CELL CYCLE-DEPENDENT DUPLICATION AND BIDIRECTIONAL MIGRATION OF SEQA-ASSOCIATED DNA-PROTEIN COMPLEXES IN ESCHERICHIA-COLI

Using immunofluorescence microscopy, we have found that SeqA protein, a regulator of replication initiation, is localized as discrete fluore scent foci in E. coli wild-type cells. Surprisingly, SeqA foci were ob served also in an oriC deletion mutant. Statistical analysis revealed that a SeqA focus is localized at midcell in newborn cells. The SeqA f ocus is duplicated and tethered at midcell until an FtsZ ring is forme d. Subsequently, these foci migrate in opposite directions toward cell quarter sites and remain tethered there until the cell divides. The c ell cycle-dependent bidirectional migration of SeqA-DNA complexes is q uite different from the migration pattern of oriC DNA copies. MukB pro tein is required for correct localization of SeqA complexes by an unkn own mechanism.