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Chromosomal initiation in Bacillus subtilis may involve two closely linked origins
Molecular & General Genetics : MGG
|June 1, 1987
Summary
Bacillus subtilis DNA replication initiates at specific fragments. The dnaB37 mutant system identified BS6 as the primary replication origin, but novobiocin shifted initiation to BS5, suggesting flexible origin usage.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Synchronous DNA replication is crucial for studying initiation.
- Previous methods for synchrony in Bacillus subtilis, like thymine starvation, have limitations.
Purpose of the Study:
- To identify the first DNA fragments replicated in Bacillus subtilis using a synchronized system.
- To investigate the role of DNA gyrase and the dnaB protein in replication origin selection.
Main Methods:
- Utilized a dnaB37 initiation mutant of Bacillus subtilis returned to permissive temperature for synchronous replication.
- Analyzed replication initiation using restriction fragment mapping (BS6 and BS5).
- Investigated the effects of novobiocin (DNA gyrase inhibitor) and rifamycin on replication.
Main Results:
- Identified a 4 kb BamHI-SalI fragment (BS6) as the initial replication site under normal conditions.
- Novobiocin treatment inhibited replication from BS6 and shifted initiation to a nearby fragment (BS5).
- Rifamycin suppressed replication from both putative origins, and all replication was dependent on dnaB.
Conclusions:
- Bacillus subtilis may possess multiple replication origins that can be utilized flexibly.
- DNA gyrase activity influences the choice of replication origin.
- The dnaB protein is essential for replication initiation from both identified origins.