Legume symbiotic nitrogen fixation by beta-proteobacteria is widespread in nature

Chen , W.M. and Moulin , L. and Bontemps, C. and et al, . (2003) Legume symbiotic nitrogen fixation by beta-proteobacteria is widespread in nature. Journal of Bacteriology, 185 (24). pp. 7266-7272.

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Following the initial discovery of two legume-nodulating Burkholderia strains (L. Moulin, A. Munive, B. Dreyfus, and C. Boivin-Masson, Nature 411:948-950, 2001), we identified as nitrogen-fixing legume symbionts at least 50 different strains of Burkholderia caribensis and Ralstonia taiwanensis, all belonging to the beta-subclass of proteobacteria, thus extending the phylogenetic diversity of the rhizobia. R. taiwanensis was found to represent 93% of the Mimosa isolates in Taiwan, indicating that beta-proteobacteria can be the specific symbionts of a legume. The nod genes of rhizobial beta-proteobacteria (beta-rhizobia) are very similar to those of rhizobia from the alpha-subclass (alpha-rhizobia), strongly supporting the hypothesis of the unique origin of common nod genes. The beta-rhizobial nod genes are located on a 0.5-Mb plasmid, together with the nifH gene, in R. taiwanensis and Burkholderia phymatum. Phylogenetic analysis of available nodA gene sequences clustered beta-rhizobial sequences in two nodA lineages intertwined with alpha-rhizobial sequences. On the other hand, the beta-rhizobia were grouped with free-living nitrogen-fixing beta-proteobacteria on the basis of the nifH phylogenetic tree. These findings suggest that beta-rhizobia evolved from diazotrophs through multiple lateral nod gene transfers.

Item Type: Article
Additional Information: We thank Y. Prin for help in microscopy studies and M.Dukhan for help with photographs. We also thank D. Barker and J. Batut for comments and suggestions. W.-M. Chen was supported by a grant from the National Science Council, Taipei, Taiwan, Republic of China (NSC 91-2320-B-022-001).
Uncontrolled Keywords: Legume, Symbiotic nitrogen fixation, Beta bacteria
Author Affiliation: Laboratory of Microbiology, Department of Seafood Science, National Kaohsiung Institute of Marine Technology, Taiwan.
Subjects: Plant Protection
Soil Science and Microbiology
Crop Improvement
Divisions: Chickpea
Common Bean
Depositing User: Mr Arbind Seth
Date Deposited: 20 Feb 2013 11:12
Last Modified: 20 Feb 2013 11:12
Official URL: http://dx.doi.org/10.1128/​JB.185.24.7266-7272.200...
URI: http://eprints.icrisat.ac.in/id/eprint/9626

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