The study of the microbiota (the group of microorganisms that live inside our body) has had a great boom in recent decades, showing that many diseases can be affected both positively and negatively by microorganisms. However, the study of the microbiota presents numerous difficulties due to the great variety of microorganisms it encompasses and the great possibility of interactions between them and with our cells .
What is the gut microbiota?
This causes a large amount of data to be generated that is almost impossible to unravel in order to find the “golden bacteria”, the one capable of curing a disease or preventing its appearance. The reality is much more complex, where the communication network between bacteria, viruses, fungi and us is similar to a central computer connected by thousands of cables.
The microbiota of our organism is different between different individuals, since it is affected by multiple factors, some genetic and others environmental. Also, inside a person, their microbiota is not the same in their intestine, their skin or their mouth. Each organ has a microenvironment that is, in part, conditioned by the different populations of microorganisms that inhabit it .
Recent studies have found relationships between populations of microorganisms and the development of cancer, autoimmune diseases, Alzheimer’s, and autism spectrum disorders. In addition, there is also evidence of interactions between the microbiota and the effect of some treatments, both enhancers and inhibitors.
For these reasons, knowing how this close communication develops can be essential in the control of diseases and the development of treatments. This interaction has been the focus of a study recently published in the journal Cell Host & Microbe by scientists at several Spanish research centers, where they have shown that one type of virus affects some cognitive functions in humans, mice and flies .
Some viruses are our ‘friends’
The virus in question is a bacteriophage, a virus that infects bacteria, and this one in particular, uses the bacteria of our intestine as hosts. The part of the study focused on humans includes more than 1,000 people who are asked to perform a battery of cognitive tests that collect information on concentration or verbal memory, among others. In general, those who scored better on the cognitive tests had higher levels of the bacteriophages Caudovirales and Siphoviridae .
Next, they performed fecal transplants from healthy humans containing high or low levels of Caudovirales , one of these bacteriophages, into mice. After the transplant, the mice underwent a test where they were presented with a new object used to assess memory. The results confirmed that those mice to which the bacteriophage was transplanted had an improvement in memory functions than those that did not receive it.
Finally, experiments with a Siphoviridae -supplemented diet in Drosophila melanogaster , the fruit fly, confirmed an improvement in memory. The results in animal models not only corroborated the observations in humans, but also demonstrated that the benefit could be acquired through fecal transplantation (mice) or diet (flies) . In both cases, they confirmed the results in the memory tests with analysis of genetic markers in the brain.
How does this communication take place?
This study presents clear evidence that some bacteriophages are beneficial for a type of cognitive process associated with memory. However, the mechanism of action is not so clear. Today we know that there is a close communication between our immune system and the bacteria that inhabit our intestine .
The defense cells or molecules of our body are responsible for scanning bacterial populations in search of any that may pose a threat. Those that, apparently, are not dangerous, settle down and perform their function. However, these regulatory representatives maintain communication with the bacteria and in some cases coordinate.
If we introduce bacteriophages into this salad of cells, they may shape the functioning of the bacteria they infect and, in turn, have an effect on our cells .
The process by which these bacteriophages manage to have such a determining effect as to be seen in an improvement in human memory is tremendously sophisticated and incredible. In addition to that it could open the door to the development of alternative treatments or complementary diets for diseases associated with cognitive problems. Although it is clear that there is still a long way to go, it is no less interesting for that.
References:
Brody. 2020. The gut microbiome. Nature. doi: 10.1038/d41586-020-00194-2
Mayneris-Perxachs et al. 2022. Caudovirales bacteriophages are associated with improved executive function and memory in flies, mice, and humans. Cell Host Microbe. doi: 10.1016/j.chom.2022.01.013
Â
Â
