title: A replication-inhibited unsegregated nucleoid at mid-cell blocks Z-ring formation and cell division independently of SOS and the SlmA nucleoid occlusion protein in Escherichia coli.
abstract: Chromosome replication and cell division of Escherichia coli are coordinated with growth such that wild-type cells divide once and only once after each replication cycle. To investigate the nature of this coordination, the effects of inhibiting replication on Z-ring formation and cell division were tested in both synchronized and exponentially growing cells with only one replicating chromosome. When replication elongation was blocked by hydroxyurea or nalidixic acid, arrested cells contained one partially replicated, compact nucleoid located mid-cell. Cell division was strongly inhibited at or before the level of Z-ring formation. DNA cross-linking by mitomycin C delayed segregation, and the accumulation of about two chromosome equivalents at mid-cell also blocked Z-ring formation and cell division. Z-ring inhibition occurred independently of SOS, SlmA-mediated nucleoid occlusion, and MinCDE proteins and did not result from a decreased FtsZ protein concentration. We propose that the presence of a compact, incompletely replicated nucleoid or unsegregated chromosome masses at the normal mid-cell division site inhibits Z-ring formation and that the SOS system, SlmA, and MinC are not required for this inhibition.
authors.affiliation: Department of Molecular Biosciences, University of Texas, Austin, Texas, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Cambridge
authors.forename: Alexandra
authors.initials: A
authors.lastname: Blinkova
authors.forename: David
authors.initials: D
authors.lastname: Magnan
authors.forename: David
authors.initials: D
authors.lastname: Bates
authors.forename: James R
authors.initials: JR
authors.lastname: Walker
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division; D002876:Chromosomes, Bacterial / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004261:DNA Replication; D004926:Escherichia coli / Q000187:drug effects / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000378:metabolism; D006918:Hydroxyurea / Q000633:toxicity; D008565:Membrane Proteins / Q000378:metabolism; D009268:Nalidixic Acid / Q000633:toxicity; D013014:SOS Response, Genetics
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D029968:Escherichia coli Proteins; C071525:FtsZ protein, Bacteria; D008565:Membrane Proteins; C462942:MinC protein, E coli; C093548:MinE protein, E coli; C502032:SlmA protein, E coli; D009268:Nalidixic Acid; D000251:Adenosine Triphosphatases; C072069:MinD protein, E coli; D006918:Hydroxyurea