Abstract
DNA replication initiation is orchestrated in many prokaryotes by the replication initiator DnaA. Two models for regulation of DnaA activity in Escherichia coli have been proposed: the switch between an active and inactive form of DnaA, and the titration of DnaA on the E. coli chromosome. Although proposed decades ago, experimental evidence of a titration-based control mechanism is still lacking. Here, we first identified a conserved high-density region of binding motifs near the origin of replication, an advantageous trait for titration of DnaA. We then investigated the mobility of DnaA by single-particle tracking microscopy in wild-type and deletion mutants E. coli strains, while monitoring cellular size and DNA content. Our results indicate that the chromosome of E. coli controls the free amount of DnaA in a growth rate-dependent fashion. Finally, we provide insights on the relevance of DnaA titration in stabilising DNA replication by preventing re-initiation events during slow growth.
Competing Interest Statement
The authors have declared no competing interest.
