title: Symbiotic and taxonomic diversity of rhizobia isolated from Acacia tortilis subsp. raddiana in Africa.
abstract: A collection of rhizobia isolated from Acacia tortilis subsp. raddiana from various sites in the North and South of Sahara was analyzed for their diversity at both taxonomic and symbiotic levels. On the basis of whole cell protein (SDS-PAGE) and 16S rDNA sequence analysis, most of the strains were found to belong to the Sinorhizobium and Mesorhizobium genera where they may represent several different genospecies. Despite their chromosomal diversity, most A. tortilis Mesorhizobium and Sinorhizobium symbionts exhibited very similar symbiotic characters. Nodulation tests showed that the strains belong to the Acacia-Leucaena-Prosopis nodulation group, although mainly forming non-fixing nodules on species other than A. tortilis. Most of the strains tested responded similarly to flavonoid nod gene inducers, as estimated by using heterologous nodA-lacZ fusions. Thin layer chromatography analysis of the Nod factors synthesized by overproducing strains showed that most of the strains exhibited similar profiles. The structures of Nod factors produced by four different Sinorhizobium sp. strains were determined and found to be similar to other Acacia-Prosopis-Leucaena nodulating rhizobia of the Sinorhizobium-Mesorhizobium-Rhizobium branch. They are chitopentamers, N-methylated and N-acylated by common fatty acids at the terminal non reducing sugar. The molecules can also be 6-O sulfated at the reducing end and carbamoylated at the non reducing end. The phylogenetic analysis of available NodA sequences, including new sequences from A. tortilis strains, confirmed the clustering of the NodA sequences of members of the Acacia-Prosopis-Leucaena nodulation group.
authors.affiliation: Laboratoire des Symbioses Tropicales et Méditerranéennes, IRD-INRA-CIRAD-ENSAM, Baillarguet, Montpellier, France.
authors.forename: Salif
authors.initials: S
authors.lastname: Ba
authors.forename: Anne
authors.initials: A
authors.lastname: Willems
authors.forename: Philippe
authors.initials: P
authors.lastname: de Lajudie
authors.forename: Philippe
authors.initials: P
authors.lastname: Roche
authors.forename: Habib
authors.initials: H
authors.lastname: Jeder
authors.forename: Paola
authors.initials: P
authors.lastname: Quatrini
authors.forename: Marc
authors.initials: M
authors.lastname: Neyra
authors.forename: Myriam
authors.initials: M
authors.lastname: Ferro
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Promé
authors.forename: Monique
authors.initials: M
authors.lastname: Gillis
authors.forename: Catherine
authors.initials: C
authors.lastname: Boivin-Masson
authors.forename: Jean
authors.initials: J
authors.lastname: Lorquin
mesh_terms: D000045:Acacia / Q000382:microbiology*; D000217:Acyltransferases / Q000032:analysis / Q000235:genetics; D000349:Africa; D020561:Alphaproteobacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D001426:Bacterial Proteins; D002240:Carbohydrate Sequence; D002855:Chromatography, Thin Layer; D004591:Electrophoresis, Polyacrylamide Gel; D005419:Flavonoids / Q000378:metabolism; D014644:Genetic Variation; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D018517:Plant Roots / Q000382:microbiology; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D013045:Species Specificity; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D005419:Flavonoids; D008070:Lipopolysaccharides; D000217:Acyltransferases; C060770:NodA protein, Rhizobiales