They have changed with our bodies for hundreds of thousands of years

When the first humans left Africa, they were accompanied by their gut microbes

There are clear differences in the composition of microbes and the diversity of the gut microbiome between people living in different countries around the world, for example, different populations may have different species living in their guts, or different strains

Recently, a group of scientists studying microbial evolution and microbiome have discovered that microbes have not only diversified as their early modern human hosts traveled around the world, but that they have co-evolved

Microbes share evolutionary history with humans

Scientists first hypothesized that humans have a global footprint and are genetically diverse, as are

Just as human diversity makes Asians and Europeans look distinctly different, so

To assess this, researchers need to pair

So the team used existing data from Cameroon, South Korea and the United Kingdom, and recruited additional mothers and their young children
in Gabon, Vietnam and Germany.

They collected saliva samples from adults to determine their genotype or genetic signature, while they collected stool samples to sequence
the genomes of gut microbes.

The researchers used data from 839 adults and 386 children in the
analysis.

To assess the evolutionary history of humans and gut microbes, they also built phylogenetic trees
for each person, as well as 59 strains of the most common microbial species.

Comparing the phylogenetic trees of humans with microbes showed that their degree of matching showed a gradient
.

The phylogenetic tree of some bacteria does not match humans at all; Others match up quite well, indicating that these species share a common diversity
with humans.

In fact, some microbial species have been co-evolving
for hundreds of thousands of years.

The phylogenetic tree of human participants (left) and a closely matched bacterial species (right) suggest that humans and this bacterium co-diversify
during evolution.

(Photo: Suzuki et al.
, Science Volume 377, abm 7759 (2022), CC BY-NC-ND)

They also found that microbes that co-evolved with humans had a unique set of genes and traits compared to those that didn't
.

Microbes that "mate" humans typically have smaller genomes, are more sensitive to oxygen and temperature, and are mostly unable to tolerate conditions below a person's
body temperature.
In contrast, gut microbes that are less evolutionarily related to humans have some of the characteristics and genes
of bacteria that live freely in the external environment.

This finding suggests that co-diverse microbes depend heavily on the human body's environmental conditions and must spread rapidly from one person to another, either from generation to generation, or between people living in the same community
.
The team noted that mothers and their children had the same strains of the microbe in their guts, confirming this pattern
of transmission.

In contrast, microbes without a common diversity are more likely to survive well in in vitro environments and spread
more widely through water and soil.

The study found that the gut microbiome co-evolved with the human host, which provides another way to look at the human gut microbiome
.
The gut microbiome has passed from person to person for hundreds or even thousands of generations, and as humans have changed, so has their gut microbe
.

As a result, some gut microbes act as if they were part of the human genome, and they are genetic packages passed down from generation to generation, shared
among relevant individuals.
Personalized medicine and genetic testing are starting to make treatments more individual-specific and effective
.

Understanding which microbes have long-term "partnerships" with people may help researchers develop microbiome-based treatments that target different populations
.

Clinicians are already using "local" probiotics from gut microbes from community members to treat malnutrition
.
The discovery could also help scientists better understand how microbes can ecologically and evolutionarily "live freely" from the environment to those that depend on the human gut
.

Commonly diverse microbes have traits and genes reminiscent of symbiotic bacteria that live in insect hosts
.

These common characteristics suggest that other animal hosts may also have gut microbes
that have been co-diverse with them during evolution.
Paying special attention to microbes with a history of co-evolution with humans helps to understand the critical role
they play in human well-being.

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Original Author:

Taichi A.
Suzuki (Postdoctoral Associate Fellow in Microbiome Science, Max Planck Institute for Biological Research)

Ruth Ley (Head of the Department of Microbiome Science, Max Planck Institute for Biology)

Compiler: Måka

Typesetting: Wen Wen

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https://theconversation.
com/humans-evolved-with-their-microbiomes-like-genes-your-gut-microbes-pass-from-one-generation-to-the-next-190713

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Cover art: NIH

First image: NIH