ABSTRACT
We isolated 71 slow-growing bacterial strains from nodules of 27 native leguminous plants species in Senegal (West-Africa) belonging to the genera Abrus, Alysicarpus, Bryaspis, Chamaecrista, Cassia, Crotalaria, Desmodium, Eriosema, Indigofera, Moghania, Rhynchosia, Sesbania, Tephrosia, and Zornia playing an ecological role and having agronomic potential in arid regions. The isolates were characterised by restriction fragment length polymorphism (RFLP) analysis of PCR-amplified 16S rDNA and comparative SDS-PAGE of whole-cell proteins; reference strains of the different known rhizobial species and groups were included as references. We conclude that these nodule isolates are diverse, and form several phylogenetic subgroups inside Bradyrhizobium. Nodulation tests performed on 5 plant species demonstrated host specificity among the strains studied.
ABSTRACT
A group of nodule isolates from Neptunia natans, an indigenous stemnodulated tropical legume found in waterlogged areas of Senegal, was studied. Polyphasic taxonomy was performed, including SDS-PAGE of total proteins, auxanography using API galleries, host-plant specificity, PCR-RFLP of the internal transcribed spacer region between the 16S and the 23S rRNA coding genes, 16S rRNA gene sequencing and DNA-DNA hybridization. It was demonstrated that this group is phenotypically and phylogenetically separate from the known species of Rhizobium, Sinorhizobium, Mesorhizobium, Agrobacterium, Bradyrhizobium and Azorhizobium. Its closest phylogenetic neighbour, as deduced by 16S rRNA gene sequencing, is Agrobacterium vitis (96.2% sequence homology). The name Allorhizobium undicola gen. nov., sp. nov., is proposed for this group of bacteria, which are capable of efficient nitrogen-fixing symbiosis with Neptunia natans, and the type strain is ORS 992T (= LMG 11875T).
Subject(s)
Fabaceae/microbiology , Plants, Medicinal , Rhizobiaceae/classification , Rhizobiaceae/physiology , Base Composition , Carbohydrate Metabolism , Electrophoresis, Polyacrylamide Gel , Genes, rRNA , Molecular Sequence Data , Nitrogen Fixation , Nucleic Acid Hybridization , Phenotype , Phylogeny , Polymerase Chain Reaction/methods , Polymorphism, Restriction Fragment Length , RNA, Ribosomal, 16S/genetics , RNA, Ribosomal, 23S/genetics , Rhizobiaceae/genetics , Senegal , Sequence Analysis, DNA , Symbiosis , Terminology as TopicABSTRACT
A collection of strains isolated from root nodules of Acacia species in Senegal was analysed previously by electrophoresis of total cell protein, auxanographic tests, rRNA-DNA hydridization, 16S rRNA gene sequencing, DNA base composition and DNA-DNA hybridization [de Lajudie, P., Willems, A., Pot, B. & 7 other authors (1994). Int J Syst Bacteriol 44, 715-733]. Strains from Acacia were shown to belong to two groups, Sinorhizobium terangae, and a so-called gel electrophoretic cluster U, which also included some reference strains from Brazil. Further taxonomic characterization of this group using the same techniques plus repetitive extragenic palindromic-PCR and nodulation tests is presented in this paper. Reference strains from Sudan and a number of new rhizobia isolated from nodules of Acacia senegal, Acacia tortilis subsp. raddiana and Prosopis juliflora in Senegal were included. As a result of this polyphasic approach, the creation of a new species, Mesorhizobium plurifarium, is proposed for a genotypically and phenotypically distinct group corresponding to the former cluster U and containing strains isolated from Acacia, Leucaena, Prosopis and Chamaecrista in West Africa (Senegal), East Africa (Sudan) and South America (Brazil). The type strain of Mesorhizobium plurifarium ORS 1032 has been deposited in the LMG collection as LMG 11892.
Subject(s)
Rhizobiaceae/genetics , Acacia/microbiology , Bacterial Proteins/analysis , Base Composition , Base Sequence , DNA, Bacterial , Electrophoresis, Polyacrylamide Gel , Gene Amplification , Molecular Sequence Data , Nucleic Acid Hybridization , Phylogeny , Polymerase Chain Reaction , RNA, Ribosomal, 16S , Rhizobiaceae/chemistry , Rhizobiaceae/classification , Sequence Analysis, RNA , Sodium Dodecyl SulfateABSTRACT
One hundred reference strains representing all species belonging to the different phylogenetic lineages of the viridans streptococci were examined by means of one-dimensional whole-organism protein electrophoresis. For most of the species examined, multiple strains characterized by DNA-DNA hybridization were included and, wherever described, representatives of different biochemical variants were analysed. Most species were clearly differentiated. The data support the viewpoint that members of the Streptococcus anginosus group constitute a single species and indicate that Streptococcus mitis biovar 2 is a heterogeneous taxon comprising strains from several streptococcal species.
Subject(s)
Genetic Heterogeneity , Streptococcus/chemistry , Streptococcus/genetics , Bacterial Proteins/analysis , Classification , Electrophoresis/standards , RNA, Bacterial/analysis , RNA, Ribosomal/analysis , Reproducibility of Results , Streptococcus/classification , Streptococcus mutans/chemistry , Streptococcus mutans/classification , Streptococcus mutans/genetics , Streptococcus oralis/chemistry , Streptococcus oralis/classification , Streptococcus oralis/genetics , Streptococcus sanguis/chemistry , Streptococcus sanguis/classification , Streptococcus sanguis/genetics , Streptococcus sobrinus/chemistry , Streptococcus sobrinus/classification , Streptococcus sobrinus/geneticsABSTRACT
The taxonomic positions of strains previously assigned to Pseudomonas diminuta and Pseudomonas vesicularis were investigated by a polyphasic approach. The results of DNA-rRNA hybridization studies indicated that these two species belong to a separate genus in the alpha subclass (rRNA superfamily IV) of the Proteobacteria, for which the name Brevundimonas is proposed. Genus delineation and species delineation were determined by comparing the results of numerical analyses of whole-cell protein patterns, fatty acid compositions, and phenotypic characteristics and by measuring DNA base ratios and degrees of DNA relatedness. Taxonomic characteristics of Brevundimonas diminuta and Brevundimonas vesicularis strains were compared with characteristics of reference strains belonging to the following phylogenetically related taxa: a group of organisms gathered in Enevold Falsen group 21, the genera Sphingomonas and Rhizomonas, and the generically misclassified organisms [Pseudomonas] echinoides and "[Pseudomonas] riboflavina."
