Public Release: 

Forsyth scientists define the bacteria that live in the mouth, throat and gut

Forsyth Institute

For the first time, scientists have defined the bacteria that inhabit multiple sites along the healthy human digestive tract in a large number of individuals. To prevent and control bacterial diseases, it is essential to first identify which bacteria are responsible for keeping us in good health. As part of the Human Microbiome Project, the Forsyth Institute-led team examined bacteria found in adults at 10 sites along the digestive tract, including seven mouth surfaces, the tonsils, the throat and stool samples. This work lays an important foundation for future research on systemic and digestive tract diseases and the development of new treatments for diseases of the digestive tract.

The researchers noted that the bacterial communities from these ten sites separated into four types based on which bacteria were present. They then went beyond determining "who is there" and explored the metabolic capabilities of these microbes based on their gene content. They observed that, although the composition of the bacterial communities varied among the diverse sites, a core set of metabolic genes was present throughout. This indicates common functions are needed for bacterial communities living on mucosal surfaces along the human digestive tract. They also noted that the abundance of genes for some metabolic processes varied by body site, suggesting that some functions were more important in specific habitats. This in-depth analysis was made possible through the unprecedented effort of the Human Microbiome Project, which produced over 22 million bacterial identification tags and over 2 terabases of sequence data for the bacterial genetic information, from over 200 healthy adult subjects.

This study, which will be published in Genome Biology on June 13, 2012, was led by Dr. Jacques Izard, Assistant Member of Staff at The Forsyth Institute. The work was done in collaboration with Dr. Nicola Segata, Harvard School of Public Health; Dr. Susan Kinder Haake, UCLA School of Dentistry; Dr. Peter Mannon, University of Alabama at Birmingham; Dr. Katherine P. Lemon, Assistant Member of Staff at Forsyth and a pediatric infectious diseases specialist at Boston Children's Hospital; Dr. Levi Waldron, Harvard School of Public Health; Dr. Dirk Gevers, The Broad Institute; and Dr. Curtis Huttenhower, Harvard School of Public Health.

The National Institutes of Health Human Microbiome Project is seeking to identify and sequence the thousands of species of bacteria that inhabit human body surfaces. Within the human body, bacteria or microbial cells are estimated to outnumber human cells 10:1. Microbes inhabit just about every surface of the human body, inside the mouth, on the skin, in the gut, up the nose, etc. Most microorganisms live in harmony with their human hosts and are essential for humans to thrive, although a few sometimes cause illness. Studying human-bacteria interactions could lead to new ways to monitor human health status and to new methods for preventing or treating oral and systemic diseases. The Forsyth Institute's efforts are supported by the National Institute of Dental and Craniofacial Research and the National Cancer Institute of NIH.

"We hope that this work will provide a valuable reference for future scientific study investigating both health and disease," said Dr. Izard. "By gaining an understanding of complex microbiome, we can learn more about its role in the onset of diseases of the digestive tract and improving disease management and outcome."

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The Forsyth Institute is the world's leading independent organization dedicated to scientific research and education in oral health and related biomedical sciences. Established in 1910, Forsyth's goal is to lead the discovery, communication and application of breakthroughs in oral health and disease prevention that will significantly improve the health and well-being of the nation and the world. For more information about Forsyth, visit its website at www.forsyth.org.

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