Gut microbes found in feces avoid triggering immune reactions that could lead to conditions like inflammatory bowel disease (IBD) by creating a mucus barrier that separates them from immune cells, a study shows. The discovery helps explain why antibiotics can create digestive problems. It also provides a path toward potential new IBD therapeutic strategies, researchers said. The study, "Proximal colon–derived O-glycosylated mucus encapsulates and modulates the microbiota," was published in the journal Science. The colon houses a rich microbial ecosystem known as the gut microbiome, whose composition and status is directly related to human health. "The colon is not just a digestive organ, but an immune organ," Lijun Xia, MD, PhD, the study's principal investigator, said in a press release. "Our microbiome begins to develop at the moment of birth and evolves throughout our lives. It's essential for the growth and maturation of the acquired immune system in our body," Xia said. "When it's not well developed or cared for, it doesn't operate as it should, which can lead to diseases." As waste materials — feces — pass through the colon, they becomes encapsulated in two layers of sticky mucus, known as b1 and b2. Specialized cells lining the intestines, called goblet cells, produce this mucus as a defense mechanism to keep potentially harmful gut microbes separated from the rest of the colon — including immune cells present in the colon. Scientists at the Oklahoma Medical Research Foundation were surprised to find evidence that the gut microbes themselves trigger the production of this mucus. "Colon mucus segregates the intestinal microbiota from host tissues, but how it organizes to function throughout the colon is unclear," they wrote.