Researchers at Cambridge have spotted something unexpected in the guts of healthy people across 39 countries: a mysterious bacterium called CAG-170 that almost nobody knew about until now.
The catch is that CAG-170 has never been successfully grown in a lab. Scientists know it only through its genetic signature — a fingerprint left in microbiome samples from over 11,000 people. Yet despite being largely invisible to traditional study, this hidden microbe keeps showing up in the same places: in the guts of people without chronic illness.
The Pattern
When researchers compared healthy individuals to people living with inflammatory bowel disease, obesity, chronic fatigue syndrome, and 10 other conditions, the pattern was clear. Healthy people consistently had higher levels of CAG-170. Lower levels appeared alongside dysbiosis — that out-of-balance gut state linked to everything from IBS to anxiety.
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Start Your News DetoxWhat makes CAG-170 potentially important is what it appears to do. Its genes carry instructions for producing large amounts of Vitamin B12 and breaking down all kinds of carbohydrates, sugars, and fibers. The researchers suspect CAG-170 doesn't feed us directly — instead, it feeds other beneficial bacteria, essentially running the ecosystem that keeps our gut functioning.
"We looked at the gut microbes of thousands of people across 39 countries and 13 different diseases," said Dr. Alexandre Almeida, lead author of the study published in Cell Host & Microbe. "We consistently found that people with these diseases had lower levels of CAG-170 bacteria in their gut."
This discovery emerged from earlier work mapping the gut's hidden world. Almeida's team had already identified over 4,600 bacterial species living in human guts — more than 3,000 of them never documented before. CAG-170 was among these invisible players. "Around two-thirds of the species in our gut microbiome were previously unknown," Almeida noted. "Now we've found that some of these are a fundamental component of human health."
What Comes Next
The probiotic industry has largely relied on the same bacterial species for decades, even as research reveals entirely new cast members in the microbiome story. If scientists can figure out how to culture CAG-170 in the lab — a significant technical hurdle — it could lead to probiotics designed around these newly discovered health-linked bacteria rather than the old standbys.
For now, CAG-170 offers researchers a new marker: a genetic fingerprint of what a healthy gut microbiome might look like across different populations and geographies. That's the kind of baseline that eventually leads to targeted treatments.
