A massive international collaboration led by Cambridge scientists has spotlighted a little‑known cluster of gut microbes, labeled CAG‑170, that shows up far more often in people who are free of chronic disease.
These microbes have so far been identified only through DNA signatures; they cannot yet be cultivated in the laboratory, making direct study challenging.
By mining metagenomic data from over 11,000 stool samples collected across 39 nations, the researchers discovered a clear pattern: individuals without conditions such as inflammatory bowel disease, obesity, or chronic fatigue consistently harbored higher levels of CAG‑170.
Further genetic probing revealed that CAG‑170 is equipped to synthesize substantial amounts of vitamin B12 and possesses enzymes that break down complex carbohydrates, sugars, and dietary fibers.
The team believes the vitamin B12 is likely shared with neighboring microbes, helping to keep the whole gut ecosystem balanced rather than directly nourishing the host.
These insights position CAG‑170 as a promising indicator of a thriving microbiome and open the door to probiotic formulations designed to boost its presence.
Dr. Alexandre Almeida, who heads the project, explained: “Our analysis suggests that members of the ‘hidden microbiome’ like CAG‑170 act as silent workhorses, aiding digestion and supporting the broader microbial community.”
He added, “When we examined thousands of samples from 39 countries spanning 13 diseases—including Crohn’s disease and obesity—we repeatedly observed lower CAG‑170 counts in the sick groups.”
The findings were published in Cell Host & Microbe.
Building the Unified Human Gastrointestinal Genome Catalogue
This work builds on an earlier effort by Almeida’s group to create a comprehensive reference of gut microbial genomes, known as the Unified Human Gastrointestinal Genome catalogue.
Using metagenomic sequencing, the catalogue mapped over 4,600 bacterial species, more than 3,000 of which were previously undocumented, highlighting how much of our internal world remains unexplored.
Each species, including CAG‑170, received a detailed genetic fingerprint that now allows scientists to detect them in any gut sample.
Three Independent Analyses Confirm the Health Connection
The investigators performed three separate examinations:
- Comparison of 11,000+ microbiome profiles from healthy volunteers and patients with 13 distinct ailments, consistently showing higher CAG‑170 levels in the healthy group.
- A focused survey of more than 6,000 disease‑free individuals to pinpoint microbes that best stabilize the gut ecosystem, where CAG‑170 again topped the list.
- An assessment of dysbiosis‑related samples, revealing that reduced CAG‑170 abundance correlated with an increased risk of microbial imbalance, a factor linked to conditions like irritable bowel syndrome, rheumatoid arthritis, and mood disorders.
What This Means for Future Probiotics
Even though each person carries a unique microbial blend, the overarching goal of the gut community is to support bodily functions. By defining what a “healthy” microbiome looks like, researchers hope to detect deviations early and restore balance through targeted probiotic blends.
Almeida notes that current probiotic products rely on a handful of well‑studied strains that were identified decades ago. Discoveries like CAG‑170 suggest a new generation of supplements could be far more effective by nurturing previously overlooked microbes.
Because most CAG‑170 members cannot yet be grown in the lab, future work will need to develop novel culturing techniques before these bacteria can be harnessed for therapeutic use.