Fuse or die: how to survive the loss of Dam in Vibrio cholerae

Marie-Eve Val (1) , Sean Patrick Kennedy (2) , Alfonso Soler-Bistué (1) , Valérie Barbe (3) , Christiane Bouchier (1) , Magaly Ducos-Galand (1) , Ole Skovgaard (4) , Didier Mazel (1)

1 PGB - Plasticité du Génome Bactérien - Bacterial Genome Plasticity
2 MetaGenoPolis
3 GENOSCOPE - Genoscope - Centre national de séquençage [Evry]
4 Department of Science, Systems and Models

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 repli-cation, 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.

Domaines: Biochimie, Biologie Moléculaire

Marie-Eve Val, Sean Patrick Kennedy, Alfonso Soler-Bistué, Valérie Barbe, Christiane Bouchier, et al.. Fuse or die: how to survive the loss of Dam in Vibrio cholerae. Molecular Microbiology, 2014, 91 (4), pp.665 - 678. ⟨10.1111/mmi.12483⟩. ⟨inserm-01285641⟩