IBBM   21076
INSTITUTO DE BIOTECNOLOGIA Y BIOLOGIA MOLECULAR
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Genomic analysis, transfer capabilities and symbiovars in Rhizobium
Autor/es:
ALTHABEGOITI, M. J.; ORMEÑO-ORRILLO, E.; LOZANO, L.; TORRES TEJERIZO, G.; GÓNZALEZ, V; MARTÍNEZ-ROMERO, E.
Lugar:
Cuatro Ciénegas
Reunión:
Congreso; III Congreso de Bioquímica y Biología Molecular de Bacteria; 2013
Resumen:
Rhizobia
are soil, rhizospheric and nodule bacteria. A large proportion of their genome,
nearly 50 %, is plasmid borne. Nodulation and nitrogen fixation capabilities as
well as host-legume specificity is plasmid encoded in Rhizobium in the so called symbiotic plasmids. The term symbiovar (sv.)
has been proposed to refer to symbiotic specificity and accounts for the
existence of different specificities in a single species and for the same
specificity in different rhizobial lineages, in relation to plasmid lateral
transfer (1). Most Phaseolus vulgaris nodulating bacteria
correspond to ?tropici? or ?phaseoli? symbiovars and those pSyms have a high
frequency of transfer among rhizobia. The ?phaseoli? pSym is found in distantly
related species. We have analyzed the genomes of a diversity of rhizobia (6, 7), including Rhizobium grahamii that represents a new group of rhizobia that has
been poorly characterized until now (2, 3).
R. grahamii has a broad-host-range
that includes Leucaena leucocephala
and P. vulgaris bean although it is a
poor competitor for bean nodulation in the presence of Rhizobium etli or Rhizobium
phaseoli strains. In R. grahamii
CCGE502 chromosome an integrated plasmid was found, supporting the already
described genomic plasticity (4). The
genomic comparison of symbiotic plasmids suggests that these plasmids are species-specific
in the grahamii group. In sv. ?phaseoli? or sv. ?tropici?, pSyms display high
conservation, around 90% and 99%, respectively (5, 6). We were unable to transfer the R. grahamii CCGE502 pSym and a larger plasmid to other rhizobial
hosts but we could transfer the symbiotic plasmid to Agrobacterium tumefaciens with transfer dependent on homoserine
lactones. The conjugative transfer properties of R. grahamii CCGE502 plasmids may explain their divergence and
narrow distribution in related rhizobial species.