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Published on: April 9, 2018
The eclipse period of Escherichia coli
U von Freiesleben1, M A Krekling, F G Hansen
1Department of Microbiology, The Technical University of Denmark, Building 301, DK-2800 Lyngby, Denmark.
The EMBO Journal
|November 18, 2000
Summary
The minimal time for DNA replication initiation in E. coli, known as the eclipse, is about 25-30 minutes. SeqA protein is crucial for this process, linking replication timing to chromosome organization.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- DNA replication initiation is tightly regulated in bacteria.
- The 'eclipse' period, the minimal time between successive initiations from the same origin, is a key regulatory checkpoint.
- Understanding the molecular mechanisms governing the eclipse is crucial for bacterial cell cycle control.
Purpose of the Study:
- To determine the minimal time between successive initiations on the same origin (eclipse) in Escherichia coli.
- To investigate the roles of Dam methyltransferase and SeqA protein in regulating the eclipse period.
- To elucidate the relationship between SeqA function, DNA replication timing, and chromosome organization.
Main Methods:
- Measurement of the minimal time between successive initiations in E. coli.
- Analysis of the inverse relationship between eclipse length and Dam methyltransferase levels.
- DnaA titration studies to assess SeqA's role in initial complex formation at oriC.
- Assessment of chromosome partitioning and nucleoid distribution in SeqA-deficient cells.
Main Results:
- The minimal eclipse period in E. coli was determined to be approximately 25-30 minutes.
- An inverse correlation between eclipse length and Dam methyltransferase levels suggests the eclipse corresponds to origin hemimethylation.
- SeqA protein is essential for the eclipse, preventing multiple DnaA binding events at oriC.
- Increased SeqA levels did not correlate with eclipse length but impacted chromosome partitioning and cell division, evidenced by aberrant nucleoid distribution in SeqA-deficient cells.
Conclusions:
- The SeqA protein plays a critical role in establishing and maintaining the DNA replication eclipse period in E. coli.
- SeqA's function in regulating the eclipse is likely linked to its role in chromosome organization.
- These findings provide insights into the coordination of DNA replication initiation and cell division in bacteria.
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