title: Characterization of extrachromosomal replicons present in the extended host range Rhizobium sp. LPU83.
abstract: In several rhizobia, bacteria that inhabit the soil in free-living conditions and associate in symbiosis with the root of legumes as nitrogen-fixing organisms, plasmid DNA can constitute a high percentage of the genome. We have characterized acid-tolerant isolates of rhizobia-here represented by the strain Rhizobium sp. LPU83-that have an extended nodulation-host range including alfalfa, the common bean, and Leucena leucocephala. In this study we analyzed the plasmids of R. sp. LPU83 in order to characterize their role in the evolution of Medicago symbionts and their involvement in symbiotic behavior. The pLPU83a plasmid was found to be transmissible with no associated phenotypic traits. The symbiotic plasmid pLPU83b could be transferred at very low frequencies under laboratory conditions only when pLPU83a was present; could restore nodulation to a strain cured of its symbiotic plasmid, S. meliloti A818; but could not restore the full nitrogen fixation associated with alfalfa.
authors.affiliation: IBBM - Instituto de Biotecnología y Biología Molecular, CCT-CONICET-La Plata - Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calles 47 y 115, La Plata, Argentina.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Torres Tejerizo
authors.forename: María Florencia
authors.initials: MF
authors.lastname: Del Papa
authors.forename: María
authors.initials: M
authors.lastname: de los Angeles Giusti
authors.forename: Walter
authors.initials: W
authors.lastname: Draghi
authors.forename: Mauricio
authors.initials: M
authors.lastname: Lozano
authors.forename: Antonio
authors.initials: A
authors.lastname: Lagares
authors.forename: Mariano
authors.initials: M
authors.lastname: Pistorio
mesh_terms: D003227:Conjugation, Genetic / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D007887:Fabaceae / Q000235:genetics / Q000382:microbiology*; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D009586:Nitrogen Fixation / Q000235:genetics / Q000502:physiology; D018517:Plant Roots / Q000235:genetics / Q000382:microbiology; D012093:Replicon / Q000235:genetics* / Q000502:physiology; D012231:Rhizobium / Q000235:genetics* / Q000502:physiology; D013559:Symbiosis / Q000235:genetics
chemical_list: D018744:DNA, Plant