title: Analysis of the chromosome sequence of the legume symbiont Sinorhizobium meliloti strain 1021.
abstract: Sinorhizobium meliloti is an alpha-proteobacterium that forms agronomically important N(2)-fixing root nodules in legumes. We report here the complete sequence of the largest constituent of its genome, a 62.7% GC-rich 3,654,135-bp circular chromosome. Annotation allowed assignment of a function to 59% of the 3,341 predicted protein-coding ORFs, the rest exhibiting partial, weak, or no similarity with any known sequence. Unexpectedly, the level of reiteration within this replicon is low, with only two genes duplicated with more than 90% nucleotide sequence identity, transposon elements accounting for 2.2% of the sequence, and a few hundred short repeated palindromic motifs (RIME1, RIME2, and C) widespread over the chromosome. Three regions with a significantly lower GC content are most likely of external origin. Detailed annotation revealed that this replicon contains all housekeeping genes except two essential genes that are located on pSymB. Amino acid/peptide transport and degradation and sugar metabolism appear as two major features of the S. meliloti chromosome. The presence in this replicon of a large number of nucleotide cyclases with a peculiar structure, as well as of genes homologous to virulence determinants of animal and plant pathogens, opens perspectives in the study of this bacterium both as a free-living soil microorganism and as a plant symbiont.
authors.affiliation: Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, Unité Mixte de Recherche (UMR) 215 Centre National de la Recherche Scientifique (CNRS), Institut National de la Recherche Agronomique, Castanet Tolosan Cedex, France.
authors.forename: D
authors.initials: D
authors.lastname: Capela
authors.forename: F
authors.initials: F
authors.lastname: Barloy-Hubler
authors.forename: J
authors.initials: J
authors.lastname: Gouzy
authors.forename: G
authors.initials: G
authors.lastname: Bothe
authors.forename: F
authors.initials: F
authors.lastname: Ampe
authors.forename: J
authors.initials: J
authors.lastname: Batut
authors.forename: P
authors.initials: P
authors.lastname: Boistard
authors.forename: A
authors.initials: A
authors.lastname: Becker
authors.forename: M
authors.initials: M
authors.lastname: Boutry
authors.forename: E
authors.initials: E
authors.lastname: Cadieu
authors.forename: S
authors.initials: S
authors.lastname: Dréano
authors.forename: S
authors.initials: S
authors.lastname: Gloux
authors.forename: T
authors.initials: T
authors.lastname: Godrie
authors.forename: A
authors.initials: A
authors.lastname: Goffeau
authors.forename: D
authors.initials: D
authors.lastname: Kahn
authors.forename: E
authors.initials: E
authors.lastname: Kiss
authors.forename: V
authors.initials: V
authors.lastname: Lelaure
authors.forename: D
authors.initials: D
authors.lastname: Masuy
authors.forename: T
authors.initials: T
authors.lastname: Pohl
authors.forename: D
authors.initials: D
authors.lastname: Portetelle
authors.forename: A
authors.initials: A
authors.lastname: Pühler
authors.forename: B
authors.initials: B
authors.lastname: Purnelle
authors.forename: U
authors.initials: U
authors.lastname: Ramsperger
authors.forename: C
authors.initials: C
authors.lastname: Renard
authors.forename: P
authors.initials: P
authors.lastname: Thébault
authors.forename: M
authors.initials: M
authors.lastname: Vandenbol
authors.forename: S
authors.initials: S
authors.lastname: Weidner
authors.forename: F
authors.initials: F
authors.lastname: Galibert
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics; D002455:Cell Division / Q000235:genetics; D002465:Cell Movement / Q000235:genetics; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics; D002876:Chromosomes, Bacterial / Q000235:genetics*; D004260:DNA Repair / Q000235:genetics; D004261:DNA Replication / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D004270:DNA, Circular / Q000235:genetics; D004734:Energy Metabolism / Q000235:genetics; D007887:Fabaceae / Q000382:microbiology; D020440:Gene Duplication; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D010946:Plants, Medicinal; D012093:Replicon / Q000235:genetics; D017422:Sequence Analysis, DNA; D015398:Signal Transduction / Q000235:genetics; D016962:Sinorhizobium meliloti / Q000235:genetics*; D013559:Symbiosis; D014158:Transcription, Genetic / Q000235:genetics; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; D004270:DNA, Circular