The Process Pathway Model of bacterial growth

Abstract

The growth profile of microorganisms in an enclosed environment, such as a bioreactor or flask, is a well studied and characterized system. Despite a long history of examination, there are still many competing mathematical models used to describe an output of the microorganisms, namely the number of bacteria as a function of time. However, these descriptions are either purely phenomenological and give no intuition as to the biological mechanisms underlying the growth curves, or extremely complex and become computationally unfeasible at the population level. In this paper, we develop the Process Pathway Model by modifying a model of sequential processes, which was first used to model robustness in metabolic pathways, and demonstrate that the Process Pathway Model encapsulates many features and temperature dependence of bacterial growth. We verify the predictions of the model against growth data for multiple species of microorganisms, and confirm that the model generates accurate predictions on temperature dependence of bacterial growth. The model has five free parameters, and the simplifying assumptions used to build the model are built upon biologically realistic notions. The Process Pathway Model accurately models a microorganisms growth profile at an intermediate level of complexity that is computationally feasible. This model can be used as both an conceptual model for thinking about systems of bacterial growth, as well as a computational model that operates at level of complexity that is amenable to large scale simulation. This balance in accuracy and intuitiveness was accomplished by using realistic biological assumptions to simplify the underlying biology, which may point the way forward for future models of this type.