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A ComGA-dependent checkpoint limits growth during the escape from competence.
B J Haijema1, J Hahn, J Haynes
1Public Health Research Institute, 455 First Ave, New York, NY 10016, USA.
Molecular Microbiology
|April 12, 2001
Summary
Competent Bacillus subtilis cells delay growth and division to ensure genetic transformation. The ComGA protein is crucial for this growth arrest, allowing time for DNA uptake and integration.
Area of Science:
- Microbiology
- Cell Biology
- Genetics
Background:
- Competence for transformation in Bacillus subtilis is a transient state adopted by a small subpopulation of cells.
- Competent cells exhibit a delayed resumption of growth and cell division after exiting competence.
- Understanding the molecular mechanisms underlying this growth arrest is crucial for comprehending bacterial adaptation and genetic exchange.
Purpose of the Study:
- To investigate the cellular basis for the prolonged lag in growth and division observed in competent Bacillus subtilis cells.
- To identify the key molecular players involved in regulating the cell cycle during the escape from competence.
- To elucidate the role of the ComGA protein in mediating the competence-specific growth arrest.
Main Methods:
- Microscopic characterization of competent and non-competent Bacillus subtilis cells.
- Utilized a translational fusion of ComK (competence transcription factor) with GFP as a marker for competent cells.
- Investigated the role of the late competence gene comGA through mutational analysis.
Main Results:
- ComK synthesis is an 'all or nothing' event, with only 5-10% of cells becoming competent.
- Competent cells maintain a stationary phase-like morphology (single cells, single nucleoids, lack of FtsZ rings) for up to 2 hours after transfer to fresh medium.
- The late competence protein ComGA is essential for blocking chromosome replication and cell division in competent cells; its absence leads to premature cell cycle resumption.
Conclusions:
- ComGA plays a critical role in maintaining the growth arrest of competent cells, likely to facilitate DNA transformation.
- The competence-specific growth arrest is regulated by ComGA, ensuring that cell division is postponed until ComK is degraded.
- ComGA's function in growth inhibition is separable from its role in transformation, highlighting distinct regulatory roles.
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