Replication initiation of the second bacterial chromosome of Vibrio cholerae

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Genome replication and transmission are the characteristics of life, and these processes rely on several highly controlled mechanisms. The first of these mechanisms is the initiation of the replication. Interestingly, at least 10% of bacteria have a multipartite genome, composed of one main chromosome and of one to several secondary chromosomes, called chromids. Chromids are essential and their faithful transmission is indispensable to bacterial viability. Thus, a tight control of their replication in coordination with the cell cycle is required. While the mechanism for the main bacterial chromosome replication initiation is well described, the one for secondary chromosome is still poorly understood. The Vibrio cholerae chromid is the paradigm of secondary chromosomes and its replication initiation relies on the specific factor RctB. However, the mechanisms underlying its replication initiation, as well as the DNA and protein partners involved are at most superficially known. In this project, we aim at determining the mechanisms, the partners and the different steps of this essential stage of the cell cycle, from the molecular to the cellular levels by combining biochemical and single molecule experiments with genetic experiments in collaboration, up to the reconstitution of this process in vitro.