Yale. US: Stability in the composition of the hundred trillion bacterial cells
in the human gastrointestinal tract is crucial to health, but scientists
have been perplexed how our microbiota withstands an onslaught of
toxins, dietary changes, and immune response to infections or
antibiotics with little change.
Research from Yale published in
the Jan. 9 issue of the journal Science identifies a strategy that
commensal, or non-harmful, gut bacteria employ to preserve this stable
relationship with their host during inflammation.
“It has been a
puzzle that many immune responses target all bacteria,” said Andrew
Goodman, assistant professor of microbial pathogenesis and a member of
the Microbial Sciences Institute at Yale’s West Campus. “Yet healthy
individuals maintain the same beneficial microbes for decades even when
exposed to a host of environmental disturbances.’’
Research has
shown that disruptions in the gut microbiome can lead to severe health
consequences, including obesity, recurrent infections, and diseases such
as irritable bowel syndrome. Instability in the microbiome has been
linked to diseases as diverse as autism and cancer. Doctors may one day
be able to manipulate the microbiome to treat patients, but scientists
first need to understand the molecular machinery of the vast gut
microbiome, which contains a hundred times more genes than the human
genome.
The new study represents a first step, Goodman said. The
Yale team found that in mice and humans, microbiome stability is
maintained by a single gene that allows bacteria to resist high levels
of inflammation-associated antimicrobial peptides. Commensal bacteria
that lack this mechanism were promptly removed from the gut during
inflammation in mice.
“We were surprised that a single factor
could have such a large effect,” Goodman said. “This study opens the
door for new approaches to understand how commensal bacteria interact
with their hosts.”
Thomas W. Cullen of Yale is the lead author of the study.
Primary funding for the work was provided by the National Institutes of Health.