Figure 1. The duration of C increased with increasing HU concentration.

A: Cells were grown exponentially in glu-CAA-uri at 37°C in the presence of 0, 2.5, 5 or 10 mM HU for about eight generations to OD₄₅₀ = 0.15, then fixed in 70% ethanol after incubation for 4–5 generation times in rifampicin and cephalexin. The number of cells is plotted against the DNA content. B: The durations of the C periods obtained by growth with the different HU concentrations. C periods were found from the oriC/terC ratio obtained by quantitative PCR and Southern blot analysis of cells used in A (see Materials and Methods). The C period of cells grown with 10 mM HU is drawn as a broken line because in this case the C period is aberrant due to replication fork stalling and reversal.