This past week the Human Microbiome Project released the results of a study examining the genetic code of human microbiota collected for more than 15 sites across the bodies of 242 normal, healthy individuals. Studies of the microbiome are revealing that the bacteria that cohabitate within and on the surface of our bodies are tied in many ways to our lifespan health, and are expected to offer clues to why health differs for seemingly similar people and reveal critical points at which changes to the microbiome may lead to adverse health outcomes.
For a more detailed review of recent studies of the human microbiome, see this commentary by Carl Zimmer from the New York Times.