INSTITUTO DE BIOTECNOLOGIA Y BIOLOGIA MOLECULAR
Unidad Ejecutora - UE
congresos y reuniones científicas
Sequencing aproach and characterization of the broad host range Rhizobium sp. LPU83 plasmids.
TORRES TEJERIZO G, M F DEL PAPA, W DRAGHI, M LOZANO, M Á GIUSTI, C MARTINI, E SALAS, I SALTO, D WIBERG, R SZCZEPANOWSKI, S WEIDNER , A SCHLÜTER , A PÜHLER , A LAGARES, Y M PISTORIO
San Carlos de Bariloche
Conferencia; International Plasmid Biology Conference 2010; 2010
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 (1, 2). 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. The draft nucleotide sequence of this strain was established by a de novo sequencing approach carried out on a GS FLX system (454 Life Sciences, Roche). Different strategies have been used for completing the chromosome of LPU83. Afterwards, we have determinate all the contigs that belongs to the plasmids of LPU83 and analyzed them. The predicted coding sequences were annotated and categorized by functional class by the use of COG. With this classification, genes for Amino Acid metabolism and transport, Transcription, Carbohydrate metabolism and transport, and DNA replication, recombination and repair were well represented. As expected of the previously results of the plasmid mobilization experiments, we have found three gene cluster with homology with previously report Mpf/Dtr systems. Recently, we have closed the sequence of the small plasmid, pLPU83a. The complete nucleotide sequence of LPU83 plasmids will be helpful to extend the knowledge of the peculiar phenotypic and taxonomic characteristics of strain LPU83.