Development of in vitro models of the human intestinal microbiome
Authors: Doherty Laurel A , Whitman Jordan , Arcidiacono Steven , Pantoja‐Feliciano Ida , Racicot Kenneth , Soares Jason W 
Published: June 2021

The gut microbiome is a key modulator of human health, metabolism, and immune function. Extensive study on the role of the microbiome has taken place since its significance was realized, with the majority of efforts characterizing its relationship to nutrient availability and disease state. Studies predominantly focus on the large intestine, rapidly emerging as a nexus for human health with less known regarding the small intestine microbiome due to its relative accessibility. Of particular interest is the relationship between stress and induced perturbations to the microbiome. Research has largely focused on chronic health states whereas acute stressors mostly experienced by athletes and Soldiers, such as sudden changes in diet and sporadic duration of fasted and fed states, have largely been unexplored thus far. Here, we present our efforts to utilize in vitro fermentation as a modelling tool to simulate the large and small intestine microbial ecosystems and support derivation of a link between nutrition, military‐relevant stressors and the gut microbiome with health and performance. In vitro fermentation affords greater flexibility and accessibility compared to animal or human clinical trials and can be utilized to inform in vivo studies. Efforts to develop a continuous culture model of the gut microbiome, the Joint Army Automated Colon‐on‐a‐bench (jA2COB), will be presented, as will our most recent efforts to model the small intestine microbiome. Use of an automated, parallel bioreactor platform enabled real‐time monitoring and control of numerous fermentation parameters including pH, anaerobicity, and fermentation volume. Inocula for jA2COB were prepared from fresh fecal donations pooled from multiple individuals and grown in separate anaerobic bioreactors representing the domains of the colon alone or in sequence, either separately under batch conditions for 24–48 hours and in sequence for up to five weeks. Aliquots were removed at discrete intervals throughout the study to monitor phylogenetic population dynamics via denaturing gradient gel electrophoresis and 16S rRNA sequencing. To date, jA2COB has been employed to explore biotransformation of polyphenolic compounds and stress‐induced alterations to microbial metabolism for nutritional inputs; results will be presented. To model the small intestine microbiome, a polymicrobial community representative of major small intestine phyla and functions was designed as an analogue. The polymicrobial community fermented in a microaerophilic environment representative of the ileum; preliminary results indicate synergistic growth behavior between species. Progress on small intestine model architecture will also be presented. Use of in vitro fermentation to model the human intestinal microbiota will enable broader investigation of the effect of Soldier‐relevant stressors on gut health and may act as a precursor to human or animal studies. Insight gleaned from these models, alone or in concert with in vivo studies, can inform nutritional strategies to restore and maintain Soldier gut homeostasis.Support or Funding InformationFunded through in‐house support from Soldier Performance Optimization Directorate ‐ NSRDEC.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.