It is known that people in different regions of the world differ in certain characteristics – this also includes the properties of the intestinal microflora. A genetic study is now revealing the background to this microbial diversity: the gut microbes have evolved in parallel with the dispersal histories of their hosts. It is also becoming clear that some of these organisms display characteristics that reflect their strong dependence on the human gut environment. As the researchers emphasized, the study findings have not only evolutionary significance, but also medical significance: microbiome therapies can be improved for specific populations.
We are changing habitats: in our gut lives a brilliant community of microorganisms, which has become the focus of science in recent decades. It is becoming increasingly clear the complex role the gut microbiome plays in human health: physical and even mental problems can be traced back to a disruption in the partnership with the tiny creatures within us. In addition to the health significance, scientists are also investigating how this system has evolved over the course of evolution. In principle, it is known that the gut microbiome can vary between populations and individuals: many microbial species are common, but some strains are very different.
The international research team led by the Max Planck Institute for Biology in Tübingen investigated the assumption that certain types and strains of gut microbes accompanied groups of people as they spread around the world and produced certain characteristics in parallel. To investigate this potential shared diversification between gut bacteria and the human population, scientists sequenced and analyzed thousands of bacterial genomes from a total of 1,225 individuals from different parts of Europe, Asia and Africa. Based on certain genetic characteristics, they were able to draw conclusions about the evolutionary history of microbes.
The historical link between microbes and humans
In the case of 59 microbial species, the researchers developed family trees in this way. They were then able to compare it to the proportions of their human hosts, which they derived from genetic analyzes of saliva samples. As they report, their analyzes revealed that more than 60 percent of the microbial species examined show a parallel history of evolution with their human hosts. This means that this species evolved in the human gut over hundreds of thousands of years as humans spread across the Earth.
“It is also notable that those lineages that closely followed our evolutionary history are now more dependent on the gut environment,” says lead researcher Ruth Lee of the Max Planck Institute for Biology. Based on genetic information, it became clear that some microbial strains that evolved with humans are highly specialized for living conditions in the human gut: they have relatively small genomes and react sensitively to deviations in oxygen content and temperature. As a result, they have almost no chance of surviving outside the human body. “The study results fundamentally change our view of the human gut microbiome,” says Lai.
“Some gut microbes behave as if they were part of the human genome,” says lead author Taichi Suzuki of the Max Planck Institute for Biology. To depend on the environment of the human body. We were able to show that some human gut bacteria have progressed along this spectrum toward irreversible dependency than previously thought. “In contrast, gut populations, which have shown a weaker link to human history, have significantly more characteristics of free-living bacteria,” a scientist reports.
Microbiome therapies adapt to groups
Finally, they emphasized that the findings could also have implications for the medical impact on human microbial communities. What is meant here are remedies for people with health problems that can be traced back to an unfavorable composition of the intestinal flora. You can benefit from giving so-called probiotics or from transferring “healthy” mixtures of your gut microbiome. Findings regarding differences between gut microbiome strains for different populations may be useful because they may respond better to their ‘microbes’. “The microbiome is a therapeutic target for personalized medicine, and our findings underscore the importance of a population-specific approach to microbiome-based therapies,” the researchers wrote.
Source: Max Planck Institute for Biology Tübingen, Specialized article: Science, doi: 10.1126 / science.abm7759
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