Human microbiome project outlines new methods for cataloguing microbes

New studies led by Harvard School of Public Health (HSPH) researchers have helped identify and analyse the vast human ''microbiome'' - the more than five million microbial genes that exist inside the human body.

Human Microbiome Project researchers Nicola Segata (l), Curtis Huttenhower

Scientists estimate that each person carries about 100 times as many microbial genes as human genes, and they want to learn more about the role that microbes - organisms like bacteria, viruses, and fungi that live in the stomach, in the mouth, on the skin, or elsewhere - play in normal bodily functions, like development or immunity, as well as in disease.

Several HSPH studies were conducted as part of the Human Microbiome Project (HMP), a multidisciplinary effort involving nearly 250 members from nearly 80 research institutions that is publishing five years of research in several journals simultaneously.

As a result of this effort, HMP Consortium researchers now calculate that there are more than 10,000 microbial species that live in humans; previously, only a few hundred bacterial species had been isolated.

Between 81 per cent and 99 per cent of the genera, or basic family groupings, of these microorganisms in healthy adults were found during this study. These included several opportunistic pathogens - microorganisms that typically harmlessly coexist with the rest of the microbiome and their human hosts, but which can cause disease under unusual circumstances.

See a map of diversity in the human microbiome.