What is already known
The composition of the gut microbiota can vary depending on diet and lifestyle, yet microbiota studies are biased toward industrialized populations. These populations have a low microbiota diversity, likely due to antibiotic use, a diet rich in processed foods and reduced physical contact with animals and soil.
What this research adds
Researchers analyzed stool samples from 167 members of the Hadza hunter-gatherer community in Tanzania and found that these individuals tend to have more diverse gut microbes than people in Nepal and California. The Hadza had on average 730 bacterial species in their guts, whereas people in California had just 277 species. More than 1,000 of the genome sequences recovered from the Hadza samples had not been previously recorded.
Conclusions
The findings provide insights into how industrialized lifestyles have influenced the composition of the human gut microbiota.
The composition of the gut microbiota can vary depending on diet and lifestyle, yet microbiota studies are biased toward industrialized populations. Now, researchers have discovered more than a thousand new microbial species in members of a hunter-gatherer community in Tanzania.
The study, published in Cell, also shows that people from this community have a more diverse gut microbiota than people in other communities. The findings provide insights into how industrialized lifestyles have influenced the composition of the human gut microbiota.
Scientists have known that industrialized populations have a low microbiota diversity, likely due to antibiotic use, a diet rich in processed foods and reduced physical contact with animals and soil. Previous work has suggested that ancient microbiotas more closely resemble those of modern, non-industrialized populations rather than those of industrialized ones.
However, the authors say, “recent efforts to establish comprehensive databases of gut-associated genomes and genes have shown that populations living non-industrial lifestyles have not been sequenced sufficiently to capture the extent of microbiome diversity.”
The team, led by Matthew Carter at Stanford University School of Medicine, collected and analyzed stool samples from 167 members of the Hadza people — a hunter-gatherer society in northern Tanzania — between 2013 and 2014. As a comparison, the team analyzed the gut microbiotas of 12 people in California and 56 Nepali people from forager and agrarian communities.
New genomes
The researchers sequenced more than 90,000 genomes from microbes found in the human gut, including bacteria, viruses and archaea. More than 1,000 of the genome sequences recovered from the Hadza samples had not been previously recorded.
Compared with individuals from other communities, the Hadza tend to have more diverse gut microbes, the researchers found. People from the Hadza population had on average 730 bacterial species in their guts, whereas people in California had just 277 species. The guts of Nepali foragers contained 317 species and those of Nepali agrarians 436 species.
The gut microbiotas of industrialized populations often contained genes involved in oxidative stress, likely as a result of these microbiotas being adapted to chronic inflammation, the researchers found.
Diverse microbiota
The Hadza people have high levels of gut bacteria called Spirochaetota, of which the most prevalent species is Treponema succinifaciens. This microbe has been previously associated with a non-industrialized lifestyle and with ancient microbiotas.
When the researchers analyzed the Nepali microbiotas, they found T. succinifaciens only in some samples. The microbe wasn’t present in samples from people in California. This result suggests that as societies become more industrialized, gut microbes adapt to the changing gut environment, the researchers say.
“Our results conclusively show that the differences between industrialized and non-industrialized microbiomes go well beyond simple taxonomic membership and diversity,” the authors say. “These findings have substantial implications for how the microbiome may be investigated toward improving the health of both industrialized and non-industrialized populations.”
