Size of quorum sensing communities

Area of Science:

• Microbiology
• Systems Biology
• Biophysics

Background:

• Bacteria coordinate collective behavior through cell-cell communication systems called quorum sensing.
• Quorum sensing relies on the production and exchange of signal molecules, often involving positive feedback for switching collective behaviors.
• A precise definition of bacterial biofilm 'size' has been lacking, hindering a complete understanding of these systems.

Purpose of the Study:

• To establish a robust and appropriate measure for bacterial biofilm size.
• To refine the understanding of quorum sensing dynamics by incorporating a size parameter.
• To separate the effects of positive feedback from smoother activation in bacterial collectives.

Main Methods:

• Developing a mathematical model for bacterial biofilm size.
• Incorporating geometric factors based on colony shape and boundary conditions (e.g., spherical, hemispherical, disk-shaped).
• Analyzing the influence of the surrounding medium and flow conditions on the size measure.

Main Results:

• A factorized expression for biofilm size was derived, combining cell density and a geometric factor.
• The geometric factor accounts for different boundary conditions and colony shapes.
• The new size measure successfully separates the 'all-or-none' switching behavior from continuous activation.

Conclusions:

• The proposed size measure, integrating cell density and geometric factors, accurately reflects biofilm size.
• This provides a more comprehensive understanding of quorum sensing regulation in bacterial ensembles.
• The findings offer a simplified yet powerful tool for studying bacterial collective behaviors.