Simultaneous regulation of cell size and chromosome replication in bacteria

30 October 2015

Ariel Amir
School of Engineering and Applied Sciences
Harvard University


Bacteria are able to maintain a narrow distribution of cell sizes by regulating the timing of cell divisions. In rich nutrient conditions, cells divide faster than their chromosomes replicate, implying that cells maintain multiple rounds of chromosome replication. How are these processes coupled and controlled? I will show that both cell size and chromosome replication may be simultaneously regulated by following a simple and effective control mechanism, in which "initiators" are accumulated at origins of replication as the cell grows, and trigger initiation of new rounds of DNA replication. This model is consistent with the experimentally observed correlations between various events in the cell cycle, and explains the exponential dependence of cell size on the growth rate. Furthermore, the model predicts a bimodal distribution of cell size at initiation of DNA replication, which is yet to be tested.

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