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Private link between signal and response in Bacillus subtilis quorum sensing
Anna Oslizlo1, Polonca Stefanic, Iztok Dogsa
1Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia.
Summary
Bacteria use quorum sensing (QS) for group behavior. This study reveals a dual role for QS signal production, acting both externally and internally, to maintain stable bacterial communities and prevent cheating.
Area of Science:
- Microbiology
- Bacterial Communication
- Systems Biology
Background:
- Bacteria coordinate group behaviors via quorum sensing (QS), a process involving secreted signal molecules.
- The canonical QS model emphasizes extracellular signaling, where signals activate responses in multiple cells.
- The ComQXPA QS system in Bacillus subtilis is a well-studied example of bacterial communication.
Purpose of the Study:
- To investigate the link between QS signaling input and response output in Bacillus subtilis.
- To characterize the phenotype and fitness of comQ null mutants lacking ComX signal production.
- To elucidate the dual role of ComQ in both activating and repressing the QS system.
Main Methods:
- Phenotypic analysis of comQ null mutants in Bacillus subtilis.
- Fitness assays to evaluate the impact of QS mutations.
- Coculture experiments to study social selection mechanisms.
Main Results:
- ComQ exhibits a dual role: activating QS extracellularly and repressing it intracellularly.
- comQ mutants display an overactive QS system, leading to surfactin overproduction and reduced fitness.
- Surfactin mediates social selection against signal-null mutants in cocultures with signal producers.
Conclusions:
- The private repressor function of ComQ protects QS systems from loss-of-function mutations.
- Bacillus subtilis employs a sophisticated QS system combining intracellular and extracellular signaling for stability.
- This dual-action signaling mechanism contributes to the evolutionarily stable functioning of bacterial communities.
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