Mono- to Multilayer Transition in Growing Bacterial Colonies

Area of Science:

• Microbiology
• Biophysics
• Mathematical Biology

Background:

• Bacterial biofilm development involves a transition from monolayers to multilayered structures.
• This transition occurs in microcolonies of a few hundred cells across various bacterial species.
• Understanding the triggers for this structural change is key to controlling biofilm formation.

Purpose of the Study:

• To investigate the mechanical and stochastic factors driving the transition from bacterial monolayers to multilayered structures.
• To model the onset of multilayer formation in bacterial microcolonies.

Main Methods:

• Numerical simulations of bacterial colony growth.
• Analytical modeling of mechanical stresses and cell-substrate interactions.
• Statistical analysis of asynchronous cell division and its impact on colony structure.

Main Results:

• The monolayer-to-multilayer transition is driven by a competition between growth-induced stresses and cell-substrate restoring forces.
• The transition initiates when individual cells become unstable to rotation, a localized and deterministic event.
• Asynchronous cell division introduces stochasticity, with the first division approximated by a Poisson process.

Conclusions:

• The onset of multilayer formation in bacterial colonies is a mixed deterministic-stochastic process.
• The rate of the first cell division acts as an order parameter for this transition.
• This study provides a framework for understanding and potentially controlling biofilm architecture.