Abstract
ABSTRACTUnderstanding how bacteria coordinate growth with cell cycle events to maintain cell size homeostasis remains a grand challenge in biology. The period of chromosome replication (C period) is a key stage in the bacterial cell cycle. However, the mechanism of in vivo regulation of the C period remains unclear. In this study, we found that titration of the expression of ribonucleotide reductase (RNR), which changes the intracellular deoxynucleoside triphosphate (dNTP) pools, enables significant perturbations of the C period, leading to a substantial change in cell size and DNA content. Our work demonstrates that the intracellular dNTP pool is indeed an important parameter that controls the progression of chromosome replication. Specially, RNR overexpression leads to a shortened C period compared with that of a wild-type strain growing under different nutrient conditions, indicating that the dNTP substrate levels are subsaturated under physiological conditions. In addition, perturbing the C period does not significantly change the D period, indicating that these two processes are largely independent from each other. Overall, titration of ribonucleotide reductase expression can serve as a standard model system for studying the coordination between chromosome replication, cell division, and cell size.
Highlights
Understanding how bacteria coordinate growth with cell cycle events to maintain cell size homeostasis remains a grand challenge in biology
Our work demonstrates that the intracellular deoxynucleoside triphosphate (dNTP) pool is an important parameter that controls the progression of chromosome replication
Cell cycle progression is closely related to cell size, much less is known about how bacterial cells manage to control the length of time of their cell cycle
Summary
Understanding how bacteria coordinate growth with cell cycle events to maintain cell size homeostasis remains a grand challenge in biology. Through introducing a genetic circuit into Escherichia coli for titrating the expression of ribonucleotide reductase, we achieve substantial perturbation of the C period and cell size. Our work indicates that bacterial cells manage to maintain subsaturated dNTP levels under different nutrient conditions, leading to a submaximal speed of DNA replication fork movement.
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