Lactococcus lactis, a nonpathogenic, lactic-acid bacterium commonly used in the production of fermented foods, is the gold standard for probiotic gene-editing strategies, due to its well-studied genome and its safety properties.221 One of the first recombinant L. lactis, from the pioneer work by Steidler and colleagues, was designed to treat IBD by secreting IL-10 in-situ in the colon in two murine models of disease.230 In one of the models, chronic colitis was induced by administration of DSS and the efficacy of L. lactis-secreting IL-10 (LL-mIL10) to treat symptoms was tested. This evidence concerns the gene IL10 and irritable bowel syndrome.