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Accueil > Animation Scientifique > Victor Gonzalez du Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México

lundi 13 septembre 2010

Victor Gonzalez du Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México

Salle de réunion, Bâtiment Mendel 5e étage

Séminaire de l’UMR5557 :

"The multireplicon pangenome of Rhizobium etli in relation to the mobile genetic elements"


Related publication : Conserved Symbiotic Plasmid DNA Sequences in the Multireplicon Pangenomic Structure of Rhizobium etli.

Strains of the same bacterial species often show considerablegenomic variation. To examine the extent of such variation in Rhizobium etli, the complete genome sequence of R. etli CIAT652and the partial genomic sequences of six additional R. etlistrains having different geographical origins were determined.The sequences were compared with each other and with the previouslyreported genome sequence of R. etli CFN42. DNA sequences commonto all strains constituted the greater part of these genomesand were localized in both the chromosome and large plasmids.About 700 to 1,000 kb of DNA that did not match sequences ofthe complete genomes of strains CIAT652 and CFN42 was uniqueto each R. etli strain. These sequences were distributed throughoutthe chromosome as individual genes or chromosomal islands andin plasmids, and they encoded accessory functions, such as transportof sugars and amino acids, or secondary metabolism ; they alsoincluded mobile elements and hypothetical genes. Sequences correspondingto symbiotic plasmids showed high levels of nucleotide identity(about 98 to 99%), whereas chromosomal sequences and the sequenceswith matches to other plasmids showed lower levels of identity(on average, about 90 to 95%). We concluded that R. etli hasa pangenomic structure with a core genome composed of both chromosomaland plasmid sequences, including a highly conserved symbioticplasmid, despite the overall genomic divergence.

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