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How microbes keep us healthy

Human Microbiome Project unravels the mystery

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October 22nd, 2013
Microbe
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For the past five years, scientists have been studying a fragile and little understood eco-system the human body. Specifically, they studied trillions of microorganisms such as fungi, bacteria, and other microbes that thrive on humans. Until recently, the idea of microbes may have caused most people to reach for some hand sanitizer, but as we are just beginning to learn, the majority of microbes live in harmony with our own human cells. In fact, most microbes actually help us stay healthy. They get a bad reputation from bacteria like E. coli or a virus like influenza. By studying the good microbes, scientists believe they will be better equipped to fight bad ones. Surprisingly little is known about how microbes function and impact human health. In 2008, the National Institutes of Health (NIH) launched the Human Microbiome Project (HMP) to explore the role microbes play in human health and disease. Researchers studied five key areas of the body: the nose, gut, mouth, skin, and urogenital tract. More than 5,000 samples were collected from 242 healthy U.S. volunteers.

Discoveries

The project s findings were announced last year with great fanfare. NIH Director Francis S. Collins, M.D., Ph.D., says, Like 15th century explorers describing the outline of a new continent, HMP researchers employed a new technological strategy to define, for the first time, the normal microbial makeup of the human body. HMP created a remarkable reference database by using genome sequencing techniques to detect microbes in healthy volunteers. This lays the foundation for accelerating infectious disease research previously impossible without this community resource. Some of the HMP s more interesting and understandable findings include: Microbes outnumber human cells ten to one. Because of their small size, microbes comprise only 1% to 3% of an average person s body mass. A 200-pound adult carries about six pounds of microbes. Microbe genes are more responsible for human survival than human genes.

Skin

To understand the microbes found on human skin, researchers took skin samples from 20 specific sites on the bodies of ten healthy volunteers. Their goal was to explore the microbiome of normal healthy skin. They hoped to identify all of the DNA, or genomes, of all of the microbes that inhabit human skin. Researchers identified more than 112,000 bacterial gene sequences and detected bacteria belonging to 19 different phyla and 205 different genera. The diversity of the bacteria they found at the species level was much greater than expected. The most diversity is seen on the forearm (44 species on average) and the least diversity exists behind the ear (19 species on average). They also found that moist and dry skin had a broader variety of microbes than oily skin. The discoveries made about the biology of normal human skin could ultimately help scientists combat skin diseases such as psoriasis and eczema and fight dangerous infections such as antibiotic-resistant staphylococcus aureus, a bacterium that can cause serious, even life-threatening, infections.

Gut

Probiotic has become a buzzword in recent years. It s on yogurt containers and infused into juices, but what are probiotics? They re microbes, specifically, microbes that aid in digestion. Humans don t have all the enzymes we need to digest our own diet, says Lita Proctor, Ph.D., and program manager of the HMP. Microbes in the gut break down many of the proteins, lipids, and carbohydrates in our diet into nutrients that we can then absorb. Moreover, the microbes produce beneficial compounds, like vitamins and anti-inflammatories that our genome cannot produce. Does that mean there is conclusive evidence that eating expensive probiotic foods purchased at the grocery store will improve our health? The jury is still out on that. While consuming yogurt or other probiotic-rich foods won t hurt you, most experts agree that there is a lot more to be learned about using probiotics to treat health conditions. There are over 400 strains of probiotic bacteria present in the normal human gut and science is only beginning to understand how those strains function. With greater understanding of how microbes impact digestion, scientists hope to find new and better ways of treating debilitating and chronic diseases such as Crohn s disease. Experimental procedures such as introducing certain microbes to the digestive tract already show significant promise in treating ulcerative colitis. Enabling disease-specific studies is the whole point of the Human Microbiome Project, says Barbara Meth , Ph.D., of the J. Craig Venter Institute, Rockville, Md., and lead co-author of the Nature paper on the framework for current and future human microbiome research. Now that we understand what the normal human microbiome looks like, we should be able to understand how changes in the microbiome are associated with, or even cause, illnesses. michele.harris@erickson.com

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