Development of a Transcriptional Biosensor for Hydrogen Sulfide that Functions under Aerobic and Anaerobic Conditions

Hydrogen sulfide (H ₂ S) is a gaseous gut metabolite with disputed effects on gastrointestinal health. Monitoring H ₂ S concentration in the gut would provide insight into its role in disease, but is complicated by sulfide’s reactivity and volatility. Here we develop a transcriptional sulfide biosensor in E. coli . The sensor relies on enzymatic oxidation of sulfide catalyzed by a sulfide:quinone reductase (Sqr) to polysulfides, which bind to the repressor SqrR, triggering unbinding from the promoter and transcription of the reporter. Through promoter engineering and improving soluble SqrR expression, we optimized the system to provide an operational range of 50 µM - 750 µM and dynamic range of 18 aerobically. To enable sensing in anaerobic environments, we identified an Sqr from Wolinella succinogenes that uses menaquinone, facilitating reoxidation through the anaerobic electron transport chain by fumarate or nitrate. Use of this homolog resulted in an anaerobic H ₂ S response up to 750 µM. This sensor could ultimately enable spatially and temporally resolved measurements of H ₂ S in the gastrointestinal tract to elucidate the role of this metabolite in disease, and potentially as a non-invasive diagnostic.