Causative Role of Anoxic Environment in Bacterial Regulation of Human Intestinal Function

Introduction Life on Earth depends on oxygen; human tissues require oxygen signaling, whereas many microorganisms, including bacteria, thrive in anoxic environments. Despite these differences, human tissues and bacteria coexist in close proximity to each other such as in the intestine. How oxygen governs intestinal-bacterial interactions remains poorly understood. Methods To address to this gap, we created a dual-oxygen environment in a microfluidic device to study the role of oxygen in regulating the regulation of intestinal enzymes and proteins by gut bacteria. Two-layer microfluidic devices were designed using a fluid transport model and fabricated using soft lithography. An oxygen-sensitive material was integrated to determine the oxygen levels. The intestinal cells were cultured in the upper chamber of the device. The cells were differentiated, upon which bacterial strains, a facultative anaerobe, Escherichia coli Nissle 1917, and an obligate anaerobe, Bifidobacterium Adolescentis, were cultured with the intestinal cells. Results The microfluidic device successfully established a dual-oxygen environment. Of particular importance in our findings was that both strains significantly upregulated mucin proteins and modulated several intestinal transporters and transcription factors but only under the anoxic-oxic oxygen gradient, thus providing evidence of the role of oxygen on bacterial-epithelial signaling. Conclusions Our work that integrates cell and molecular biology with bioengineering presents a novel strategy to engineer an accessible experimental system to provide tailored oxygenated environments. The work could provide new avenues to study intestine-microbiome signaling and intestinal tissue engineering, as well as a novel perspective on the indirect effects of gut bacteria on tissues including tumors.