A mysterious group of gut bacteria known as CAG-170 appears in higher numbers among healthy individuals, according to a new study. Researchers analyzed microbiomes from over 11,000 people across 39 countries and found this genus strongly associated with good health and balanced gut ecosystems. The findings suggest potential roles in producing vitamin B12 and supporting other microbes, though causality remains unclear.
The human gut hosts more than 4,600 bacterial species, many of which influence immune function, sleep, ageing, and mental health risks. About two-thirds belong to the 'hidden microbiome,' detected only through genomic analysis since they cannot yet be cultured in labs. 'A burning question still remains: are these species just bystanders or relevant to human health?' said Alexandre Almeida at the University of Cambridge.
Almeida's team examined genetic fingerprints from gut samples of over 11,000 participants from 39 countries, mainly in Europe, North America, and Asia. Half the participants had no diagnosed conditions, while the other half suffered from one of 13 illnesses, such as inflammatory bowel disease, obesity, or chronic fatigue syndrome. They identified 715 species linked to at least one condition: 342 increased in disease states and 373 in healthy ones.
The genus CAG-170 showed the strongest health correlation. 'Consistently across different conditions, we found that CAG-170 seem to be markedly increased in health compared to disease,' Almeida noted. Further analysis revealed CAG-170's association with lower dysbiosis, or microbial imbalance, promoting healthier gut compositions.
Genomic study of CAG-170 uncovered genes for producing high vitamin B12 levels and enzymes that degrade carbohydrates and fibers. These bacteria do not appear to use the vitamin themselves but support co-occurring species that do. 'It seems like CAG-170 are taking more of an altruistic approach and providing metabolic support to the rest of the microbiome,' Almeida explained.
Nicola Segata at the University of Trento called this an important step in understanding microbiome-health links, though he emphasized the interconnectedness of microbes and the body as a single system. Determining if CAG-170 drives health or results from it requires further trials, potentially involving diet or probiotics. Challenges in culturing these bacteria persist, but providing arginine—an amino acid they cannot produce—might aid their growth. The research appears in Cell Host & Microbe.
