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Updated: Jun 14, 2026
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A Visual Assay to Monitor T6SS-mediated Bacterial Competition
Published on: March 20, 2013
Lethal protein produced in response to competition between sibling bacterial colonies
Avraham Be'er1, Gil Ariel, Oren Kalisman
1Department of Physics, Center for Nonlinear Dynamics, University of Texas, Austin, TX 78712, USA.
Summary
Paenibacillus dendritiformis bacteria use a lethal factor, sibling lethal factor (Slf), to control colony growth. Subtilisin regulates Slf production, promoting growth at low levels and triggering lysis at high levels between colonies.
Area of Science:
- Microbiology
- Bacterial self-regulation
- Protein interactions
Background:
- Paenibacillus dendritiformis colonies exhibit mutual growth inhibition on low-nutrient media.
- Secretions contain subtilisin and a 12 kDa protein, sibling lethal factor (Slf).
Purpose of the Study:
- To elucidate the mechanism of growth inhibition and self-regulation in P. dendritiformis colonies.
- To characterize the roles of subtilisin and sibling lethal factor (Slf) in bacterial colony dynamics.
Main Methods:
- Analysis of bacterial secretions.
- Purification and testing of subtilisin and Slf.
- Production and activation of recombinant dendritiformis sibling bacteriocin.
- Mathematical modeling of colony growth.
Main Results:
- Subtilisin promotes P. dendritiformis colony growth, while Slf causes cell lysis.
- A 20 kDa inactive precursor protein is cleaved by subtilisin into active 12 kDa Slf.
- Subtilisin acts as a growth regulator, promoting expansion below a threshold and triggering Slf secretion above it.
- Mathematical modeling supports the proposed regulatory mechanism.
Conclusions:
- Subtilisin regulates P. dendritiformis colony growth by controlling the activation of the bacteriocin Slf.
- This self-regulation mechanism, involving protease-activated bacteriocins, may be widespread in other bacterial species.
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