A new study by researchers at Instituto Gulbenkian de Ciência (IGC) in Portugal revealed that when the body has its own immune system compromised, as happens in patients with inflammatory bowel disease (IBD),nthe composition of the gut bacteria (microbiota) changes, and the predictability and speed of the adaptation process of the microbiota is affected. The study was published in the journal Nature Communications and is entitled “Adaptive immunity increases the pace and predictability of evolutionary change in commensal gut bacteria”.
It is well-established that the human health is strongly associated with the diversity of the microbiota that inhabits the intestinal tract and the way how the immune system tolerates it. Gut bacteria have to adapt and evolve depending on the environment they inhabit and the different stimuli they may receive, such as diet. This evolution leads to a higher diversity in microbiota, and the immune system acts as a surveillance mechanism to prevent the development of harmful bacteria and diseases.
It has been hypothesized that the immune system can, in fact, influence the evolution of gut bacteria, although this possibility has never been proven. IGC researchers have proven experimentally, for the first time, that the hypothesis is correct.
Researchers investigated how the bacteria Escherichia coli, which is one of the first bacteria to colonize the intestine at birth, evolved using two type of mice: healthy mice and mice with a defective immune system (without lymphocytes). The team found that diet induced rapid metabolic adaptations in healthy mice, whereas this adaptation was slower in immune-compromised animals. Furthermore, the same type of beneficial adaptations was observed in several healthy mice. In contrast, mice with a defective immune system exhibited a large range of different adaptations and variations, making it difficult to predict the evolution course of the microbiota in these mice.
“We observed that this feature is due to changes in the composition of the community of bacteria in the intestine, which is more similar across individuals with a healthy immune system, and is quite diverse in animals with an immune compromised system.” explained the study’s first author João Batista in an IGC’s press release.
Based on their findings, researchers suggested that the treatment of intestinal conditions that are caused by an impaired immune system, as is the case in IBD, should be based on personalized medicine, where the microbiota composition of the patient is taken into account.
“Our work shows that it is possible to predict the evolution of commensal bacteria in healthy organisms, but the same is not true in organisms with problems in their immune system. Therefore, the use of generalist therapies to treat people suffering from intestine pathologies that result from an impaired immune system, such as inflammatory bowel disease, may not be the best approach. Instead, therapies based on personalized medicine should be considered, accordingly to the composition of gut bacteria of each person.” noted the study’s co-senior author Dr. Isabel Gordo.
“This research was possible due to the collaborative spirit that exists in the IGC, that brings together research groups from different fields. Hence, we merged our expertise in evolutionary biology and immunology to study the complex interactions between the vertebrate immune system, composed of a myriad of different cells, and the gut microbiota, composed of another myriad of different bacteria. We learned that the immune system acts as a normalizer of the gut microbiota composition.” said the study’s co-senior author Dr. Jocelyne Demengeot.
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