THE EFFECT OF DIURNAL FLUCTUATIONS IN INTESTINAL FLOW AND GEOMETRY ON SHAPING THE MICROBIAL POPULATIONS IN THE HUMAN LARGE INTESTINE

The microbial population within the large intestine (LI) strongly influences human physiology, with its size and composition being key factors determining microbe-host interactions [1].However, our understanding of how microbiota size emerges as consequences of food intake, digestion, the active movement of luminal contents, and microbial growth characteristics remains limited.Different in-vitro setups, involving bioreactors [2, 3] and microfluidics [4][5][6][7], and mathematical models [5,8,9], have been employed to emulate the fundamentals of this ecosystem.However, these systems do not account for crucial intestinal characteristics, including the strong diurnal fluctuation of flow and nutrient supply, the flexibility of the intestinal volume, and the presence of a cecum.To address these crucial, albeit neglected, components, we introduce a new mathematical modeling framework here that integrates considerations of diurnal food intake, digestion, intestinal fluid passage, intestinal cycles of expansion-contraction, and microbial growth physiology in a gut-like channel.