(A) DnaB-YPet imaged at 2 min intervals in strains with and without the dnaC2 allele at 37°C (non-permissive for the temperature sensitive strain). In the temperature sensitive strain, either a complex is observed in the first frame (e. g. cells 1–3) or the cell generally does not develop complexes during the time course (e. g. cell 4). When a complex is observed, it most commonly disappears before the end of the time course. Once disappearance has occurred (red arrows), no new stable complexes are observed in the majority of cells (85%). In contrast, the wild type strain (e. g. cells 5–6) shows intermittent foci (as observed in the dynamics experiments at 30°C), and complexes may be assembled later in the time series. (B) Probability of observing a focus as a function of time in cells where at least one trajectory is observed. DnaC is involved both in initiation of replication at the origin and the rescue of stalled forks. The theoretical ‘Null hypothesis’ curve (red) assumes a continuous 40 min replication cycle imaged for a random 20 min window. However, the probability of observing a focus in the dnaC2 allele (blue, N = 72) decreases more quickly suggesting that the helicase is disassembled prior to completion of replication. Additionally, in the wild type strain, the probability of observing a focus is roughly independent of time, indicating that both disassembly and re-assembly events are present.