Genomic heterogeneity of strains nodulating XXXX ( @entity13474 .) and description of Rhizobium mediterraneum sp. nov.

@entity73141 @entity49694 @entity13474
The genetic diversity of @entity13474 strains was studied by using 30 isolates obtained from nodules on @entity13474 growing in uninoculated fields over a wide geographic range. The following taxonomic approaches were used: DNA-DNA relatedness analysis, restriction fragment length polymorphism analysis of the amplified 16S ribosomal DNA (rDNA) intergenic spacer (IGS), and total 16S rRNA sequence analysis. The division of @entity13474 -infective strains into two major phylogenetic groups (groups A and B) that has been described previously was confirmed by the polymorphism of the 16S IGS rDNA. We identified a total of five genomic species, including the previously described species @entity73141 . All of the group B strains except one were homogeneous and belonged to a single genomic species corresponding to @entity73141 . Group A was heterogeneous, containing three genomic species and five strains that remained unclassified, and its members had very different PCR restriction fragment length polymorphism profiles. The complete 16S rRNA sequences of strains representing the two major groups, @entity73141 UPM-Ca7T (T = type strain) and genomic species 2 strain UPM-Ca36T, exhibited 19 mismatches. Both of these strains belonged to the @entity49694 -Rhizobium huakuii branch; @entity73141 UPM-Ca7T was closely related to @entity49694 , and strain UPM-Ca36T was clearly separated from @entity73141 and closely related to R. huakuii. Thus, genomic species 2 could be distinguished from @entity73141 by its 16S rRNA sequence, by DNA relatedness data, by the polymorphism of the 16S IGS rDNAs, and by previously described multilocus enzyme electrophoresis results and phenotypic characteristics. Therefore, we propose that strains belonging to genomic species 2 should be classified in a new species, Rhizobium mediterraneum, and that strain UPM-Ca36 should be the type strain.
