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Published on: August 25, 2018
Rhizobium etli taxonomy revised with novel genomic data and analyses
Martha G López-Guerrero1, Ernesto Ormeño-Orrillo, Encarna Velázquez
1Centro de Ciencias Genómicas, UNAM, Cuernavaca, Morelos, Mexico.
Systematic and Applied Microbiology
|August 4, 2012
Summary
Rhizobium phaseoli and Rhizobium etli strains were reclassified based on genomic and hybridization data. This study clarifies the taxonomy of Phaseolus vulgaris rhizobial symbionts.
Area of Science:
- Microbiology
- Plant-microbe interactions
- Genomics
Background:
- Accurate bacterial taxonomy is crucial for understanding symbiotic relationships.
- Phaseolus vulgaris (common bean) relies on rhizobial symbionts for nitrogen fixation.
- Previous classifications of rhizobial strains were ambiguous.
Purpose of the Study:
- To determine the precise taxonomic position of specific Phaseolus vulgaris rhizobial strains.
- To resolve taxonomic discrepancies using genomic and phylogenetic analyses.
- To reclassify strains based on robust evidence.
Main Methods:
- Phylogenetic analysis using concatenated conserved genomic fragments.
- Whole-genome Average Nucleotide Identity (ANI) calculations.
- DNA-DNA hybridization (DDH) experiments.
Main Results:
- Phylogenetic and ANI analyses supported a distinct group for strains CIAT 652, Ch24-10, and CNPAF 512, separate from Rhizobium etli CFN 42(T).
- DNA-DNA hybridization values were borderline for R. etli but high for Rhizobium phaseoli ATCC 14482(T).
- Strains 8C-3 and Brasil5 were reclassified as R. phaseoli based on ANIm analysis.
Conclusions:
- Strains CIAT 652, Ch24-10, and CNPAF 512 are reclassified as Rhizobium phaseoli.
- The speciation between R. phaseoli and R. etli is a relatively recent evolutionary event.
- This reclassification clarifies the taxonomy of common bean rhizobia.
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