Understanding the Human Gut Microbiota: A Mathematical Approach

In order to explore the dynamics of the human gut microbiota, we used a system of ordinary differential equations to mathematically model the biomass of three microorganism populations: Bacteroides thetaiotaomicron, Eubacterium rectale, and Methanobrevibacter smithii. Additionally, we modeled the concentrations of relevant nutrients necessary to sustain these populations over time. This system highlights the interactions and the competition among these species in order to further understand their dynamics. These three microorganisms were specifically chosen due to the system’s end product, butyrate, which aids in developing the intestinal barrier in the human gut. The basis of the mathematical model assumes the gut acts as a chemostat, with bacteria and nutrients exiting the gut at a rate proportional to the volume of the chemostat, the rate of volumetric flow, and the biomass or concentration of the particular population or nutrient. We performed global sensitivity analysis using Sobol’ sensitivities in order to estimate the importance of model parameters and to understand our results.