Concurrent processes set E. coli cell division

A cell can divide only upon completion of chromosome segregation, or its daughters would lose genetic material [1, 2]. In E. coli bacteria, the prevalent view is that cells divide a fixed amount of time after they start to copy the chromosomes [3, 4], and a known pathway prevents cells from dividing if the chromosomes interfere with the cytokinesis machinery [5]. However, whether completion of segregation is typically the bottleneck process for the decision to divide has never been stringently tested on single cells. We show how key trends in single-cell data lead to challenge the classic idea of replication-segregation limiting cell division. Instead, the data agree with a model where two concurrent processes (setting replication initiation and inter-division time) set cell division on competing time scales. During each cell cycle, division is set by the slowest process (an \" ...