Dataset Information

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.

SUBMITTER: Capela D

PROVIDER: S-EPMC55546 | biostudies-literature | 2001 Aug

REPOSITORIES: biostudies-literature

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Analysis of the chromosome sequence of the legume symbiont Sinorhizobium meliloti strain 1021.

Capela D D Barloy-Hubler F F Gouzy J J Bothe G G Ampe F F Batut J J Boistard P P Becker A A Boutry M M Cadieu E E Dréano S S Gloux S S Godrie T T Goffeau A A Kahn D D Kiss E E Lelaure V V Masuy D D Pohl T T Portetelle D D Pühler A A Purnelle B B Ramsperger U U Renard C C Thébault P P Vandenbol M M Weidner S S Galibert F F

Proceedings of the National Academy of Sciences of the United States of America 20010731 17

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 onl ...[more]

PMID: 11481430

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Project description:In α-proteobacteria, strict regulation of cell cycle progression is necessary for the specific cellular differentiation required for adaptation to diverse environmental niches. The symbiotic lifestyle of Sinorhizobium meliloti requires a drastic cellular differentiation that includes genome amplification. To achieve polyploidy, the S. meliloti cell cycle program must be altered to uncouple DNA replication from cell division. In the α-proteobacterium Caulobacter crescentus, cell cycle regulated transcription plays an important role in control of cell cycle progression but this has not been demonstrated in other α-proteobacteria. Here we describe a robust method for synchronizing cell growth that enabled the first global analysis of S. meliloti cell cycle regulated gene expression. The objective of the microarray-based cell cycle gene expression analysis was to determine which genes were transcriptionally regulated as a funciton of a cell cycle in order to understand the contribution of transcriptional regulation to the timing of cell cycle events. The microarray analysis identified 462 genes with cell cycle regulated transcripts, including several key cell cycle regulators, and genes involved in motility, attachment, and cell division. Only 28% of the 462 S. meliloti cell cycle regulated genes were also transcriptionally cell cycle regulated in C. crescentus. Furthermore, CtrA and DnaA binding motif analysis revealed little overlap between the cell cycle-dependent regulons of CtrA and DnaA in S. meliloti and C. crescentus. The predicted S. meliloti cell cycle regulon of CtrA, but not that of DnaA, was strongly conserved in more closely related α-proteobacteria with similar ecological niches as S. meliloti, suggesting that the CtrA cell cycle regulatory network may control functions of central importance to the specific lifestyles of α-proteobacteria. Gene expression levels were quantified in synchronously growing S. meliloti cultures across 8 time points and compared to gene expression levels in unsynchronized culture via a two-color custom agilent array

Dataset Information

Analysis of the chromosome sequence of the legume symbiont Sinorhizobium meliloti strain 1021.

Publications

Analysis of the chromosome sequence of the legume symbiont Sinorhizobium meliloti strain 1021.

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