title: Imaging centromere-based incompatibilities: Insights into the mechanism of incompatibility mediated by low-copy number plasmids.
abstract: In bacteria, low-copy number plasmids are faithfully segregated at cell division by active partition systems that rely on plasmid-specific centromere sequences. When an identical centromere is present on a second plasmid, faithful partition is impaired causing plasmid loss. Depending on the copy number of the co-resident replicon, several mechanisms have been proposed to account for this centromere-based plasmid incompatibility. To gain further insights into these mechanisms, we analyzed the positioning of the F plasmid in the presence of incompatible low- and high-copy number plasmids carrying the F centromere. Our data are fully compatible with the titration hypothesis when extra-centromeres are present on high-copy number plasmids. Interestingly, our plasmids' localization data revealed that the strong incompatibility phenotype, observed when extra centromeres are present on a partition defective low-copy number plasmid, does not directly result from a partition deficiency as previously proposed. We provide a new and simple hypothesis for explaining the strong incompatibility phenotype based on the timing of replication of low-copy number plasmids.
authors.affiliation: Laboratoire de Microbiologie et Génétique Moléculaires, Centre National pour la Recherche Scientifique, F-31000 Toulouse, France; Laboratoire de Microbiologie et Génétique Moléculaires, Université de Toulouse, UPS, F-31000 Toulouse, France.
authors.forename: Roxanne
authors.initials: R
authors.lastname: Diaz
authors.affiliation: Laboratoire de Microbiologie et Génétique Moléculaires, Centre National pour la Recherche Scientifique, F-31000 Toulouse, France; Laboratoire de Microbiologie et Génétique Moléculaires, Université de Toulouse, UPS, F-31000 Toulouse, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Rech
authors.affiliation: Laboratoire de Microbiologie et Génétique Moléculaires, Centre National pour la Recherche Scientifique, F-31000 Toulouse, France; Laboratoire de Microbiologie et Génétique Moléculaires, Université de Toulouse, UPS, F-31000 Toulouse, France. Electronic address: jean-yves.bouet@ibcg.biotoul.fr.
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Bouet
mesh_terms: D002503:Centromere / Q000235:genetics; D004261:DNA Replication; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D005144:F Factor / Q000235:genetics*; D018628:Gene Dosage; D008856:Microscopy, Fluorescence; D009154:Mutation
chemical_list: D004269:DNA, Bacterial
keywords: Centromere; ParABS; Plasmid incompatibility; Plasmid partition; Random positioning; SopABC