Designing replicons: rules from the maintenance functions

Laboratoire de Microbiologie et Génétique Moléculaires, Centre de Biologie Intégrative (CBI), Centre National de la Recherche Scientifique (CNRS), Université de Toulouse, UPS, 31000 Toulouse, France

Beside unique main chromosomes, bacterial genomes contain a plethora of secondary replicons differing in copy number, composition and size. They carry various functions involved in their maintenance: some are mandatory, such as replication origins and a mean of resolving dimeric forms, while others are accessory, such as addiction modules or active portioning systems. Using enterobacteria as models and a combination of bioinformatic and experimental approaches, we are attempting to define the rules and reasons for the distribution of maintenance function, allowing to design a la carte replicons. I will summarize the recent advances and focus on the role of replicon size in determining partitioning and dimer resolution functions.