Genetic and phenetic analyses of Bradyrhizobium strains nodulating peanut (Arachis hypogaea L.) roots

Abstract

Seventeen Bradyrhizobium sp. strains and one Azorhizobium strain were compared on the basis of five genetic and phenetic features: (i) partial sequence analyses of the 16S rRNA gene (rDNA), (ii) randomly amplified DNA polymorphisms (RAPD) using three oligonucleotide primers, (iii) total cellular protein profiles, (iv) utilization of 21 aliphatic and 22 aromatic substrates, and (v) intrinsic resistances to seven antibiotics. Partial 16S rDNA analysis revealed the presence of only two rDNA homology (i.e., identity) groups among the 17 Bradyrhizobium strains. The partial 16S rDNA sequences of Bradyrhizobium sp. strains form a tight similarity (>95%) cluster with Rhodopseudomonas palustris, Nitrobacter species, Afipia species, and Blastobacter denitrificans but were less similar to other members of the ␣-Proteobacteria, including other members of the Rhizobiaceae family. Clustering the Bradyrhizobium sp. strains for their RAPD profiles, protein profiles, and substrate utilization data revealed more diversity than rDNA analysis. Intrinsic antibiotic resistance yielded strainspecific patterns that could not be clustered. High rDNA similarity appeared to be a prerequisite, but it did not necessarily lead to high similarity values between RAPD profiles, protein profiles, and substrate utilization. The various relationship structures, coming forth from each of the studied features, had low compatibilities, casting doubt on the usefulness of a polyphasic approach in rhizobial taxonomy.

Phenotypic and genotypic characterizations of rhizobia isolated from root nodules of peanut (Arachis hypogaea L.) grown in Moroccan soils

“…The nodulation ability of all isolates was confirmed by the formation of typically reddish nodules. The isolation of fast-growing rhizobia from peanut nodules is worth [3,4,14,15]. Our findings reveal peanut as a broad-range host and coincide with recent work by Taurian et al [5,16] which reported efficient native populations of fast-growing rhizobia associated to this species in central Argentina.…”

Biodiversity of rhizobia isolated from a wide range of forest legumes in Brazil

“…SDS-PAGE of total proteins can often reveal genetic variation within a species, but does not give reliable information on more distant genetic relationships (de Lajudie et al 1994;Dupuy et al 1994;Van Rossum et al 1995). In our study, isolates with the same 16S rRNA partial sequence often had quite dissimilar SDS-PAGE patterns, while strains with the same SDS-PAGE pattern belonged to the same or closely related 16S groups (Table 1).…”

Phenotypic and molecular characterization of chickpea rhizobia isolated from different areas of Morocco

“…These results may indicate that the tolerance of strains to antibiotics and heavy metals is not correlated with their growth rate, but it could also be related to the bacterial species. Stowers (1985) and van Rossum et al 1995) reported that fast-growing rhizobia could metabolize a wider range of Nour et al (1994aNour et al ( , 1994b, showed that chickpea rhizobia strains from Morocco (more than 90% of them being very slow growers), could utilize a broad range of carbohydrates. On the other hand, some carbon sources such as b-methyl-xyloside and amethyl-glucoside were exclusively metabolized by some stains of cluster III and cluster I, respectively.…”