A large-scale global study has identified a previously overlooked group of gut bacteria, named CAG-170, that appears to be consistently present in the gut microbiomes of healthy individuals. Researchers suggest this bacterial group may play a crucial role in maintaining gut health and overall wellbeing.
The research, led by scientists at the University of Cambridge and published on in the journal Cell Host & Microbe, analyzed gut microbiome samples from over 11,000 people across 39 countries. The findings consistently showed higher levels of CAG-170 in individuals without chronic diseases, including inflammatory bowel disease, obesity and chronic fatigue syndrome.
A Challenging Bacteria to Study
CAG-170 presents a unique challenge to researchers because, despite its apparent importance, most of its constituent bacteria have proven difficult to cultivate in the laboratory. Scientists primarily identify CAG-170 through its genetic fingerprints, limiting detailed study until recently. The team employed advanced computational methods to track the bacteria’s genetic signature within the vast datasets of gut microbiome samples.
Consistent Link to Health Across Populations
The study revealed a clear pattern: individuals identified as healthy consistently exhibited higher levels of CAG-170 compared to those with various health conditions. This correlation held true across diverse populations and geographical locations. Specifically, lower levels of CAG-170 were observed in individuals with inflammatory bowel disease, obesity, and chronic fatigue syndrome.
Further analysis of the genetic makeup of CAG-170 bacteria revealed their capacity to produce significant amounts of vitamin B12, as well as enzymes that break down a wide range of carbohydrates, sugars, and fibers commonly found in the human diet. Researchers hypothesize that the vitamin B12 produced by CAG-170 may primarily benefit other gut bacteria, rather than directly supporting human health, suggesting a role in fostering a balanced gut ecosystem.
Potential for Future Applications
The researchers suggest that CAG-170 could potentially serve as a biomarker for gut microbiome health, offering a way to assess the overall balance and function of an individual’s gut. The findings could pave the way for the development of novel probiotics specifically designed to support and maintain healthy levels of CAG-170 in the gut.
“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,” notes Alexandre Almeida, PhD, a principal investigator in the University of Cambridge’s Department of Veterinary Medicine.
Dr. Almeida added that analyzing the gut microbes of thousands of people across 39 countries, including those with conditions like Crohn’s disease and obesity, consistently showed lower levels of CAG-170 in individuals with these diseases.
Mapping the Unknown Microbiome
This research builds upon a previous project led by Dr. Almeida, which aimed to create a comprehensive reference library of microbial genomes found in the human gut, known as the “Unified Human Gastrointestinal Genome Catalog.” The team utilized metagenomics, a technique that analyzes all the microbial genomes within a sample simultaneously, allowing them to identify and categorize different bacterial species.
This work uncovered over 4,600 different bacterial species residing in the gut, with more than 3,000 previously unknown to science. This highlights the vast diversity of the gut microbiome and the significant amount of microbial life that remains unexplored.
The reference genomes act as genetic fingerprints, enabling scientists to identify specific species, including CAG-170, in other samples. Dr. Almeida noted that approximately two-thirds of the species found in the gut microbiome were previously unknown, and their roles were unclear, until studies like this began to reveal their potential importance.
Supporting Evidence from Multiple Analyses
The researchers conducted three separate analyses to support their findings. The primary analysis involved over 11,000 samples, primarily from Europe, North America, and Asia, encompassing both healthy individuals and those with 13 different diseases, including colorectal cancer, Parkinson’s disease, and multiple sclerosis. CAG-170 consistently showed the strongest association with good health across all countries.
A second analysis, involving over 6,000 healthy individuals, further confirmed that CAG-170 was the bacterial group most strongly linked to gut ecosystem stability. The third analysis focused on gut microbiome imbalances (dysbiosis), revealing that lower levels of CAG-170 were associated with an increased risk of dysbiosis, which is linked to long-term conditions such as irritable bowel syndrome, rheumatoid arthritis, anxiety, and depression.
Future Directions and Potential Therapies
The human gut microbiome comprises trillions of bacteria representing approximately 4,600 different species. While its composition varies from person to person, its primary function is to aid the body in efficient operation. Scientists hope that a better understanding of a healthy microbiome will clarify how it changes during disease and lead to methods for restoring balance, potentially through targeted probiotic development.
Dr. Almeida pointed out that the probiotic industry has not yet fully incorporated recent advances in microbiome research, often relying on bacterial strains used for decades. The discovery of groups like CAG-170 suggests that new bacterial combinations could offer greater health benefits.
Further research is needed to develop methods for cultivating CAG-170 bacteria in the lab, allowing for more direct study and potentially translating these findings into tangible therapeutic interventions. The majority of CAG-170 bacteria are currently difficult to grow in laboratory settings, hindering detailed investigation.
