|Van Berkum, Peter|
Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2009
Publication Date: 4/1/2009
Citation: Van Berkum, P.B., Elia, P.E., Peix, A., Garcia-Fraile, P., Leon-Barrios, M., Velazquez, E. 2009. Rhizobia from Lanzarote, the Canary Islands, that nodulate Phaseolus vulgars have characteristics in common with Sinorhizobium meliloti isolates from mainland Spain. Applied and Environmental Microbiology. 75(8):2354-2359. Interpretive Summary: Certain crops called legumes, important to North American agriculture, require bacteria called rhizobia to be associated with them in order to produce nitrogen for growth and production. We compared rhizobia bacteria of beans growing in Lanzarote, the Canary Islands, with those of alfalfa and of a tree that occurs naturally in southern Mexico and discovered that all three groups are closely related. Since, alfalfa rhizobia occur naturally on the island of Lanzarote we concluded that they may have received the genes controlling the association with beans from introduced rhizobia of the tree. Therefore, our results indicate that within the soils of agricultural fields bacterial genes are easily and rapidly transferred between different species. This information will be valuable to companies who sell bacterial preparations for different leguminous crops because the bacteria identified in this work may have valuable properties not found in the bacteria used currently. Also, geneticists, evolutionary biologists, microbiologists and environmental scientists will find this information useful in their studies to determine how these bacteria can interact with each other and with crop plants.
Technical Abstract: Common bean and Medicago rhizobia isolated from five locations on the island of Lanzarote, the Canary Islands, by partial analysis of 10 chromosomal genes were shown to exhibit close similarity to Sinorhizobium meliloti. Several bean isolates from Lanzarote, mainland Spain and Tunisia nodulated Leucaena leucocephala probably because of the presence of a nodO gene in their genomes similar to that of the strain BR816. The derived gene products of aspartate-semialdehyde dehydrogenase (asd) and uridylate kinase (pyrH) were used to determine the similarity between the chromosomes of the bean isolates from Lanzarote having the nodO gene and rhizobial strains isolated from L. leucocephala that were of diverse geographic origin. Each of the two gene products were similar among the bean isolates, the Leucaena strains, and references used for S. meliloti and S. fredii. However, incongruence in the two bifurcating trees drawn from the two alignments indicated a history of genetic recombination. The presence of bean-nodulating Sinorhizobium on Lanzarote possibly is explained by the spread of Leucaena rhizobia to Europe subsequent to colonization of the Americas. Alternatively, they are descendents from recombinants of local bacteria with S. meliloti chromosomes that were recipients of symbiotic plasmids from the introduced Leucaena rhizobia.