Sometimes I read something that seems obvious in retrospect, but sounds so bizarre upon first glance. From the Nov 22,2010 New Yorker article on fermented foods - "Nature's Spoils":
"There is no such thing as an individual," Lynn Margulis, a biologist at the University of Massachusetts at Amherst, told me recently. "What we see as animals are partly just integrated sets of bacteria." Nearly all the DNA in our bodies belongs to microorganisms: they outnumber our cells nine to one. They process the nutrients in our guys, produce the chemicals that trigger sleep, ferment the sweat on our skin and the glucose in our muscles.  They work with the immune system to mediate chemical reactinos and drive out the most common infections. Even our own cells are kept alive by mitochonidria - the tiny microbial engines in our cytoplasm. Bacteria are us.