title: Nitrogen-fixing sinorhizobia with Medicago laciniata constitute a novel biovar (bv. medicaginis) of S. meliloti.
abstract: Sixty-eight new rhizobial isolates were obtained from root-nodules of Medicago laciniata and from Mediterranean soils in Tunisia and France. All of them were identified as Sinorhizobium meliloti on the basis of PCR-RFLP analyses of 16S rDNA and the intergenic spacer sequence between 16S and 23S rDNAs. DNA/DNA hybridization, phenotypic characterization and 16S rRNA gene sequencing led to the conclusion that they belong the same taxon. All new isolates shared the ability to nodulate and fix nitrogen with M. laciniata except 11 of them not capable of fixing nitrogen with this plant and originating from French soils containing no efficiently adapted symbionts with M. laciniata. The nitrogen-fixing rhizobia on M. laciniata differed markedly from the other S. meliloti or Sinorhizobium medicae isolates and references in their symbiotic traits such as nifDK RFLP diversity, nodA sequences and nitrogen effectiveness with tree other different annual Medicago species (M. truncatula, M. polymorpha and M. sauvagei). Two infrasubspecific (biovar) divisions are therefore proposed within S. meliloti: bv. medicaginis for Sinorhizobium efficient on M. laciniata and bv. meliloti for the classically known S. meliloti group represented by the strains ATCC9930(T) and RCR 2011 efficient on M. sativa.
authors.affiliation: Laboratoire des Symbioses Tropicales et Méditerranéennes Cirad Ensa.M Ird UmII, TA10/J, Campus International de Baillarguet, 34 398 Montpellier Cedex 5, France.
authors.forename: Maria Del Carmen
authors.initials: Mdel C
authors.lastname: Villegas
authors.forename: Sophie
authors.initials: S
authors.lastname: Rome
authors.forename: Lucette
authors.initials: L
authors.lastname: Mauré
authors.forename: Odile
authors.initials: O
authors.lastname: Domergue
authors.forename: Louis
authors.initials: L
authors.lastname: Gardan
authors.forename: Xavier
authors.initials: X
authors.lastname: Bailly
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Cleyet-Marel
authors.forename: Brigitte
authors.initials: B
authors.lastname: Brunel
mesh_terms: D000217:Acyltransferases / Q000737:chemistry / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D001483:Base Sequence; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D005602:France; D014644:Genetic Variation; D029902:Medicago / Q000382:microbiology*; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation / Q000502:physiology*; D009693:Nucleic Acid Hybridization; D010641:Phenotype; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000235:genetics; D053204:Root Nodules, Plant / Q000382:microbiology; D017422:Sequence Analysis, DNA; D016962:Sinorhizobium meliloti / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D013559:Symbiosis / Q000502:physiology; D014416:Tunisia
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D021903:DNA, Ribosomal Spacer; D012336:RNA, Ribosomal, 16S; D000217:Acyltransferases; C060770:NodA protein, Rhizobiales