# Spreading of non-motile bacteria on a hard agar plate: Comparison between agent-based and stochastic simulations

## TL;DR

This study compares agent-based and stochastic continuum models to understand how non-motile bacteria colonies spread on agar, revealing how nutrient levels and noise influence colony morphology.

## Contribution

It introduces a combined analysis of agent-based and stochastic models to explain bacterial colony spreading and morphology transitions.

## Key findings

- Population fluctuations are inherent in agent-based models.
- Decreasing nutrient concentration causes a transition from DLA to Eden-like morphology.
- Intrinsic noise and non-linear diffusivity drive morphology changes.

## Abstract

We study spreading of a non-motile bacteria colony on a hard agar plate by using agent-based and continuum models. We show that the spreading dynamics depends on the initial nutrient concentration, the motility and the inherent demographic noise. Population fluctuations are inherent in an agent based model whereas, for the continuum model we model them by using a stochastic Langevin equation. We show that the intrinsic population fluctuations coupled with non-linear diffusivity lead to a transition from Diffusion Limited Aggregation (DLA) type morphology to an Eden-like morphology on decreasing the initial nutrient concentration.