[...] researchers who studied seven families in Illinois, Washington and California could easily match up who lived where using their microscopic roommates, almost like CSI for germs. Thursday's study is part of an effort to understand how the trillions of mostly beneficial bacteria that live in and on our bodies — what's called the human microbiome — interact with bugs in the environment to affect our health. Right at birth, babies start picking up microbes on the skin, in the nose, in the gut that eventually make up living communities that will share their bodies throughout life. For six weeks, participants collected samples of the microscopic bugs living on and around them by swabbing the hands, feet, noses and paws of everyone in the household, plus doorknobs, light switches, floors and countertops. Back in the laboratory, Gilbert's team identified the bugs by their DNA, and they reported Thursday in the journal Science that people substantially affect the microbial communities in their homes. Like Pigpen's trailing cloud of dust in the Peanuts comic strip, when three families moved — one of them from a hotel room to a house — it took about a day for the microbes in their new homes to closely resemble those in the old ones.