About one hundred trillion microbes live inside us and form what is called a “microbiome”, which is like a little world, or rather a universe. One hundred trillion means that if you plant one blade of grass for each microbe living in your gut, you could cover a million football fields. It’s all incredibly complex.
This description by computational microbiologist Dan Knights gives us an idea of just how complicated – and fascinating – the study of microbiome composition and its effects on our body is.
For some years many research groups have been working in this area, and some very interesting and results are beginning to emerge. Sometimes, they are surprising.
We know that the microbiome plays an important role in several metabolic diseases and that many bowel-related diseases are increasing dramatically in developed countries around the world.
These considerations suggested the idea to investigate under what conditions and in what way the microbiome changes in non-human primates, i.e. monkeys:
We wanted to find out what happens to the monkeys’ microbiome when they are transferred from the jungle to a zoo. Does their microbiome change? Do they acquire new microbes? Do they lose any? Is it a good or bad thing? From their DNA, we discovered that two species which in nature had two different sets of microbes, in the zoo had lost much of that diversity and had acquired other microbes.
In practice, Knights’ team found that two different monkey species, after their arrival in the zoo, change and become very similar to each other in their microbiomes, even if they consume a different diet and are hosted in different continents.
Something similar happens to people who move from one continent to another:
Most immigrant and refugee groups arrive in the United States in good metabolic health but, within a few years, they become at high risk of developing obesity and diabetes like other Americans. We have found that when people from these groups arrive in the USA, they lose a large part of their original microbiome, around 20 percent, while those who become obese lose around one third of the microbes.
The causes of this phenomenon are not yet clear:
We know that just moving to the USA is enough to cause a radical change in a person’s microbiome, and probably not for the better. Are these microbes causing obesity, or is it obesity that is causing a change in the microbes? This is a point we’re studying, and the tests we currently have in my laboratory, together with tests from other laboratories around the world, tell us that certain changes in the microbiome lead to obesity and to several other modern – typically western – diseases.
The good news is that the microbiome can also change positively: the next frontier of research will be to identify the factors that induce disease and to understand, based on them, how we can modify the microbiome to improve our health:
One of the next steps we will take is to collect and preserve the microbes of healthy people from all over the world to be kept as microbial culture resources for those ethnic groups and, possibly, for use as protection in their adaptation to modern society, and also to protect future generations from the risk of developing these diseases.