Trillions of bacteria living in and on the human body play a vital role in preserving health. But C-section births, antibiotics and excessive hygiene have been disturbing our microbial balance and possibly contributing to intestinal ailments, obesity, allergies and autism.
Deep in the Amazon basin, where traditional hunter-gatherers still live, researchers gave the indigenous population a lesson in biology. They used posters to explain to the inhabitants of the rain forest that a human being is never alone. Invisible, tiny creatures known as bacteria live on and inside our bodies -- and they can be quite useful.
The lesson was part of a project to research the bacteria of the local people. "When we asked them for samples of their feces, the people laughed," said one of the participating biologists, Maria Gloria Dominguez-Bello, from the University of Puerto Rico. Researchers succeeded in winning their trust, and the inhabitants of 10 huts allowed them to take swab samples, not only from their stool, but also from their hands, feet, noses and mouths.
The search for microbes aims to shed light on the nature of mankind's original bacterial flora. These indigenous test subjects have had almost no contact with outside civilization. Their bacteria are a virtually unadulterated product of evolution. Microorganisms help digest food, supply the body with vitamins, train the immune system and ward off harmful pathogens.
But how do these tiny benefactors fair when their host is exposed to a Western lifestyle? To answer this question, researchers not only took swabs from the traditional people living in the rainforest, but also from people in more highly developed locations in the Amazon basin, in larger settlements, in the Peruvian provincial capital Iquitos, and in Manaus, a Brazilian city with a population of nearly 2 million.
The 200 collected samples are still being analyzed in an American laboratory. But results might indicate that a Western lifestyle is harmful to bacterial colonists. Indeed, the use of antibiotics along with the rising number of cesarean section births, the increasing popularity of small families and excessive hygiene are threatening the microscopic helpers. "We believe these changes (in the microbial diversity) might be behind some of the most common diseases associated with modernity," says Dominguez-Bello.
Similar concerns are shared by Martin Blaser, a professor of microbiology at New York University in Manhattan, who also took part in the expedition to the Amazon region. "Our bacteria are not accidental; we have them for a reason," says Blaser. "Some of these useful guys are disappearing. As a consequence, human physiology is changing and therefore human health."
Physicians and biologists used to merely view these infinitesimally small creatures as pathogens, bacilli that weigh only 0.000000000001 grams but can kill a human being weighing 100,000 grams. But for some time now, scientists have recognized the vital importance of these microorganisms that accompany us every day. A balance between these permanent residents and their human hosts is crucial to maintaining what we call good health.
"We always looked at the bad guys," says Willem de Vos, a microbiologist at Wageningen University in the Netherlands. "But now we're looking at the good guys to understand how they preserve our health."