ABSTRACT
A gram-negative, motile, non-spore-forming rod, designated NS12(T), was isolated from macerated petioles of Rumex sp. after enrichment with oxalate. On the basis of 16S rRNA gene sequence similarity, strain NS12(T) was phylogenetically related to the genera Azorhizobium and Xanthobacter in the class Alphaproteobacteria. Strain NS12(T) was most closely related to Azorhizobium doebereinerae BR 5401(T) and Azorhizobium caulinodans ORS 571(T) (98.3 and 97.3â% 16S rRNA gene sequence similarity, respectively). Membership of the genus Xanthobacter was excluded by phenotypic characterization. The whole-cell fatty acid compositions of the isolate was typical of members of the genus Azorhizobium with C18â:â1ω7c, cyclo-C19â:â0ω8c, 11-methyl-C18â:â1ω7c and C16â:â0 as the main components. The results of DNA-DNA hybridization and physiological tests allowed the genotypic and phenotypic differentiation of strain NS12(T) from the two members of the genus Azorhizobium. Therefore it is concluded that the isolate represents a novel species of the genus Azorhizobium, for which the name Azorhizobium oxalatiphilum sp. nov. is proposed. The type strain is NS12(T) (â=âDSM 18749(T)â=âCCM 7897(T)). The description of the genus Azorhizobium is also emended.
Subject(s)
Azorhizobium/classification , Phylogeny , Rumex/microbiology , Azorhizobium/genetics , Azorhizobium/isolation & purification , Bacterial Typing Techniques , DNA, Bacterial/genetics , Fatty Acids/analysis , Genotype , Molecular Sequence Data , Nucleic Acid Hybridization , Phenotype , Quinones/analysis , RNA, Ribosomal, 16S/genetics , Sequence Analysis, DNAABSTRACT
Herb legumes have great potential for rehabilitation of semi-arid degraded soils in Sahelian ecosystems as they establish mutualistic symbiosis with N(2)-fixing rhizobia. A phylogenetic analysis was performed for 78 root nodule bacteria associated with the common Sahelian herb legume Zornia glochidiata Reichb ex DC in Senegal. Based on ITS (rDNA16S-23S) and recA sequences, these strains were shown to belong to the two genera Bradyrhizobium and Azorhizobium. Strains of this latter, although frequent, formed small and ineffective nodules and suggested a parasitism rather than a symbiotic association. A potential negative effect of Azorhizobium on Zornia growth was tested for when inoculated alone or in association with a Bradyrhizobium strain. Bradyrhizobium isolates were distributed in four groups. Groups A and B were two sister clades in a larger monophyletic group also including Bradyrhizobium liaoningense, Bradyrhizobium yuanmingense, and Bradyrhizobium japonicum. Strains of cluster D fell in a sister clade of the photosynthetic Bradyrhizobium sp. group, including ORS278, whereas group C appeared to be divergent from all known Bradyrhizobium clusters. Amplified fragment length polymorphism (AFLP) clustering was congruent with ITS and recA phylogenies, but displayed much more variability. However, within the main Bradyrhizobium clades, no obvious relationship could be detected between clustering and geographical origin of the strains. Each sub-cluster included strains sampled from different locations. Conversely, Azorhizobium strains showed a tendency in the phylogeny to group together according to the site of sampling. The predominance of ineffective Azorhizobium strains in the nodules of Zornia roots, the large Bradyrhizobium genetic diversity and the geographical genetic diversity pattern are explored.
Subject(s)
Azorhizobium , Bradyrhizobium , Fabaceae/microbiology , Genetic Variation , Plant Roots/microbiology , Amplified Fragment Length Polymorphism Analysis , Azorhizobium/classification , Azorhizobium/genetics , Azorhizobium/isolation & purification , Azorhizobium/physiology , Bacterial Typing Techniques , Bradyrhizobium/classification , Bradyrhizobium/genetics , Bradyrhizobium/isolation & purification , Bradyrhizobium/physiology , DNA, Bacterial/analysis , DNA, Ribosomal Spacer/analysis , Genes, rRNA , Molecular Sequence Data , Nitrogen Fixation , Phylogeny , RNA, Ribosomal, 16S/genetics , RNA, Ribosomal, 23S/genetics , Rec A Recombinases/genetics , Senegal , Sequence Analysis, DNA , Species Specificity , SymbiosisABSTRACT
Thirty-four rhizobium strains were isolated from root nodules of the fast-growing woody native species Sesbania virgata in different regions of southeast Brazil (Minas Gerais and Rio de Janeiro States). These isolates had cultural characteristics on YMA quite similar to Azorhizobium caulinodans (alkalinization, scant extracellular polysaccharide production, fast or intermediate growth rate). They exhibited a high similarity of phenotypic and genotypic characteristics among themselves and to a lesser extent with A. caulinodans. DNA:DNA hybridization and 16SrRNA sequences support their inclusion in the genus Azorhizobium, but not in the species A. caulinodans. The name A. doebereinerae is proposed, with isolate UFLA1-100 (=BR5401, =LMG9993=SEMIA 6401) as the type strain.
