# Bacterial constipation: Mucin-degrading intestinal commensal bacteria cause constipation

## TL;DR

Certain gut bacteria that break down mucin can work together to cause constipation by reducing lubrication in the colon.

## Contribution

Discovery that cooperative mucin degradation by Akkermansia muciniphila and Bacteroides thetaiotaomicron causes constipation.

## Key findings

- Increased levels of A. muciniphila and B. thetaiotaomicron correlate with constipation in humans.
- Co-colonization of mice with both bacteria induces constipation, while single colonization does not.
- Disabling sulfatase activity in B. thetaiotaomicron reduces constipation in mice.

## Abstract

The contribution of gut microbes to constipation remains mechanistically underexplored, despite constipation being one of the most prevalent gastrointestinal disorders. Here, we identify cooperative induction of constipation by two mucin-degrading gut commensals: Akkermansia muciniphila and Bacteroides thetaiotaomicron. In constipated patients with Parkinson’s disease (PD) and chronic idiopathic constipation (CIC), we observed that A. muciniphila and B. thetaiotaomicron were increased. Gnotobiotic mice colonized with either bacterium exhibited no constipation, whereas mice co-colonized with both bacteria developed constipation. Fecal mucins but not gastric mucins carry terminal sulfates. As fecal transcriptome of gnotobiotic mice suggested a sulfatase-dependent mechanism, we generated an anaerobic sulfatase-maturating enzyme (anSME)-deficient B. thetaiotaomicron strain that cannot catabolize the terminal sulfates of mucins. In the absence of anSME, constipation was ameliorated in co-colonized gnotobiotic mice. The synergic effect of the two bacteria is in accordance with our observation that A. muciniphila alone and constipation are not correlated in humans. As a bunch of intestinal bacteria other than B. thetaiotaomicron also catabolize mucin sulfates, they may substitute for B. thetaiotaomicron in patients with constipation. We propose bacterial constipation, in which cooperative degradation of colonic mucins by sulfatases and glycosylases by two commensal bacteria reduces lubrication and induces fecal dehydration, leading to the development of constipation. Targeting microbial sulfatase activity may be a promising therapeutic approach for patients with bacterial constipation.