Researchers led by the University of Cambridge report that an uncultured group of gut bacteria known as CAG-170 appears more abundant in healthy people and is less common in several chronic diseases, based on analysis of more than 11,000 gut metagenomes from 39 countries.
A large international study led by researchers at the University of Cambridge has identified a little-known group of gut bacteria—known as CAG-170—that appears more frequently and at higher levels in healthy people.
The researchers searched for CAG-170’s genetic “fingerprint” in gut microbiome data from 11,115 metagenomes spanning 39 countries. Across the dataset, healthy individuals showed higher levels of CAG-170 than people living with a range of noncommunicable diseases.
The findings were published in Cell Host & Microbe. The dataset included healthy participants and people diagnosed with 13 diseases, including Crohn’s disease, obesity, colorectal cancer, Parkinson’s disease and multiple sclerosis. The analysis also found lower CAG-170 levels in people with conditions such as inflammatory bowel disease and chronic fatigue syndrome.
Because most members of CAG-170 remain uncultured—meaning scientists cannot yet grow most of them in the lab—the team relied on computational and genetic analyses to infer what the bacteria might do. Those analyses suggested CAG-170 has the capacity to produce large amounts of vitamin B12 and carries enzymes involved in breaking down carbohydrates, sugars and fibers.
Researchers said the vitamin B12 produced by CAG-170 is likely to support other beneficial microbes in the gut rather than directly benefiting the human host, pointing to a potential role in maintaining balance across the broader gut ecosystem.
Dr. Alexandre Almeida of the University of Cambridge’s Department of Veterinary Medicine, who led the study, said: “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.”
He added: “We looked at the gut microbes of thousands of people across 39 countries and 13 different diseases including Crohn’s and obesity. We consistently found that people with these diseases had lower levels of CAG-170 bacteria in their gut.”
The study builds on earlier efforts to map the genetic diversity of the human gut microbiome, including Almeida’s work on the Unified Human Gastrointestinal Genome (UHGG) catalogue. That catalogue compiled reference genomes representing thousands of gut prokaryotic species, many of which lack cultured representatives.
In this new research, the team reported that three separate analyses supported CAG-170’s link with health: comparisons between healthy and disease cohorts, assessments of which microbes appear most stabilizing within healthy microbiomes, and analyses of dysbiosis—an imbalanced gut microbiome state that has been associated in past research with long-term conditions including irritable bowel syndrome, rheumatoid arthritis, and anxiety and depression.
Researchers said CAG-170 could eventually help define what a healthy gut microbiome looks like and might serve as a future marker of gut health. They also suggested that, if scientists can learn how to culture these bacteria and test them directly, the findings could inform more targeted probiotic approaches than those commonly used today.
The human gut contains billions of bacteria spanning thousands of species. While the composition varies widely person to person, researchers said the overall function of the microbiome is broadly aimed at supporting normal body processes.
