Microbes: The trillions of creatures governing your health

From Smithsonian:

The modern microbiome era started in the late 1990s, when David Relman, an infectious disease physician at Stanford University, decided to get a sample of the microbes in his own mouth. It’s a simple process: A dentist scrapes a sort of elongated Q-tip across the outer surface of a tooth, or the gums, or the inside of a cheek. These samples typically look like nothing at all. (“You have to have a lot of faith in the invisible,” one dentistry professor advises.)

…It’s not just that there are more than 1,000 possible microbial species in your mouth. The census, as it currently stands, also counts 150 behind your ear, 440 on the insides of your forearm and any of several thousand in your intestines. In fact, microbes inhabit almost every corner of the body, from belly button to birth canal, all told more than 10,000 species. Looked at in terms of the microbes they host, your mouth and your gut are more different than a hot spring and an ice cap, according to Rob Knight, a microbial ecologist at the University of Colorado. Even your left and right hands may have only 17 percent of their bacterial species in common, according to a 2010 study. But the real news is that the microbial community makes a significant difference in how we live and even how we think and feel. Recent studies have linked changes in the microbiome to some of the most pressing medical problems of our time, including obesity, allergies, diabetes, bowel disorders and even psychiatric problems like autism, schizophrenia and depression. Just within the past year, for instance, researchers have found that:

•Infants exposed to antibiotics in the first six months of life are 22 percent more likely to be overweight as toddlers than unexposed infants, perhaps because antibiotics knock down essential microbes.
•A lack of normal gut microbes early in life disturbs the central nervous system in rodents, and may permanently alter serotonin levels in the adult brain. Scientists suspect that the same could hold for humans.
•Just giving enough food to starving children may not permanently fix their malnutrition unless they also have the “right” digestive micro-organisms, according to a study of kids in Malawi.

More here.