Members of an isolated Amazonian tribe carry the most diverse collection of bacteria ever seen in humans, according to a new study.
The Yanomami people of South America harbor nearly double the microbial diversity found in people from the United States. Researchers say the Yanomami may reap important health benefits from these bacteria, now absent in the typical Western gut.
"These results suggest that westernization significantly affects human microbiome diversity," the researchers conclude in a paper published today in Science Advances.
The findings stem from growing scientific interest in the human microbiome (simply put, all the microscopic organisms found throughout your body) and how it affects our immune system, metabolism and overall health.
"In our modern lifestyle, we may be missing microbes we co-evolved with ancestrally," said UC San Diego's Rob Knight, a co-author of the new study who was based at the University of Colorado Boulder during the bulk of research.
"Re-supplying those microbes may hold the key to understanding a lot of chronic diseases," Knight said.
The Yanomami lead a hunter-gatherer lifestyle largely unchanged over thousands of years. Some tribal villages have no documented contact with the outside world.
In 2009, a medical team made first contact with a Yanomami village in southern Venezuela. Before administering any vaccines or antibiotics, they swabbed villagers' mouths, skin and feces. Researchers wanted to collect these microbial samples because they provide a rare look at what may have been living in the bodies of human ancestors.
Sequencing the Yanomami microbiome yielded surprises, including microbial genes that confer resistance to a host of antibiotics — even synthetic antibiotics. Researchers say that's a mystery, because these villagers had never been exposed to manmade drugs.
Senior author Jose Clemente of the Icahn School of Medicine at Mount Sinai says the Yanomami provided an opportunity to study our "microbial past."
The Yanomami he and his colleagues studied had not been exposed to Western products, processed foods or modern medicine. Clemente says their expansive microbiome suggests, "even minimal exposure to Western practices ... can result in a drastic loss of bacterial diversity."
The Yanomami could be acquiring all these microbes from closer contact with soil, known to contain bacteria that naturally wards off antibiotics.
They've also avoided a host of culprits researchers have proposed to explain declining microbial diversity in the developed world. The usual suspects include poor diet, excessive hygiene practices, over-prescription of antibiotics and the growing use of c-section (newborns are exposed to lots of microbes during vaginal birth).
One of the study's authors, Maria Dominguez-Bello of the NYU School of Medicine, said, "The implications of this work are relevant to health because immune and metabolic disorders might be related to a degraded microbiome."
