Figure 1.

Examples of fluorescently-labeled origin and terminus foci in wild-type and mutant cells. Origin and terminus regions of the parental (MC1000, a-c), ΔmreB (d), ΔmreC (e) and ΔmreD (f) strains were labeled with Yfp-TetR and Cfp-LacI, respectively, and examined as described in Materials and Methods. ori, origin (Yfp-TetR); ter, terminus (Cfp-LacI). Representative cells were selected to show cells with: (a) One terminus and one origin focus; neither origin nor terminus region have yet been replicated; (b and f) one terminus and two origin foci; the origin has been replicated and the two foci have moved away from midcell toward the poles prior to duplication of the terminus focus; (c) two terminus and four origin foci, in which the midcell terminus focus and the two progeny origin foci have undergone replication; (d and e) ΔmreB (d) and ΔmreC (e) cells that contain one or two origin foci but lack visible terminus foci (Original magnification×600).