Researchers at Nagoya University have identified two types of gut bacteria that appear to work together to degrade the protective mucus layer of the colon, contributing to chronic constipation. The bacteria in question are Akkermansia muciniphila and Bacteroides thetaiotaomicron. The study was published in the journal Gut Microbes.

The mucus layer lines the walls of the colon and is also a component of fecal matter. It retains moisture, facilitates stool passage, and protects the epithelium from harmful bacteria. When this barrier thins, stool becomes dry and hard.

The study showed that the degradation occurs in stages. First, B. thetaiotaomicron produces an enzyme called sulfatase, which removes sulfate groups from mucin. Normally, these groups protect mucus from breakdown. Once this “protection” is removed, A. muciniphila begins actively digesting the mucin.

As a result, mucus levels decrease, stool loses moisture, and constipation develops. According to the authors, the problem in such cases is not slowed intestinal motility, as commonly thought, but the loss of the mucus barrier. This explains why standard laxatives and motility-stimulating drugs are often ineffective.

The researchers also noted a link to Parkinson’s disease. Patients with Parkinson’s — who often experience constipation decades before tremors appear — were found to have elevated levels of these mucus-degrading bacteria. Previously, such symptoms were mainly attributed to nervous system dysfunction.

“We genetically modified B. thetaiotaomicron so that it could no longer activate the sulfatase enzyme that removes sulfate groups from mucin,” said lead author Tomonari Hamaguchi of Nagoya University. “When we introduced these modified bacteria together with Akkermansia muciniphila into the guts of germ-free mice, the animals did not develop constipation: the mucin remained intact and protected.”

The experiment demonstrated that blocking sulfatase activity prevents mucus layer degradation. The authors suggest this could pave the way for therapies targeting specific bacterial enzymes.

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