A combination of cellular automata and agent-based models for simulating the root surface colonization by bacteria

Models of root colonization by bacteria facilitate conceptual and practical understanding of fundamental processes that influence plant health, mineral nutrition, and stress tolerance. In this study, we explored the use of cellular automata and agent-based models to simulate the primary colonization of roots by bacteria as determined by selected parameters related to bacterial growth (nutrient uptake, fitness, reproduction and starvation) and environmental constraints (space, nutrient depletion, and pH). The results were then compared with observations from experiments examining the colonization of plant roots by a GFP – strain of Escherichia coli. The latter experiments were conducted with plants grown in agar medium containing calcium phosphate that allowed visualization of bacterial distribution (aggregates and abundance) and phosphate solubilization at root microsites. The numerical models revealed outcomes for diverse numerical scenarios, which agreed with the in vivo data and provided a basic framework for describing bacterial colonization of plant roots. Further efforts will be required to evaluate factors affecting the competence and ecology of bacterial communities at rhizosphere microsites, but offer promise for the development of precise predictive models with practical applications for agriculture.