Ability to digest fibre dependent on species of gut bacteria
11 February 2014
Sweden's KTH Royal Institute of Technology has recently
discovered how our ability to benefit from fibre is dependent on a
group of bacteria called Bacteroidetes to digest the
complex carbohydrates in the fibre.
Fibre is an essential part of a healthy diet, but until now,
scientists were not sure exactly how complex sugars known as
xyloglucans are broken down in the human gut. Xyloglucans account
for a quarter of the dry weight of many common fruits and
vegetables. The study was published in the journal Nature
The researchers traced the molecular mechanism for the digestion
of xyloglucans to a genetic sequence in one of the species of the
bacteria, Bacteroides ovatus.
“Bacteroides ovatus and its complex system of enzymes provide a
crucial part of our digestive toolkit," says Harry Brumer, who began
the study four years ago with a research team at the Division of
Glycoscience in the KTH School of Biotechnology. Brumer continued
the work over the last two years at University of British Columbia,
where he is a professor in the Michael Smith Laboratories and
Department of Chemistry. The research partners also include
University of York and the University of Michigan.
"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. In
fact, this system is so important, it is found in at least 92% of
humans surveyed worldwide so far," Brumer says.
The findings can be useful to researchers developing new
probiotic or dietary treatments for microbial imbalances that cause,
or are a result of, bowel diseases, he says.
“The probiotics field is a complex one, which includes many
regulatory issues; but one could imagine making defined treatments
based on specific microbes, based on their individual, inherent
metabolic capacities, to improve the balance of the microbiota and
overall human heath,” he says.
The research may also prove useful for the future of biomass
technology. “The basic enzymology and structural biology gives new
insight into the function of carbohydrate-active enzyme families,
which can suggest ways to improve these biocatalysts for biomass
utilisation, in such areas as materials or fermentation to chemicals
and fuels,” Brumer says.
The next step for the research team will include investigating
whether these bacteria work in concert – or competition – with other
gut bacteria to target complex carbohydrates. “Right now, we are
excited to explore similar complex loci to find out how other common
dietary polysaccharides are broken down,” he says. “Very little is
known at the molecular level in this area, even for very common
1. Larsbrink, J, et al. A discrete genetic locus confers
xyloglucan metabolism in select human gut Bacteroidetes" Nature,