Types of gut microbiota affect intake of nutrients

Every person’s intestinal system falls into one of three clearly distinguishable types of gut microbiota, comparable to blood types. These types are not related to race, native country or diet, according to a new metagenomics study by an international consortium of scientists including Jeroen Raes, of the VIB and Vrije Universiteit Brussel.

Metagenomics is the study of the genetic material of complete ecosystems, in this case the human gut.

An estimated 100,000 billion individual bacteria live in our intestines. They form our gut microbiota. These bacteria play a crucial role in protecting our health. They help to covert food into energy and protect us against attacks by pathogens. In exchange for these benefits, our bodies provide the bacteria with habitat and nutrition.

“The three gut types can explain why the uptake of medicines and nutrients varies from person to person,” says bioinformatician Jeroen Raes of the VIB and Vrije Universiteit Brussel, one of the two lead researchers in the study.

“This knowledge could form the basis of personalised therapies. Treatments and doses could be determined on the basis of the gut type of the patient.”

Improved knowledge of the gut types could also lead to other medical applications, such as the early diagnosis of intestinal cancer, Crohn’s disease and the adverse effects of obesity.

The types of gut microbiota (called enterotypes) can be classified into three large, clearly distinguishable groups: Bacteroides, Prevotella and Ruminococcus. They are named for the bacteria that dominate the intestines of the respective groups. It is still unclear whether people can change from one group to another during their lives.

Scientists do not yet have a conclusive explanation for the existence of the types of gut microbiota, but all the evidence indicates that only a limited number of stable biotic communities are possible in our intestines. In this way they are comparable to other ecosystems in nature, such as forests, tundra, tropical jungles, savannahs and others.

Ecosystems have a tendency to evolve towards a stable equilibrium, with certain species that become dominant and others that occupy niches. This also appears to apply to our intestines.

The study shows a connection between human characteristics and gut microbiota. For instance, correlations were found between the Body Mass Index (BMI) and the strains of bacteria in the gut. The more efficiently the bacteria can extract energy from the food, the greater the chance that the person has a high BMI (and therefore struggles with obesity). The researchers found that the presence of certain bacterial genes could serve as diagnostic and/or predictive markers for obesity. This finding is currently undergoing further testing in a clinical study in a group of over 100 individuals. This involves examining the DNA of the complete gut microbiome of those.

It is notable that the vitamin production between the different groups varies strongly. People that belong to the Bacteroides group have more gut bacteria that produce vitamins C, B2, B5 and H. The Prevotella group showed higher numbers of B1 and folic acid-producing flora.

In the past, the study of gut microflora was very difficult. The problem was that most gut bacteria cannot be cultivated in a lab and only survive in the intestines. A different approach is now used. Instead of cultivating the bacteria, the genetic information (DNA) of all the bacteria is studied together (metagenomics). This generates a vast amount of data that is analysed using powerful computers.