How a versatile gut bacterium helps us get our daily dietary fibre

UBC researchers have discovered the genetic machinery that turns a common gut bacterium into the swiss army knife of the digestive tract -- helping us to metabolize a main component of dietary fibre from the cell walls of fruits and vegetables.

The findings illuminate the specialized roles played by key members of the vast microbial community living in the human gut, and could inform the development of tailored microbiota transplants to improve intestinal health after antibiotic use or illness. The research will be published in the journal Nature on Sunday.

“While they are vital to our diet, the long chains of natural polymeric carbohydrates that make up dietary fibre are impossible for humans to digest without the aid of our resident bacteria,” says UBC professor Harry Brumer, with UBC’s Michael Smith Laboratories and Department of Chemistry, and senior author of the study.

“This newly discovered sequence of genes enables Bacteroides ovatus to chop up xyloglucan, a major type of dietary fibre found in many vegetables -- from lettuce leaves to tomato fruits. B. ovatus and its complex system of enzymes provide a crucial part of our digestive toolkit.”

About 92 per cent of the population harbours bacteria with a variant of the gene sequence, according to the researchers’ survey of public genome data from 250 adult humans.

“The next question is whether other groups in the consortium of gut bacteria work in concert with, or in competition with, Bacteroides ovatus to target these, and other, complex carbohydrates,” says Brumer.

Background

The bacterial communities living in the human gut -- roughly 100 trillion microorganisms -- account for 50 per cent of the weight of the contents of the lower digestive tract in humans. Up to 10 per cent of our daily caloric intake can come from the breakdown of dietary fibre by our gut bacteria.

Researchers from the University of Michigan, the University of York, and the Swedish Royal Institute of Technology were also involved in the study.

Link to publication (DOI: 10.1038/nature12907): http://dx.doi.org/10.1038/nature12907