Scientists at Nagoya University have identified two types of gut bacteria that work together to cause chronic constipation. The bacteria, Akkermansia muciniphila and Bacteroides thetaiotaomicron, degrade the intestinal mucus layer that keeps the colon lubricated and stool hydrated. When this mucus is excessively broken down, stool becomes dry and difficult to pass.
This research, published in Gut Microbes, sheds light on why conventional treatments for chronic constipation often do not work for many people. The study also found that individuals with Parkinson's disease, who frequently experience severe constipation years before other symptoms appear, have increased levels of these mucus-degrading bacteria. While it was previously thought that nerve degeneration was responsible for constipation in Parkinson’s patients, the findings suggest bacterial activity plays a significant role.
Doctors have long believed slow movement of food through the intestines is the main reason behind constipation. However, some people suffer from chronic idiopathic constipation (CIC), where no clear cause is found. Similarly, Parkinson’s disease patients can struggle with severe and persistent constipation for decades before other neurological symptoms develop.
The researchers shifted focus from nerve and muscle function to colonic mucin—a gel-like substance lining the large intestine and present in stool—which maintains moisture and protects intestinal walls from bacteria. Their investigation revealed that B. thetaiotaomicron removes protective sulfate groups from colonic mucin using specific enzymes. Afterward, A. muciniphila breaks down and consumes the exposed mucin.
Normally, sulfate groups attached to mucin molecules prevent bacterial degradation. If too much mucin is lost due to excessive bacterial action, stool loses its moisture content and hardens—leading to constipation. Since this issue stems from mucin depletion rather than slow gut movement, standard laxatives or drugs designed to increase motility may not be effective.
The study demonstrated that inhibiting sulfatase—the enzyme used by B. thetaiotaomicron—can stop these bacteria from breaking down mucin. This suggests that future drugs targeting sulfatase could potentially treat bacterial forms of constipation in humans.
According to the researchers: "For millions of patients with treatment-resistant constipation, including those with Parkinson's disease, this discovery offers hope for new therapies that address the root microbial causes of their condition."
