A "good" bacterium called Bacteroides fragilis, which is present in the gut produces a sugar molecule that may offer a potential new treatment for inflammatory bowel disease, scientists at the California Institute of Technology have found.
Sarkis K. Mazmanian, an assistant professor of biology at Caltech, said that the sugar molecule identified by his team is called polysaccharide A (PSA).
He attributed the discovery about the molecule's action to experiments on mice, wherein changes were introduced in the animals' intestinal bacteria by exposing them to a pathogenic bacterium called Helicobacter hepaticus.
This microbe was chosen because it is known to cause a disease in the mice that is similar to Crohn's disease and ulcerative colitis.
However, when the researchers co-colonized the animals with B. fragilis, they were protected from the disease, as were animals that were given oral doses of just the PSA molecule.
Mazmanian said that the experiment enabled his colleagues to know that PSA induced particular immune-system cells called CD4+ T cells to produce interleukin-10 (IL-10), a molecule that has previously been shown to suppress inflammation--and offer protection from inflammatory bowel disease.
"Thus, bacteria help reprogram our own immune system to promote health," he said.
"The most immediate and obvious implication is that PSA may potentially be developed as a natural therapeutic for inflammatory bowel disease," he added.
Mazmanian said that his team's work suggested that a the interplay between various groups of bacteria living in the intestines had profound effects on human health.
"Perhaps disease results from the absence of beneficial bacteria and their good effects," he said.
"This study is the first demonstration of that. What it hopefully will do is allow people to re-evaluate our opinions of bacteria. Not all are bad and some, maybe many, are beneficial," he added.