title: The Sinorhizobium meliloti chromosomal origin of replication.
abstract: The predicted chromosomal origin of replication (oriC) from the alfalfa symbiont Sinorhizobium meliloti is shown to allow autonomous replication of a normally non-replicating plasmid within S. meliloti cells. This is the first chromosomal replication origin to be experimentally localized in the Rhizobiaceae and its location, adjacent to hemE, is the same as for oriC in Caulobacter crescentus, the only experimentally characterized alphaproteobacterial oriC. Using an electrophoretic mobility shift assay and purified S. meliloti DnaA replication initiation protein, binding sites for DnaA were mapped in the S. meliloti oriC region. Mutations in these sites eliminated autonomous replication. S. meliloti that expressed DnaA from a plasmid lac promoter was observed to form pleomorphic filamentous cells, suggesting that cell division was perturbed. Interestingly, this cell phenotype is reminiscent of differentiated bacteroids found inside plant cells in alfalfa root nodules.
authors.affiliation: Center for Environmental Genomics, Department of Biology, McMaster University, 1280 Main St West, Hamilton, Ontario, Canada L8S 4K1.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Sibley
authors.affiliation: Center for Environmental Genomics, Department of Biology, McMaster University, 1280 Main St West, Hamilton, Ontario, Canada L8S 4K1.
authors.forename: Shawn R
authors.initials: SR
authors.lastname: MacLellan
authors.affiliation: Center for Environmental Genomics, Department of Biology, McMaster University, 1280 Main St West, Hamilton, Ontario, Canada L8S 4K1.
authors.forename: Turlough
authors.initials: T
authors.lastname: Finan
mesh_terms: D001426:Bacterial Proteins; D001665:Binding Sites; D002453:Cell Cycle / Q000502:physiology; D002876:Chromosomes, Bacterial; D004261:DNA Replication; D004269:DNA, Bacterial / Q000302:isolation & purification*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018741:Replication Origin; D016962:Sinorhizobium meliloti / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria