Mechanisms of chromosomal DNA replication in Escherichia coli and Bacillus subtilis

Faithful DNA replication, which is a highly orchestrated process, is essential in all living organisms to ensure accurate transmission of genetic information to their descendants. In this review, we summarize the molecular mechanisms and dynamics of DNA replication in Escherichia coli and compare them with those of the phylogenetically distant Bacillus subtilis. Although the central features of replication initiation, elongation, termination, and restart are broadly conserved, distinct mechanisms have evolved to adapt each bacterium to its complex environment. This review highlights the players and outlines both the shared and divergent molecular mechanisms governing how the multi-component replication machines, the replisomes, are assembled at the origin of chromosomal replication, oriC, on a circular genome, undergo bidirectional replication elongation, and are ultimately disassembled upon reaching the terminus of replication, ter, region. In response to stress, (a) replication restart mechanism(s) operating at sites other than oriC re-assemble the replisome, allowing unidirectional DNA synthesis to resume, thereby ensuring completion of the cell cycle and maintenance of cell viability.