Discovered Tribe's Bacteria May Point to Our Past

By Brenda Goodman, MA
WebMD Health News

Reviewed by Arefa Cassoobhoy, MD, MPH

April 17, 2015 -- A tribe of Indians found in the remote mountains of Venezuela may have a lot to teach us about the connection between gut bacteria and our health.

The Yanomami Indians have nearly twice as many different kinds of bacteria living in their intestines as Americans do.

Researchers say the discovery offers a peek at an unspoiled microbiome, the collection of trillions of bacteria that live in and on our bodies. We're still learning about the roles these friendly microbes play in our health. But studies have shown they influence our weight, our digestion, our immune responses, and they help keep disease-causing pathogens from making us sick.

As scientists have begun to appreciate the importance of the microbiome, there's been growing concern that modern practices may be changing it in ways that lead to disease. These trends include everything from more and more processed foods in our diets, to the rise in C-sections (which deny infants the chance to be protected by Mom's bacteria), to the overuse of antibiotics.

And though the villagers told medical workers they'd never before had contact with outsiders, scientists found the bacteria living in and on their bodies had genes to shield it from modern antibiotics. This suggests that the problem of antibiotic resistance may be tougher to undo than experts once thought.

"This population of Yanomami Indians that we studied are naive to [modern] practices. They present a unique opportunity to put our microbial past under the microscope, if you wish, and characterize for the first time a microbiome that perhaps could be similar to that of our ancestors," says researcher Jose Clemente, PhD, an assistant professor of genetics and genomics at the Mount Sinai School of Medicine, in a news briefing.

Researchers say the tribe was spotted by helicopter in 2008. A medical team made contact with the group in 2009. They asked permission to collect samples of bacteria swabbed from their mouths, skin, and feces. They collected samples from 34 of the 54 villagers who ranged in age from 4 to 50.

There were some signs of modern life amongst tribe members' belongings, including T-shirts, metal cans, and machetes. Researchers believe they got these items through trade with other Yanomami groups that had made contact with the outside world.

Samples of their bacteria were flown back to the U.S. and analyzed from 2011 to 2014.

Bacteria and Our Health

The findings, published in the journal Science Advances, seem to be part of a pattern.

Samples collected from other rural hunter-gatherer peoples, like the Hadza in Tanzania and the Matses in Peru, also show that they have many more kinds of bacteria living in their intestines compared to people in more-developed countries. The more industrialized the society, the fewer different kinds of bacteria they have, studies show.

What isn't known is whether having a more diverse stew of bacteria in our intestines translates to better health. That's a theory called the "missing microbes" hypothesis. And the study found a bit of evidence to back it.

For example, some of the bacteria unique to the Yanomami, but missing in many other populations, are known to have health benefits. A species called Oxalobacter formigenes, for instance, breaks down a chemical called oxalate, which is a major component of kidney stones.

Researchers are starting a library of the microbes they found in the hopes it can be mined for insights.

Another major mystery from the study was the discovery of antibiotic-resistant genes, since the villagers had never taken modern drugs.

Researchers say they expected to find some of those defenses. Antibiotics were first discovered in nature from molds, and studies have shown that soil bacteria have genes that protect them from natural compounds that might try to kill them.

Study author Gautam Dantas, PhD, an assistant professor of pathology and immunology at Washington University, says tribe members also had bacteria with genes resistant to modern drugs that are not made naturally in soil.

"It confirms to us that bacteria have incredible metabolic and evolutionary potential to rapidly adapt to things that we throw at them," he says.

"When you use antibiotics, whether it's in agriculture or in the clinic, you amplify the amounts [of resistance]. You allow it to get into many more bacteria. … Bacteria that might be resistant to one or two antibiotics, now quickly become resistant to 5, 10, 15 antibiotics," Dantas says.

What that may mean is that antibiotics may have an even shorter shelf-life when it comes to their ability to kill bacteria than once thought.

Experts who were not involved in the research say it's critical to understanding the connection between our bacteria and our health.

"Probing microbiomes from far-flung reaches of the human population is very important to understand the limits of what the human body can manage and what can [live on] us," says George Weinstock, PhD, associate director of microbial genomics at The Jackson Laboratory. "Moreover, these organisms may include some that have not been studied before and which may have beneficial contributions to human health."

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