Germs used to be viewed as only bad, but scientists who have taken navel-gazing to a new level are finding that the ones living in your belly button coexist quite nicely with the rest of your body's microbes.
Setting out to dispel the notion that all skin bacteria cause disease, researchers from North Carolina State University swabbed the navels of 391 volunteers from across the country, sequenced the DNA from each sample and published photos of the cultures anonymously online on the Bellybutton Bacteria Culture database.
Preliminary results, scheduled to be presented Aug. 12 at the Ecological Society of America's annual meeting in Austin, Texas, revealed similarities in navel bacteria among family members and a wide diversity of microbes present in any given person.
"The overall concept is compelling," said Dr. Bruce Hirsch, an attending physician in infectious diseases at North Shore University Hospital in Manhasset, N.Y. "When I grew up, germs were bad. But the vast majority of the time, they're good or neutral," he said.
"I think of the human body as more of a forest than a tree," added Hirsch, who was not involved in the study. "Bacteria are a normal part of health, and each human body has more bacteria cells than human cells."
The Bellybutton Bacteria Culture database has become one of the most watched citizen-science projects in the nation, the study authors said, with about 55,000 visitors to the website in just three months. The rate of voluntary participation at sampling events shot up from 17 percent to 80 percent when passers-by were informed of the project's purpose.
The researchers chose to sample belly button bacteria because the area is generally protected from excretions, soaps and ultraviolet ray exposure. They also felt it would generate excitement about the study from participants, whose gender, ethnic background, age and hygienic habits were recorded. More than 80 percent of the samples were viable in cell culture dishes.
Hirsch noted that the results of the study — which are a work in progress and have not undergone peer review — are not detailed and did not yield many conclusions. But he said most bacteria are good "and their very presence crowds out more dangerous bacteria."
"I'm amazed at how the body responds to infection and how often we see spectacular successes in the way it responds," he said. "The human body is incredible. When we look at it from a bacterial perspective, it's like a new world."
Philip M. Tierno Jr., author of The Secret Life of Germs and director of clinical microbiology and immunology at NYU Langone Medical Center, said it's not news to him that there's a greater diversity of bacteria on the skin than many people think.
The number and types of microbes found in belly buttons may not be representative of what's found on the rest of the human body because of its depth, where lint and other "cellular debris" can accumulate, said Tierno, also a clinical professor of microbiology and pathology at New York University School of Medicine.
"Only 10 percent of you is you, which should give you an idea of how important microbes are," he said. "Ninety percent is bacteria or microbial cells, although body cells are bigger."