After 5 years of examining thousands of tissues from hundreds of volunteers, a consortium of scientists has created a microbial map of the healthy human body that will guide researchers in determining how microorganisms may contribute to such illnesses as Crohn disease, esophageal cancer, and psoriasis.
The Human Microbiome Project (HMP) Consortium reported that a healthy body is teeming with trillions of microorganisms—bacteria, viruses, archaea, and eukaryotes. In fact, the research shows that the body has 10 times as many microbial cells as human cells. Some of these microbes play a role in disease, but usually they all live in harmony to carry out such essential functions as digesting fats and generating vitamins and anti-inflammatory compounds.
The HMP is managed by the National Human Genome Research Institute and funded by the National Institutes of Health (NIH) Common Fund. NIH Director Francis Collins, MD, PhD, likened the consortium’s work to that of “15th century explorers describing the outline of a new continent.” He said the microbial map “lays the foundation for accelerating infectious disease research previously impossible without this community resource.”
Researchers used DNA sequencing techniques to study more than 5000 specimens from 242 healthy men and women. Specimens came from 15 body sites, including the mouth, nose, skin, lower intestine, and vagina. The variation in microorganisms from site to site can be as great as those in the Sahara desert and the Amazon rainforest, the researchers said.
The mapping project shows that microbes contribute more genes that encode life-sustaining proteins (8 million) than the human genome (22 000). One surprise they discovered is that microbes can play interchangeable roles in supporting metabolic processes.
“It appears that bacteria can pinch hit for each other,” said Curtis Huttenhower, PhD, of the Harvard School of Public Health and a coauthor of one of the Nature studies. “It matters whether the metabolic function is present, not which microbial species provides it.”
The data will be available in public databases, including those of the National Center for Biotechnology Information and the HMP Data Analysis and Coordinating Center.