Mechanically driven growth of quasi-two-dimensional microbial colonies

Area of Science:

• Microbiology
• Biophysics
• Mathematical Biology

Background:

• Bacterial colony growth is typically modeled using nutrient diffusion and reaction-diffusion equations.
• Established models like Fisher-Kolmogorov may not fully capture complex colony dynamics.
• Mechanical interactions between bacteria are often overlooked in growth models.

Purpose of the Study:

• To develop a model for bacterial colony growth incorporating mechanical interactions.
• To investigate how mechanical forces influence colony velocity and shape.
• To explain observed transitions between circular and branching colony morphologies.

Main Methods:

• A computational model simulating rod-shaped bacteria on solid substrates.
• Incorporation of mechanical interactions (pushing) and nutrient consumption.
• Analysis of colony front velocity, shape, and growth patterns.

Main Results:

• Mechanical interactions, not just nutrient diffusion, govern colony front velocity and shape.
• Colony velocity is influenced by bacterial elasticity and surface adhesion.
• Non-linear radius growth is predicted for 2D colonies unless branching occurs.

Conclusions:

• Mechanical forces are critical for accurately modeling bacterial colony expansion.
• The model explains the transition from circular to branching colonies observed experimentally.
• This work offers a new perspective on microbial growth dynamics and pattern formation.