Scientists Discover a 'Hidden' Gut Bacteria That Could Be the Key to Better Health

A global study of over 11,000 people across 39 countries has identified a little-known group of gut bacteria called CAG-170 that appears to be fundamental to good health. Researchers at the University of Cambridge discovered that people with diseases like inflammatory bowel disease, obesity, and chronic fatigue syndrome consistently had lower levels of this bacteria compared to healthy individuals. The findings suggest CAG-170 could become a new marker for gut health and inspire a new generation of probiotics designed specifically to support these beneficial microbes.

What Makes CAG-170 So Special?

CAG-170 is part of what scientists call the "hidden microbiome"—bacteria that have never been successfully grown in a laboratory, so researchers only know them through their genetic fingerprints. Despite this mystery, the bacteria appear to play a crucial role in keeping our digestive systems and overall health in balance.

When researchers analyzed what CAG-170 actually does inside our guts, they found something remarkable: these bacteria have the capacity to produce high levels of vitamin B12 and enzymes that break down a wide range of carbohydrates, sugars, and fibers. The research suggests that the vitamin B12 produced by CAG-170 likely supports other species of gut bacteria, helping maintain a healthy microbial ecosystem.

"Our work has revealed that CAG-170 bacteria—part of the 'hidden microbiome'—appear to be key players in human health, likely by helping us to digest the main components of our food and keeping the whole microbiome running smoothly," said Dr. Alexandre Almeida, a researcher in the University of Cambridge's Department of Veterinary Medicine who led the study.

How Did Researchers Find This Hidden Bacteria?

The discovery came from an ambitious project called the Unified Human Gastrointestinal Genome catalogue, which catalogued the genetic fingerprints of all bacteria found in the human gut. This earlier work revealed something surprising: approximately two-thirds of the bacterial species in our gut microbiome were previously unknown to science.

Using this genetic catalogue as a reference, the Cambridge team searched for CAG-170's genetic fingerprint in gut samples from thousands of people. They examined samples from:

• Geographic Diversity: Participants from 39 countries, primarily in Europe, North America, and Asia, ensuring the findings weren't limited to one region or population.
• Health Status Comparison: Both healthy individuals and people with 13 different diseases including Crohn's disease, colorectal cancer, Parkinson's disease, and multiple sclerosis.
• Sample Size: Over 11,000 individual gut microbiome samples analyzed using multiple computational approaches to verify the findings.

The consistency of the results across different countries and disease types was striking. No matter where the researchers looked, people with diseases had significantly lower levels of CAG-170 compared to healthy individuals.

What Does This Mean for Gut Health and Disease?

The research also examined people with dysbiosis—a condition where the gut microbiome becomes imbalanced. The team found that lower levels of CAG-170 were linked with a higher likelihood of having this gut imbalance. Dysbiosis is connected to many long-term health conditions, including irritable bowel syndrome (IBS), rheumatoid arthritis, and anxiety and depression.

This connection suggests that CAG-170 might serve as an early warning sign. If doctors could measure CAG-170 levels in a patient's gut, they might be able to identify microbiome problems before they develop into serious health issues.

"The probiotic industry hasn't really kept up with gut microbiome research—people are still using the same probiotic species that were being used decades ago," Dr. Almeida explained. "We're now discovering new groups of bacteria like CAG-170 with important links to our health, and probiotics aimed at supporting them could have a much greater health benefit".

What's Next for Probiotics and Personalized Health?

The discovery opens the door to developing a new generation of probiotics specifically designed to support and maintain healthy levels of CAG-170 in the gut. Rather than relying on bacteria that have been used in probiotic supplements for decades, scientists could now create targeted formulations based on what we're learning about these newly discovered microbes.

The research also highlights how much we still have to learn about our gut bacteria. The fact that CAG-170 couldn't be grown in a laboratory until now shows why traditional microbiome research has missed so much. By using genetic analysis instead of relying only on bacteria that can be cultured, scientists are discovering entirely new players in the gut health story.

The study was published in the journal Cell Host & Microbe and represents a significant step toward understanding what a truly healthy gut microbiome looks like—and how we might restore balance when things go wrong.