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Dynamics of Escherichia coli chromosome segregation during multifork replication

J Bacteriol. 2007 Dec;189(23):8660-6. doi: 10.1128/JB.01212-07. Epub 2007 Sep 28.

Abstract

Slowly growing Escherichia coli cells have a simple cell cycle, with replication and progressive segregation of the chromosome completed before cell division. In rapidly growing cells, initiation of replication occurs before the previous replication rounds are complete. At cell division, the chromosomes contain multiple replication forks and must be segregated while this complex pattern of replication is still ongoing. Here, we show that replication and segregation continue in step, starting at the origin and progressing to the replication terminus. Thus, early-replicated markers on the multiple-branched chromosomes continue to separate soon after replication to form separate protonucleoids, even though they are not segregated into different daughter cells until later generations. The segregation pattern follows the pattern of chromosome replication and does not follow the cell division cycle. No extensive cohesion of sister DNA regions was seen at any growth rate. We conclude that segregation is driven by the progression of the replication forks.

Publication types

  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromosome Segregation / physiology*
  • Chromosomes, Bacterial / genetics
  • Chromosomes, Bacterial / metabolism*
  • DNA Replication Timing
  • DNA Replication*
  • Escherichia coli / cytology*
  • Escherichia coli / genetics
  • Genetic Markers

Substances

  • Genetic Markers