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Actually, All Men Are Islands

“Scientists estimate that there are about 1,000 different species of microbes living in the human gut and about as many more separate species on human skin,” reports this story from the Sacramento Bee. The microbes form colonies that settle in different areas of the body, which Jeffrey Gordon, a microbiologist at Washington University in St. Louis compares to the ecosystems that plants and animals form on islands on Earth.

Only about 10 percent of the trillions of cells that make up a person are truly human — the remaining 90 percent are bacteria, viruses, and other microbes that have a tremendous influence on human health, for good and bad. According to a recent study by Julia Segre, a microbiologist at the National Human Genome Research Institute in Bethesda, Maryland, the most populous region for human skin microbes is the forearm, which accommodates 44 different species. And childhood admonitions to wash behind your ears notwithstanding, that part of the body is actually the most barren, with only 15 native species.

The National Institutes of Health recently launched a $115 million, five-year project to identify, analyze using DNA sequencing, and catalog hundreds of microbial species resident in or on the human body, with the goals of determining which ones are harmful, figuring out how¬† to prevent or treat diseases they cause, and determining whether individuals share a core human microbiome. The Human Microbiome Project is modeled after the Human Genome Project, which completed a “finished” sequence of the human genome in 2003.

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