The results show that bacteriophages present in the gut microbiota influence the relationship between the microbiome and the brain. In addition, the work opens the door to new lines of research such as the study of possible dietary supplements with this virus in isolation to improve people’s cognitive abilities.

The study has been led by Jordi Mayneris-Perxachs and José Manuel Fernández-Real, from the IDIBGI and CIBEROBN Nutrition, Eumetabolism and Health group, and has been carried out in collaboration with the Neuropharmacology research group led by Rafael Maldonado at the Pompeu Fabra University; the Human Microbiome group of Andrés Moya and Vicente Pérez-Brocal, from the FISABIO Foundation; the Institute for Integrative Systems Biology (I²SysBio, joint centre of the UV and the Spanish National Research Council-CSIC); CIBERESP and the University of Alicante (UA).

Bacteriophages, a type of virus that replicates within bacteria, represent one of the largest gaps in our understanding of the human microbiome. This research has focused on the study of two types of bacteriophages prevalent in the intestinal microbiota: the Caudovirales and the Microviridae. In a sample of 114 people, expanded to 942 subjects (participants of the IDIBGI Aging Image Project), the research team found that “individuals with more Caudovirales had better performance of executive processes and verbal memory, and, on the other hand, the presence of higher levels of Microviridae was related to a greater deterioration of the executive capacities of the brain”, affirms José Manuel Fernández-Real, head of the Nutrition, Eumetabolism and Health group at IDIBGI and CIBEROBN.

Dairy products, a possible way to acquire Caudovirales

To find out how people can access these viruses, the scientific team conducted food surveys of the participants to learn about their diet. Interestingly, individuals who had more Caudovirales in their gut microbiota consumed more dairy products on a regular basis. A finding supported by the scientific literature in this area: some previous research indicated that people who drank more dairy products had better cognitive functions.

In order to further reinforce the result, an experiment was carried out with mice, using the microbiota present in the different samples of human faeces, for which they transplanted it into the intestine of rodents. The mice that received a microbiota rich in Caudovirales presented a better cognitive performance and more memory than other mice.

A second confirmatory experiment was performed using flies (Drosophila melanogaster) as the animal model, also known as fruit flies. First, a group of flies was fed with whey, and they showed more memory than the other group of Drosophila that ingested the sterilised whey and, therefore, without virus. The experiment was repeated, but in this case the flies’ diet was supplemented with the isolated bacteriophages. The results were replicated again. By looking at a cluster of genes in the fly brain, the authors found that the presence of Caudovirales upregulated genes associated with memory.

Article: Mayneris-Perxachs et al., «Caudovirales bacteriophages are associated with improved executive function and memory in flies, mice, and humans», Cell Host & Microbe (2022), https://doi.org/10.1016/j.chom.2022.01.013