In the ongoing war against bacteria, however, it is easy to forget that many species of these single-celled organisms actually are innocuous ? and some are even beneficial. In fact, billions and billions of bacteria call the human body home, and many of these perform duties essential to their physical well-being. Moreover, when administered in adequate amounts, certain bacteria can promote gastrointestinal health and help prevent common infections. These bacteria, called probiotics, long have been part of the yogurt scene and now are making their way into other dairy products.