Abstract
PurposeThe aim of this study was to estimate the level of genomic and phenotypic diversity as well as the genus and species position of bacterial strains isolated from root nodules of Lembotropis nigricans (family Fabaceae).MethodsThe genomic diversity of studied L. nigricans nodule symbionts was examined by using BOX-PCR and AFLP (amplified fragment length polymorphism) fingerprinting techniques. To assign bacteria to the genus, numerical analysis of phenotypic features and comparative analysis of 16S rDNA sequences were performed. The comparative analysis of combined atpD, dnaK, gyrB, and rpoB gene sequences (multilocus sequence analysis, MLSA) was used to determine the most closely related species to the studied bacteria.ResultsBoth BOX-PCR and AFLP techniques revealed a high level of genomic heterogeneity of L. nigricans nodulators. Among 33 studied bacteria, 32 genotypes were delineated by the AFLP method and 27 genotypes were identified by the BOX-PCR fingerprinting. The numerical analysis of 86 phenotypic characteristics of L. nigricans nodule isolates and reference rhizobia showed that studied bacteria belong to the genus Bradyrhizobium. Affiliation of L. nigricans nodule isolates to the genus Bradyrhizobium was supported by comparative analysis of 16S rDNA sequences and the concatenation of atpD, dnaK, gyrB, and rpoB gene sequences. MLSA indicated also that L. nigricans microsymbionts are members of Bradyrhizobium japonicum.ConclusionL. nigricans root nodule symbionts are members of Bradyrhizobium japonicum and exhibit high phenotypic and genomic diversity important for their survival in soil.
Highlights
Magdalena Wójcik and Michał Kalita contributed to this work.The GenBank accession numbers for sequences generated in this study are as follows: MK183761-MK183771 (16S rRNA), MK202810MK202820, MK202821-MK202831, MK202832MK202842, MK202843-MK202853.Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Rhizobia are soil-inhabiting bacteria capable of establishing nitrogen-fixing symbiosis with plant species of the family Fabaceae
Among 33 studied bacteria, 32 genotypes were delineated by the AFLP method and 27 genotypes were identified by the BOX-polymerase chain reaction (PCR) fingerprinting
A total of 48 bacterial strains, including 33 L. nigricans symbionts and 15 reference strains, representing different species of the genera: Bradyrhizobium, Ensifer, Mesorhizobium, and Rhizobium were analyzed for 86 phenotypic properties
Summary
Genisteae encompassing more than 600 species distributed among 25 genera is one of the largest tribes within the legume family (Cardoso et al 2013). There are published reports on the phylogeny and taxonomy of bacterial strains isolated from root nodules of 77 plant species of the tribe Genisteae. Based on these reports, it was concluded that the strains of the genus Bradyrhizobium form a predominant group infecting Genisteae legumes (Stępkowski et al 2018). There are no data available on rhizobia of 14 Genisteae genera. One of such plant genus is Lembotropis comprising two species: Lembotropis nigricans L. nigricans (black broom) is distributed in Central and Southeastern Europe; its exact range is hard to estimate since it has been grown as an
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