If that doesn't make you feel a bit bloated, think about this: An adult human will have about 30 feet of intestine coiled inside her. To a microbe, that's something like 7 million body lengths. For a 6-foot man, 7 million body lengths is around the distance between Boston and Myanmar.
Lurking down in that vast digestive backcountry inside each of us are as many as 30 strains of a bacterium known as Escherichia coli. E. coli is a humble germ, thousands of times smaller than a human cell. It's shaped like a Cheeto and smells like a toilet. It also happens to be the organism scientists most frequently use to explore the molecular foundations of life.
"Aside from ourselves," contends acclaimed science writer Carl Zimmer in his superb new book, "Microcosm: E. coli and the New Science of Life," "we have chronicled no other species so thoroughly."
E. coli, Zimmer reminds us, is a diverse species. There are the benign, sugar-eating colonizers of the guts of newborns. There are strains that shield us from dangerous pathogens. And there are strains that make us terribly sick, like O157:H7, the bacteria that periodically show up in undercooked fast-food hamburgers or on cable news shows. E. coli caused Pembroke residents last week to boil their water.
There are also innumerable colonies of E. coli in biotechnology and microbiology labs around the world. Every day pharmaceutical companies manipulate E. coli to produce human-growth hormone, insulin, vitamins, and even the rennet used to make cheese. Biologists use E. coli to map metabolic pathways. Geneticists use E. coli to investigate why genetically identical organisms sometimes behave in radically different ways. Scientists are even using E. coli to try to understand why we age and die. In many ways "Microcosm" is a sort of correction, an appreciation, an attempt to demonstrate just how indispensable a humble bacterium has been to human life in 2008. It is, in a sense, a paean to a microbe.
