Leveraging Synthetic Biology and Gut-on-a-Chip Systems to Study Gut Metabolite-Host Interactions: A Case Study in H2s

Microbial metabolism in the human gut is increasingly linked with a range of host diseases. Hydrogen sulfide (H₂S) is a gaseous microbial metabolite whose role in gut diseases is debated, with contradictory results stemming from experimental difficulties associated with accurate dosing and measuring H₂S, and the use of model systems that do not accurately represent the human gut environment. Here, we engineered E. coli to titrate H₂S across the physiological range in a gut microphysiological system (chip) supportive of the co-culture of microbes and host cells. The chip was engineered to maintain H₂S gas tension and enabled visualization of co-culture in real-time with confocal microscopy. Engineered strains colonized the chip and were metabolically active for two days, during which they produced H₂S across a sixteen-fold range and induced changes in host gene expression and metabolism in an H₂S concentration-dependent manner. These results validate a platform for studying the mechanisms underlying microbe-host interactions.

These findings motivated the development of microbes capable of sequestering or producing intestinal H₂S from different sulfur sources found in the human intestine. First, we engineered a synthetic pathway that converts H₂S to glutathione. The strain consumed H₂S at a rate of 1 mM H₂S/hr-OD₆₀₀, approximately 10-fold higher than wild type. Next, we engineered a synthetic pathway to convert glutathione to H₂S which can produce 0.3 mM H₂S/hr-OD₆₀₀ compared to no H₂S production in the wild type. These engineered microbes may be used to modify the intestinal metabolome to drive changes in human disease pathology.