Members of an isolated Amazon tribe in Venezuela (pictured) have the most diverse gut bacteria ever documented in humans.

Credit: Robert Caputo/Aurora Photos

Maria Gloria Dominguez-Bello at New York University School of Medicine analysed oral, faecal and skin bacteria from 34 Yanomami villagers who had never met anyone from the West until 2009. The researchers found almost double the genetic diversity in the faecal bacteria compared with the microbiomes of US residents. The faecal and oral bacteria also carried genes for antibiotic resistance, even though the people had no known exposure to the drugs.

In a separate study, Jens Walter at the University of Alberta in Edmonton, Andrew Greenhill at Federation University Australia in Churchill and their colleagues looked at the gut microbiomes of people from two rural areas of Papua New Guinea. They found that the bacteria were extremely diverse and included lineages not seen in US populations. Using ecological modelling, the authors attributed the increased diversity to low sanitation levels, which increased the swapping of bacteria between people.

Science Adv. 1, e1500183 (2015); Cell Rep. http://doi.org/3vh (2015)