Hugh Pickens writes "Every human body harbors about 100 trillion bacterial cells, outnumbering human cells 10 to one. There's been a growing consensus among scientists that bacteria are not simply random squatters, but organized communities that evolve with us and are passed down from generation to generation. 'Human beings are not really individuals; they're communities of organisms,' says microbiologist Margaret McFall-Ngai. 'This could be the basis of a whole new way of looking at disease.' Recently, for example, evidence has surfaced that obesity may well include a microbial component. Jeffrey Gordon's lab at the Washington University School of Medicine in St. Louis published findings that lean and obese twins — whether identical or fraternal — harbor strikingly different bacterial communities that are not just helping to process food directly; they actually influence whether that energy is ultimately stored as fat in the body. Last year, the National Institutes of Health launched the Human Microbiome Project to characterize the role of microbes in the human body, a formal recognition of bacteria's far-reaching influence, including their contributions to human health and certain illnesses. William Karasov, a physiologist and ecologist at University of Wisconsin-Madison, believes that the consequences of this new approach will be profound. 'We've all been trained to think of ourselves as human,' says Karasov, adding that bacteria have usually been considered only as the source of infections, or as something benign living in the body. Now, Karasov says, it appears 'we are so interconnected with our microbes that anything studied before could have a microbial component that we hadn't thought about.'"