title: Orderly Replication and Segregation of the Four Replicons of Burkholderia cenocepacia J2315.
abstract: Bacterial genomes typically consist of a single chromosome and, optionally, one or more plasmids. But whole-genome sequencing reveals about ten per-cent of them to be multipartite, with additional replicons which by size and indispensability are considered secondary chromosomes. This raises the questions of how their replication and partition is managed without compromising genome stability and of how such genomes arose. Vibrio cholerae, with a 1 Mb replicon in addition to its 3 Mb chromosome, is the only species for which maintenance of a multipartite genome has been investigated. In this study we have explored the more complex genome of Burkholderia cenocepacia (strain J2315). It comprises an extra replicon (c2) of 3.21 Mb, comparable in size to the3.87Mb main chromosome (c1), another extra replicon(c3) of 0.87 Mb and a plasmid of 0.09 Mb. The replication origin of c1 is typically chromosomal and those of c2 and c3 are plasmid-like; all are replicated bidirectionally. Fluorescence microscopy of tagged origins indicates that all initiate replication at mid-cell and segregate towards the cell quarter positions sequentially, c1-c2-p1/c3. c2 segregation is as well-phased with the cell cycle as c1, implying that this plasmid-like origin has become subject to regulation not typical of plasmids; in contrast, c3 segregates more randomly through the cycle. Disruption of individual Par systems by deletion of parAB or by addition of parS sites showed each Par system to govern the positioning of its own replicon only. Inactivation of c1, c2 and c3 Par systems not only reduced growth rate, generated anucleate cells and compromised viability but influenced processes beyond replicon partition, notably regulation of replication, chromosome condensation and cell size determination. In particular, the absence of the c1 ParA protein altered replication of all three chromosomes, suggesting that the partition system of the main chromosome is a major participant in the choreography of the cell cycle.
authors.affiliation: Laboratoire de Microbiologie et Génétique Moléculaires, Centre National de Recherche Scientifique / Université Paul Sabatier, Toulouse, France.
authors.forename: Wen-Li
authors.initials: WL
authors.lastname: Du
authors.affiliation: Laboratoire de Microbiologie et Génétique Moléculaires, Centre National de Recherche Scientifique / Université Paul Sabatier, Toulouse, France.
authors.forename: Nelly
authors.identifier: 0000-0002-2381-6956
authors.initials: N
authors.lastname: Dubarry
authors.affiliation: Laboratoire de Microbiologie et Génétique Moléculaires, Centre National de Recherche Scientifique / Université Paul Sabatier, Toulouse, France.
authors.forename: Fanny M
authors.initials: FM
authors.lastname: Passot
authors.affiliation: Laboratoire de Biologie Moléculaire Eucaryote, Centre National de Recherche Scientifique / Université Paul Sabatier, Toulouse, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Kamgoué
authors.affiliation: Centre for Bacterial Cell Biology, Institute for Cell & Molecular Biosciences, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Heath
authors.initials: H
authors.lastname: Murray
authors.affiliation: Laboratoire de Microbiologie et Génétique Moléculaires, Centre National de Recherche Scientifique / Université Paul Sabatier, Toulouse, France.
authors.forename: David
authors.identifier: 0000-0002-8656-4725
authors.initials: D
authors.lastname: Lane
authors.affiliation: Laboratoire de Microbiologie et Génétique Moléculaires, Centre National de Recherche Scientifique / Université Paul Sabatier, Toulouse, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Pasta
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D057508:Burkholderia cenocepacia / Q000235:genetics*; D002453:Cell Cycle; D020090:Chromosome Segregation; D002875:Chromosomes / Q000648:ultrastructure; D002876:Chromosomes, Bacterial / Q000378:metabolism; D004261:DNA Replication; D004926:Escherichia coli / Q000235:genetics; D017353:Gene Deletion; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D008856:Microscopy, Fluorescence; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D018741:Replication Origin; D012093:Replicon; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; C052883:chromosome partition proteins, bacterial