title: The eclipse period of Escherichia coli.
abstract: The minimal time between successive initiations on the same origin (the eclipse) in Escherichia coli was determined to be approximately 25-30 min. An inverse relationship was found between the length of the eclipse and the amount of Dam methyltransferase in the cell, indicating that the eclipse corresponds to the period of origin hemimethylation. The SeqA protein was absolutely required for the eclipse, and DnaA titration studies suggested that the SeqA protein prevented the binding of multiple DnaA molecules on oriC (initial complex formation). No correlation between the amount of SeqA and eclipse length was revealed, but increased SeqA levels affected chromosome partitioning and/or cell division. This was corroborated further by an aberrant nucleoid distribution in SeqA-deficient cells. We suggest that the SeqA protein's role in maintaining the eclipse is tied to a function in chromosome organization.
authors.affiliation: Department of Microbiology, The Technical University of Denmark, Building 301, DK-2800 Lyngby, Denmark.
authors.forename: U
authors.initials: U
authors.lastname: von Freiesleben
authors.forename: M A
authors.initials: MA
authors.lastname: Krekling
authors.forename: F G
authors.initials: FG
authors.lastname: Hansen
authors.forename: A
authors.initials: A
authors.lastname: Løbner-Olesen
mesh_terms: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002453:Cell Cycle; D002455:Cell Division; D002876:Chromosomes, Bacterial / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D007700:Kinetics; D009154:Mutation; D051738:Origin Recognition Complex; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000378:metabolism; D014157:Transcription Factors; D014764:Viral Proteins
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; D029968:Escherichia coli Proteins; C114650:OriC chromosomal replication origin; D051738:Origin Recognition Complex; C089746:SeqA protein, E coli; D014157:Transcription Factors; D014764:Viral Proteins; C058693:Dam methyltransferase; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); C499294:dam protein, E coli