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Updated: Jul 15, 2026
06:10
Following Cell-fate in E. coli After Infection by Phage Lambda
Published on: October 14, 2011
Modulation of lambda plasmid and phage DNA replication by Escherichia coli SeqA protein
Magdalena Narajczyk1, Sylwia Barańska1, Anna Szambowska1
1Department of Molecular Biology, University of Gdańsk, 80-822 Gdańsk, Poland.
Microbiology (Reading, England)
|April 28, 2007
Summary
SeqA protein indirectly regulates lambda phage and plasmid replication by affecting replication complex stability and transcriptional activation. SeqA dysfunction impairs lambda plasmid replication, particularly under stress conditions.
Area of Science:
- Molecular Biology
- Microbiology
- Genetics
Background:
- SeqA protein is a key negative regulator of Escherichia coli chromosome replication.
- SeqA's role in regulating other replicons, like lambda phage and plasmid, is not fully understood.
- Previous studies show seqA mutants have reduced lambda plasmid copy number and lower activity of the lambda p(R) promoter.
Purpose of the Study:
- To investigate the detailed mechanisms of SeqA-mediated regulation of lambda phage and plasmid replicons.
- To determine if SeqA directly regulates lambda DNA replication or influences it indirectly.
- To elucidate the impact of SeqA on replication complex stability and transcriptional activation of lambda origins.
Main Methods:
- In vitro DNA replication assays to assess direct SeqA influence on ori lambda.
- Density-shift experiments to monitor lambda DNA replication intermediates and modes post-infection.
- Analysis of lambda replication complex stability and lambda O protein presence in seqA mutants.
- Measurement of lambda plasmid replication efficiency in relA seqA double mutants under amino acid starvation.
Main Results:
- SeqA showed no significant direct effect on ori lambda-dependent DNA replication in vitro.
- Density-shift experiments indicated early sigma replication intermediates and preferential rolling-circle replication in seqA mutants.
- Lambda plasmid replication directionality was only slightly affected, but replication complex stability decreased in seqA mutants.
- SeqA dysfunction impaired lambda plasmid replication in amino acid-starved relA seqA mutants.
Conclusions:
- SeqA indirectly modulates lambda DNA replication, likely by influencing replication complex stability and transcriptional activation of ori lambda.
- The regulation of lambda replication by SeqA differs from its regulation of the E. coli chromosome origin (oriC).
- SeqA's role in regulating viral replicons highlights its broader importance in DNA metabolism beyond chromosomal replication.
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