Space and time on the membrane: modelling Type VI secretion system dynamics as a state-dependent random walk

Area of Science:

• Microbiology
• Biophysics
• Computational Biology

Background:

• The type six secretion system (T6SS) is a complex machine used by bacteria for inter-bacterial killing.
• T6SS function relies on assembly, spatial positioning, and firing dynamics within the bacterial cell membrane.
• Regulation of T6SS assembly and firing kinetics impacts bacterial competitiveness.

Purpose of the Study:

• To develop a mathematical model for the spatial motion and assembly/disassembly of the T6SS.
• To investigate how spatial and temporal factors influence T6SS firing phenotypes.
• To explore the role of diffusion coefficients in determining bacterial attack ranges.

Main Methods:

• Mathematical modeling of T6SS dynamics on the cell membrane.
• Representation of T6SS motion as a state-dependent random walk.
• Parameter inference from existing literature to simulate firing behaviors.

Main Results:

• The model captures both the assembly/disassembly and spatial movement of the T6SS.
• Simulations demonstrate how combined spatial and temporal effects generate diverse firing phenotypes.
• Variations in diffusion coefficients were sufficient to produce local or global firing patterns.

Conclusions:

• Mathematical modeling provides a framework for understanding T6SS firing mechanisms.
• Bacterial cell-cell interactions mediated by T6SS are significantly influenced by membrane dynamics.
• Diffusion rates are critical determinants of T6SS attack range and bacterial competition strategies.