The bacteria living in our gut may have powerful effects on us, but we aren’t entirely at their mercy. We now have the first evidence of the mechanism our bodies use to keep these microbial hangers-on in check.
There are a lot of microbes inside us. Although the idea that we contain 10 times as many microbes as cells of our own now seems to be untrue (see “Not outnumbered”), it is still likely that we have a roughly equal number of each, prompting the question of how we stop our guests from misbehaving.
Shirong Liu and his colleagues at Harvard Medical School in Boston may have uncovered the answer. They discovered that cells lining the gut in mice and humans produce short strands of genetic material called microRNAs. These strands can get inside bacteria and switch on certain genes, which encourages the growth of specific types of bacteria.
Diverse microbiome
Mice that produce fewer microRNAs in their gut have a more diverse microbiome, and are more susceptible to colitis – inflammation in the lining of the colon. The team suggests that gut microRNAs have evolved as a way for us to shape the community of bacteria living inside us, and specifically nurture the ones that help us prevent disease.
“The concept is interesting,” says Tim Spector of King’s College London. “This emphasises our symbiotic relationship with microbes.”
The microbiome is already a target for medical researchers looking for ways to prevent disease, through diet or perhaps drugs. MicroRNAs designed to enhance or suppress specific bacteria could be a powerful tool, Liu says.
“The manipulation of the microbiome with microRNAs could represent a new therapeutic frontier once the mechanisms are fully elucidated,” says Andrea Masotti at Bambino Gesù Children’s Hospital in Rome, Italy.