Engineered probiotics that sequester arsenite in a mouse gastrointestinal system.

Chronic exposure to inorganic arsenic remains a major global health concern, as arsenite is frequently present in contaminated food and drinking water and readily absorbed through the gastrointestinal (GI) tract. Once internalized, arsenite accumulates in tissues and contributes to long-term health effects, including cancer, organ dysfunction, and neurological disorders. Despite extensive efforts to reduce environmental contamination, there are currently no practical strategies to prevent dietary arsenite from entering the human body during digestion. Here, we report a synthetic biology-based approach that uses engineered probiotics to detect and sequester arsenite directly within the GI tract before systemic absorption occurs. We engineered Escherichia coli Nissle 1917 (EcN), a probiotic strain, to function as a living arsenite-interception system. Central to this design is an arsenite-responsive genetic toggle switch that activates chelator expression upon exposure and sustains production under biostatic conditions, while automatically shutting off during active cell division to limit metabolic burden and enhance biosafety. In parallel, we engineered an arsenite-binding protein derived from the transcriptional regulator ArsR to eliminate DNA-binding activity while retaining high-affinity metal binding, yielding a non-toxic chelator suitable for intracellular sequestration. The resulting engineered strain efficiently removed arsenite from its surrounding environment in vitro while maintaining robust cell viability and growth. To translate these findings to an in vivo context, we developed a mass-transfer model describing arsenite distribution among the stomach lumen, engineered bacteria, and epithelial cells. This model guided the selection of a bacterial dose predicted to substantially deplete lumenal arsenite prior to epithelial uptake. Using this strategy, we demonstrated in a mouse GI model that oral administration of engineered EcN markedly reduced arsenite entry into the bloodstream compared with wild-type EcN or no-bacteria controls. Together, these results establish a programmable probiotic platform for intercepting dietary arsenite and highlight a potential strategy for preventing absorption of environmental toxicants using living microbial therapeutics.