FIG. 1.

Theoretical accumulation of DNA in an exponential culture of E. coli treated with rifampin. The method used to find the number of replication origins and the C period from the accumulation of DNA after stopping initiations with rifampin (Rif) is illustrated. Solid line, DNA in genome equivalents (Geq) in a given volume of culture, normalized to 1.0 at t = 0 when rifampin is added to the culture; stippled line, number of replication origins (Ori); dotted line, number of replication termini (Ter). The horizontal distance between the origin and terminus curve corresponds to C, and the vertical distance between the origin and DNA curve (ΔG) represents the number of origins per genome equivalent of DNA. Relat., relative.