We may not like thinking about it, but germs crawl eternally over every speck of our planet. Our own bodies are bacterial condos, with established relationships between the upstairs and downstairs neighbors. Without these regular residents, our guts are easily taken over by less congenial newcomers looking for low-rent space. What keeps us healthy is an informed coexistence with microbes, rather than the micro-genocide that seems to be the rage lately. Germophobic parents can now buy kids' dinnerware, placemats, even clothing imbedded with antimicrobial chemicals. Anything that will stand still, if we mean to eat it, we shoot full of antibiotics. And yet, more than 5,000 people in the United States die each year from pathogens in our food. Sterility is obviously the wrong goal, especially as a substitute for careful work.