Probiotic bacteria are designed as factoriesto produce one or multiple therapeutic biomolecules, with geneticallyengineered probiotics expressing therapeutic proteins in an induciblemanner preferred over a constitutive manner, as it allows for easiercontrol of biomolecule production and prevents overdosing. In an experimental study, the administrationof IL-10-secreting Lactococcus lactis induced a 50% reduction of colitis in DSS-treated mice and preventedthe onset of colitis in IL-10­(−/−) mice. The gene discussed is IL10; the disease is colitis.