Morelos bear newly described nodule bacteria.
Fig. 6. Effects of Rhizobium on Leucaena plants. Plants without bacteria in the middle
Environmental and Symbiotic Microbiology Group