bacteria

Scientists are even discovering ecosystems in our bodies where they weren’t supposed to exist. Lungs have traditionally been considered to be sterile because microbiologists have never been able to rear microbes from them. A team of scientists at Imperial College London recently went hunting for DNA instead. Analyzing lung samples from healthy volunteers, they discovered 128 species of bacteria. Every square centimeter of our lungs is home to 2,000 microbes.

"Mycobacterium vaccae is a natural soil bacterium which people likely ingest or breathe in when they spend time in nature," says Dorothy Matthews of The Sage Colleges in Troy, New York, who conducted the research with her colleague Susan Jenks.