Universality in Bacterial Colonies

TL;DR

This study uses detailed simulations to analyze the scaling behavior of bacterial colony growth patterns, revealing a richer universality class with multiple sub-phases influenced by nutrient levels.

Contribution

It introduces a quantitative framework to classify bacterial colony patterns and proposes the existence of up to four distinct sub-phases based on nutrient conditions.

Findings

Identification of multiple sub-phases in bacterial growth patterns

Proposal of a new universality class for colony expansion

Evidence of emergent disorder due to bacterial competition

Abstract

The emergent spatial patterns generated by growing bacterial colonies have been the focus of intense study in physics during the last twenty years. Both experimental and theoretical investigations have made possible a clear qualitative picture of the different structures that such colonies can exhibit, depending on the medium on which they are growing. However, there are relatively few quantitative descriptions of these patterns. In this paper, we use a mechanistically detailed simulation framework to measure the scaling exponents associated with the advancing fronts of bacterial colonies on hard agar substrata, aiming to discern the universality class to which the system belongs. We show that the universal behavior exhibited by the colonies can be much richer than previously reported, and we propose the possibility of up to four different sub-phases within the medium-to-high nutrient concentration regime. We hypothesize that the quenched disorder that characterizes one of these sub-phases is an emergent property of the growth and division of bacteria competing for limited space and nutrients.