The basis of this thesis has been the curiosity, however modest, to understand how DNA replication happens in vivo, particularly during the onset of DNA damage and beyond. DNA damage is a recurring phenomenon, which a (bacterial) cell faces in its lifetime from the environment or even its inherent metabolism. While we understand much about replication in general from decades of research, our understanding is not comprehensive without understanding how replication is affected, when the cell is under DNA damage and/ or under repair. In terms of genome replication, the effects of DNA damage may be at the level of: a. Replisome components b. Accessory components of the replisome In this thesis and with a limited time span of a PhD research, I (along with my colleagues) have reported on one component each of the two categories stated above in the bacterial model Escherichia coli. In the former case, we have investigated the replicative helicase DnaB and in the latter case, the translesion DNA polymerase IV (Pol IV).