TipN’s involvement with centromere segregation in Caulobacter crescentus

Abstract

ABSTRACTBacteria’s ability to maintain chromosomal integrity throughout their life cycle is crucial for their survival. InCaulobacter crescentus, the polar factor TipN has been proposed to be involved with the partitioning system ParABS. However, cells withtipNknocked out display subtleparSsegregation defects. We hypothesized that TipN’s role withparSsegregation is obscured by other forces that are ParABS-independent. To test our hypothesis, we removed one of those forces – chromosome replication – and analyzed the role of TipN with ParA. We first demonstrate that ParA retains its ability to transport the centromeric regionparSfrom the stalked pole to the opposite pole in the absence of chromosome replication. Our data revealed that in the absence of chromosome replication, TipN becomes essential for ParA’s ability to transportparS. Furthermore, we identify a potential connection between the replication initiator DnaA and TipN. Although TipN is not essential for viability,tipNknockout cells lose viability when the regulation of DnaA levels is altered. Our data suggest that the DnaA-dependent susceptibility oftipNknockout cells is connected toparSsegregation. Collectively, this work provides insights into the complex regulation involved in the coordination of chromosome replication and segregation in bacteria.