How do microorganisms live in a human’s microbiome?

Microbes inhabit just about every part of the human body, living on the skin, in the gut, and up the nose. Sometimes they cause sickness, but most of the time, microorganisms live in harmony with their human hosts, providing vital functions essential for human survival. For the first time, a consortium of researchers organized by the National Institutes of Health has mapped the normal microbial makeup of healthy humans, producing numerous insights and even a few surprises.

Researchers found, for example, that nearly everyone routinely carries pathogens, microorganisms known to cause illnesses. In healthy individuals, however, pathogens cause no disease; they simply coexist with their host and the rest of the human microbiome, the collection of all microorganisms living in the human body. Researchers must now figure out why some pathogens turn deadly and under what conditions, likely revising current concepts of how microorganisms cause disease.

In a series of coordinated scientific reports published on June 14, 2012, in Nature and several journals in the Public Library of Science (PLoS), some 200 members of the Human Microbiome Project (HMP) Consortium from nearly 80 universities and scientific institutions report on five years of research. HMP has received $153 million since its launch in fiscal year 2007 from the NIH Common Fund, which invests in high-impact, innovative, trans-NIH research. Individual NIH institutes and centers have provided an additional $20 million in co-funding for HMP consortium research.

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