Cannibalism enhances biofilm development in Bacillus subtilis

Area of Science:

• Microbiology
• Bacterial Physiology
• Biofilm Formation

Background:

• Bacillus subtilis employs cannibalism, involving self-lysis via skf and sdp toxins, to delay sporulation and sustain the population.
• This process releases nutrients, feeding the remaining cells and postponing the formation of dormant spores.
• The role of cannibalism in relation to other cellular behaviors, like biofilm formation, remains to be fully elucidated.

Purpose of the Study:

• To investigate the link between cannibalism and extracellular matrix production in Bacillus subtilis.
• To determine if the same cell subpopulation engages in both cannibalism and matrix formation.
• To understand the regulatory mechanisms and functional implications of this dual behavior.

Main Methods:

• Utilized genetic manipulation to track and identify subpopulations involved in cannibalism and matrix production.
• Employed microscopy techniques to visualize biofilm structure and cell-cell interactions.
• Analyzed gene expression related to toxin production, resistance, and matrix synthesis.
• Investigated the response to signaling molecules like surfactin and external antimicrobials.

Main Results:

• Identified a single subpopulation of Bacillus subtilis responsible for both cannibalism (skf and sdp toxin production) and extracellular matrix formation.
• Demonstrated that surfactin triggers both cannibalism and matrix production in this specific subpopulation.
• Showed that cannibalized cell nutrients are preferentially utilized by the toxin-resistant, matrix-producing cells, enhancing their growth and matrix production.
• Confirmed that this cannibal/matrix-producing subpopulation is also induced by external antimicrobials, suggesting a defensive role.

Conclusions:

• Cannibalism and matrix production are coupled behaviors in Bacillus subtilis, executed by the same resistant cell subpopulation.
• This coordinated response, triggered by surfactin, allows for nutrient recycling and enhanced biofilm integrity.
• The cannibalistic/matrix-producing subpopulation acts as a defense mechanism against environmental stressors, including antibiotics, promoting community survival.