Molecular mechanisms of bacterial DNA replication

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The faithful duplication of genetic material is imperative for the proliferation of all life. Initiating this process requires that the DNA double helix is locally unwound at specific sites termed “origins” to assemble a replicative machinery on each of the parental strands to synthesize the new DNA. Despite the fundamental importance of DNA replication, we still do not have a comprehensive picture of this process, especially not in the most abundant lifeform on earth, bacteria. Specifically, the initiation of bacterial DNA replication is not comprehensively understood. This is in particular due to the fact that we still do not know the function of many essential sequence elements in the bacterial replication origin. Important progress in elucidating bacterial origin functions was recently made by studying the origin of replication of Bacillus subtilis. This genetically tractable organism harbors an origin typical for bacteria and has proven to be an excellent model for the study of bacterial DNA replication. It was in this model organism that the “DnaA-trios” were discovered. These new essential sequence elements are widely conserved amongst bacteria and act as a basal system for origin unwinding. Critically however, the structure and function of essential origin sequences that reside distal to the DnaA-trios remain unknown.The proposed research project will elucidate the structure and function of these regions of the Bacillus subtilis origin of replication. To this end, I will systematically mutate origin sequence elements and the interacting replication initiator protein DnaA and characterize the consequences on DNA replication initiation in vivo and in vitro. The proposed study will significantly advance our knowledge about the general setup and function of bacterial replication origins and represents an essential foundation for a mechanistic understanding of bacterial DNA replication. Uncovering the mechanistic basis of DNA replication initiation in bacteria is essential for a better control of bacterial growth in industrial applications and when fighting infectious diseases. No currently known antibiotic directly targets DNA replication proteins; the development of compounds interfering with the activity or the assembly of the DNA replication machinery would yield a new group of antibiotics.