For therapies targeting diseases of the gastrointestinal tract, we and others envision probiotic bac-teria that synthesize and excrete biotherapeutics at disease sites. Toward this goal, we have engi-neered commensalE. colithat selectively synthesize and secrete a model biotherapeutic in thepresence of nitric oxide (NO), an intestinal biomarker for Crohn's disease (CD). This is accomplishedby co-expressing the pore forming protein TolAIII with the biologic, granulocyte macrophage-colony stimulating factor (GM-CSF). We have additionally engineered these bacteria to accumulateat sites of elevated NO by engineering their motility circuits and controlling pseudotaxis. Impor-tantly, because we have focused onin vitrotest beds, motility and biotherapeutics production arespatiotemporally characterized. Together, the targeted recognition, synthesis, and biomoleculedelivery comprises a“smart”probiotics platform that may have utility in the treatment ofCD. Further, this platform could be modified to accommodate other pursuits by swapping the pro-moter and therapeutic gene to reflect other disease biomarkers and treatments, respectively