IBBM   21076
INSTITUTO DE BIOTECNOLOGIA Y BIOLOGIA MOLECULAR
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Genome sequencing of the broad-host-range Rhizobium sp. LPU83 and characterization of its chromosomal phylogenetic relationships
Autor/es:
TORRES TEJERIZO, G.A.; DEL PAPA, M.F.; LOZANO, M.; GIUSTI, M. A.; MARTINI, C.; SALAS, M.E.; SALTO, I.; LAGARES, A.; PISTORIO, M.
Lugar:
Tucumán
Reunión:
Congreso; VII Congreso Argentino de Microbiología General, SAMIGE Del Bicentenario; 2011
Institución organizadora:
SAMIGE
Resumen:
Alfalfa (Medicago
sativa) is the most widely cultivated forage legume for cattle and animal
feeding over the world. In Argentina, over 6 million hectares of land are
cultivated with alfalfa, where the productive symbiosis with N2-fixation
efficient rhizobia represents a crucial condition for insuring the entry of
fixed atmospheric nitrogen into agricultural soils (1). A distinctive feature of alfalfa is the marked
specificity of this legume towards its microsymbiont partners E. meliloti or E. medicae, but a different population of
rhizobia represented by the strains Rhizobium sp. Or191 and
LPU83 are present in fields and are able to nodulate alfalfa (2, 3). These
rhizobia are acid-tolerant and have an extended host range; moreover, they
possess the ability to nodulate Phaseolus
vulgaris (3) and Leucaena leucocephala (2), among
other legumes, and are highly competitive for the nodulation of alfalfa in acid
soils. A phylogenetic analysis of the 16s rRNA gene showed
that the Oregon-like strains were related to the bean-, pea-, and
clover-nodulating rhizobia. In contrast, the phylogenetic analysis of the nodC gene indicated that the E. meliloti
nodC gene, is the most closely related one, thus suggesting that both nodC genes originated from a common
ancestor. Moreover, the collected genetic information has revealed that
the genomic structure of these rhizobial isolates is complex in terms of
sequence similarities shared with other rhizobia. Such a "patched"
genetic composition has obviously imposed severe restrictions to the classical
taxonomy of these rhizobia. In order to more
completely characterize the genetics of the Oregon-like strains, Rhizobium sp. LPU83 was fully sequenced.
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) using the Titanium sequencing
chemistry. An in-depth phylogenetic study was performed involving concatenation
of these seven genes (dnaK, glnA, gltA, gyrB, recA, rpoB, and thrC). The
LPU83 strain is located close to a clade where Rhizobium etli and Rhizobium leguminosarum were situated,
as had been observed previously for other housekeeping genes. Interestingly, in
this tree LPU83 appears to be a precursor of this linage.
The
complete LPU83 genomic sequence together with future information from new,
likewise entirely sequenced rhizobial genomes will constitute key information towards
a more complete characterization and reconstruction of the Oregon-like genomic
genealogy.
1. A.
Perticari et al., Divulgación Técnica del Instituto de
Microbiología Agrícola.CICA-INTA, Castelar, Argentina, (1989).
2. M. F. Del Papa et al., Appl Environ
Microbiol 65, 1420 (Apr, 1999).
3. B. D. Eardly, D. B. Hannaway, P. J.
Bottomley, Appl Environ Microbiol 50, 1422 (Dec, 1985).