title: Fuse or die: how to survive the loss of Dam in Vibrio cholerae.
abstract: Dam methylates GATC sequences in γ-proteobacteria genomes, regulating several cellular functions including replication. In Vibrio cholerae, which has two chromosomes, Dam is essential for viability, owing to its role in chr2 replication initiation. In this study, we isolated spontaneous mutants of V. cholerae that were able to survive the deletion of dam. In these mutants, homologous recombination and chromosome dimer resolution are essential, unless DNA mismatch repair is inactivated. Furthermore, the initiator of chr2 replication, RctB, is no longer required. We show that, instead, replication of chr2 is insured by spontaneous fusion with chr1 and piggybacking its replication machinery. We report that natural fusion of chr1 and chr2 occurred by two distinct recombination pathways: homologous recombination between repeated IS elements and site-specific recombination between dif sites. Lastly, we observed a preferential fusion of the two chromosomes in their terminus of replication.
authors.affiliation: Department of Genomes and Genetics, Institut Pasteur, F-75015, Paris, France; CNRS, UMR3525, F-75015, Paris, France.
authors.forename: Marie-Eve
authors.initials: ME
authors.lastname: Val
authors.forename: Sean P
authors.initials: SP
authors.lastname: Kennedy
authors.forename: Alfonso J
authors.initials: AJ
authors.lastname: Soler-Bistué
authors.forename: Valérie
authors.initials: V
authors.lastname: Barbe
authors.forename: Christiane
authors.initials: C
authors.lastname: Bouchier
authors.forename: Magaly
authors.initials: M
authors.lastname: Ducos-Galand
authors.forename: Ole
authors.initials: O
authors.lastname: Skovgaard
authors.forename: Didier
authors.initials: D
authors.lastname: Mazel
mesh_terms: D002876:Chromosomes, Bacterial; D004261:DNA Replication; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D050296:Microbial Viability; D011995:Recombination, Genetic; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000172:deficiency* / Q000378:metabolism*; D014734:Vibrio cholerae / Q000235:genetics*
chemical_list: C058693:Dam methyltransferase; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific)