Ruminococcus bromii alleviates constipation by pullulanase-driven resistant starch degradation and microbiota modulation.

Constipation is a prevalent gastrointestinal disorder associated with alterations in the gut microbiota. However, the potential microbial targets and their underlying mechanisms remain to be explored. Our analysis found the genus Ruminococcus was depleted in constipated patients. We then tested four species, R. bromii, R. torques, R. obeum, and R. gnavus, in constipated mice, finding all alleviated symptoms. R. bromii was most effective, with its pullulanase enzyme being key to degrading resistant starch. This degradation boosted short-chain fatty acid production and fostered beneficial bacteria like Akkermansia and Bifidobacterium. A subsequent clinical trial confirmed that the constipation-relieving effect of dietary resistant starch was dependent on the presence and abundance of R. bromii in the gut. This study identifies R. bromii as a key microbial mediator for constipation relief through resistant starch metabolism, positioning it as a promising candidate for targeted probiotic or synbiotic therapies.