Modeling Adaptive Mutation of Enteric Bacteria in Surface Water Using Agent-Based Methods

Abstract

Mechanistic models of enteric bacteria fate and transport in surface waters are important tools for research and management. The existing modeling approach typically assumes that bacteria die in a first-order fashion, but a recent study suggests that bacteria can mutate relatively rapidly to a strain better adapted to the surface water environment. We built an agent-based model that simulates individual wild-type and mutant Escherichia coli cells. The bacteria die, grow on the natural assimilable organic carbon available to E. coli, divide and mutate. We apply the model to laboratory experiments (from the literature and new ones) and the Charles River in Boston. Laboratory applications include decay, growth, and competition (between wild-type and mutant) in various types of surface water. For decay experiments, the stochastic mutation process in the model can produce both first-order and biphasic decay patterns, which is consistent with observations in the literature. For the Charles River, the model can reproduce the main patterns observed in the field data. The model applications provide evidence in support of the mutation mechanism. However, the mutation model does not produce better predictions for the Charles River than a previous model based on labile and resistant subpopulations.