Because the collection of bacteria, or microbiome, from people living in industrialized countries is about 40 percent less diverse, the scientists suspect that certain aspects of a more urban lifestyle could be reducing the diversity of the trillions of bacteria that live on and in our bodies.
“We have found unprecedented diversity in fecal, skin, and oral samples collected from the Yanomami villagers,” Maria Dominguez-Bello, an associate professor of medicine at NYU Langone Medical Center, said in a press release. She is the senior author of the study, which is published in the latest issue of the journal Science Advances.
The Yanomami are believed to have lived in total seclusion from the outside world until 2009, when they were first contacted by a medical expedition. They are among a rare population of people who are unexposed to modern antibiotics.
Dominguez-Bello continued, “Our results bolster a growing body of data suggesting a link between, on the one hand, decreased bacterial diversity, industrialized diets, and modern antibiotics, and on the other, immunological and metabolic diseases — such as obesity, asthma, allergies, and diabetes, which have dramatically increased since the 1970s.”
She added, “We believe there is something environmental occurring in the past 30 years that is driving these diseases. We think the microbiome could be involved.”
She and her team analyzed bacterial samples collected and preserved from 34 of the known 54 Yanomami villagers. Among the volunteers, 28 gave skin and oral swab samples, while 11 gave fecal samples.
Bacterial DNA from the Yanomami was then compared to samples from populations in the United States, as well as to samples from the Amazonian Guahibo Amerindians in Venezuela and residents of rural Malawian communities in southeast Africa. The latter communities represent tribal populations with more exposure to Western culture than the Yanomami, who have subsisted by hunting and gathering for hundreds of generations.
“There is a gradient of diversity in feces and skin that is inversely proportional to exposure to antibiotics and processed foods,” explained co-author Jose Clemente, who is an assistant professor of genetics and genomics at the Icahn School of Medicine at Mount Sinai. “Even minimal exposure greatly decreases diversity and removes potentially beneficial bacteria from our microbiome.”
Among the Yanomami skin samples, the researchers found no single dominant type of bacteria. This was in contrast to the U.S. skin samples, which showed lower diversity and relatively higher proportions of Staphylococcus, Corynebacterium, Neisseriaceae, and Propionibacterium. While these bacteria are common and usually harmless, they can cause serious infections, such as the well know “staph infections” that can be difficult to treat.
A genetic analysis of gut and oral bacteria also revealed that the Yanomami villagers had bacteria containing genes coding for antibiotic resistance. The bacterial genes conferred resistance not only to natural antibiotics found in the soil, but also to synthetic antibiotics.
“During the 1940s and 1950s, in the heyday of pharmaceutical antibiotic development, most antibiotics were derived from naturally occurring bacteria in the soil,” said co-author Gautam Dantas, who is an associate professor of pathology, immunology, and biomedical engineering at the Washington University School of Medicine.
“So, we would expect that natural resistance to antibiotics would emerge over millions of years of evolution,” he added. “We didn’t expect to find resistance to modern synthetic antibiotics. The silenced antibiotic-resistant genes show that you don’t need exposure to antibiotics to possess antibiotic-resistant genes.”
Read more at Discovery News
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