Speaker
Description
The human gut harbors a highly dynamical microbiota shaped by the rapid turnover of bacterial biomass: While food intake by the host regularly supports fast growth of new bacteria, a substantial fraction of the bacterial population is also lost with every major bowel movement. The dynamics of the turnover depend strongly on the consumed diet and the speed with which bacteria grow. But the turnover is also tightly controlled by the hosts itself which regulates muscle contractions and the movement of intestinal content depending on digestion status and the local abundance of bacteria. We here present a mathematical modeling framework to investigate how these factors and their interplay shape the spatio-temporal densities of bacteria along the human large intestine. Our analysis shows how rapid changes in densities are strongly coupled to meal intake and largely shaped by the gastrocolic reflex which triggers the emptying of the proximal colon before large amounts of luminal fluids and nutrients enter from the small intestine. Because of these dynamics, bacterial densities within the proximal colon are often very low and bacteria present in the appendix can act as an important reservoir which shapes the bacterial population along the large intestine. Our results thus also highlight possible physiological roles of the appendix: the promotion of efficient bacterial growth and the stabilization of the microbiota composition which prevents pathogens or other bacteria entering from the small intestine from taking over the population.
